| 1 | /** |
| 2 | * Copyright (c) Meta Platforms, Inc. and affiliates. |
| 3 | * |
| 4 | * This source code is licensed under the MIT license found in the |
| 5 | * LICENSE file in the root directory of this source tree. |
| 6 | */ |
| 7 | |
| 8 | import { |
| 9 | CompilerDiagnostic, |
| 10 | CompilerError, |
| 11 | Effect, |
| 12 | SourceLocation, |
| 13 | ValueKind, |
| 14 | } from '..'; |
| 15 | import { |
| 16 | BasicBlock, |
| 17 | BlockId, |
| 18 | DeclarationId, |
| 19 | Environment, |
| 20 | FunctionExpression, |
| 21 | GeneratedSource, |
| 22 | getHookKind, |
| 23 | HIRFunction, |
| 24 | Hole, |
| 25 | IdentifierId, |
| 26 | Instruction, |
| 27 | InstructionKind, |
| 28 | InstructionValue, |
| 29 | isArrayType, |
| 30 | isJsxType, |
| 31 | isMapType, |
| 32 | isPrimitiveType, |
| 33 | isRefOrRefValue, |
| 34 | isSetType, |
| 35 | makeIdentifierId, |
| 36 | Phi, |
| 37 | Place, |
| 38 | SpreadPattern, |
| 39 | Type, |
| 40 | ValueReason, |
| 41 | } from '../HIR'; |
| 42 | import { |
| 43 | eachInstructionValueOperand, |
| 44 | eachPatternItem, |
| 45 | eachTerminalOperand, |
| 46 | eachTerminalSuccessor, |
| 47 | } from '../HIR/visitors'; |
| 48 | |
| 49 | import { |
| 50 | assertExhaustive, |
| 51 | getOrInsertDefault, |
| 52 | getOrInsertWith, |
| 53 | Set_isSuperset, |
| 54 | } from '../Utils/utils'; |
| 55 | import { |
| 56 | printAliasingEffect, |
| 57 | printAliasingSignature, |
| 58 | printIdentifier, |
| 59 | printInstruction, |
| 60 | printInstructionValue, |
| 61 | printPlace, |
| 62 | } from '../HIR/PrintHIR'; |
| 63 | import {FunctionSignature} from '../HIR/ObjectShape'; |
| 64 | import prettyFormat from 'pretty-format'; |
| 65 | import {createTemporaryPlace} from '../HIR/HIRBuilder'; |
| 66 | import { |
| 67 | AliasingEffect, |
| 68 | AliasingSignature, |
| 69 | hashEffect, |
| 70 | MutationReason, |
| 71 | } from './AliasingEffects'; |
| 72 | import {ErrorCategory} from '../CompilerError'; |
| 73 | |
| 74 | const DEBUG = false; |
| 75 | |
| 76 | /** |
| 77 | * Infers the mutation/aliasing effects for instructions and terminals and annotates |
| 78 | * them on the HIR, making the effects of builtin instructions/functions as well as |
| 79 | * user-defined functions explicit. These effects then form the basis for subsequent |
| 80 | * analysis to determine the mutable range of each value in the program — the set of |
| 81 | * instructions over which the value is created and mutated — as well as validation |
| 82 | * against invalid code. |
| 83 | * |
| 84 | * At a high level the approach is: |
| 85 | * - Determine a set of candidate effects based purely on the syntax of the instruction |
| 86 | * and the types involved. These candidate effects are cached the first time each |
| 87 | * instruction is visited. The idea is to reason about the semantics of the instruction |
| 88 | * or function in isolation, separately from how those effects may interact with later |
| 89 | * abstract interpretation. |
| 90 | * - Then we do abstract interpretation over the HIR, iterating until reaching a fixpoint. |
| 91 | * This phase tracks the abstract kind of each value (mutable, primitive, frozen, etc) |
| 92 | * and the set of values pointed to by each identifier. Each candidate effect is "applied" |
| 93 | * to the current abtract state, and effects may be dropped or rewritten accordingly. |
| 94 | * For example, a "MutateConditionally <x>" effect may be dropped if x is not a mutable |
| 95 | * value. A "Mutate <y>" effect may get converted into a "MutateFrozen <error>" effect |
| 96 | * if y is mutable, etc. |
| 97 | */ |
| 98 | export function inferMutationAliasingEffects( |
| 99 | fn: HIRFunction, |
| 100 | {isFunctionExpression}: {isFunctionExpression: boolean} = { |
| 101 | isFunctionExpression: false, |
| 102 | }, |
| 103 | ): void { |
| 104 | const initialState = InferenceState.empty(fn.env, isFunctionExpression); |
| 105 | |
| 106 | // Map of blocks to the last (merged) incoming state that was processed |
| 107 | const statesByBlock: Map<BlockId, InferenceState> = new Map(); |
| 108 | |
| 109 | for (const ref of fn.context) { |
| 110 | // TODO: using InstructionValue as a bit of a hack, but it's pragmatic |
| 111 | const value: InstructionValue = { |
| 112 | kind: 'ObjectExpression', |
| 113 | properties: [], |
| 114 | loc: ref.loc, |
| 115 | }; |
| 116 | initialState.initialize(value, { |
| 117 | kind: ValueKind.Context, |
| 118 | reason: new Set([ValueReason.Other]), |
| 119 | }); |
| 120 | initialState.define(ref, value); |
| 121 | } |
| 122 | |
| 123 | const paramKind: AbstractValue = isFunctionExpression |
| 124 | ? { |
| 125 | kind: ValueKind.Mutable, |
| 126 | reason: new Set([ValueReason.Other]), |
| 127 | } |
| 128 | : { |
| 129 | kind: ValueKind.Frozen, |
| 130 | reason: new Set([ValueReason.ReactiveFunctionArgument]), |
| 131 | }; |
| 132 | |
| 133 | if (fn.fnType === 'Component') { |
| 134 | CompilerError.invariant(fn.params.length <= 2, { |
| 135 | reason: |
| 136 | 'Expected React component to have not more than two parameters: one for props and for ref', |
| 137 | loc: fn.loc, |
| 138 | }); |
| 139 | const [props, ref] = fn.params; |
| 140 | if (props != null) { |
| 141 | inferParam(props, initialState, paramKind); |
| 142 | } |
| 143 | if (ref != null) { |
| 144 | const place = ref.kind === 'Identifier' ? ref : ref.place; |
| 145 | const value: InstructionValue = { |
| 146 | kind: 'ObjectExpression', |
| 147 | properties: [], |
| 148 | loc: place.loc, |
| 149 | }; |
| 150 | initialState.initialize(value, { |
| 151 | kind: ValueKind.Mutable, |
| 152 | reason: new Set([ValueReason.Other]), |
| 153 | }); |
| 154 | initialState.define(place, value); |
| 155 | } |
| 156 | } else { |
| 157 | for (const param of fn.params) { |
| 158 | inferParam(param, initialState, paramKind); |
| 159 | } |
| 160 | } |
| 161 | |
| 162 | /* |
| 163 | * Multiple predecessors may be visited prior to reaching a given successor, |
| 164 | * so track the list of incoming state for each successor block. |
| 165 | * These are merged when reaching that block again. |
| 166 | */ |
| 167 | const queuedStates: Map<BlockId, InferenceState> = new Map(); |
| 168 | function queue(blockId: BlockId, state: InferenceState): void { |
| 169 | let queuedState = queuedStates.get(blockId); |
| 170 | if (queuedState != null) { |
| 171 | // merge the queued states for this block |
| 172 | state = queuedState.merge(state) ?? queuedState; |
| 173 | queuedStates.set(blockId, state); |
| 174 | } else { |
| 175 | /* |
| 176 | * this is the first queued state for this block, see whether |
| 177 | * there are changed relative to the last time it was processed. |
| 178 | */ |
| 179 | const prevState = statesByBlock.get(blockId); |
| 180 | const nextState = prevState != null ? prevState.merge(state) : state; |
| 181 | if (nextState != null) { |
| 182 | queuedStates.set(blockId, nextState); |
| 183 | } |
| 184 | } |
| 185 | } |
| 186 | queue(fn.body.entry, initialState); |
| 187 | |
| 188 | const hoistedContextDeclarations = findHoistedContextDeclarations(fn); |
| 189 | |
| 190 | const context = new Context( |
| 191 | isFunctionExpression, |
| 192 | fn, |
| 193 | hoistedContextDeclarations, |
| 194 | findNonMutatedDestructureSpreads(fn), |
| 195 | ); |
| 196 | |
| 197 | let iterationCount = 0; |
| 198 | while (queuedStates.size !== 0) { |
| 199 | iterationCount++; |
| 200 | if (iterationCount > 100) { |
| 201 | CompilerError.invariant(false, { |
| 202 | reason: `[InferMutationAliasingEffects] Potential infinite loop`, |
| 203 | description: `A value, temporary place, or effect was not cached properly`, |
| 204 | loc: fn.loc, |
| 205 | }); |
| 206 | } |
| 207 | for (const [blockId, block] of fn.body.blocks) { |
| 208 | const incomingState = queuedStates.get(blockId); |
| 209 | queuedStates.delete(blockId); |
| 210 | if (incomingState == null) { |
| 211 | continue; |
| 212 | } |
| 213 | |
| 214 | statesByBlock.set(blockId, incomingState); |
| 215 | const state = incomingState.clone(); |
| 216 | inferBlock(context, state, block); |
| 217 | |
| 218 | for (const nextBlockId of eachTerminalSuccessor(block.terminal)) { |
| 219 | queue(nextBlockId, state); |
| 220 | } |
| 221 | } |
| 222 | } |
| 223 | return; |
| 224 | } |
| 225 | |
| 226 | function findHoistedContextDeclarations( |
| 227 | fn: HIRFunction, |
| 228 | ): Map<DeclarationId, Place | null> { |
| 229 | const hoisted = new Map<DeclarationId, Place | null>(); |
| 230 | function visit(place: Place): void { |
| 231 | if ( |
| 232 | hoisted.has(place.identifier.declarationId) && |
| 233 | hoisted.get(place.identifier.declarationId) == null |
| 234 | ) { |
| 235 | // If this is the first load of the value, store the location |
| 236 | hoisted.set(place.identifier.declarationId, place); |
| 237 | } |
| 238 | } |
| 239 | for (const block of fn.body.blocks.values()) { |
| 240 | for (const instr of block.instructions) { |
| 241 | if (instr.value.kind === 'DeclareContext') { |
| 242 | const kind = instr.value.lvalue.kind; |
| 243 | if ( |
| 244 | kind == InstructionKind.HoistedConst || |
| 245 | kind == InstructionKind.HoistedFunction || |
| 246 | kind == InstructionKind.HoistedLet |
| 247 | ) { |
| 248 | hoisted.set(instr.value.lvalue.place.identifier.declarationId, null); |
| 249 | } |
| 250 | } else { |
| 251 | for (const operand of eachInstructionValueOperand(instr.value)) { |
| 252 | visit(operand); |
| 253 | } |
| 254 | } |
| 255 | } |
| 256 | for (const operand of eachTerminalOperand(block.terminal)) { |
| 257 | visit(operand); |
| 258 | } |
| 259 | } |
| 260 | return hoisted; |
| 261 | } |
| 262 | |
| 263 | class Context { |
| 264 | internedEffects: Map<string, AliasingEffect> = new Map(); |
| 265 | instructionSignatureCache: Map<Instruction, InstructionSignature> = new Map(); |
| 266 | effectInstructionValueCache: Map<AliasingEffect, InstructionValue> = |
| 267 | new Map(); |
| 268 | applySignatureCache: Map< |
| 269 | AliasingSignature, |
| 270 | Map<AliasingEffect, Array<AliasingEffect> | null> |
| 271 | > = new Map(); |
| 272 | catchHandlers: Map<BlockId, Place> = new Map(); |
| 273 | functionSignatureCache: Map<FunctionExpression, AliasingSignature> = |
| 274 | new Map(); |
| 275 | isFuctionExpression: boolean; |
| 276 | fn: HIRFunction; |
| 277 | hoistedContextDeclarations: Map<DeclarationId, Place | null>; |
| 278 | nonMutatingSpreads: Set<IdentifierId>; |
| 279 | |
| 280 | constructor( |
| 281 | isFunctionExpression: boolean, |
| 282 | fn: HIRFunction, |
| 283 | hoistedContextDeclarations: Map<DeclarationId, Place | null>, |
| 284 | nonMutatingSpreads: Set<IdentifierId>, |
| 285 | ) { |
| 286 | this.isFuctionExpression = isFunctionExpression; |
| 287 | this.fn = fn; |
| 288 | this.hoistedContextDeclarations = hoistedContextDeclarations; |
| 289 | this.nonMutatingSpreads = nonMutatingSpreads; |
| 290 | } |
| 291 | |
| 292 | cacheApplySignature( |
| 293 | signature: AliasingSignature, |
| 294 | effect: Extract<AliasingEffect, {kind: 'Apply'}>, |
| 295 | f: () => Array<AliasingEffect> | null, |
| 296 | ): Array<AliasingEffect> | null { |
| 297 | const inner = getOrInsertDefault( |
| 298 | this.applySignatureCache, |
| 299 | signature, |
| 300 | new Map(), |
| 301 | ); |
| 302 | return getOrInsertWith(inner, effect, f); |
| 303 | } |
| 304 | |
| 305 | internEffect(effect: AliasingEffect): AliasingEffect { |
| 306 | const hash = hashEffect(effect); |
| 307 | let interned = this.internedEffects.get(hash); |
| 308 | if (interned == null) { |
| 309 | this.internedEffects.set(hash, effect); |
| 310 | interned = effect; |
| 311 | } |
| 312 | return interned; |
| 313 | } |
| 314 | } |
| 315 | |
| 316 | /** |
| 317 | * Finds objects created via ObjectPattern spread destructuring |
| 318 | * (`const {x, ...spread} = ...`) where a) the rvalue is known frozen and |
| 319 | * b) the spread value cannot possibly be directly mutated. The idea is that |
| 320 | * for this set of values, we can treat the spread object as frozen. |
| 321 | * |
| 322 | * The primary use case for this is props spreading: |
| 323 | * |
| 324 | * ``` |
| 325 | * function Component({prop, ...otherProps}) { |
| 326 | * const transformedProp = transform(prop, otherProps.foo); |
| 327 | * // pass `otherProps` down: |
| 328 | * return <Foo {...otherProps} prop={transformedProp} />; |
| 329 | * } |
| 330 | * ``` |
| 331 | * |
| 332 | * Here we know that since `otherProps` cannot be mutated, we don't have to treat |
| 333 | * it as mutable: `otherProps.foo` only reads a value that must be frozen, so it |
| 334 | * can be treated as frozen too. |
| 335 | */ |
| 336 | function findNonMutatedDestructureSpreads(fn: HIRFunction): Set<IdentifierId> { |
| 337 | const knownFrozen = new Set<IdentifierId>(); |
| 338 | if (fn.fnType === 'Component') { |
| 339 | const [props] = fn.params; |
| 340 | if (props != null && props.kind === 'Identifier') { |
| 341 | knownFrozen.add(props.identifier.id); |
| 342 | } |
| 343 | } else { |
| 344 | for (const param of fn.params) { |
| 345 | if (param.kind === 'Identifier') { |
| 346 | knownFrozen.add(param.identifier.id); |
| 347 | } |
| 348 | } |
| 349 | } |
| 350 | |
| 351 | // Map of temporaries to identifiers for spread objects |
| 352 | const candidateNonMutatingSpreads = new Map<IdentifierId, IdentifierId>(); |
| 353 | for (const block of fn.body.blocks.values()) { |
| 354 | if (candidateNonMutatingSpreads.size !== 0) { |
| 355 | for (const phi of block.phis) { |
| 356 | for (const operand of phi.operands.values()) { |
| 357 | const spread = candidateNonMutatingSpreads.get(operand.identifier.id); |
