Language: match expression (PHP 8)

[PurHur]

Problem

match ($x) { ... } is not compiled (Expr_Match maps to #143 in UnsupportedRegistry). Routers and modern PHP use match for clean path dispatch; 003-MiniWebApp uses switch today (#96 ✅) but future refactors may prefer match.

Goal

match with literal / int / string arms and a default arm (no guard expressions in v1):

echo match ($method) {
    'GET' => 'get',
    'POST' => 'post',
    default => 'other',
};

VM + JIT + AOT parity with Zend for simple arms.

Implementation hints

Layer	Files	Notes
Compiler	lib/Compiler.php compileExpr	Lower to chained compare + jump or reuse #96 switch machinery
CFG	php-cfg Expr_Match arms	One block per arm; default as fall-through
VM	lib/VM.php	New opcode or desugar to TYPE_SWITCH
JIT	lib/JIT.php	Mirror switch LLVM branch tree
Lint	lib/Lint/UnsupportedRegistry.php	Remove Expr_Match → 143 when done

Tests

• test/compliance/cases/language_match_*.phpt
• Optional: refactor snippet in examples/003-MiniWebApp only after VM green (Reference app: MiniWebApp runtime green (lint 0, VM serve, routes) #539)

Acceptance criteria

docker run --rm -i -w /compiler php-compiler:22.04-dev bash -lc '
  tar -xf - && php bin/vm.php -r "echo match (2) { 1 => \"a\", 2 => \"b\", default => \"c\" };"
'

Prints b. JIT/AOT compile the same snippet without throw.

Dependencies

• JIT: Implement switch/case opcodes (TYPE_CASE) — VM works, JIT stubbed #96 switch (reuse lowering)
• Independent of Language: Class methods and property access in JIT #58 OOP (nice-to-have for routers)

Verification

./script/ci-local.sh --filter VMTest — local/Docker only (#394 GHA off).

Links

• 🗺️ ROADMAP: Self-host + web-capable PHP subset (living) #78 ROADMAP Phase 1
• Web: MiniWebApp routing pattern (front controller + path dispatch) #210 routing spec (may reference match later)

[PurHur]

Implementation hints (batch 47 — expanded)

match is sugar for a switch with strict comparison (===). Not used in 003-MiniWebApp today; lands after core switch is stable.

Compiler strategy

Step	File	Notes
Desugar	lib/Compiler.php	Expr_Match → chain of JumpIf + compare blocks (or extend existing Switch_ lowering #192 ✅)
Condition	each arm	=== between subject and arm expression (no coercion)
Default	MatchArm default	fall-through to default block
Lint	lib/Lint/UnsupportedRegistry.php	Remove when VM green

VM

• Reuse TYPE_SWITCH / compare opcodes if switch already handles int/string
• Subject evaluated once into temp slot

JIT

• Mirror switch JIT table (Language: while, do-while, and for loops (CFG → VM → JIT) #192 path) with strict compare opcodes
• Defer arm side-effects with bindings until selected arm runs

PHPT

test/compliance/cases/language/match_scalar.phpt
test/compliance/cases/language/match_default.phpt

Capabilities

• script/capability-syntax-lib.php — row match expression → yes when VM passes
• Regenerate docs/capabilities-syntax.md

Verify

./script/ci-fast.sh --filter match

Dependencies

• Language: while, do-while, and for loops (CFG → VM → JIT) #192 ✅ loops/switch baseline
• Language: Null coalescing operator (??) in compiler pipeline #99 ✅ ?? (similar CFG plumbing)

[PurHur]

Implemented in #1243 (php-cfg match lowering + compliance PHPTs).