Port TypeScript #62722: Widen reverse mapped type properties

[Copilot]

Reverse mapped type inference was returning unwidened literal types, causing them to be treated as valid sources for Excess Property Checking (EPC). This produced spurious errors like 'default' does not exist in type '{ type: unknown; }' when using reverse mapped types with literal-valued properties.

Ported from microsoft/TypeScript#62722.

• Wrap inferReverseMappedTypeWorker return with getWidenedType() so inferred property types like false widen to boolean

// Before
return core.OrElse(c.getTypeFromInference(inference), c.unknownType)

// After
return c.getWidenedType(core.OrElse(c.getTypeFromInference(inference), c.unknownType))

• Baseline updates: 4 .diff files and 2 error baselines deleted (Go now matches TS output for these cases)

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[Copilot]

Pull request overview

Ports TypeScript behavior for reverse mapped type inference by widening inferred property types to avoid spurious Excess Property Checking (EPC) errors, and updates/removes baselines accordingly.

Changes:

• Widen the return type of inferReverseMappedTypeWorker via getWidenedType(...).
• Update .types baselines for reverse mapped type inference widening scenarios.
• Remove now-unneeded .diff baselines and clear error baselines that should no longer report EPC errors.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
internal/checker/inference.go	Widen reverse mapped type inference results to avoid propagating literal types into EPC.
testdata/baselines/reference/submodule/compiler/reverseMappedTypeInferenceWidening2.types	Updates expected type output for the “widening2” scenario.
testdata/baselines/reference/submodule/compiler/reverseMappedTypeInferenceWidening1.types	Updates expected type output for the “widening1” scenario.
testdata/baselines/reference/submodule/compiler/reverseMappedTypeInferenceWidening2.types.diff	Removes obsolete baseline diff after output alignment.
testdata/baselines/reference/submodule/compiler/reverseMappedTypeInferenceWidening1.types.diff	Removes obsolete baseline diff after output alignment.
testdata/baselines/reference/submodule/compiler/reverseMappedTypeInferenceWidening2.errors.txt.diff	Removes obsolete error diff baseline (errors no longer expected).
testdata/baselines/reference/submodule/compiler/reverseMappedTypeInferenceWidening1.errors.txt.diff	Removes obsolete error diff baseline (errors no longer expected).
testdata/baselines/reference/submodule/compiler/reverseMappedTypeInferenceWidening2.errors.txt	Clears expected errors (now none).
testdata/baselines/reference/submodule/compiler/reverseMappedTypeInferenceWidening1.errors.txt	Clears expected errors (now none).