| 358 | if (spread != null) { |
| 359 | candidateNonMutatingSpreads.delete(spread); |
| 360 | } |
| 361 | } |
| 362 | } |
| 363 | } |
| 364 | for (const instr of block.instructions) { |
| 365 | const {lvalue, value} = instr; |
| 366 | switch (value.kind) { |
| 367 | case 'Destructure': { |
| 368 | if ( |
| 369 | !knownFrozen.has(value.value.identifier.id) || |
| 370 | !( |
| 371 | value.lvalue.kind === InstructionKind.Let || |
| 372 | value.lvalue.kind === InstructionKind.Const |
| 373 | ) || |
| 374 | value.lvalue.pattern.kind !== 'ObjectPattern' |
| 375 | ) { |
| 376 | continue; |
| 377 | } |
| 378 | for (const item of value.lvalue.pattern.properties) { |
| 379 | if (item.kind !== 'Spread') { |
| 380 | continue; |
| 381 | } |
| 382 | candidateNonMutatingSpreads.set( |
| 383 | item.place.identifier.id, |
| 384 | item.place.identifier.id, |
| 385 | ); |
| 386 | } |
| 387 | break; |
| 388 | } |
| 389 | case 'LoadLocal': { |
| 390 | const spread = candidateNonMutatingSpreads.get( |
| 391 | value.place.identifier.id, |
| 392 | ); |
| 393 | if (spread != null) { |
| 394 | candidateNonMutatingSpreads.set(lvalue.identifier.id, spread); |
| 395 | } |
| 396 | break; |
| 397 | } |
| 398 | case 'StoreLocal': { |
| 399 | const spread = candidateNonMutatingSpreads.get( |
| 400 | value.value.identifier.id, |
| 401 | ); |
| 402 | if (spread != null) { |
| 403 | candidateNonMutatingSpreads.set(lvalue.identifier.id, spread); |
| 404 | candidateNonMutatingSpreads.set( |
| 405 | value.lvalue.place.identifier.id, |
| 406 | spread, |
| 407 | ); |
| 408 | } |
| 409 | break; |
| 410 | } |
| 411 | case 'JsxFragment': |
| 412 | case 'JsxExpression': { |
| 413 | // Passing objects created with spread to jsx can't mutate them |
| 414 | break; |
| 415 | } |
| 416 | case 'PropertyLoad': { |
| 417 | // Properties must be frozen since the original value was frozen |
| 418 | break; |
| 419 | } |
| 420 | case 'CallExpression': |
| 421 | case 'MethodCall': { |
| 422 | const callee = |
| 423 | value.kind === 'CallExpression' ? value.callee : value.property; |
| 424 | if (getHookKind(fn.env, callee.identifier) != null) { |
| 425 | // Hook calls have frozen arguments, and non-ref returns are frozen |
| 426 | if (!isRefOrRefValue(lvalue.identifier)) { |
| 427 | knownFrozen.add(lvalue.identifier.id); |
| 428 | } |
| 429 | } else { |
| 430 | // Non-hook calls check their operands, since they are potentially mutable |
| 431 | if (candidateNonMutatingSpreads.size !== 0) { |
| 432 | // Otherwise any reference to the spread object itself may mutate |
| 433 | for (const operand of eachInstructionValueOperand(value)) { |
| 434 | const spread = candidateNonMutatingSpreads.get( |
| 435 | operand.identifier.id, |
| 436 | ); |
| 437 | if (spread != null) { |
| 438 | candidateNonMutatingSpreads.delete(spread); |
| 439 | } |
| 440 | } |
| 441 | } |
| 442 | } |
| 443 | break; |
| 444 | } |
| 445 | default: { |
| 446 | if (candidateNonMutatingSpreads.size !== 0) { |
| 447 | // Otherwise any reference to the spread object itself may mutate |
| 448 | for (const operand of eachInstructionValueOperand(value)) { |
| 449 | const spread = candidateNonMutatingSpreads.get( |
| 450 | operand.identifier.id, |
| 451 | ); |
| 452 | if (spread != null) { |
| 453 | candidateNonMutatingSpreads.delete(spread); |
| 454 | } |
| 455 | } |
| 456 | } |
| 457 | } |
| 458 | } |
| 459 | } |
| 460 | } |
| 461 | |
| 462 | const nonMutatingSpreads = new Set<IdentifierId>(); |
| 463 | for (const [key, value] of candidateNonMutatingSpreads) { |
| 464 | if (key === value) { |
| 465 | nonMutatingSpreads.add(key); |
| 466 | } |
| 467 | } |
| 468 | return nonMutatingSpreads; |
| 469 | } |
| 470 | |
| 471 | function inferParam( |
| 472 | param: Place | SpreadPattern, |
| 473 | initialState: InferenceState, |
| 474 | paramKind: AbstractValue, |
| 475 | ): void { |
| 476 | const place = param.kind === 'Identifier' ? param : param.place; |
| 477 | const value: InstructionValue = { |
| 478 | kind: 'Primitive', |
| 479 | loc: place.loc, |
| 480 | value: undefined, |
| 481 | }; |
| 482 | initialState.initialize(value, paramKind); |
| 483 | initialState.define(place, value); |
| 484 | } |
| 485 | |
| 486 | function inferBlock( |
| 487 | context: Context, |
| 488 | state: InferenceState, |
| 489 | block: BasicBlock, |
| 490 | ): void { |
| 491 | for (const phi of block.phis) { |
| 492 | state.inferPhi(phi); |
| 493 | } |
| 494 | |
| 495 | for (const instr of block.instructions) { |
| 496 | let instructionSignature = context.instructionSignatureCache.get(instr); |
| 497 | if (instructionSignature == null) { |
| 498 | instructionSignature = computeSignatureForInstruction( |
| 499 | context, |
| 500 | state.env, |
| 501 | instr, |
| 502 | ); |
| 503 | context.instructionSignatureCache.set(instr, instructionSignature); |
| 504 | } |
| 505 | const effects = applySignature(context, state, instructionSignature, instr); |
| 506 | instr.effects = effects; |
| 507 | } |
| 508 | const terminal = block.terminal; |
| 509 | if (terminal.kind === 'try' && terminal.handlerBinding != null) { |
| 510 | context.catchHandlers.set(terminal.handler, terminal.handlerBinding); |
| 511 | } else if (terminal.kind === 'maybe-throw' && terminal.handler !== null) { |
| 512 | const handlerParam = context.catchHandlers.get(terminal.handler); |
| 513 | if (handlerParam != null) { |
| 514 | CompilerError.invariant(state.kind(handlerParam) != null, { |
| 515 | reason: |
| 516 | 'Expected catch binding to be initialized with a DeclareLocal Catch instruction', |
| 517 | loc: terminal.loc, |
| 518 | }); |
| 519 | const effects: Array<AliasingEffect> = []; |
| 520 | for (const instr of block.instructions) { |
| 521 | if ( |
| 522 | instr.value.kind === 'CallExpression' || |
| 523 | instr.value.kind === 'MethodCall' |
| 524 | ) { |
| 525 | /** |
| 526 | * Many instructions can error, but only calls can throw their result as the error |
| 527 | * itself. For example, `c = a.b` can throw if `a` is nullish, but the thrown value |
| 528 | * is an error object synthesized by the JS runtime. Whereas `throwsInput(x)` can |
| 529 | * throw (effectively) the result of the call. |
| 530 | * |
| 531 | * TODO: call applyEffect() instead. This meant that the catch param wasn't inferred |
| 532 | * as a mutable value, though. See `try-catch-try-value-modified-in-catch-escaping.js` |
| 533 | * fixture as an example |
| 534 | */ |
| 535 | state.appendAlias(handlerParam, instr.lvalue); |
| 536 | const kind = state.kind(instr.lvalue).kind; |
| 537 | if (kind === ValueKind.Mutable || kind == ValueKind.Context) { |
| 538 | effects.push( |
| 539 | context.internEffect({ |
| 540 | kind: 'Alias', |
| 541 | from: instr.lvalue, |
| 542 | into: handlerParam, |
| 543 | }), |
| 544 | ); |
| 545 | } |
| 546 | } |
| 547 | } |
| 548 | terminal.effects = effects.length !== 0 ? effects : null; |
| 549 | } |
| 550 | } else if (terminal.kind === 'return') { |
| 551 | if (!context.isFuctionExpression) { |
| 552 | terminal.effects = [ |
| 553 | context.internEffect({ |
| 554 | kind: 'Freeze', |
| 555 | value: terminal.value, |
| 556 | reason: ValueReason.JsxCaptured, |
| 557 | }), |
| 558 | ]; |
| 559 | } |
| 560 | } |
| 561 | } |
| 562 | |
| 563 | /** |
| 564 | * Applies the signature to the given state to determine the precise set of effects |
| 565 | * that will occur in practice. This takes into account the inferred state of each |
| 566 | * variable. For example, the signature may have a `ConditionallyMutate x` effect. |
| 567 | * Here, we check the abstract type of `x` and either record a `Mutate x` if x is mutable |
| 568 | * or no effect if x is a primitive, global, or frozen. |
| 569 | * |
| 570 | * This phase may also emit errors, for example MutateLocal on a frozen value is invalid. |
| 571 | */ |
| 572 | function applySignature( |
| 573 | context: Context, |
| 574 | state: InferenceState, |
| 575 | signature: InstructionSignature, |
| 576 | instruction: Instruction, |
| 577 | ): Array<AliasingEffect> | null { |
| 578 | const effects: Array<AliasingEffect> = []; |
| 579 | /** |
| 580 | * For function instructions, eagerly validate that they aren't mutating |
| 581 | * a known-frozen value. |
| 582 | * |
| 583 | * TODO: make sure we're also validating against global mutations somewhere, but |
| 584 | * account for this being allowed in effects/event handlers. |
| 585 | */ |
| 586 | if ( |
| 587 | instruction.value.kind === 'FunctionExpression' || |
| 588 | instruction.value.kind === 'ObjectMethod' |
| 589 | ) { |
| 590 | const aliasingEffects = |
| 591 | instruction.value.loweredFunc.func.aliasingEffects ?? []; |
| 592 | const context = new Set( |
| 593 | instruction.value.loweredFunc.func.context.map(p => p.identifier.id), |
| 594 | ); |
| 595 | for (const effect of aliasingEffects) { |
| 596 | if (effect.kind === 'Mutate' || effect.kind === 'MutateTransitive') { |
| 597 | if (!context.has(effect.value.identifier.id)) { |
| 598 | continue; |
| 599 | } |
| 600 | const value = state.kind(effect.value); |
| 601 | switch (value.kind) { |
| 602 | case ValueKind.Frozen: { |
| 603 | const reason = getWriteErrorReason({ |
| 604 | kind: value.kind, |
| 605 | reason: value.reason, |
| 606 | }); |
| 607 | const variable = |
| 608 | effect.value.identifier.name !== null && |
| 609 | effect.value.identifier.name.kind === 'named' |
| 610 | ? `\`${effect.value.identifier.name.value}\`` |
| 611 | : 'value'; |
| 612 | const diagnostic = CompilerDiagnostic.create({ |
| 613 | category: ErrorCategory.Immutability, |
| 614 | reason: 'This value cannot be modified', |
| 615 | description: reason, |
| 616 | }).withDetails({ |
| 617 | kind: 'error', |
| 618 | loc: effect.value.loc, |
| 619 | message: `${variable} cannot be modified`, |
| 620 | }); |
| 621 | if ( |
| 622 | effect.kind === 'Mutate' && |
| 623 | effect.reason?.kind === 'AssignCurrentProperty' |
| 624 | ) { |
| 625 | diagnostic.withDetails({ |
| 626 | kind: 'hint', |
| 627 | message: `Hint: If this value is a Ref (value returned by \`useRef()\`), rename the variable to end in "Ref".`, |
| 628 | }); |
| 629 | } |
| 630 | effects.push({ |
| 631 | kind: 'MutateFrozen', |
| 632 | place: effect.value, |
| 633 | error: diagnostic, |
| 634 | }); |
| 635 | } |
| 636 | } |
| 637 | } |
| 638 | } |
| 639 | } |
| 640 | |
| 641 | /* |
| 642 | * Track which values we've already aliased once, so that we can switch to |
| 643 | * appendAlias() for subsequent aliases into the same value |
| 644 | */ |
| 645 | const initialized = new Set<IdentifierId>(); |
| 646 | |
| 647 | if (DEBUG) { |
| 648 | console.log(printInstruction(instruction)); |
| 649 | } |
| 650 | |
| 651 | for (const effect of signature.effects) { |
| 652 | applyEffect(context, state, effect, initialized, effects); |
| 653 | } |
| 654 | if (DEBUG) { |
| 655 | console.log( |
| 656 | prettyFormat(state.debugAbstractValue(state.kind(instruction.lvalue))), |
| 657 | ); |
| 658 | console.log( |
| 659 | effects.map(effect => ` ${printAliasingEffect(effect)}`).join('\n'), |
| 660 | ); |
| 661 | } |
| 662 | if ( |
| 663 | !(state.isDefined(instruction.lvalue) && state.kind(instruction.lvalue)) |
| 664 | ) { |
| 665 | CompilerError.invariant(false, { |
| 666 | reason: `Expected instruction lvalue to be initialized`, |
| 667 | loc: instruction.loc, |
| 668 | }); |
| 669 | } |
| 670 | return effects.length !== 0 ? effects : null; |
| 671 | } |
| 672 | |
| 673 | function applyEffect( |
| 674 | context: Context, |
| 675 | state: InferenceState, |
| 676 | _effect: AliasingEffect, |
| 677 | initialized: Set<IdentifierId>, |
| 678 | effects: Array<AliasingEffect>, |
| 679 | ): void { |
| 680 | const effect = context.internEffect(_effect); |
| 681 | if (DEBUG) { |
| 682 | console.log(printAliasingEffect(effect)); |
| 683 | } |
| 684 | switch (effect.kind) { |
| 685 | case 'Freeze': { |
| 686 | const didFreeze = state.freeze(effect.value, effect.reason); |
| 687 | if (didFreeze) { |
| 688 | effects.push(effect); |
| 689 | } |
| 690 | break; |
| 691 | } |
| 692 | case 'Create': { |
| 693 | CompilerError.invariant(!initialized.has(effect.into.identifier.id), { |
| 694 | reason: `Cannot re-initialize variable within an instruction`, |
| 695 | description: `Re-initialized ${printPlace(effect.into)} in ${printAliasingEffect(effect)}`, |
| 696 | loc: effect.into.loc, |
| 697 | }); |
| 698 | initialized.add(effect.into.identifier.id); |
| 699 | |
| 700 | let value = context.effectInstructionValueCache.get(effect); |
| 701 | if (value == null) { |
| 702 | value = { |
| 703 | kind: 'ObjectExpression', |
| 704 | properties: [], |
| 705 | loc: effect.into.loc, |
| 706 | }; |
| 707 | context.effectInstructionValueCache.set(effect, value); |
| 708 | } |
| 709 | state.initialize(value, { |
| 710 | kind: effect.value, |
| 711 | reason: new Set([effect.reason]), |
| 712 | }); |
| 713 | state.define(effect.into, value); |
| 714 | effects.push(effect); |
| 715 | break; |
| 716 | } |
| 717 | case 'ImmutableCapture': { |
| 718 | const kind = state.kind(effect.from).kind; |
| 719 | switch (kind) { |
| 720 | case ValueKind.Global: |
| 721 | case ValueKind.Primitive: { |
| 722 | // no-op: we don't need to track data flow for copy types |
| 723 | break; |
| 724 | } |
| 725 | default: { |
| 726 | effects.push(effect); |
| 727 | } |
| 728 | } |
| 729 | break; |
| 730 | } |
| 731 | case 'CreateFrom': { |
| 732 | CompilerError.invariant(!initialized.has(effect.into.identifier.id), { |
| 733 | reason: `Cannot re-initialize variable within an instruction`, |
