Fix enum crash when namespace and enum share a name

[Sumit G (smg99)]

Fixes #64668

Problem

The compiler could panic when a namespace and enum shared the same name and the enum initializer accessed a member from the namespace object.

Fix

• Guard enum value computation so it only runs for actual EnumDeclaration nodes.
• Treat ModuleBlock as a member container for generic member-list access to avoid falling through to a non-enum node.
• Added a regression test covering the merged namespace/enum case.

Validation

• cd tsc && go test -run 'TestLocal/enumMemberListModuleBlock' ./internal/testrunner
• Reproduced the original crash before the fix with go build -o /tmp/tsc ./cmd/tsc && /tmp/tsc /tmp/ts_memberlist_bug.ts, which now emits the expected TS18033 diagnostic instead of panicking.

AI disclosure

This PR was authored with GitHub Copilot assistance and reviewed before submission.

[Copilot]

🟡 Changes recommended

The unrelated ModuleBlock member-list expansion weakens an established AST API invariant.

1 open finding

• Avoid exposing arbitrary namespace statements as module members · New

What changed in this PR

Prevents a compiler panic when merged namespace/enum member access reaches enum value computation.

Changes:

• Guards enum computation by node kind.
• Expands MemberList to module blocks.
• Adds regression coverage and baselines.

File	Description
tsc/​internal/​checker/​checker.go	Guards enum value computation.
tsc/​internal/​ast/​ast.go	Adds module blocks to MemberList.
tsc/​testdata/​tests/​cases/​compiler/​enumMemberListModuleBlock.ts	Adds regression case.
tsc/​testdata/​baselines/​reference/​compiler/​enumMemberListModuleBlock.errors.txt	Captures expected diagnostic.
tsc/​testdata/​baselines/​reference/​compiler/​enumMemberListModuleBlock.js	Captures emitted JavaScript.
tsc/​testdata/​baselines/​reference/​compiler/​enumMemberListModuleBlock.symbols	Captures symbol output.
tsc/​testdata/​baselines/​reference/​compiler/​enumMemberListModuleBlock.types	Captures type output.

🧠 Review effort: Balanced

---

💡 Add a code-review agent skill for context-aware, tailored reviews. Learn more in the docs.

[Sumit G (smg99)]

Addressed the AST API invariant review: removed the unrelated KindModuleBlock branch from Node.MemberList() in commit d064a4c, retaining only the targeted enum guard and regression case. The Microsoft CLA remains pending contributor authorization; I have not accepted it automatically.

[Jake Bailey (jakebailey)]

If you're not a person who can sign a CLA, I don't think you should be sending PRs

[Sumit G (smg99)]

@microsoft-github-policy-service agree

[Sumit G (smg99)]

To clarify: I am submitting this PR personally, as an independent individual contributor, not on behalf of my employer or any company. I can sign the Microsoft CLA in my individual capacity if GitHub still requires it; please let me know if any contributor verification remains outstanding. The earlier AST MemberList review finding has already been addressed in d064a4c.