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nyash-codex 8b44c5009f fix(mir): fix else block scope bug - PHI materialization order

Root Cause:
- Else blocks were not propagating variable assignments to outer scope
- Bug 1 (if_form.rs): PHI materialization happened before variable_map reset,
  causing PHI nodes to be lost
- Bug 2 (phi.rs): Variable merge didn't check if else branch modified variables

Changes:
- src/mir/builder/if_form.rs:93-127
  - Reordered: reset variable_map BEFORE materializing PHI nodes
  - Now matches then-branch pattern (reset → materialize → execute)
  - Applied to both "else" and "no else" branches for consistency
- src/mir/builder/phi.rs:137-154
  - Added else_modified_var check to detect variable modifications
  - Use modified value from else_var_map_end_opt when available
  - Fall back to pre-if value only when truly not modified

Test Results:
✅ Simple block: { x=42 } → 42
✅ If block: if 1 { x=42 } → 42
✅ Else block: if 0 { x=99 } else { x=42 } → 42 (FIXED!)
✅ Stage-B body extraction: "return 42" correctly extracted (was null)

Impact:
- Else block variable assignments now work correctly
- Stage-B compiler body extraction restored
- Selfhost builder path can now function
- Foundation for Phase 21.x progress

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

2025-11-13 20:16:20 +09:00

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Nyash Language Reference – Index

This is the entry point for Nyash language documentation.

Full Language Reference (2025): reference/language/LANGUAGE_REFERENCE_2025.md
Syntax Cheat Sheet: quick-reference/syntax-cheatsheet.md
Phase 12.7 Grammar Specs (ternary, sugar; peek → match に統合):
- Overview: development/roadmap/phases/phase-12.7/grammar-specs/README.md
- Token/Grammar: development/roadmap/phases/phase-12.7/ancp-specs/ANCP-Token-Specification-v1.md
Sugar Transformations (?., ??, |> and friends): parser/sugar.rs (source) and tools/nyfmt/NYFMT_POC_ROADMAP.md
Match Expression (pattern matching): see the Language Reference and EBNF (peek was replaced by match)

Statement separation and semicolons

See: reference/language/statements.md — newline as primary separator; semicolons optional for multiple statements on one line; minimal ASI rules.

Imports and namespaces

See: reference/language/using.md — using syntax, runner resolution, and style guidance.

Variables and scope

See: reference/language/variables-and-scope.md — Block-scoped locals, assignment resolution, and strong/weak reference guidance.

Grammar (EBNF)

See: reference/language/EBNF.md — Stage‑2 grammar specification used by parser implementations.
Unified Members (stored/computed/once/birth_once): see reference/language/EBNF.md “Box Members (Phase 15)” and the Language Reference section. Default ON (disable with NYASH_ENABLE_UNIFIED_MEMBERS=0).

Member exceptions and handlers (Stage‑3)

Postfix catch/cleanup may be attached to computed/once/birth_once/method blocks when Stage‑3 is enabled. Stored members (plain name: Type [= expr]) do not support handlers.

Related implementation notes

Tokenizer: src/tokenizer.rs
Parser (expressions/statements): src/parser/expressions.rs, src/parser/statements.rs
MIR Lowering (expressions): src/mir/builder/exprs.rs and friends

Navigation tips

The “reference/language/LANGUAGE_REFERENCE_2025.md” is the canonical long‑form reference; use the Cheat Sheet for quick syntax lookup.
Phase 12.7 files capture the finalized sugar and new constructs (match (replaces peek), ternary, null‑safe).

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Nyash Language Reference – Index

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