| 734 | description: `Re-initialized ${printPlace(effect.into)} in ${printAliasingEffect(effect)}`, |
| 735 | loc: effect.into.loc, |
| 736 | }); |
| 737 | initialized.add(effect.into.identifier.id); |
| 738 | |
| 739 | const fromValue = state.kind(effect.from); |
| 740 | let value = context.effectInstructionValueCache.get(effect); |
| 741 | if (value == null) { |
| 742 | value = { |
| 743 | kind: 'ObjectExpression', |
| 744 | properties: [], |
| 745 | loc: effect.into.loc, |
| 746 | }; |
| 747 | context.effectInstructionValueCache.set(effect, value); |
| 748 | } |
| 749 | state.initialize(value, { |
| 750 | kind: fromValue.kind, |
| 751 | reason: new Set(fromValue.reason), |
| 752 | }); |
| 753 | state.define(effect.into, value); |
| 754 | switch (fromValue.kind) { |
| 755 | case ValueKind.Primitive: |
| 756 | case ValueKind.Global: { |
| 757 | effects.push({ |
| 758 | kind: 'Create', |
| 759 | value: fromValue.kind, |
| 760 | into: effect.into, |
| 761 | reason: [...fromValue.reason][0] ?? ValueReason.Other, |
| 762 | }); |
| 763 | break; |
| 764 | } |
| 765 | case ValueKind.Frozen: { |
| 766 | effects.push({ |
| 767 | kind: 'Create', |
| 768 | value: fromValue.kind, |
| 769 | into: effect.into, |
| 770 | reason: [...fromValue.reason][0] ?? ValueReason.Other, |
| 771 | }); |
| 772 | applyEffect( |
| 773 | context, |
| 774 | state, |
| 775 | { |
| 776 | kind: 'ImmutableCapture', |
| 777 | from: effect.from, |
| 778 | into: effect.into, |
| 779 | }, |
| 780 | initialized, |
| 781 | effects, |
| 782 | ); |
| 783 | break; |
| 784 | } |
| 785 | default: { |
| 786 | effects.push(effect); |
| 787 | } |
| 788 | } |
| 789 | break; |
| 790 | } |
| 791 | case 'CreateFunction': { |
| 792 | CompilerError.invariant(!initialized.has(effect.into.identifier.id), { |
| 793 | reason: `Cannot re-initialize variable within an instruction`, |
| 794 | description: `Re-initialized ${printPlace(effect.into)} in ${printAliasingEffect(effect)}`, |
| 795 | loc: effect.into.loc, |
| 796 | }); |
| 797 | initialized.add(effect.into.identifier.id); |
| 798 | |
| 799 | effects.push(effect); |
| 800 | /** |
| 801 | * We consider the function mutable if it has any mutable context variables or |
| 802 | * any side-effects that need to be tracked if the function is called. |
| 803 | */ |
| 804 | const hasCaptures = effect.captures.some(capture => { |
| 805 | switch (state.kind(capture).kind) { |
| 806 | case ValueKind.Context: |
| 807 | case ValueKind.Mutable: { |
| 808 | return true; |
| 809 | } |
| 810 | default: { |
| 811 | return false; |
| 812 | } |
| 813 | } |
| 814 | }); |
| 815 | const hasTrackedSideEffects = |
| 816 | effect.function.loweredFunc.func.aliasingEffects?.some( |
| 817 | effect => |
| 818 | // TODO; include "render" here? |
| 819 | effect.kind === 'MutateFrozen' || |
| 820 | effect.kind === 'MutateGlobal' || |
| 821 | effect.kind === 'Impure', |
| 822 | ); |
| 823 | // For legacy compatibility |
| 824 | const capturesRef = effect.function.loweredFunc.func.context.some( |
| 825 | operand => isRefOrRefValue(operand.identifier), |
| 826 | ); |
| 827 | const isMutable = hasCaptures || hasTrackedSideEffects || capturesRef; |
| 828 | for (const operand of effect.function.loweredFunc.func.context) { |
| 829 | if (operand.effect !== Effect.Capture) { |
| 830 | continue; |
| 831 | } |
| 832 | const kind = state.kind(operand).kind; |
| 833 | if ( |
| 834 | kind === ValueKind.Primitive || |
| 835 | kind == ValueKind.Frozen || |
| 836 | kind == ValueKind.Global |
| 837 | ) { |
| 838 | operand.effect = Effect.Read; |
| 839 | } |
| 840 | } |
| 841 | state.initialize(effect.function, { |
| 842 | kind: isMutable ? ValueKind.Mutable : ValueKind.Frozen, |
| 843 | reason: new Set([]), |
| 844 | }); |
| 845 | state.define(effect.into, effect.function); |
| 846 | for (const capture of effect.captures) { |
| 847 | applyEffect( |
| 848 | context, |
| 849 | state, |
| 850 | { |
| 851 | kind: 'Capture', |
| 852 | from: capture, |
| 853 | into: effect.into, |
| 854 | }, |
| 855 | initialized, |
| 856 | effects, |
| 857 | ); |
| 858 | } |
| 859 | break; |
| 860 | } |
| 861 | case 'MaybeAlias': |
| 862 | case 'Alias': |
| 863 | case 'Capture': { |
| 864 | CompilerError.invariant( |
| 865 | effect.kind === 'Capture' || |
| 866 | effect.kind === 'MaybeAlias' || |
| 867 | initialized.has(effect.into.identifier.id), |
| 868 | { |
| 869 | reason: `Expected destination to already be initialized within this instruction`, |
| 870 | description: |
| 871 | `Destination ${printPlace(effect.into)} is not initialized in this ` + |
| 872 | `instruction for effect ${printAliasingEffect(effect)}`, |
| 873 | loc: effect.into.loc, |
| 874 | }, |
| 875 | ); |
| 876 | /* |
| 877 | * Capture describes potential information flow: storing a pointer to one value |
| 878 | * within another. If the destination is not mutable, or the source value has |
| 879 | * copy-on-write semantics, then we can prune the effect |
| 880 | */ |
| 881 | const intoKind = state.kind(effect.into).kind; |
| 882 | let destinationType: 'context' | 'mutable' | null = null; |
| 883 | switch (intoKind) { |
| 884 | case ValueKind.Context: { |
| 885 | destinationType = 'context'; |
| 886 | break; |
| 887 | } |
| 888 | case ValueKind.Mutable: |
| 889 | case ValueKind.MaybeFrozen: { |
| 890 | destinationType = 'mutable'; |
| 891 | break; |
| 892 | } |
| 893 | } |
| 894 | const fromKind = state.kind(effect.from).kind; |
| 895 | let sourceType: 'context' | 'mutable' | 'frozen' | null = null; |
| 896 | switch (fromKind) { |
| 897 | case ValueKind.Context: { |
| 898 | sourceType = 'context'; |
| 899 | break; |
| 900 | } |
| 901 | case ValueKind.Global: |
| 902 | case ValueKind.Primitive: { |
| 903 | break; |
| 904 | } |
| 905 | case ValueKind.MaybeFrozen: |
| 906 | case ValueKind.Frozen: { |
| 907 | sourceType = 'frozen'; |
| 908 | break; |
| 909 | } |
| 910 | default: { |
| 911 | sourceType = 'mutable'; |
| 912 | break; |
| 913 | } |
| 914 | } |
| 915 | |
| 916 | if (sourceType === 'frozen') { |
| 917 | applyEffect( |
| 918 | context, |
| 919 | state, |
| 920 | { |
| 921 | kind: 'ImmutableCapture', |
| 922 | from: effect.from, |
| 923 | into: effect.into, |
| 924 | }, |
| 925 | initialized, |
| 926 | effects, |
| 927 | ); |
| 928 | } else if ( |
| 929 | (sourceType === 'mutable' && destinationType === 'mutable') || |
| 930 | effect.kind === 'MaybeAlias' |
| 931 | ) { |
| 932 | effects.push(effect); |
| 933 | } else if ( |
| 934 | (sourceType === 'context' && destinationType != null) || |
| 935 | (sourceType === 'mutable' && destinationType === 'context') |
| 936 | ) { |
| 937 | applyEffect( |
| 938 | context, |
| 939 | state, |
| 940 | {kind: 'MaybeAlias', from: effect.from, into: effect.into}, |
| 941 | initialized, |
| 942 | effects, |
| 943 | ); |
| 944 | } |
| 945 | break; |
| 946 | } |
| 947 | case 'Assign': { |
| 948 | CompilerError.invariant(!initialized.has(effect.into.identifier.id), { |
| 949 | reason: `Cannot re-initialize variable within an instruction`, |
| 950 | description: `Re-initialized ${printPlace(effect.into)} in ${printAliasingEffect(effect)}`, |
| 951 | loc: effect.into.loc, |
| 952 | }); |
| 953 | initialized.add(effect.into.identifier.id); |
| 954 | |
| 955 | /* |
| 956 | * Alias represents potential pointer aliasing. If the type is a global, |
| 957 | * a primitive (copy-on-write semantics) then we can prune the effect |
| 958 | */ |
| 959 | const fromValue = state.kind(effect.from); |
| 960 | const fromKind = fromValue.kind; |
| 961 | switch (fromKind) { |
| 962 | case ValueKind.Frozen: { |
| 963 | applyEffect( |
| 964 | context, |
| 965 | state, |
| 966 | { |
| 967 | kind: 'ImmutableCapture', |
| 968 | from: effect.from, |
| 969 | into: effect.into, |
| 970 | }, |
| 971 | initialized, |
| 972 | effects, |
| 973 | ); |
| 974 | let value = context.effectInstructionValueCache.get(effect); |
| 975 | if (value == null) { |
| 976 | value = { |
| 977 | kind: 'Primitive', |
| 978 | value: undefined, |
| 979 | loc: effect.from.loc, |
| 980 | }; |
| 981 | context.effectInstructionValueCache.set(effect, value); |
| 982 | } |
| 983 | state.initialize(value, { |
| 984 | kind: fromKind, |
| 985 | reason: new Set(fromValue.reason), |
| 986 | }); |
| 987 | state.define(effect.into, value); |
| 988 | break; |
| 989 | } |
| 990 | case ValueKind.Global: |
| 991 | case ValueKind.Primitive: { |
| 992 | let value = context.effectInstructionValueCache.get(effect); |
| 993 | if (value == null) { |
| 994 | value = { |
| 995 | kind: 'Primitive', |
| 996 | value: undefined, |
| 997 | loc: effect.from.loc, |
| 998 | }; |
| 999 | context.effectInstructionValueCache.set(effect, value); |
| 1000 | } |
| 1001 | state.initialize(value, { |
| 1002 | kind: fromKind, |
| 1003 | reason: new Set(fromValue.reason), |
| 1004 | }); |
| 1005 | state.define(effect.into, value); |
| 1006 | break; |
| 1007 | } |
| 1008 | default: { |
| 1009 | state.assign(effect.into, effect.from); |
| 1010 | effects.push(effect); |
| 1011 | break; |
| 1012 | } |
| 1013 | } |
| 1014 | break; |
| 1015 | } |
| 1016 | case 'Apply': { |
| 1017 | const functionValues = state.values(effect.function); |
| 1018 | if ( |
| 1019 | functionValues.length === 1 && |
| 1020 | functionValues[0].kind === 'FunctionExpression' && |
| 1021 | functionValues[0].loweredFunc.func.aliasingEffects != null |
| 1022 | ) { |
| 1023 | /* |
| 1024 | * We're calling a locally declared function, we already know it's effects! |
| 1025 | * We just have to substitute in the args for the params |
| 1026 | */ |
| 1027 | const functionExpr = functionValues[0]; |
| 1028 | let signature = context.functionSignatureCache.get(functionExpr); |
| 1029 | if (signature == null) { |
| 1030 | signature = buildSignatureFromFunctionExpression( |
| 1031 | state.env, |
| 1032 | functionExpr, |
| 1033 | ); |
| 1034 | context.functionSignatureCache.set(functionExpr, signature); |
| 1035 | } |
| 1036 | if (DEBUG) { |
| 1037 | console.log( |
| 1038 | `constructed alias signature:\n${printAliasingSignature(signature)}`, |
| 1039 | ); |
| 1040 | } |
| 1041 | const signatureEffects = context.cacheApplySignature( |
| 1042 | signature, |
| 1043 | effect, |
| 1044 | () => |
| 1045 | computeEffectsForSignature( |
| 1046 | state.env, |
| 1047 | signature, |
| 1048 | effect.into, |
| 1049 | effect.receiver, |
| 1050 | effect.args, |
| 1051 | functionExpr.loweredFunc.func.context, |
| 1052 | effect.loc, |
| 1053 | ), |
| 1054 | ); |
| 1055 | if (signatureEffects != null) { |
| 1056 | applyEffect( |
| 1057 | context, |
| 1058 | state, |
| 1059 | {kind: 'MutateTransitiveConditionally', value: effect.function}, |
| 1060 | initialized, |
| 1061 | effects, |
| 1062 | ); |
| 1063 | for (const signatureEffect of signatureEffects) { |
| 1064 | applyEffect(context, state, signatureEffect, initialized, effects); |
| 1065 | } |
| 1066 | break; |
| 1067 | } |
| 1068 | } |
| 1069 | let signatureEffects = null; |
| 1070 | if (effect.signature?.aliasing != null) { |
| 1071 | const signature = effect.signature.aliasing; |
| 1072 | signatureEffects = context.cacheApplySignature( |
| 1073 | effect.signature.aliasing, |
| 1074 | effect, |
| 1075 | () => |
| 1076 | computeEffectsForSignature( |
| 1077 | state.env, |
| 1078 | signature, |
| 1079 | effect.into, |
| 1080 | effect.receiver, |
| 1081 | effect.args, |
| 1082 | [], |
| 1083 | effect.loc, |
| 1084 | ), |
| 1085 | ); |
| 1086 | } |
| 1087 | if (signatureEffects != null) { |
| 1088 | for (const signatureEffect of signatureEffects) { |
| 1089 | applyEffect(context, state, signatureEffect, initialized, effects); |
| 1090 | } |
| 1091 | } else if (effect.signature != null) { |
| 1092 | const legacyEffects = computeEffectsForLegacySignature( |
| 1093 | state, |
| 1094 | effect.signature, |
| 1095 | effect.into, |
| 1096 | effect.receiver, |
| 1097 | effect.args, |
| 1098 | effect.loc, |
| 1099 | ); |
| 1100 | for (const legacyEffect of legacyEffects) { |
| 1101 | applyEffect(context, state, legacyEffect, initialized, effects); |
| 1102 | } |
| 1103 | } else { |
| 1104 | applyEffect( |
| 1105 | context, |
| 1106 | state, |
| 1107 | { |
| 1108 | kind: 'Create', |
| 1109 | into: effect.into, |
| 1110 | value: ValueKind.Mutable, |
| 1111 | reason: ValueReason.Other, |
| 1112 | }, |
| 1113 | initialized, |
| 1114 | effects, |
| 1115 | ); |
| 1116 | /* |
| 1117 | * If no signature then by default: |
| 1118 | * - All operands are conditionally mutated, except some instruction |
| 1119 | * variants are assumed to not mutate the callee (such as `new`) |
| 1120 | * - All operands are captured into (but not directly aliased as) |
| 1121 | * every other argument. |
| 1122 | */ |
| 1123 | for (const arg of [effect.receiver, effect.function, ...effect.args]) { |
| 1124 | if (arg.kind === 'Hole') { |
| 1125 | continue; |
| 1126 | } |
| 1127 | const operand = arg.kind === 'Identifier' ? arg : arg.place; |
| 1128 | if (operand !== effect.function || effect.mutatesFunction) { |
| 1129 | applyEffect( |
| 1130 | context, |
| 1131 | state, |
| 1132 | { |
| 1133 | kind: 'MutateTransitiveConditionally', |
| 1134 | value: operand, |
| 1135 | }, |
| 1136 | initialized, |
| 1137 | effects, |
| 1138 | ); |
| 1139 | } |
| 1140 | const mutateIterator = |
| 1141 | arg.kind === 'Spread' ? conditionallyMutateIterator(operand) : null; |
| 1142 | if (mutateIterator) { |
| 1143 | applyEffect(context, state, mutateIterator, initialized, effects); |
| 1144 | } |
| 1145 | applyEffect( |
| 1146 | context, |
| 1147 | state, |
| 1148 | // OK: recording information flow |
| 1149 | {kind: 'MaybeAlias', from: operand, into: effect.into}, |
