fix: Fix MemberList panic on merged enum element access

[Andre Fajar N (andre-fajar-n)]

Fixes #64668
AI assistance disclosure: This patch was authored with Cursor (AI coding agent). I
have read and understood the change, and I will shepherd review and revisions myself.

Analysis

When an enum and a namespace share a name, element access like E["C"] in an enum
member initializer can resolve a namespace export (e.g. a class) via
rootSymbol.Exports()[name].
The element-access path in evaluateEntity treated any non-nil export as an enum member
and called getEnumMemberValue → computeEnumMemberValues(node.Parent) → Members().
For a class declaration, Parent is a ModuleBlock, so Node.MemberList panicked:
panic: Unhandled case in Node.MemberList: KindModuleBlock
Repro:

namespace E { export class C {} }
enum E { D = E["C"] }

The identifier/property-access path already requires SymbolFlagsEnumMember; element
access did not.

Fix

In evaluateEntity's KindElementAccessExpression branch, only constant-evaluate when
the export has SymbolFlagsEnumMember (same guard as the identifier path).
Non-enum-member exports fall through to a non-constant result and produce a normal
diagnostic (TS18033) instead of crashing.
Alternate considered: widening Node.MemberList to accept KindModuleBlock — rejected;
the bug is incorrect enum evaluation, not a missing AST list case.

[Copilot]

🟡 Changes recommended

Alias exports targeting enum members must be resolved before applying the new flag guard.

1 open finding

• Resolve aliases before checking computed enum members · New

What changed in this PR

Prevents a compiler panic when bracket access resolves to a non-enum export on a merged enum/namespace.

Changes:

• Guards enum evaluation with SymbolFlagsEnumMember.
• Adds a regression test and diagnostic, emit, type, and symbol baselines.

File	Description
tsc/​internal/​checker/​checker.go	Restricts bracket-access enum evaluation.
tsc/​testdata/​tests/​cases/​compiler/​enumInitializerNamespaceExportElementAccess.ts	Adds the crash regression case.
tsc/​testdata/​baselines/​reference/​compiler/​enumInitializerNamespaceExportElementAccess.errors.txt	Records TS18033.
tsc/​testdata/​baselines/​reference/​compiler/​enumInitializerNamespaceExportElementAccess.js	Records emitted JavaScript.
tsc/​testdata/​baselines/​reference/​compiler/​enumInitializerNamespaceExportElementAccess.symbols	Records resolved symbols.
tsc/​testdata/​baselines/​reference/​compiler/​enumInitializerNamespaceExportElementAccess.types	Records inferred types.

🧠 Review effort: Balanced

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[Copilot]

🟢 Approval recommended

The guard fixes the panic while preserving aliased enum-member evaluation with focused regression coverage.

0 open findings

1 resolved since last review

• Resolve aliases before checking computed enum members

🧠 Review effort: Balanced