Fix NaN-valued enum members creating distinct literal types

[Copilot]

Go maps use IEEE 754 equality for key comparison, where NaN != NaN. This means map lookups with NaN keys always miss, causing each NaN-valued enum member to get a distinct literal type.

enum E {
  A = NaN,
  B = NaN,
}
const a: E.A = E.B; // TS2322 in tsgo, valid in TypeScript

TypeScript's JS Map treats NaN === NaN for key purposes, so this isn't an issue there.

Changes

• getNumberLiteralType: Added a dedicated nanType *Type field to bypass the map[jsnum.Number]*Type lookup for NaN values
• getEnumLiteralType: Added enumNaNLiteralTypes map[*ast.Symbol]*Type keyed by enum symbol, so NaN members within the same enum share a type while different enums remain distinct
• Removes the enumConstantMembers.types.diff baseline (convergence with TypeScript)

[jakebailey]

Yep, this is what I expected the fix to be

[Copilot]

Pull request overview

Fixes a Go-specific bug where NaN-valued enum members produced distinct literal types because Go map lookups always miss on NaN keys (IEEE 754 NaN != NaN). The fix routes NaN values through dedicated cache fields, ensuring NaN members within the same enum share a literal type (matching TypeScript's Map behavior which treats NaN keys as equal).

Changes:

• Added dedicated nanType field to bypass map lookup for plain numeric NaN literals.
• Added enumNaNLiteralTypes map[*ast.Symbol]*Type keyed by enum symbol so NaN enum members share a type per enum.
• Added compiler test and removed obsolete enumConstantMembers.types.diff baseline (now converged with TypeScript).

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
internal/checker/checker.go	Add nanType and enumNaNLiteralTypes caches; special-case NaN in getNumberLiteralType and getEnumLiteralType.
testdata/tests/cases/compiler/enumNaNValues.ts	New regression test covering NaN members within and across enums.
testdata/baselines/reference/compiler/enumNaNValues.*	New baselines for the regression test.
testdata/baselines/reference/compiler/enumAutoIncrementValue.types	Baseline update reflecting converged literal type identity.
testdata/baselines/reference/submodule/conformance/enumConstantMembers.types	Submodule baseline now matches TS reference.
testdata/baselines/reference/submodule/conformance/enumConstantMembers.types.diff	Removed (convergence with TypeScript).