| 1150 | initialized, |
| 1151 | effects, |
| 1152 | ); |
| 1153 | for (const otherArg of [ |
| 1154 | effect.receiver, |
| 1155 | effect.function, |
| 1156 | ...effect.args, |
| 1157 | ]) { |
| 1158 | if (otherArg.kind === 'Hole') { |
| 1159 | continue; |
| 1160 | } |
| 1161 | const other = |
| 1162 | otherArg.kind === 'Identifier' ? otherArg : otherArg.place; |
| 1163 | if (other === arg) { |
| 1164 | continue; |
| 1165 | } |
| 1166 | applyEffect( |
| 1167 | context, |
| 1168 | state, |
| 1169 | { |
| 1170 | /* |
| 1171 | * OK: a function might store one operand into another, |
| 1172 | * but it can't force one to alias another |
| 1173 | */ |
| 1174 | kind: 'Capture', |
| 1175 | from: operand, |
| 1176 | into: other, |
| 1177 | }, |
| 1178 | initialized, |
| 1179 | effects, |
| 1180 | ); |
| 1181 | } |
| 1182 | } |
| 1183 | } |
| 1184 | break; |
| 1185 | } |
| 1186 | case 'Mutate': |
| 1187 | case 'MutateConditionally': |
| 1188 | case 'MutateTransitive': |
| 1189 | case 'MutateTransitiveConditionally': { |
| 1190 | const mutationKind = state.mutate(effect.kind, effect.value); |
| 1191 | if (mutationKind === 'mutate') { |
| 1192 | effects.push(effect); |
| 1193 | } else if (mutationKind === 'mutate-ref') { |
| 1194 | // no-op |
| 1195 | } else if ( |
| 1196 | mutationKind !== 'none' && |
| 1197 | (effect.kind === 'Mutate' || effect.kind === 'MutateTransitive') |
| 1198 | ) { |
| 1199 | const value = state.kind(effect.value); |
| 1200 | if (DEBUG) { |
| 1201 | console.log(`invalid mutation: ${printAliasingEffect(effect)}`); |
| 1202 | console.log(prettyFormat(state.debugAbstractValue(value))); |
| 1203 | } |
| 1204 | |
| 1205 | if ( |
| 1206 | mutationKind === 'mutate-frozen' && |
| 1207 | context.hoistedContextDeclarations.has( |
| 1208 | effect.value.identifier.declarationId, |
| 1209 | ) |
| 1210 | ) { |
| 1211 | const variable = |
| 1212 | effect.value.identifier.name !== null && |
| 1213 | effect.value.identifier.name.kind === 'named' |
| 1214 | ? `\`${effect.value.identifier.name.value}\`` |
| 1215 | : null; |
| 1216 | const hoistedAccess = context.hoistedContextDeclarations.get( |
| 1217 | effect.value.identifier.declarationId, |
| 1218 | ); |
| 1219 | const diagnostic = CompilerDiagnostic.create({ |
| 1220 | category: ErrorCategory.Immutability, |
| 1221 | reason: 'Cannot access variable before it is declared', |
| 1222 | description: `${variable ?? 'This variable'} is accessed before it is declared, which prevents the earlier access from updating when this value changes over time`, |
| 1223 | }); |
| 1224 | if (hoistedAccess != null && hoistedAccess.loc != effect.value.loc) { |
| 1225 | diagnostic.withDetails({ |
| 1226 | kind: 'error', |
| 1227 | loc: hoistedAccess.loc, |
| 1228 | message: `${variable ?? 'variable'} accessed before it is declared`, |
| 1229 | }); |
| 1230 | } |
| 1231 | diagnostic.withDetails({ |
| 1232 | kind: 'error', |
| 1233 | loc: effect.value.loc, |
| 1234 | message: `${variable ?? 'variable'} is declared here`, |
| 1235 | }); |
| 1236 | |
| 1237 | applyEffect( |
| 1238 | context, |
| 1239 | state, |
| 1240 | { |
| 1241 | kind: 'MutateFrozen', |
| 1242 | place: effect.value, |
| 1243 | error: diagnostic, |
| 1244 | }, |
| 1245 | initialized, |
| 1246 | effects, |
| 1247 | ); |
| 1248 | } else { |
| 1249 | const reason = getWriteErrorReason({ |
| 1250 | kind: value.kind, |
| 1251 | reason: value.reason, |
| 1252 | }); |
| 1253 | const variable = |
| 1254 | effect.value.identifier.name !== null && |
| 1255 | effect.value.identifier.name.kind === 'named' |
| 1256 | ? `\`${effect.value.identifier.name.value}\`` |
| 1257 | : 'value'; |
| 1258 | const diagnostic = CompilerDiagnostic.create({ |
| 1259 | category: ErrorCategory.Immutability, |
| 1260 | reason: 'This value cannot be modified', |
| 1261 | description: reason, |
| 1262 | }).withDetails({ |
| 1263 | kind: 'error', |
| 1264 | loc: effect.value.loc, |
| 1265 | message: `${variable} cannot be modified`, |
| 1266 | }); |
| 1267 | if ( |
| 1268 | effect.kind === 'Mutate' && |
| 1269 | effect.reason?.kind === 'AssignCurrentProperty' |
| 1270 | ) { |
| 1271 | diagnostic.withDetails({ |
| 1272 | kind: 'hint', |
| 1273 | message: `Hint: If this value is a Ref (value returned by \`useRef()\`), rename the variable to end in "Ref".`, |
| 1274 | }); |
| 1275 | } |
| 1276 | applyEffect( |
| 1277 | context, |
| 1278 | state, |
| 1279 | { |
| 1280 | kind: |
| 1281 | value.kind === ValueKind.Frozen |
| 1282 | ? 'MutateFrozen' |
| 1283 | : 'MutateGlobal', |
| 1284 | place: effect.value, |
| 1285 | error: diagnostic, |
| 1286 | }, |
| 1287 | initialized, |
| 1288 | effects, |
| 1289 | ); |
| 1290 | } |
| 1291 | } |
| 1292 | break; |
| 1293 | } |
| 1294 | case 'Impure': |
| 1295 | case 'Render': |
| 1296 | case 'MutateFrozen': |
| 1297 | case 'MutateGlobal': { |
| 1298 | effects.push(effect); |
| 1299 | break; |
| 1300 | } |
| 1301 | default: { |
| 1302 | assertExhaustive( |
| 1303 | effect, |
| 1304 | `Unexpected effect kind '${(effect as any).kind as any}'`, |
| 1305 | ); |
| 1306 | } |
| 1307 | } |
| 1308 | } |
| 1309 | |
| 1310 | class InferenceState { |
| 1311 | env: Environment; |
| 1312 | #isFunctionExpression: boolean; |
| 1313 | |
| 1314 | // The kind of each value, based on its allocation site |
| 1315 | #values: Map<InstructionValue, AbstractValue>; |
| 1316 | /* |
| 1317 | * The set of values pointed to by each identifier. This is a set |
| 1318 | * to accommodate phi points (where a variable may have different |
| 1319 | * values from different control flow paths). |
| 1320 | */ |
| 1321 | #variables: Map<IdentifierId, Set<InstructionValue>>; |
| 1322 | |
| 1323 | constructor( |
| 1324 | env: Environment, |
| 1325 | isFunctionExpression: boolean, |
| 1326 | values: Map<InstructionValue, AbstractValue>, |
| 1327 | variables: Map<IdentifierId, Set<InstructionValue>>, |
| 1328 | ) { |
| 1329 | this.env = env; |
| 1330 | this.#isFunctionExpression = isFunctionExpression; |
| 1331 | this.#values = values; |
| 1332 | this.#variables = variables; |
| 1333 | } |
| 1334 | |
| 1335 | static empty( |
| 1336 | env: Environment, |
| 1337 | isFunctionExpression: boolean, |
| 1338 | ): InferenceState { |
| 1339 | return new InferenceState(env, isFunctionExpression, new Map(), new Map()); |
| 1340 | } |
| 1341 | |
| 1342 | get isFunctionExpression(): boolean { |
| 1343 | return this.#isFunctionExpression; |
| 1344 | } |
| 1345 | |
| 1346 | // (Re)initializes a @param value with its default @param kind. |
| 1347 | initialize(value: InstructionValue, kind: AbstractValue): void { |
| 1348 | CompilerError.invariant(value.kind !== 'LoadLocal', { |
| 1349 | reason: |
| 1350 | '[InferMutationAliasingEffects] Expected all top-level identifiers to be defined as variables, not values', |
| 1351 | loc: value.loc, |
| 1352 | }); |
| 1353 | this.#values.set(value, kind); |
| 1354 | } |
| 1355 | |
| 1356 | values(place: Place): Array<InstructionValue> { |
| 1357 | const values = this.#variables.get(place.identifier.id); |
| 1358 | CompilerError.invariant(values != null, { |
| 1359 | reason: `[InferMutationAliasingEffects] Expected value kind to be initialized`, |
| 1360 | description: `${printPlace(place)}`, |
| 1361 | message: 'this is uninitialized', |
| 1362 | loc: place.loc, |
| 1363 | }); |
| 1364 | return Array.from(values); |
| 1365 | } |
| 1366 | |
| 1367 | // Lookup the kind of the given @param value. |
| 1368 | kind(place: Place): AbstractValue { |
| 1369 | const values = this.#variables.get(place.identifier.id); |
| 1370 | CompilerError.invariant(values != null, { |
| 1371 | reason: `[InferMutationAliasingEffects] Expected value kind to be initialized`, |
| 1372 | description: `${printPlace(place)}`, |
| 1373 | message: 'this is uninitialized', |
| 1374 | loc: place.loc, |
| 1375 | }); |
| 1376 | let mergedKind: AbstractValue | null = null; |
| 1377 | for (const value of values) { |
| 1378 | const kind = this.#values.get(value)!; |
| 1379 | mergedKind = |
| 1380 | mergedKind !== null ? mergeAbstractValues(mergedKind, kind) : kind; |
| 1381 | } |
| 1382 | CompilerError.invariant(mergedKind !== null, { |
| 1383 | reason: `[InferMutationAliasingEffects] Expected at least one value`, |
| 1384 | description: `No value found at \`${printPlace(place)}\``, |
| 1385 | loc: place.loc, |
| 1386 | }); |
| 1387 | return mergedKind; |
| 1388 | } |
| 1389 | |
| 1390 | // Updates the value at @param place to point to the same value as @param value. |
| 1391 | assign(place: Place, value: Place): void { |
| 1392 | const values = this.#variables.get(value.identifier.id); |
| 1393 | CompilerError.invariant(values != null, { |
| 1394 | reason: `[InferMutationAliasingEffects] Expected value for identifier to be initialized`, |
| 1395 | description: `${printIdentifier(value.identifier)}`, |
| 1396 | message: 'Expected value for identifier to be initialized', |
| 1397 | loc: value.loc, |
| 1398 | }); |
| 1399 | this.#variables.set(place.identifier.id, new Set(values)); |
| 1400 | } |
| 1401 | |
| 1402 | appendAlias(place: Place, value: Place): void { |
| 1403 | const values = this.#variables.get(value.identifier.id); |
| 1404 | CompilerError.invariant(values != null, { |
| 1405 | reason: `[InferMutationAliasingEffects] Expected value for identifier to be initialized`, |
| 1406 | description: `${printIdentifier(value.identifier)}`, |
| 1407 | message: 'Expected value for identifier to be initialized', |
| 1408 | loc: value.loc, |
| 1409 | }); |
| 1410 | const prevValues = this.values(place); |
| 1411 | this.#variables.set( |
| 1412 | place.identifier.id, |
| 1413 | new Set([...prevValues, ...values]), |
| 1414 | ); |
| 1415 | } |
| 1416 | |
| 1417 | // Defines (initializing or updating) a variable with a specific kind of value. |
| 1418 | define(place: Place, value: InstructionValue): void { |
| 1419 | CompilerError.invariant(this.#values.has(value), { |
| 1420 | reason: `[InferMutationAliasingEffects] Expected value to be initialized`, |
| 1421 | description: printInstructionValue(value), |
| 1422 | loc: value.loc, |
| 1423 | }); |
| 1424 | this.#variables.set(place.identifier.id, new Set([value])); |
| 1425 | } |
| 1426 | |
| 1427 | isDefined(place: Place): boolean { |
| 1428 | return this.#variables.has(place.identifier.id); |
| 1429 | } |
| 1430 | |
| 1431 | /** |
| 1432 | * Marks @param place as transitively frozen. Returns true if the value was not |
| 1433 | * already frozen, false if the value is already frozen (or already known immutable). |
| 1434 | */ |
| 1435 | freeze(place: Place, reason: ValueReason): boolean { |
| 1436 | const value = this.kind(place); |
| 1437 | switch (value.kind) { |
| 1438 | case ValueKind.Context: |
| 1439 | case ValueKind.Mutable: |
| 1440 | case ValueKind.MaybeFrozen: { |
| 1441 | const values = this.values(place); |
| 1442 | for (const instrValue of values) { |
| 1443 | this.freezeValue(instrValue, reason); |
| 1444 | } |
| 1445 | return true; |
| 1446 | } |
| 1447 | case ValueKind.Frozen: |
| 1448 | case ValueKind.Global: |
| 1449 | case ValueKind.Primitive: { |
| 1450 | return false; |
| 1451 | } |
| 1452 | default: { |
| 1453 | assertExhaustive( |
| 1454 | value.kind, |
| 1455 | `Unexpected value kind '${(value as any).kind}'`, |
| 1456 | ); |
| 1457 | } |
| 1458 | } |
| 1459 | } |
| 1460 | |
| 1461 | freezeValue(value: InstructionValue, reason: ValueReason): void { |
| 1462 | this.#values.set(value, { |
| 1463 | kind: ValueKind.Frozen, |
| 1464 | reason: new Set([reason]), |
| 1465 | }); |
| 1466 | if ( |
| 1467 | value.kind === 'FunctionExpression' && |
| 1468 | (this.env.config.enablePreserveExistingMemoizationGuarantees || |
| 1469 | this.env.config.enableTransitivelyFreezeFunctionExpressions) |
| 1470 | ) { |
| 1471 | for (const place of value.loweredFunc.func.context) { |
| 1472 | this.freeze(place, reason); |
| 1473 | } |
| 1474 | } |
| 1475 | } |
| 1476 | |
| 1477 | mutate( |
| 1478 | variant: |
| 1479 | | 'Mutate' |
| 1480 | | 'MutateConditionally' |
| 1481 | | 'MutateTransitive' |
| 1482 | | 'MutateTransitiveConditionally', |
| 1483 | place: Place, |
| 1484 | ): 'none' | 'mutate' | 'mutate-frozen' | 'mutate-global' | 'mutate-ref' { |
| 1485 | if (isRefOrRefValue(place.identifier)) { |
| 1486 | return 'mutate-ref'; |
| 1487 | } |
| 1488 | const kind = this.kind(place).kind; |
| 1489 | switch (variant) { |
| 1490 | case 'MutateConditionally': |
| 1491 | case 'MutateTransitiveConditionally': { |
| 1492 | switch (kind) { |
| 1493 | case ValueKind.Mutable: |
| 1494 | case ValueKind.Context: { |
| 1495 | return 'mutate'; |
| 1496 | } |
| 1497 | default: { |
| 1498 | return 'none'; |
| 1499 | } |
| 1500 | } |
| 1501 | } |
| 1502 | case 'Mutate': |
| 1503 | case 'MutateTransitive': { |
| 1504 | switch (kind) { |
| 1505 | case ValueKind.Mutable: |
| 1506 | case ValueKind.Context: { |
| 1507 | return 'mutate'; |
| 1508 | } |
| 1509 | case ValueKind.Primitive: { |
| 1510 | // technically an error, but it's not React specific |
| 1511 | return 'none'; |
| 1512 | } |
| 1513 | case ValueKind.Frozen: { |
| 1514 | return 'mutate-frozen'; |
| 1515 | } |
| 1516 | case ValueKind.Global: { |
| 1517 | return 'mutate-global'; |
| 1518 | } |
| 1519 | case ValueKind.MaybeFrozen: { |
| 1520 | return 'mutate-frozen'; |
| 1521 | } |
| 1522 | default: { |
| 1523 | assertExhaustive(kind, `Unexpected kind ${kind}`); |
| 1524 | } |
| 1525 | } |
| 1526 | } |
| 1527 | default: { |
| 1528 | assertExhaustive(variant, `Unexpected mutation variant ${variant}`); |
| 1529 | } |
| 1530 | } |
| 1531 | } |
| 1532 | |
