Port JS specific code for this.xxx assignment declaration typing#3680
Merged
ahejlsberg merged 2 commits intomainfrom May 2, 2026
Merged
Port JS specific code for this.xxx assignment declaration typing#3680ahejlsberg merged 2 commits intomainfrom
this.xxx assignment declaration typing#3680ahejlsberg merged 2 commits intomainfrom
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ahejlsberg
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DanielRosenwasser,
Copilot,
jakebailey and
sandersn
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Pull request overview
Ports missing TypeScript checker logic needed to correctly infer types for JavaScript this.<prop> assignment declarations (especially around self-referential assignments and empty array literals), aligning tsgo behavior with tsc for issue #3667.
Changes:
- Adds a new compiler test case covering
this.<prop>assignment-declaration type inference across constructors vs methods (and empty array literal behavior). - Updates
Checker.getWidenedTypeForAssignmentDeclarationto ignore non-contributing assignment initializer types and to avoid producing an empty union. - Extends
getAssignmentDeclarationInitializerTypewith JSthis-property self-reference detection and correct empty-array widening/diagnostics behavior.
Reviewed changes
Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.
| File | Description |
|---|---|
internal/checker/checker.go |
Adjusts JS assignment-declaration type inference to skip self-referential this.<prop> initializers and handle empty-type unions safely. |
testdata/tests/cases/compiler/thisPropertyAssignmentTyping.ts |
New regression test covering constructor vs method typing for this.<prop> assignment declarations in JS. |
testdata/baselines/reference/compiler/thisPropertyAssignmentTyping.* |
Adds expected baselines (types/symbols/errors) for the new test. |
| } | ||
| } | ||
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||
| // When this.xxx assigmment declarations occur only in methods, an assigned empty array |
| this.bar = []; // Error: Implicit any[] | ||
| this.bar.push("baz"); | ||
| this.bar; // any[] | ||
| } |
Comment on lines
+17763
to
+17766
| if ast.IsFunctionLike(node) { | ||
| return false | ||
| } | ||
| return node.ForEachChild(visit) |
jakebailey
approved these changes
May 1, 2026
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jakebailey
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jakebailey
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always love when we don't have tests for something
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This PR ports missing code for typing of
this.xxxassignment declarations in JavaScript. See here for analysis.Fixes #3667.