Fixed control flow Analysis of aliased discriminants with parenthesized initializers #61788
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Pull Request Overview
This PR fixes an issue where discriminant properties aliased through parenthesized or destructured initializers weren't correctly recognized in control-flow analysis.
- Added comprehensive tests covering both direct and parenthesized/destructured alias patterns.
- Refactored the alias resolution logic in the type checker to use a helper that skips parentheses.
- Introduced
getCandidateVariableDeclarationInitializerto centralize initializer extraction.
Reviewed Changes
Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.
| File | Description |
|---|---|
| tests/cases/conformance/controlFlow/controlFlowAliasing2.ts | New tests for aliased discriminants with various initializer forms |
| tests/baselines/reference/controlFlowAliasing2.symbols | Baseline update for the new conformance tests |
| src/compiler/checker.ts | Extracted initializer logic into a helper and updated alias-matching branches |
Comments suppressed due to low confidence (1)
src/compiler/checker.ts:29266
- [nitpick] Consider renaming this helper to something shorter like
getInitializerSkippingParensorextractInitializerfor improved readability.
function getCandidateVariableDeclarationInitializer(node: Node) {
| return declaration; | ||
| } | ||
| } | ||
| } | ||
| } | ||
| return undefined; | ||
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| function getCandidateVariableDeclarationInitializer(node: Node) { |
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Add a JSDoc comment above this helper to explain that it skips parentheses and returns an initializer only for untyped variable declarations.
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| isVariableDeclaration(parent) && !parent.type && parent.initializer && (isIdentifier(parent.initializer) || isAccessExpression(parent.initializer)) && | ||
| isMatchingReference(reference, parent.initializer) | ||
| ) { | ||
| initializer = getCandidateVariableDeclarationInitializer(declaration.parent.parent); |
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To avoid potential misuse, you might explicitly check that declaration.parent.parent is indeed a VariableDeclaration before passing it to the helper.
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| isMatchingReference(reference, declaration.initializer.expression) | ||
| ) { | ||
| return declaration.initializer; | ||
| if (initializer && isAccessExpression(initializer) && isMatchingReference(reference, initializer.expression)) { |
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[nitpick] Instead of reusing initializer for both branches, consider using separate variables (e.g., directInit and destructuredInit) to clarify the two distinct alias checks.
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fixes #61784