| 1533 | /* |
| 1534 | * Combine the contents of @param this and @param other, returning a new |
| 1535 | * instance with the combined changes _if_ there are any changes, or |
| 1536 | * returning null if no changes would occur. Changes include: |
| 1537 | * - new entries in @param other that did not exist in @param this |
| 1538 | * - entries whose values differ in @param this and @param other, |
| 1539 | * and where joining the values produces a different value than |
| 1540 | * what was in @param this. |
| 1541 | * |
| 1542 | * Note that values are joined using a lattice operation to ensure |
| 1543 | * termination. |
| 1544 | */ |
| 1545 | merge(other: InferenceState): InferenceState | null { |
| 1546 | let nextValues: Map<InstructionValue, AbstractValue> | null = null; |
| 1547 | let nextVariables: Map<IdentifierId, Set<InstructionValue>> | null = null; |
| 1548 | |
| 1549 | for (const [id, thisValue] of this.#values) { |
| 1550 | const otherValue = other.#values.get(id); |
| 1551 | if (otherValue !== undefined) { |
| 1552 | const mergedValue = mergeAbstractValues(thisValue, otherValue); |
| 1553 | if (mergedValue !== thisValue) { |
| 1554 | nextValues = nextValues ?? new Map(this.#values); |
| 1555 | nextValues.set(id, mergedValue); |
| 1556 | } |
| 1557 | } |
| 1558 | } |
| 1559 | for (const [id, otherValue] of other.#values) { |
| 1560 | if (this.#values.has(id)) { |
| 1561 | // merged above |
| 1562 | continue; |
| 1563 | } |
| 1564 | nextValues = nextValues ?? new Map(this.#values); |
| 1565 | nextValues.set(id, otherValue); |
| 1566 | } |
| 1567 | |
| 1568 | for (const [id, thisValues] of this.#variables) { |
| 1569 | const otherValues = other.#variables.get(id); |
| 1570 | if (otherValues !== undefined) { |
| 1571 | let mergedValues: Set<InstructionValue> | null = null; |
| 1572 | for (const otherValue of otherValues) { |
| 1573 | if (!thisValues.has(otherValue)) { |
| 1574 | mergedValues = mergedValues ?? new Set(thisValues); |
| 1575 | mergedValues.add(otherValue); |
| 1576 | } |
| 1577 | } |
| 1578 | if (mergedValues !== null) { |
| 1579 | nextVariables = nextVariables ?? new Map(this.#variables); |
| 1580 | nextVariables.set(id, mergedValues); |
| 1581 | } |
| 1582 | } |
| 1583 | } |
| 1584 | for (const [id, otherValues] of other.#variables) { |
| 1585 | if (this.#variables.has(id)) { |
| 1586 | continue; |
| 1587 | } |
| 1588 | nextVariables = nextVariables ?? new Map(this.#variables); |
| 1589 | nextVariables.set(id, new Set(otherValues)); |
| 1590 | } |
| 1591 | |
| 1592 | if (nextVariables === null && nextValues === null) { |
| 1593 | return null; |
| 1594 | } else { |
| 1595 | return new InferenceState( |
| 1596 | this.env, |
| 1597 | this.#isFunctionExpression, |
| 1598 | nextValues ?? new Map(this.#values), |
| 1599 | nextVariables ?? new Map(this.#variables), |
| 1600 | ); |
| 1601 | } |
| 1602 | } |
| 1603 | |
| 1604 | /* |
| 1605 | * Returns a copy of this state. |
| 1606 | * TODO: consider using persistent data structures to make |
| 1607 | * clone cheaper. |
| 1608 | */ |
| 1609 | clone(): InferenceState { |
| 1610 | return new InferenceState( |
| 1611 | this.env, |
| 1612 | this.#isFunctionExpression, |
| 1613 | new Map(this.#values), |
| 1614 | new Map(this.#variables), |
| 1615 | ); |
| 1616 | } |
| 1617 | |
| 1618 | /* |
| 1619 | * For debugging purposes, dumps the state to a plain |
| 1620 | * object so that it can printed as JSON. |
| 1621 | */ |
| 1622 | debug(): any { |
| 1623 | const result: any = {values: {}, variables: {}}; |
| 1624 | const objects: Map<InstructionValue, number> = new Map(); |
| 1625 | function identify(value: InstructionValue): number { |
| 1626 | let id = objects.get(value); |
| 1627 | if (id == null) { |
| 1628 | id = objects.size; |
| 1629 | objects.set(value, id); |
| 1630 | } |
| 1631 | return id; |
| 1632 | } |
| 1633 | for (const [value, kind] of this.#values) { |
| 1634 | const id = identify(value); |
| 1635 | result.values[id] = { |
| 1636 | abstract: this.debugAbstractValue(kind), |
| 1637 | value: printInstructionValue(value), |
| 1638 | }; |
| 1639 | } |
| 1640 | for (const [variable, values] of this.#variables) { |
| 1641 | result.variables[`$${variable}`] = [...values].map(identify); |
| 1642 | } |
| 1643 | return result; |
| 1644 | } |
| 1645 | |
| 1646 | debugAbstractValue(value: AbstractValue): any { |
| 1647 | return { |
| 1648 | kind: value.kind, |
| 1649 | reason: [...value.reason], |
| 1650 | }; |
| 1651 | } |
| 1652 | |
| 1653 | inferPhi(phi: Phi): void { |
| 1654 | const values: Set<InstructionValue> = new Set(); |
| 1655 | for (const [_, operand] of phi.operands) { |
| 1656 | const operandValues = this.#variables.get(operand.identifier.id); |
| 1657 | // This is a backedge that will be handled later by State.merge |
| 1658 | if (operandValues === undefined) continue; |
| 1659 | for (const v of operandValues) { |
| 1660 | values.add(v); |
| 1661 | } |
| 1662 | } |
| 1663 | |
| 1664 | if (values.size > 0) { |
| 1665 | this.#variables.set(phi.place.identifier.id, values); |
| 1666 | } |
| 1667 | } |
| 1668 | } |
| 1669 | |
| 1670 | /** |
| 1671 | * Returns a value that represents the combined states of the two input values. |
| 1672 | * If the two values are semantically equivalent, it returns the first argument. |
| 1673 | */ |
| 1674 | function mergeAbstractValues( |
| 1675 | a: AbstractValue, |
| 1676 | b: AbstractValue, |
| 1677 | ): AbstractValue { |
| 1678 | const kind = mergeValueKinds(a.kind, b.kind); |
| 1679 | if ( |
| 1680 | kind === a.kind && |
| 1681 | kind === b.kind && |
| 1682 | Set_isSuperset(a.reason, b.reason) |
| 1683 | ) { |
| 1684 | return a; |
| 1685 | } |
| 1686 | const reason = new Set(a.reason); |
| 1687 | for (const r of b.reason) { |
| 1688 | reason.add(r); |
| 1689 | } |
| 1690 | return {kind, reason}; |
| 1691 | } |
| 1692 | |
| 1693 | type InstructionSignature = { |
| 1694 | effects: ReadonlyArray<AliasingEffect>; |
| 1695 | }; |
| 1696 | |
| 1697 | function conditionallyMutateIterator(place: Place): AliasingEffect | null { |
| 1698 | if ( |
| 1699 | !( |
| 1700 | isArrayType(place.identifier) || |
| 1701 | isSetType(place.identifier) || |
| 1702 | isMapType(place.identifier) |
| 1703 | ) |
| 1704 | ) { |
| 1705 | return { |
| 1706 | kind: 'MutateTransitiveConditionally', |
| 1707 | value: place, |
| 1708 | }; |
| 1709 | } |
| 1710 | return null; |
| 1711 | } |
| 1712 | |
| 1713 | /** |
| 1714 | * Computes an effect signature for the instruction _without_ looking at the inference state, |
| 1715 | * and only using the semantics of the instructions and the inferred types. The idea is to make |
| 1716 | * it easy to check that the semantics of each instruction are preserved by describing only the |
| 1717 | * effects and not making decisions based on the inference state. |
| 1718 | * |
| 1719 | * Then in applySignature(), above, we refine this signature based on the inference state. |
| 1720 | * |
| 1721 | * NOTE: this function is designed to be cached so it's only computed once upon first visiting |
| 1722 | * an instruction. |
| 1723 | */ |
| 1724 | function computeSignatureForInstruction( |
| 1725 | context: Context, |
| 1726 | env: Environment, |
| 1727 | instr: Instruction, |
| 1728 | ): InstructionSignature { |
| 1729 | const {lvalue, value} = instr; |
| 1730 | const effects: Array<AliasingEffect> = []; |
| 1731 | switch (value.kind) { |
| 1732 | case 'ArrayExpression': { |
| 1733 | effects.push({ |
| 1734 | kind: 'Create', |
| 1735 | into: lvalue, |
| 1736 | value: ValueKind.Mutable, |
| 1737 | reason: ValueReason.Other, |
| 1738 | }); |
| 1739 | // All elements are captured into part of the output value |
| 1740 | for (const element of value.elements) { |
| 1741 | if (element.kind === 'Identifier') { |
| 1742 | effects.push({ |
| 1743 | kind: 'Capture', |
| 1744 | from: element, |
| 1745 | into: lvalue, |
| 1746 | }); |
| 1747 | } else if (element.kind === 'Spread') { |
| 1748 | const mutateIterator = conditionallyMutateIterator(element.place); |
| 1749 | if (mutateIterator != null) { |
| 1750 | effects.push(mutateIterator); |
| 1751 | } |
| 1752 | effects.push({ |
| 1753 | kind: 'Capture', |
| 1754 | from: element.place, |
| 1755 | into: lvalue, |
| 1756 | }); |
| 1757 | } else { |
| 1758 | continue; |
| 1759 | } |
| 1760 | } |
| 1761 | break; |
| 1762 | } |
| 1763 | case 'ObjectExpression': { |
| 1764 | effects.push({ |
| 1765 | kind: 'Create', |
| 1766 | into: lvalue, |
| 1767 | value: ValueKind.Mutable, |
| 1768 | reason: ValueReason.Other, |
| 1769 | }); |
| 1770 | for (const property of value.properties) { |
| 1771 | if (property.kind === 'ObjectProperty') { |
| 1772 | effects.push({ |
| 1773 | kind: 'Capture', |
| 1774 | from: property.place, |
| 1775 | into: lvalue, |
| 1776 | }); |
| 1777 | } else { |
| 1778 | effects.push({ |
| 1779 | kind: 'Capture', |
| 1780 | from: property.place, |
| 1781 | into: lvalue, |
| 1782 | }); |
| 1783 | } |
| 1784 | } |
| 1785 | break; |
| 1786 | } |
| 1787 | case 'Await': { |
| 1788 | effects.push({ |
| 1789 | kind: 'Create', |
| 1790 | into: lvalue, |
| 1791 | value: ValueKind.Mutable, |
| 1792 | reason: ValueReason.Other, |
| 1793 | }); |
| 1794 | // Potentially mutates the receiver (awaiting it changes its state and can run side effects) |
| 1795 | effects.push({kind: 'MutateTransitiveConditionally', value: value.value}); |
| 1796 | /** |
| 1797 | * Data from the promise may be returned into the result, but await does not directly return |
| 1798 | * the promise itself |
| 1799 | */ |
| 1800 | effects.push({ |
| 1801 | kind: 'Capture', |
| 1802 | from: value.value, |
| 1803 | into: lvalue, |
| 1804 | }); |
| 1805 | break; |
| 1806 | } |
| 1807 | case 'NewExpression': |
| 1808 | case 'CallExpression': |
| 1809 | case 'MethodCall': { |
| 1810 | let callee; |
| 1811 | let receiver; |
| 1812 | let mutatesCallee; |
| 1813 | if (value.kind === 'NewExpression') { |
| 1814 | callee = value.callee; |
| 1815 | receiver = value.callee; |
| 1816 | mutatesCallee = false; |
| 1817 | } else if (value.kind === 'CallExpression') { |
| 1818 | callee = value.callee; |
| 1819 | receiver = value.callee; |
| 1820 | mutatesCallee = true; |
| 1821 | } else if (value.kind === 'MethodCall') { |
| 1822 | callee = value.property; |
| 1823 | receiver = value.receiver; |
| 1824 | mutatesCallee = false; |
| 1825 | } else { |
| 1826 | assertExhaustive( |
| 1827 | value, |
| 1828 | `Unexpected value kind '${(value as any).kind}'`, |
| 1829 | ); |
| 1830 | } |
| 1831 | const signature = getFunctionCallSignature(env, callee.identifier.type); |
| 1832 | effects.push({ |
| 1833 | kind: 'Apply', |
| 1834 | receiver, |
| 1835 | function: callee, |
| 1836 | mutatesFunction: mutatesCallee, |
| 1837 | args: value.args, |
| 1838 | into: lvalue, |
| 1839 | signature, |
| 1840 | loc: value.loc, |
| 1841 | }); |
| 1842 | break; |
| 1843 | } |
| 1844 | case 'PropertyDelete': |
| 1845 | case 'ComputedDelete': { |
| 1846 | effects.push({ |
| 1847 | kind: 'Create', |
| 1848 | into: lvalue, |
| 1849 | value: ValueKind.Primitive, |
| 1850 | reason: ValueReason.Other, |
| 1851 | }); |
| 1852 | // Mutates the object by removing the property, no aliasing |
| 1853 | effects.push({kind: 'Mutate', value: value.object}); |
| 1854 | break; |
| 1855 | } |
| 1856 | case 'PropertyLoad': |
| 1857 | case 'ComputedLoad': { |
| 1858 | if (isPrimitiveType(lvalue.identifier)) { |
| 1859 | effects.push({ |
| 1860 | kind: 'Create', |
| 1861 | into: lvalue, |
| 1862 | value: ValueKind.Primitive, |
| 1863 | reason: ValueReason.Other, |
| 1864 | }); |
| 1865 | } else { |
| 1866 | effects.push({ |
| 1867 | kind: 'CreateFrom', |
| 1868 | from: value.object, |
| 1869 | into: lvalue, |
| 1870 | }); |
| 1871 | } |
| 1872 | break; |
| 1873 | } |
| 1874 | case 'PropertyStore': |
| 1875 | case 'ComputedStore': { |
| 1876 | /** |
| 1877 | * Add a hint about naming as "ref"/"-Ref", but only if we weren't able to infer any |
| 1878 | * type for the object. In some cases the variable may be named like a ref, but is |
| 1879 | * also used as a ref callback such that we infer the type as a function rather than |
| 1880 | * a ref. |
| 1881 | */ |
| 1882 | const mutationReason: MutationReason | null = |
| 1883 | value.kind === 'PropertyStore' && |
| 1884 | value.property === 'current' && |
| 1885 | value.object.identifier.type.kind === 'Type' |
| 1886 | ? {kind: 'AssignCurrentProperty'} |
| 1887 | : null; |
| 1888 | effects.push({ |
| 1889 | kind: 'Mutate', |
| 1890 | value: value.object, |
| 1891 | reason: mutationReason, |
| 1892 | }); |
| 1893 | effects.push({ |
| 1894 | kind: 'Capture', |
| 1895 | from: value.value, |
| 1896 | into: value.object, |
| 1897 | }); |
| 1898 | effects.push({ |
| 1899 | kind: 'Create', |
| 1900 | into: lvalue, |
| 1901 | value: ValueKind.Primitive, |
| 1902 | reason: ValueReason.Other, |
| 1903 | }); |
| 1904 | break; |
| 1905 | } |
| 1906 | case 'ObjectMethod': |
| 1907 | case 'FunctionExpression': { |
| 1908 | /** |
| 1909 | * We've already analyzed the function expression in AnalyzeFunctions. There, we assign |
| 1910 | * a Capture effect to any context variable that appears (locally) to be aliased and/or |
| 1911 | * mutated. The precise effects are annotated on the function expression's aliasingEffects |
| 1912 | * property, but we don't want to execute those effects yet. We can only use those when |
| 1913 | * we know exactly how the function is invoked — via an Apply effect from a custom signature. |
| 1914 | * |
| 1915 | * But in the general case, functions can be passed around and possibly called in ways where |
