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Add instantiated symbol mapper into context mapper when reprinting nodes we instantiate before printing - #64680
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Wesley Wigham (weswigham) wants to merge 1 commit into
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…des we instantiate
Wesley Wigham (weswigham)
requested review from
Gabriela Araujo Britto (gabritto) and
Jake Bailey (jakebailey)
and
a balanced review from Copilot
October 7, 2026 22:50
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🟡 Changes recommended
Mapper self-composition can over-instantiate types, and the regression test does not reproduce the linked issue’s required signature shape.
2 open findings
What changed in this PR
Fixes declaration emit leaking uninstantiated type parameters by propagating symbol mappers during type-node serialization.
Changes:
- Composes instantiated-symbol mappers into node-builder context.
- Adds compiler and transpile regression coverage.
- Updates affected type and declaration baselines.
| File | Description |
|---|---|
tsc/internal/checker/nodebuilderimpl.go |
Propagates instantiated-symbol mappers. |
tsc/internal/checker/pseudotypenodebuilder.go |
Falls back when direct nodes require mapping. |
tsc/testdata/tests/cases/compiler/declarationEmitUninstantiatedConditionalTypeParameters.ts |
Adds declaration-emit regression test. |
tsc/testdata/tests/cases/transpile/declarationEmitUnresolvedGenericAnnotations.ts |
Tests unresolved generic annotations. |
tsc/testdata/baselines/reference/transpile/declarationEmitUnresolvedGenericAnnotations.d.ts |
Records transpile declaration output. |
tsc/testdata/baselines/reference/compiler/declarationEmitUninstantiatedConditionalTypeParameters.js |
Records declaration emit. |
tsc/testdata/baselines/reference/compiler/declarationEmitUninstantiatedConditionalTypeParameters.symbols |
Records symbol output. |
tsc/testdata/baselines/reference/compiler/declarationEmitUninstantiatedConditionalTypeParameters.types |
Records inferred types. |
tsc/testdata/baselines/reference/compiler/declarationsWithRecursiveInternalTypesProduceUniqueTypeParams.types |
Updates recursive-type output. |
tsc/testdata/baselines/reference/compiler/es2018ObjectAssign.types |
Updates union ordering. |
tsc/testdata/baselines/reference/conformance/usePromiseFinally(target=es2015).types |
Updates Promise type ordering. |
tsc/testdata/baselines/reference/conformance/parserRealSource8.types |
Updates instantiated method display. |
tsc/testdata/baselines/reference/conformance/parserRealSource14.types |
Updates instantiated array method display. |
🧠 Review effort: Balanced
Comment on lines
+2305
to
+2307
| if symbol != nil && symbol.CheckFlags&ast.CheckFlagsInstantiated != 0 { | ||
| b.ctx.mapper = b.ch.combineTypeMappers(b.ch.valueSymbolLinks.Get(symbol).mapper, oldMapper) | ||
| } |
Comment on lines
+13
to
+14
| interface Builder<TOutputOut> { | ||
| query<T>(resolver: () => T): { output: TOutputOut extends "unset" ? T : TOutputOut }; |
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Fixes #64614
The instantiated symbol mapper from the inferred
querycall wasn't being included in the type we were serializing, so we producing uninstantiated type parameters. By merging it into the node builder context mapper, it correctly propagates down into the nodes we try and serialize for the return type for that signature (...and in turn evaluates it, producing a follow-onanyfrom the missing import, but the project hasnoImplicitAny: falseso what are you gonna do)