| 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 {CompilerDiagnostic, Effect} from '..'; |
| 9 | import {ErrorCategory} from '../CompilerError'; |
| 10 | import { |
| 11 | HIRFunction, |
| 12 | IdentifierId, |
| 13 | isRefOrRefLikeMutableType, |
| 14 | Place, |
| 15 | } from '../HIR'; |
| 16 | import { |
| 17 | eachInstructionValueOperand, |
| 18 | eachTerminalOperand, |
| 19 | } from '../HIR/visitors'; |
| 20 | import {AliasingEffect} from '../Inference/AliasingEffects'; |
| 21 | |
| 22 | /** |
| 23 | * Validates that functions with known mutations (ie due to types) cannot be passed |
| 24 | * where a frozen value is expected. Example: |
| 25 | * |
| 26 | * ``` |
| 27 | * function Component() { |
| 28 | * const cache = new Map(); |
| 29 | * const onClick = () => { |
| 30 | * cache.set(...); |
| 31 | * } |
| 32 | * useHook(onClick); // ERROR: cannot pass a mutable value |
| 33 | * return <Foo onClick={onClick} /> // ERROR: cannot pass a mutable value |
| 34 | * } |
| 35 | * ``` |
| 36 | * |
| 37 | * Because `onClick` function mutates `cache` when called, `onClick` is equivalent to a mutable |
| 38 | * variables. But unlike other mutables values like an array, the receiver of the function has |
| 39 | * no way to avoid mutation — for example, a function can receive an array and choose not to mutate |
| 40 | * it, but there's no way to know that a function is mutable and avoid calling it. |
| 41 | * |
| 42 | * This pass detects functions with *known* mutations (Store or Mutate, not ConditionallyMutate) |
| 43 | * that are passed where a frozen value is expected and rejects them. |
| 44 | */ |
| 45 | export function validateNoFreezingKnownMutableFunctions(fn: HIRFunction): void { |
| 46 | const contextMutationEffects: Map< |
| 47 | IdentifierId, |
| 48 | Extract<AliasingEffect, {kind: 'Mutate'} | {kind: 'MutateTransitive'}> |
| 49 | > = new Map(); |
| 50 | |
| 51 | function visitOperand(operand: Place): void { |
| 52 | if (operand.effect === Effect.Freeze) { |
| 53 | const effect = contextMutationEffects.get(operand.identifier.id); |
| 54 | if (effect != null) { |
| 55 | const place = effect.value; |
| 56 | const variable = |
| 57 | place != null && |
| 58 | place.identifier.name != null && |
| 59 | place.identifier.name.kind === 'named' |
| 60 | ? `\`${place.identifier.name.value}\`` |
| 61 | : 'a local variable'; |
| 62 | fn.env.recordError( |
| 63 | CompilerDiagnostic.create({ |
| 64 | category: ErrorCategory.Immutability, |
| 65 | reason: 'Cannot modify local variables after render completes', |
| 66 | description: `This argument is a function which may reassign or mutate ${variable} after render, which can cause inconsistent behavior on subsequent renders. Consider using state instead`, |
| 67 | }) |
| 68 | .withDetails({ |
| 69 | kind: 'error', |
| 70 | loc: operand.loc, |
| 71 | message: `This function may (indirectly) reassign or modify ${variable} after render`, |
| 72 | }) |
| 73 | .withDetails({ |
| 74 | kind: 'error', |
| 75 | loc: effect.value.loc, |
| 76 | message: `This modifies ${variable}`, |
| 77 | }), |
| 78 | ); |
| 79 | } |
| 80 | } |
| 81 | } |
| 82 | |
| 83 | for (const block of fn.body.blocks.values()) { |
| 84 | for (const instr of block.instructions) { |
| 85 | const {lvalue, value} = instr; |
| 86 | switch (value.kind) { |
| 87 | case 'LoadLocal': { |
| 88 | const effect = contextMutationEffects.get(value.place.identifier.id); |
| 89 | if (effect != null) { |
| 90 | contextMutationEffects.set(lvalue.identifier.id, effect); |
| 91 | } |
| 92 | break; |
| 93 | } |
| 94 | case 'StoreLocal': { |
| 95 | const effect = contextMutationEffects.get(value.value.identifier.id); |
| 96 | if (effect != null) { |
| 97 | contextMutationEffects.set(lvalue.identifier.id, effect); |
| 98 | contextMutationEffects.set( |
| 99 | value.lvalue.place.identifier.id, |
| 100 | effect, |
| 101 | ); |
| 102 | } |
| 103 | break; |
| 104 | } |
| 105 | case 'FunctionExpression': { |
| 106 | if (value.loweredFunc.func.aliasingEffects != null) { |
| 107 | const context = new Set( |
| 108 | value.loweredFunc.func.context.map(p => p.identifier.id), |
| 109 | ); |
| 110 | effects: for (const effect of value.loweredFunc.func |
| 111 | .aliasingEffects) { |
| 112 | switch (effect.kind) { |
| 113 | case 'Mutate': |
| 114 | case 'MutateTransitive': { |
| 115 | const knownMutation = contextMutationEffects.get( |
| 116 | effect.value.identifier.id, |
| 117 | ); |
| 118 | if (knownMutation != null) { |
| 119 | contextMutationEffects.set( |
| 120 | lvalue.identifier.id, |
| 121 | knownMutation, |
| 122 | ); |
| 123 | } else if ( |
| 124 | context.has(effect.value.identifier.id) && |
| 125 | !isRefOrRefLikeMutableType(effect.value.identifier.type) |
| 126 | ) { |
| 127 | contextMutationEffects.set(lvalue.identifier.id, effect); |
| 128 | break effects; |
| 129 | } |
| 130 | break; |
| 131 | } |
| 132 | case 'MutateConditionally': |
| 133 | case 'MutateTransitiveConditionally': { |
| 134 | const knownMutation = contextMutationEffects.get( |
| 135 | effect.value.identifier.id, |
| 136 | ); |
| 137 | if (knownMutation != null) { |
| 138 | contextMutationEffects.set( |
| 139 | lvalue.identifier.id, |
| 140 | knownMutation, |
| 141 | ); |
| 142 | } |
| 143 | break; |
| 144 | } |
| 145 | } |
| 146 | } |
| 147 | } |
| 148 | break; |
| 149 | } |
| 150 | default: { |
| 151 | for (const operand of eachInstructionValueOperand(value)) { |
| 152 | visitOperand(operand); |
| 153 | } |
| 154 | } |
| 155 | } |
| 156 | } |
| 157 | for (const operand of eachTerminalOperand(block.terminal)) { |
| 158 | visitOperand(operand); |
| 159 | } |
| 160 | } |
| 161 | } |