| 1916 | * we don't know how to interpret their precise effects. For example: |
| 1917 | * |
| 1918 | * ``` |
| 1919 | * const a = {}; |
| 1920 | * |
| 1921 | * // We don't want to consider a as mutating here, this just declares the function |
| 1922 | * const f = () => { maybeMutate(a) }; |
| 1923 | * |
| 1924 | * // We don't want to consider a as mutating here either, it can't possibly call f yet |
| 1925 | * const x = [f]; |
| 1926 | * |
| 1927 | * // Here we have to assume that f can be called (transitively), and have to consider a |
| 1928 | * // as mutating |
| 1929 | * callAllFunctionInArray(x); |
| 1930 | * ``` |
| 1931 | * |
| 1932 | * So for any context variables that were inferred as captured or mutated, we record a |
| 1933 | * Capture effect. If the resulting function is transitively mutated, this will mean |
| 1934 | * that those operands are also considered mutated. If the function is never called, |
| 1935 | * they won't be! |
| 1936 | * |
| 1937 | * This relies on the rule that: |
| 1938 | * Capture a -> b and MutateTransitive(b) => Mutate(a) |
| 1939 | * |
| 1940 | * Substituting: |
| 1941 | * Capture contextvar -> function and MutateTransitive(function) => Mutate(contextvar) |
| 1942 | * |
| 1943 | * Note that if the type of the context variables are frozen, global, or primitive, the |
| 1944 | * Capture will either get pruned or downgraded to an ImmutableCapture. |
| 1945 | */ |
| 1946 | effects.push({ |
| 1947 | kind: 'CreateFunction', |
| 1948 | into: lvalue, |
| 1949 | function: value, |
| 1950 | captures: value.loweredFunc.func.context.filter( |
| 1951 | operand => operand.effect === Effect.Capture, |
| 1952 | ), |
| 1953 | }); |
| 1954 | break; |
| 1955 | } |
| 1956 | case 'GetIterator': { |
| 1957 | effects.push({ |
| 1958 | kind: 'Create', |
| 1959 | into: lvalue, |
| 1960 | value: ValueKind.Mutable, |
| 1961 | reason: ValueReason.Other, |
| 1962 | }); |
| 1963 | if ( |
| 1964 | isArrayType(value.collection.identifier) || |
| 1965 | isMapType(value.collection.identifier) || |
| 1966 | isSetType(value.collection.identifier) |
| 1967 | ) { |
| 1968 | /* |
| 1969 | * Builtin collections are known to return a fresh iterator on each call, |
| 1970 | * so the iterator does not alias the collection |
| 1971 | */ |
| 1972 | effects.push({ |
| 1973 | kind: 'Capture', |
| 1974 | from: value.collection, |
| 1975 | into: lvalue, |
| 1976 | }); |
| 1977 | } else { |
| 1978 | /* |
| 1979 | * Otherwise, the object may return itself as the iterator, so we have to |
| 1980 | * assume that the result directly aliases the collection. Further, the |
| 1981 | * method to get the iterator could potentially mutate the collection |
| 1982 | */ |
| 1983 | effects.push({kind: 'Alias', from: value.collection, into: lvalue}); |
| 1984 | effects.push({ |
| 1985 | kind: 'MutateTransitiveConditionally', |
| 1986 | value: value.collection, |
| 1987 | }); |
| 1988 | } |
| 1989 | break; |
| 1990 | } |
| 1991 | case 'IteratorNext': { |
| 1992 | /* |
| 1993 | * Technically advancing an iterator will always mutate it (for any reasonable implementation) |
| 1994 | * But because we create an alias from the collection to the iterator if we don't know the type, |
| 1995 | * then it's possible the iterator is aliased to a frozen value and we wouldn't want to error. |
| 1996 | * so we mark this as conditional mutation to allow iterating frozen values. |
| 1997 | */ |
| 1998 | effects.push({kind: 'MutateConditionally', value: value.iterator}); |
| 1999 | // Extracts part of the original collection into the result |
| 2000 | effects.push({ |
| 2001 | kind: 'CreateFrom', |
| 2002 | from: value.collection, |
| 2003 | into: lvalue, |
| 2004 | }); |
| 2005 | break; |
| 2006 | } |
| 2007 | case 'NextPropertyOf': { |
| 2008 | effects.push({ |
| 2009 | kind: 'Create', |
| 2010 | into: lvalue, |
| 2011 | value: ValueKind.Primitive, |
| 2012 | reason: ValueReason.Other, |
| 2013 | }); |
| 2014 | break; |
| 2015 | } |
| 2016 | case 'JsxExpression': |
| 2017 | case 'JsxFragment': { |
| 2018 | effects.push({ |
| 2019 | kind: 'Create', |
| 2020 | into: lvalue, |
| 2021 | value: ValueKind.Frozen, |
| 2022 | reason: ValueReason.JsxCaptured, |
| 2023 | }); |
| 2024 | for (const operand of eachInstructionValueOperand(value)) { |
| 2025 | effects.push({ |
| 2026 | kind: 'Freeze', |
| 2027 | value: operand, |
| 2028 | reason: ValueReason.JsxCaptured, |
| 2029 | }); |
| 2030 | effects.push({ |
| 2031 | kind: 'Capture', |
| 2032 | from: operand, |
| 2033 | into: lvalue, |
| 2034 | }); |
| 2035 | } |
| 2036 | if (value.kind === 'JsxExpression') { |
| 2037 | if (value.tag.kind === 'Identifier') { |
| 2038 | // Tags are render function, by definition they're called during render |
| 2039 | effects.push({ |
| 2040 | kind: 'Render', |
| 2041 | place: value.tag, |
| 2042 | }); |
| 2043 | } |
| 2044 | if (value.children != null) { |
| 2045 | // Children are typically called during render, not used as an event/effect callback |
| 2046 | for (const child of value.children) { |
| 2047 | effects.push({ |
| 2048 | kind: 'Render', |
| 2049 | place: child, |
| 2050 | }); |
| 2051 | } |
| 2052 | } |
| 2053 | for (const prop of value.props) { |
| 2054 | if ( |
| 2055 | prop.kind === 'JsxAttribute' && |
| 2056 | prop.place.identifier.type.kind === 'Function' && |
| 2057 | (isJsxType(prop.place.identifier.type.return) || |
| 2058 | (prop.place.identifier.type.return.kind === 'Phi' && |
| 2059 | prop.place.identifier.type.return.operands.some(operand => |
| 2060 | isJsxType(operand), |
| 2061 | ))) |
| 2062 | ) { |
| 2063 | // Any props which return jsx are assumed to be called during render |
| 2064 | effects.push({ |
| 2065 | kind: 'Render', |
| 2066 | place: prop.place, |
| 2067 | }); |
| 2068 | } |
| 2069 | } |
| 2070 | } |
| 2071 | break; |
| 2072 | } |
| 2073 | case 'DeclareLocal': { |
| 2074 | // TODO check this |
| 2075 | effects.push({ |
| 2076 | kind: 'Create', |
| 2077 | into: value.lvalue.place, |
| 2078 | // TODO: what kind here??? |
| 2079 | value: ValueKind.Primitive, |
| 2080 | reason: ValueReason.Other, |
| 2081 | }); |
| 2082 | effects.push({ |
| 2083 | kind: 'Create', |
| 2084 | into: lvalue, |
| 2085 | // TODO: what kind here??? |
| 2086 | value: ValueKind.Primitive, |
| 2087 | reason: ValueReason.Other, |
| 2088 | }); |
| 2089 | break; |
| 2090 | } |
| 2091 | case 'Destructure': { |
| 2092 | for (const patternItem of eachPatternItem(value.lvalue.pattern)) { |
| 2093 | const place = |
| 2094 | patternItem.kind === 'Identifier' ? patternItem : patternItem.place; |
| 2095 | if (isPrimitiveType(place.identifier)) { |
| 2096 | effects.push({ |
| 2097 | kind: 'Create', |
| 2098 | into: place, |
| 2099 | value: ValueKind.Primitive, |
| 2100 | reason: ValueReason.Other, |
| 2101 | }); |
| 2102 | } else if (patternItem.kind === 'Identifier') { |
| 2103 | effects.push({ |
| 2104 | kind: 'CreateFrom', |
| 2105 | from: value.value, |
| 2106 | into: place, |
| 2107 | }); |
| 2108 | } else { |
| 2109 | // Spread creates a new object/array that captures from the RValue |
| 2110 | effects.push({ |
| 2111 | kind: 'Create', |
| 2112 | into: place, |
| 2113 | reason: ValueReason.Other, |
| 2114 | value: context.nonMutatingSpreads.has(place.identifier.id) |
| 2115 | ? ValueKind.Frozen |
| 2116 | : ValueKind.Mutable, |
| 2117 | }); |
| 2118 | effects.push({ |
| 2119 | kind: 'Capture', |
| 2120 | from: value.value, |
| 2121 | into: place, |
| 2122 | }); |
| 2123 | } |
| 2124 | } |
| 2125 | effects.push({kind: 'Assign', from: value.value, into: lvalue}); |
| 2126 | break; |
| 2127 | } |
| 2128 | case 'LoadContext': { |
| 2129 | /* |
| 2130 | * Context variables are like mutable boxes. Loading from one |
| 2131 | * is equivalent to a PropertyLoad from the box, so we model it |
| 2132 | * with the same effect we use there (CreateFrom) |
| 2133 | */ |
| 2134 | effects.push({kind: 'CreateFrom', from: value.place, into: lvalue}); |
| 2135 | break; |
| 2136 | } |
| 2137 | case 'DeclareContext': { |
| 2138 | // Context variables are conceptually like mutable boxes |
| 2139 | const kind = value.lvalue.kind; |
| 2140 | if ( |
| 2141 | !context.hoistedContextDeclarations.has( |
| 2142 | value.lvalue.place.identifier.declarationId, |
| 2143 | ) || |
| 2144 | kind === InstructionKind.HoistedConst || |
| 2145 | kind === InstructionKind.HoistedFunction || |
| 2146 | kind === InstructionKind.HoistedLet |
| 2147 | ) { |
| 2148 | /** |
| 2149 | * If this context variable is not hoisted, or this is the declaration doing the hoisting, |
| 2150 | * then we create the box. |
| 2151 | */ |
| 2152 | effects.push({ |
| 2153 | kind: 'Create', |
| 2154 | into: value.lvalue.place, |
| 2155 | value: ValueKind.Mutable, |
| 2156 | reason: ValueReason.Other, |
| 2157 | }); |
| 2158 | } else { |
| 2159 | /** |
| 2160 | * Otherwise this may be a "declare", but there was a previous DeclareContext that |
| 2161 | * hoisted this variable, and we're mutating it here. |
| 2162 | */ |
| 2163 | effects.push({kind: 'Mutate', value: value.lvalue.place}); |
| 2164 | } |
| 2165 | effects.push({ |
| 2166 | kind: 'Create', |
| 2167 | into: lvalue, |
| 2168 | // The result can't be referenced so this value doesn't matter |
| 2169 | value: ValueKind.Primitive, |
| 2170 | reason: ValueReason.Other, |
| 2171 | }); |
| 2172 | break; |
| 2173 | } |
| 2174 | case 'StoreContext': { |
| 2175 | /* |
| 2176 | * Context variables are like mutable boxes, so semantically |
| 2177 | * we're either creating (let/const) or mutating (reassign) a box, |
| 2178 | * and then capturing the value into it. |
| 2179 | */ |
| 2180 | if ( |
| 2181 | value.lvalue.kind === InstructionKind.Reassign || |
| 2182 | context.hoistedContextDeclarations.has( |
| 2183 | value.lvalue.place.identifier.declarationId, |
| 2184 | ) |
| 2185 | ) { |
| 2186 | effects.push({kind: 'Mutate', value: value.lvalue.place}); |
| 2187 | } else { |
| 2188 | effects.push({ |
| 2189 | kind: 'Create', |
| 2190 | into: value.lvalue.place, |
| 2191 | value: ValueKind.Mutable, |
| 2192 | reason: ValueReason.Other, |
| 2193 | }); |
| 2194 | } |
| 2195 | effects.push({ |
| 2196 | kind: 'Capture', |
| 2197 | from: value.value, |
| 2198 | into: value.lvalue.place, |
| 2199 | }); |
| 2200 | effects.push({kind: 'Assign', from: value.value, into: lvalue}); |
| 2201 | break; |
| 2202 | } |
| 2203 | case 'LoadLocal': { |
| 2204 | effects.push({kind: 'Assign', from: value.place, into: lvalue}); |
| 2205 | break; |
| 2206 | } |
| 2207 | case 'StoreLocal': { |
| 2208 | effects.push({ |
| 2209 | kind: 'Assign', |
| 2210 | from: value.value, |
| 2211 | into: value.lvalue.place, |
| 2212 | }); |
| 2213 | effects.push({kind: 'Assign', from: value.value, into: lvalue}); |
| 2214 | break; |
| 2215 | } |
| 2216 | case 'PostfixUpdate': |
| 2217 | case 'PrefixUpdate': { |
| 2218 | effects.push({ |
| 2219 | kind: 'Create', |
| 2220 | into: lvalue, |
| 2221 | value: ValueKind.Primitive, |
| 2222 | reason: ValueReason.Other, |
| 2223 | }); |
| 2224 | effects.push({ |
| 2225 | kind: 'Create', |
| 2226 | into: value.lvalue, |
| 2227 | value: ValueKind.Primitive, |
| 2228 | reason: ValueReason.Other, |
| 2229 | }); |
| 2230 | break; |
| 2231 | } |
| 2232 | case 'StoreGlobal': { |
| 2233 | const variable = `\`${value.name}\``; |
| 2234 | effects.push({ |
| 2235 | kind: 'MutateGlobal', |
| 2236 | place: value.value, |
| 2237 | error: CompilerDiagnostic.create({ |
| 2238 | category: ErrorCategory.Globals, |
| 2239 | reason: |
| 2240 | 'Cannot reassign variables declared outside of the component/hook', |
| 2241 | description: `Variable ${variable} is declared outside of the component/hook. Reassigning this value during render is a form of side effect, which can cause unpredictable behavior depending on when the component happens to re-render. If this variable is used in rendering, use useState instead. Otherwise, consider updating it in an effect. (https://react.dev/reference/rules/components-and-hooks-must-be-pure#side-effects-must-run-outside-of-render)`, |
| 2242 | }).withDetails({ |
| 2243 | kind: 'error', |
| 2244 | loc: instr.loc, |
| 2245 | message: `${variable} cannot be reassigned`, |
| 2246 | }), |
| 2247 | }); |
| 2248 | effects.push({kind: 'Assign', from: value.value, into: lvalue}); |
| 2249 | break; |
| 2250 | } |
| 2251 | case 'TypeCastExpression': { |
| 2252 | effects.push({kind: 'Assign', from: value.value, into: lvalue}); |
| 2253 | break; |
| 2254 | } |
| 2255 | case 'LoadGlobal': { |
| 2256 | effects.push({ |
| 2257 | kind: 'Create', |
| 2258 | into: lvalue, |
| 2259 | value: ValueKind.Global, |
| 2260 | reason: ValueReason.Global, |
| 2261 | }); |
| 2262 | break; |
| 2263 | } |
| 2264 | case 'StartMemoize': |
| 2265 | case 'FinishMemoize': { |
| 2266 | if (env.config.enablePreserveExistingMemoizationGuarantees) { |
| 2267 | for (const operand of eachInstructionValueOperand(value)) { |
| 2268 | effects.push({ |
| 2269 | kind: 'Freeze', |
| 2270 | value: operand, |
| 2271 | reason: ValueReason.HookCaptured, |
| 2272 | }); |
| 2273 | } |
| 2274 | } |
| 2275 | effects.push({ |
| 2276 | kind: 'Create', |
| 2277 | into: lvalue, |
| 2278 | value: ValueKind.Primitive, |
| 2279 | reason: ValueReason.Other, |
| 2280 | }); |
| 2281 | break; |
| 2282 | } |
| 2283 | case 'TaggedTemplateExpression': |
| 2284 | case 'BinaryExpression': |
| 2285 | case 'Debugger': |
| 2286 | case 'JSXText': |
| 2287 | case 'MetaProperty': |
| 2288 | case 'Primitive': |
| 2289 | case 'RegExpLiteral': |
| 2290 | case 'TemplateLiteral': |
| 2291 | case 'UnaryExpression': |
