fix(transpiler): fold const enum members that reference const variables

[robobun]

Summary

• Fixes const enum members not being constant-folded when they reference const variables with constant initializers (e.g., const x = 5)
• Pre-populates const_values for simple const declarations before the enum preprocessing pass runs, in both the tree-shaking and non-tree-shaking code paths
• Also checks should_fold_typescript_constant_expressions in handleIdentifier so that const_values are used during enum folding even without the global inlining feature flag

Before: const multiplier = 5; const enum E { A = 1 * multiplier } → kept multiplier as a runtime reference
After: correctly folds to const enum E { A = 5 }, matching TypeScript behavior

Closes #19581

Test plan

• New regression tests in test/regression/issue/19581.test.ts that verify:
  • Enum members referencing const variables are folded in --no-bundle mode
  • Full folding works with --minify (e.g., console.log(25))
  • Simple const variable references in enum values are folded
• All tests fail with USE_SYSTEM_BUN=1 (confirming the bug)
• All tests pass with bun bd test
• Existing test/bundler/esbuild/ts.test.ts tests pass (57/57)
• Existing test/bundler/esbuild/default.test.ts tests pass (150/150)

🤖 Generated with Claude Code

[robobun]

^{Updated 9:54 AM PT - Feb 19th, 2026}

❌ Your commit 2d295315 has 2 failures in Build #37596 (All Failures):

• test/integration/next-pages/test/dev-server.test.ts - 1 failing on 🍎 14 aarch64
• test/js/third_party/mongodb/mongodb.test.ts - 1 failing on 🐧 25.04 x64
• test/js/third_party/mongodb/mongodb.test.ts - 1 failing on 🐧 13 x64
• test/js/third_party/mongodb/mongodb.test.ts - 1 failing on 🐧 3.23 aarch64
• test/js/third_party/mongodb/mongodb.test.ts - 1 failing on 🐧 3.23 x64
• test/js/third_party/mongodb/mongodb.test.ts - 1 failing on 🐧 3.23 x64-baseline
• test/js/third_party/mongodb/mongodb.test.ts - 1 failing on 🍎 14 x64
• test/js/third_party/mongodb/mongodb.test.ts - 1 failing on 🍎 13 x64
• test/js/third_party/mongodb/mongodb.test.ts - 1 failing on 🍎 14 aarch64
• test/js/third_party/mongodb/mongodb.test.ts - 1 failing on 🍎 13 aarch64

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🧪   To try this PR locally:

bunx bun-pr 27167

That installs a local version of the PR into your bun-27167 executable, so you can run:

bun-27167 --bun

[claude]

✅ 2d295 — Looks good!

Reviewed 4 files across src/ast/ and test/regression/issue/: enables const enum members to reference const variables with constant initializers by pre-populating the const_values map before enum preprocessing runs.

[Jarred-Sumner]

Do not add an extra loop over all the statements. Read over esbuild's implementation and understand what they do.

[github-actions]

Closing this PR because it has been inactive for more than 90 days.