| 2292 | case 'UnsupportedNode': { |
| 2293 | effects.push({ |
| 2294 | kind: 'Create', |
| 2295 | into: lvalue, |
| 2296 | value: ValueKind.Primitive, |
| 2297 | reason: ValueReason.Other, |
| 2298 | }); |
| 2299 | break; |
| 2300 | } |
| 2301 | } |
| 2302 | return { |
| 2303 | effects, |
| 2304 | }; |
| 2305 | } |
| 2306 | |
| 2307 | /** |
| 2308 | * Creates a set of aliasing effects given a legacy FunctionSignature. This makes all of the |
| 2309 | * old implicit behaviors from the signatures and InferReferenceEffects explicit, see comments |
| 2310 | * in the body for details. |
| 2311 | * |
| 2312 | * The goal of this method is to make it easier to migrate incrementally to the new system, |
| 2313 | * so we don't have to immediately write new signatures for all the methods to get expected |
| 2314 | * compilation output. |
| 2315 | */ |
| 2316 | function computeEffectsForLegacySignature( |
| 2317 | state: InferenceState, |
| 2318 | signature: FunctionSignature, |
| 2319 | lvalue: Place, |
| 2320 | receiver: Place, |
| 2321 | args: Array<Place | SpreadPattern | Hole>, |
| 2322 | loc: SourceLocation, |
| 2323 | ): Array<AliasingEffect> { |
| 2324 | const returnValueReason = signature.returnValueReason ?? ValueReason.Other; |
| 2325 | const effects: Array<AliasingEffect> = []; |
| 2326 | effects.push({ |
| 2327 | kind: 'Create', |
| 2328 | into: lvalue, |
| 2329 | value: signature.returnValueKind, |
| 2330 | reason: returnValueReason, |
| 2331 | }); |
| 2332 | if (signature.impure && state.env.config.validateNoImpureFunctionsInRender) { |
| 2333 | effects.push({ |
| 2334 | kind: 'Impure', |
| 2335 | place: receiver, |
| 2336 | error: CompilerDiagnostic.create({ |
| 2337 | category: ErrorCategory.Purity, |
| 2338 | reason: 'Cannot call impure function during render', |
| 2339 | description: |
| 2340 | (signature.canonicalName != null |
| 2341 | ? `\`${signature.canonicalName}\` is an impure function. ` |
| 2342 | : '') + |
| 2343 | 'Calling an impure function can produce unstable results that update unpredictably when the component happens to re-render. (https://react.dev/reference/rules/components-and-hooks-must-be-pure#components-and-hooks-must-be-idempotent)', |
| 2344 | }).withDetails({ |
| 2345 | kind: 'error', |
| 2346 | loc, |
| 2347 | message: 'Cannot call impure function', |
| 2348 | }), |
| 2349 | }); |
| 2350 | } |
| 2351 | if (signature.knownIncompatible != null && state.env.enableValidations) { |
| 2352 | const errors = new CompilerError(); |
| 2353 | errors.pushDiagnostic( |
| 2354 | CompilerDiagnostic.create({ |
| 2355 | category: ErrorCategory.IncompatibleLibrary, |
| 2356 | reason: 'Use of incompatible library', |
| 2357 | description: [ |
| 2358 | 'This API returns functions which cannot be memoized without leading to stale UI. ' + |
| 2359 | 'To prevent this, by default React Compiler will skip memoizing this component/hook. ' + |
| 2360 | 'However, you may see issues if values from this API are passed to other components/hooks that are ' + |
| 2361 | 'memoized', |
| 2362 | ].join(''), |
| 2363 | }).withDetails({ |
| 2364 | kind: 'error', |
| 2365 | loc: receiver.loc, |
| 2366 | message: signature.knownIncompatible, |
| 2367 | }), |
| 2368 | ); |
| 2369 | throw errors; |
| 2370 | } |
| 2371 | const stores: Array<Place> = []; |
| 2372 | const captures: Array<Place> = []; |
| 2373 | function visit(place: Place, effect: Effect): void { |
| 2374 | switch (effect) { |
| 2375 | case Effect.Store: { |
| 2376 | effects.push({ |
| 2377 | kind: 'Mutate', |
| 2378 | value: place, |
| 2379 | }); |
| 2380 | stores.push(place); |
| 2381 | break; |
| 2382 | } |
| 2383 | case Effect.Capture: { |
| 2384 | captures.push(place); |
| 2385 | break; |
| 2386 | } |
| 2387 | case Effect.ConditionallyMutate: { |
| 2388 | effects.push({ |
| 2389 | kind: 'MutateTransitiveConditionally', |
| 2390 | value: place, |
| 2391 | }); |
| 2392 | break; |
| 2393 | } |
| 2394 | case Effect.ConditionallyMutateIterator: { |
| 2395 | const mutateIterator = conditionallyMutateIterator(place); |
| 2396 | if (mutateIterator != null) { |
| 2397 | effects.push(mutateIterator); |
| 2398 | } |
| 2399 | effects.push({ |
| 2400 | kind: 'Capture', |
| 2401 | from: place, |
| 2402 | into: lvalue, |
| 2403 | }); |
| 2404 | break; |
| 2405 | } |
| 2406 | case Effect.Freeze: { |
| 2407 | effects.push({ |
| 2408 | kind: 'Freeze', |
| 2409 | value: place, |
| 2410 | reason: returnValueReason, |
| 2411 | }); |
| 2412 | break; |
| 2413 | } |
| 2414 | case Effect.Mutate: { |
| 2415 | effects.push({kind: 'MutateTransitive', value: place}); |
| 2416 | break; |
| 2417 | } |
| 2418 | case Effect.Read: { |
| 2419 | effects.push({ |
| 2420 | kind: 'ImmutableCapture', |
| 2421 | from: place, |
| 2422 | into: lvalue, |
| 2423 | }); |
| 2424 | break; |
| 2425 | } |
| 2426 | } |
| 2427 | } |
| 2428 | |
| 2429 | if ( |
| 2430 | signature.mutableOnlyIfOperandsAreMutable && |
| 2431 | areArgumentsImmutableAndNonMutating(state, args) |
| 2432 | ) { |
| 2433 | effects.push({ |
| 2434 | kind: 'Alias', |
| 2435 | from: receiver, |
| 2436 | into: lvalue, |
| 2437 | }); |
| 2438 | for (const arg of args) { |
| 2439 | if (arg.kind === 'Hole') { |
| 2440 | continue; |
| 2441 | } |
| 2442 | const place = arg.kind === 'Identifier' ? arg : arg.place; |
| 2443 | effects.push({ |
| 2444 | kind: 'ImmutableCapture', |
| 2445 | from: place, |
| 2446 | into: lvalue, |
| 2447 | }); |
| 2448 | } |
| 2449 | return effects; |
| 2450 | } |
| 2451 | |
| 2452 | if (signature.calleeEffect !== Effect.Capture) { |
| 2453 | /* |
| 2454 | * InferReferenceEffects and FunctionSignature have an implicit assumption that the receiver |
| 2455 | * is captured into the return value. Consider for example the signature for Array.proto.pop: |
| 2456 | * the calleeEffect is Store, since it's a known mutation but non-transitive. But the return |
| 2457 | * of the pop() captures from the receiver! This isn't specified explicitly. So we add this |
| 2458 | * here, and rely on applySignature() to downgrade this to ImmutableCapture (or prune) if |
| 2459 | * the type doesn't actually need to be captured based on the input and return type. |
| 2460 | */ |
| 2461 | effects.push({ |
| 2462 | kind: 'Alias', |
| 2463 | from: receiver, |
| 2464 | into: lvalue, |
| 2465 | }); |
| 2466 | } |
| 2467 | visit(receiver, signature.calleeEffect); |
| 2468 | for (let i = 0; i < args.length; i++) { |
| 2469 | const arg = args[i]; |
| 2470 | if (arg.kind === 'Hole') { |
| 2471 | continue; |
| 2472 | } |
| 2473 | const place = arg.kind === 'Identifier' ? arg : arg.place; |
| 2474 | const signatureEffect = |
| 2475 | arg.kind === 'Identifier' && i < signature.positionalParams.length |
| 2476 | ? signature.positionalParams[i]! |
| 2477 | : (signature.restParam ?? Effect.ConditionallyMutate); |
| 2478 | const effect = getArgumentEffect(signatureEffect, arg); |
| 2479 | |
| 2480 | visit(place, effect); |
| 2481 | } |
| 2482 | if (captures.length !== 0) { |
| 2483 | if (stores.length === 0) { |
| 2484 | // If no stores, then capture into the return value |
| 2485 | for (const capture of captures) { |
| 2486 | effects.push({kind: 'Alias', from: capture, into: lvalue}); |
| 2487 | } |
| 2488 | } else { |
| 2489 | // Else capture into the stores |
| 2490 | for (const capture of captures) { |
| 2491 | for (const store of stores) { |
| 2492 | effects.push({kind: 'Capture', from: capture, into: store}); |
| 2493 | } |
| 2494 | } |
| 2495 | } |
| 2496 | } |
| 2497 | return effects; |
| 2498 | } |
| 2499 | |
| 2500 | /** |
| 2501 | * Returns true if all of the arguments are both non-mutable (immutable or frozen) |
| 2502 | * _and_ are not functions which might mutate their arguments. Note that function |
| 2503 | * expressions count as frozen so long as they do not mutate free variables: this |
| 2504 | * function checks that such functions also don't mutate their inputs. |
| 2505 | */ |
| 2506 | function areArgumentsImmutableAndNonMutating( |
| 2507 | state: InferenceState, |
| 2508 | args: Array<Place | SpreadPattern | Hole>, |
| 2509 | ): boolean { |
| 2510 | for (const arg of args) { |
| 2511 | if (arg.kind === 'Hole') { |
| 2512 | continue; |
| 2513 | } |
| 2514 | if (arg.kind === 'Identifier' && arg.identifier.type.kind === 'Function') { |
| 2515 | const fnShape = state.env.getFunctionSignature(arg.identifier.type); |
| 2516 | if (fnShape != null) { |
| 2517 | return ( |
| 2518 | !fnShape.positionalParams.some(isKnownMutableEffect) && |
| 2519 | (fnShape.restParam == null || |
| 2520 | !isKnownMutableEffect(fnShape.restParam)) |
| 2521 | ); |
| 2522 | } |
| 2523 | } |
| 2524 | const place = arg.kind === 'Identifier' ? arg : arg.place; |
| 2525 | |
| 2526 | const kind = state.kind(place).kind; |
| 2527 | switch (kind) { |
| 2528 | case ValueKind.Primitive: |
| 2529 | case ValueKind.Frozen: { |
| 2530 | /* |
| 2531 | * Only immutable values, or frozen lambdas are allowed. |
| 2532 | * A lambda may appear frozen even if it may mutate its inputs, |
| 2533 | * so we have a second check even for frozen value types |
| 2534 | */ |
| 2535 | break; |
| 2536 | } |
| 2537 | default: { |
| 2538 | /** |
| 2539 | * Globals, module locals, and other locally defined functions may |
| 2540 | * mutate their arguments. |
| 2541 | */ |
| 2542 | return false; |
| 2543 | } |
| 2544 | } |
| 2545 | const values = state.values(place); |
| 2546 | for (const value of values) { |
| 2547 | if ( |
| 2548 | value.kind === 'FunctionExpression' && |
| 2549 | value.loweredFunc.func.params.some(param => { |
| 2550 | const place = param.kind === 'Identifier' ? param : param.place; |
| 2551 | const range = place.identifier.mutableRange; |
| 2552 | return range.end > range.start + 1; |
| 2553 | }) |
| 2554 | ) { |
| 2555 | // This is a function which may mutate its inputs |
| 2556 | return false; |
| 2557 | } |
| 2558 | } |
| 2559 | } |
| 2560 | return true; |
| 2561 | } |
| 2562 | |
| 2563 | function computeEffectsForSignature( |
| 2564 | env: Environment, |
| 2565 | signature: AliasingSignature, |
| 2566 | lvalue: Place, |
| 2567 | receiver: Place, |
| 2568 | args: Array<Place | SpreadPattern | Hole>, |
| 2569 | // Used for signatures constructed dynamically which reference context variables |
| 2570 | context: Array<Place> = [], |
| 2571 | loc: SourceLocation, |
| 2572 | ): Array<AliasingEffect> | null { |
| 2573 | if ( |
| 2574 | // Not enough args |
| 2575 | signature.params.length > args.length || |
| 2576 | // Too many args and there is no rest param to hold them |
| 2577 | (args.length > signature.params.length && signature.rest == null) |
| 2578 | ) { |
| 2579 | return null; |
| 2580 | } |
| 2581 | // Build substitutions |
| 2582 | const mutableSpreads = new Set<IdentifierId>(); |
| 2583 | const substitutions: Map<IdentifierId, Array<Place>> = new Map(); |
| 2584 | substitutions.set(signature.receiver, [receiver]); |
| 2585 | substitutions.set(signature.returns, [lvalue]); |
| 2586 | const params = signature.params; |
| 2587 | for (let i = 0; i < args.length; i++) { |
| 2588 | const arg = args[i]; |
| 2589 | if (arg.kind === 'Hole') { |
| 2590 | continue; |
| 2591 | } else if (params == null || i >= params.length || arg.kind === 'Spread') { |
| 2592 | if (signature.rest == null) { |
| 2593 | return null; |
| 2594 | } |
| 2595 | const place = arg.kind === 'Identifier' ? arg : arg.place; |
| 2596 | getOrInsertWith(substitutions, signature.rest, () => []).push(place); |
| 2597 | |
| 2598 | if (arg.kind === 'Spread') { |
| 2599 | const mutateIterator = conditionallyMutateIterator(arg.place); |
| 2600 | if (mutateIterator != null) { |
| 2601 | mutableSpreads.add(arg.place.identifier.id); |
| 2602 | } |
| 2603 | } |
| 2604 | } else { |
| 2605 | const param = params[i]; |
| 2606 | substitutions.set(param, [arg]); |
| 2607 | } |
| 2608 | } |
| 2609 | |
| 2610 | /* |
| 2611 | * Signatures constructed dynamically from function expressions will reference values |
| 2612 | * other than their receiver/args/etc. We populate the substitution table with these |
| 2613 | * values so that we can still exit for unpopulated substitutions |
| 2614 | */ |
| 2615 | for (const operand of context) { |
| 2616 | substitutions.set(operand.identifier.id, [operand]); |
| 2617 | } |
| 2618 | |
| 2619 | const effects: Array<AliasingEffect> = []; |
| 2620 | for (const signatureTemporary of signature.temporaries) { |
| 2621 | const temp = createTemporaryPlace(env, receiver.loc); |
| 2622 | substitutions.set(signatureTemporary.identifier.id, [temp]); |
| 2623 | } |
| 2624 | |
| 2625 | // Apply substitutions |
| 2626 | for (const effect of signature.effects) { |
| 2627 | switch (effect.kind) { |
| 2628 | case 'MaybeAlias': |
| 2629 | case 'Assign': |
| 2630 | case 'ImmutableCapture': |
| 2631 | case 'Alias': |
| 2632 | case 'CreateFrom': |
| 2633 | case 'Capture': { |
| 2634 | const from = substitutions.get(effect.from.identifier.id) ?? []; |
| 2635 | const to = substitutions.get(effect.into.identifier.id) ?? []; |
| 2636 | for (const fromId of from) { |
| 2637 | for (const toId of to) { |
| 2638 | effects.push({ |
| 2639 | kind: effect.kind, |
| 2640 | from: fromId, |
| 2641 | into: toId, |
| 2642 | }); |
| 2643 | } |
| 2644 | } |
| 2645 | break; |
| 2646 | } |
| 2647 | case 'Impure': |
| 2648 | case 'MutateFrozen': |
| 2649 | case 'MutateGlobal': { |
| 2650 | const values = substitutions.get(effect.place.identifier.id) ?? []; |
| 2651 | for (const value of values) { |
| 2652 | effects.push({kind: effect.kind, place: value, error: effect.error}); |
| 2653 | } |
| 2654 | break; |
| 2655 | } |
| 2656 | case 'Render': { |
| 2657 | const values = substitutions.get(effect.place.identifier.id) ?? []; |
| 2658 | for (const value of values) { |
| 2659 | effects.push({kind: effect.kind, place: value}); |
| 2660 | } |
| 2661 | break; |
| 2662 | } |
| 2663 | case 'Mutate': |
| 2664 | case 'MutateTransitive': |
| 2665 | case 'MutateTransitiveConditionally': |
| 2666 | case 'MutateConditionally': { |
| 2667 | const values = substitutions.get(effect.value.identifier.id) ?? []; |
| 2668 | for (const id of values) { |
| 2669 | effects.push({kind: effect.kind, value: id}); |
| 2670 | } |
| 2671 | break; |
| 2672 | } |
| 2673 | case 'Freeze': { |
| 2674 | const values = substitutions.get(effect.value.identifier.id) ?? []; |
| 2675 | for (const value of values) { |
| 2676 | if (mutableSpreads.has(value.identifier.id)) { |
| 2677 | CompilerError.throwTodo({ |
| 2678 | reason: 'Support spread syntax for hook arguments', |
| 2679 | loc: value.loc, |
| 2680 | }); |
| 2681 | } |
| 2682 | effects.push({kind: 'Freeze', value, reason: effect.reason}); |
| 2683 | } |
| 2684 | break; |
| 2685 | } |
| 2686 | case 'Create': { |
| 2687 | const into = substitutions.get(effect.into.identifier.id) ?? []; |
| 2688 | for (const value of into) { |
| 2689 | effects.push({ |
| 2690 | kind: 'Create', |
| 2691 | into: value, |
| 2692 | value: effect.value, |
| 2693 | reason: effect.reason, |
| 2694 | }); |
| 2695 | } |
| 2696 | break; |
| 2697 | } |
| 2698 | case 'Apply': { |
| 2699 | const applyReceiver = substitutions.get(effect.receiver.identifier.id); |
| 2700 | if (applyReceiver == null || applyReceiver.length !== 1) { |
| 2701 | return null; |
| 2702 | } |
| 2703 | const applyFunction = substitutions.get(effect.function.identifier.id); |
| 2704 | if (applyFunction == null || applyFunction.length !== 1) { |
| 2705 | return null; |
| 2706 | } |
| 2707 | const applyInto = substitutions.get(effect.into.identifier.id); |
| 2708 | if (applyInto == null || applyInto.length !== 1) { |
| 2709 | return null; |
| 2710 | } |
| 2711 | const applyArgs: Array<Place | SpreadPattern | Hole> = []; |
| 2712 | for (const arg of effect.args) { |
| 2713 | if (arg.kind === 'Hole') { |
| 2714 | applyArgs.push(arg); |
| 2715 | } else if (arg.kind === 'Identifier') { |
| 2716 | const applyArg = substitutions.get(arg.identifier.id); |
| 2717 | if (applyArg == null || applyArg.length !== 1) { |
| 2718 | return null; |
| 2719 | } |
| 2720 | applyArgs.push(applyArg[0]); |
| 2721 | } else { |
| 2722 | const applyArg = substitutions.get(arg.place.identifier.id); |
| 2723 | if (applyArg == null || applyArg.length !== 1) { |
| 2724 | return null; |
| 2725 | } |
| 2726 | applyArgs.push({kind: 'Spread', place: applyArg[0]}); |
| 2727 | } |
| 2728 | } |
| 2729 | effects.push({ |
| 2730 | kind: 'Apply', |
| 2731 | mutatesFunction: effect.mutatesFunction, |
| 2732 | receiver: applyReceiver[0], |
| 2733 | args: applyArgs, |
| 2734 | function: applyFunction[0], |
| 2735 | into: applyInto[0], |
| 2736 | signature: effect.signature, |
| 2737 | loc, |
| 2738 | }); |
| 2739 | break; |
| 2740 | } |
| 2741 | case 'CreateFunction': { |
| 2742 | CompilerError.throwTodo({ |
| 2743 | reason: `Support CreateFrom effects in signatures`, |
| 2744 | loc: receiver.loc, |
| 2745 | }); |
| 2746 | } |
| 2747 | default: { |
| 2748 | assertExhaustive( |
| 2749 | effect, |
| 2750 | `Unexpected effect kind '${(effect as any).kind}'`, |
| 2751 | ); |
| 2752 | } |
| 2753 | } |
| 2754 | } |
| 2755 | return effects; |
| 2756 | } |
| 2757 | |
| 2758 | function buildSignatureFromFunctionExpression( |
| 2759 | env: Environment, |
| 2760 | fn: FunctionExpression, |
| 2761 | ): AliasingSignature { |
| 2762 | let rest: IdentifierId | null = null; |
| 2763 | const params: Array<IdentifierId> = []; |
| 2764 | for (const param of fn.loweredFunc.func.params) { |
| 2765 | if (param.kind === 'Identifier') { |
| 2766 | params.push(param.identifier.id); |
| 2767 | } else { |
| 2768 | rest = param.place.identifier.id; |
| 2769 | } |
| 2770 | } |
| 2771 | return { |
| 2772 | receiver: makeIdentifierId(0), |
| 2773 | params, |
| 2774 | rest: rest ?? createTemporaryPlace(env, fn.loc).identifier.id, |
| 2775 | returns: fn.loweredFunc.func.returns.identifier.id, |
| 2776 | effects: fn.loweredFunc.func.aliasingEffects ?? [], |
| 2777 | temporaries: [], |
| 2778 | }; |
| 2779 | } |
| 2780 | |
| 2781 | export type AbstractValue = { |
| 2782 | kind: ValueKind; |
| 2783 | reason: ReadonlySet<ValueReason>; |
| 2784 | }; |
| 2785 | |
| 2786 | export function getWriteErrorReason(abstractValue: AbstractValue): string { |
| 2787 | if (abstractValue.reason.has(ValueReason.Global)) { |
| 2788 | return 'Modifying a variable defined outside a component or hook is not allowed. Consider using an effect'; |
| 2789 | } else if (abstractValue.reason.has(ValueReason.JsxCaptured)) { |
| 2790 | return 'Modifying a value used previously in JSX is not allowed. Consider moving the modification before the JSX'; |
| 2791 | } else if (abstractValue.reason.has(ValueReason.Context)) { |
| 2792 | return `Modifying a value returned from 'useContext()' is not allowed.`; |
| 2793 | } else if (abstractValue.reason.has(ValueReason.KnownReturnSignature)) { |
| 2794 | return 'Modifying a value returned from a function whose return value should not be mutated'; |
| 2795 | } else if (abstractValue.reason.has(ValueReason.ReactiveFunctionArgument)) { |
| 2796 | return 'Modifying component props or hook arguments is not allowed. Consider using a local variable instead'; |
| 2797 | } else if (abstractValue.reason.has(ValueReason.State)) { |
| 2798 | return "Modifying a value returned from 'useState()', which should not be modified directly. Use the setter function to update instead"; |
| 2799 | } else if (abstractValue.reason.has(ValueReason.ReducerState)) { |
| 2800 | return "Modifying a value returned from 'useReducer()', which should not be modified directly. Use the dispatch function to update instead"; |
| 2801 | } else if (abstractValue.reason.has(ValueReason.Effect)) { |
| 2802 | return 'Modifying a value used previously in an effect function or as an effect dependency is not allowed. Consider moving the modification before calling useEffect()'; |
| 2803 | } else if (abstractValue.reason.has(ValueReason.HookCaptured)) { |
| 2804 | return 'Modifying a value previously passed as an argument to a hook is not allowed. Consider moving the modification before calling the hook'; |
| 2805 | } else if (abstractValue.reason.has(ValueReason.HookReturn)) { |
| 2806 | return 'Modifying a value returned from a hook is not allowed. Consider moving the modification into the hook where the value is constructed'; |
| 2807 | } else { |
| 2808 | return 'This modifies a variable that React considers immutable'; |
| 2809 | } |
| 2810 | } |
| 2811 | |
| 2812 | function getArgumentEffect( |
| 2813 | signatureEffect: Effect | null, |
| 2814 | arg: Place | SpreadPattern, |
| 2815 | ): Effect { |
| 2816 | if (signatureEffect != null) { |
| 2817 | if (arg.kind === 'Identifier') { |
| 2818 | return signatureEffect; |
| 2819 | } else if ( |
| 2820 | signatureEffect === Effect.Mutate || |
| 2821 | signatureEffect === Effect.ConditionallyMutate |
| 2822 | ) { |
| 2823 | return signatureEffect; |
| 2824 | } else { |
| 2825 | // see call-spread-argument-mutable-iterator test fixture |
| 2826 | if (signatureEffect === Effect.Freeze) { |
| 2827 | CompilerError.throwTodo({ |
| 2828 | reason: 'Support spread syntax for hook arguments', |
| 2829 | loc: arg.place.loc, |
| 2830 | }); |
| 2831 | } |
| 2832 | // effects[i] is Effect.Capture | Effect.Read | Effect.Store |
| 2833 | return Effect.ConditionallyMutateIterator; |
| 2834 | } |
| 2835 | } else { |
| 2836 | return Effect.ConditionallyMutate; |
| 2837 | } |
| 2838 | } |
| 2839 | |
| 2840 | export function getFunctionCallSignature( |
| 2841 | env: Environment, |
| 2842 | type: Type, |
| 2843 | ): FunctionSignature | null { |
| 2844 | if (type.kind !== 'Function') { |
| 2845 | return null; |
| 2846 | } |
| 2847 | return env.getFunctionSignature(type); |
| 2848 | } |
| 2849 | |
| 2850 | export function isKnownMutableEffect(effect: Effect): boolean { |
| 2851 | switch (effect) { |
| 2852 | case Effect.Store: |
| 2853 | case Effect.ConditionallyMutate: |
| 2854 | case Effect.ConditionallyMutateIterator: |
| 2855 | case Effect.Mutate: { |
| 2856 | return true; |
| 2857 | } |
| 2858 | |
| 2859 | case Effect.Unknown: { |
| 2860 | CompilerError.invariant(false, { |
| 2861 | reason: 'Unexpected unknown effect', |
| 2862 | loc: GeneratedSource, |
| 2863 | }); |
| 2864 | } |
| 2865 | case Effect.Read: |
| 2866 | case Effect.Capture: |
| 2867 | case Effect.Freeze: { |
| 2868 | return false; |
| 2869 | } |
| 2870 | default: { |
| 2871 | assertExhaustive(effect, `Unexpected effect \`${effect}\``); |
| 2872 | } |
| 2873 | } |
| 2874 | } |
| 2875 | |
| 2876 | /** |
| 2877 | * Joins two values using the following rules: |
| 2878 | * == Effect Transitions == |
| 2879 | * |
| 2880 | * Freezing an immutable value has not effect: |
| 2881 | * ┌───────────────┐ |
| 2882 | * │ │ |
| 2883 | * ▼ │ Freeze |
| 2884 | * ┌──────────────────────────┐ │ |
| 2885 | * │ Immutable │──┘ |
| 2886 | * └──────────────────────────┘ |
| 2887 | * |
| 2888 | * Freezing a mutable or maybe-frozen value makes it frozen. Freezing a frozen |
| 2889 | * value has no effect: |
| 2890 | * ┌───────────────┐ |
| 2891 | * ┌─────────────────────────┐ Freeze │ │ |
| 2892 | * │ MaybeFrozen │────┐ ▼ │ Freeze |
| 2893 | * └─────────────────────────┘ │ ┌──────────────────────────┐ │ |
| 2894 | * ├────▶│ Frozen │──┘ |
| 2895 | * │ └──────────────────────────┘ |
| 2896 | * ┌─────────────────────────┐ │ |
| 2897 | * │ Mutable │────┘ |
| 2898 | * └─────────────────────────┘ |
| 2899 | * |
| 2900 | * == Join Lattice == |
| 2901 | * - immutable | mutable => mutable |
| 2902 | * The justification is that immutable and mutable values are different types, |
| 2903 | * and functions can introspect them to tell the difference (if the argument |
| 2904 | * is null return early, else if its an object mutate it). |
| 2905 | * - frozen | mutable => maybe-frozen |
| 2906 | * Frozen values are indistinguishable from mutable values at runtime, so callers |
| 2907 | * cannot dynamically avoid mutation of "frozen" values. If a value could be |
| 2908 | * frozen we have to distinguish it from a mutable value. But it also isn't known |
| 2909 | * frozen yet, so we distinguish as maybe-frozen. |
| 2910 | * - immutable | frozen => frozen |
| 2911 | * This is subtle and falls out of the above rules. If a value could be any of |
| 2912 | * immutable, mutable, or frozen, then at runtime it could either be a primitive |
| 2913 | * or a reference type, and callers can't distinguish frozen or not for reference |
| 2914 | * types. To ensure that any sequence of joins btw those three states yields the |
| 2915 | * correct maybe-frozen, these two have to produce a frozen value. |
| 2916 | * - <any> | maybe-frozen => maybe-frozen |
| 2917 | * - immutable | context => context |
| 2918 | * - mutable | context => context |
| 2919 | * - frozen | context => maybe-frozen |
| 2920 | * |
| 2921 | * ┌──────────────────────────┐ |
| 2922 | * │ Immutable │───┐ |
| 2923 | * └──────────────────────────┘ │ |
| 2924 | * │ ┌─────────────────────────┐ |
| 2925 | * ├───▶│ Frozen │──┐ |
| 2926 | * ┌──────────────────────────┐ │ └─────────────────────────┘ │ |
| 2927 | * │ Frozen │───┤ │ ┌─────────────────────────┐ |
| 2928 | * └──────────────────────────┘ │ ├─▶│ MaybeFrozen │ |
| 2929 | * │ ┌─────────────────────────┐ │ └─────────────────────────┘ |
| 2930 | * ├───▶│ MaybeFrozen │──┘ |
| 2931 | * ┌──────────────────────────┐ │ └─────────────────────────┘ |
| 2932 | * │ Mutable │───┘ |
| 2933 | * └──────────────────────────┘ |
| 2934 | */ |
| 2935 | function mergeValueKinds(a: ValueKind, b: ValueKind): ValueKind { |
| 2936 | if (a === b) { |
| 2937 | return a; |
| 2938 | } else if (a === ValueKind.MaybeFrozen || b === ValueKind.MaybeFrozen) { |
| 2939 | return ValueKind.MaybeFrozen; |
| 2940 | // after this a and b differ and neither are MaybeFrozen |
| 2941 | } else if (a === ValueKind.Mutable || b === ValueKind.Mutable) { |
| 2942 | if (a === ValueKind.Frozen || b === ValueKind.Frozen) { |
| 2943 | // frozen | mutable |
| 2944 | return ValueKind.MaybeFrozen; |
| 2945 | } else if (a === ValueKind.Context || b === ValueKind.Context) { |
| 2946 | // context | mutable |
| 2947 | return ValueKind.Context; |
| 2948 | } else { |
| 2949 | // mutable | immutable |
| 2950 | return ValueKind.Mutable; |
| 2951 | } |
| 2952 | } else if (a === ValueKind.Context || b === ValueKind.Context) { |
| 2953 | if (a === ValueKind.Frozen || b === ValueKind.Frozen) { |
| 2954 | // frozen | context |
| 2955 | return ValueKind.MaybeFrozen; |
| 2956 | } else { |
| 2957 | // context | immutable |
| 2958 | return ValueKind.Context; |
| 2959 | } |
| 2960 | } else if (a === ValueKind.Frozen || b === ValueKind.Frozen) { |
| 2961 | return ValueKind.Frozen; |
| 2962 | } else if (a === ValueKind.Global || b === ValueKind.Global) { |
| 2963 | return ValueKind.Global; |
| 2964 | } else { |
| 2965 | CompilerError.invariant( |
| 2966 | a === ValueKind.Primitive && b == ValueKind.Primitive, |
| 2967 | { |
| 2968 | reason: `Unexpected value kind in mergeValues()`, |
| 2969 | description: `Found kinds ${a} and ${b}`, |
| 2970 | loc: GeneratedSource, |
| 2971 | }, |
| 2972 | ); |
| 2973 | return ValueKind.Primitive; |
| 2974 | } |
| 2975 | } |