perf(compiler): infer closure parameter types from declarations and call sites

[yuan-dian]

Summary

Add closure parameter type inference to the TypePHP compiler. When closure parameters have PHP type declarations or can be inferred from single call-site literal arguments, the compiler now generates native C++ types (php::Int, php::Float, php::Bool, php::Str, php::Array) instead of php::Var. This eliminates runtime type checks and enables native C++ arithmetic, resulting in significant performance improvements.

Performance

Benchmark	Before	After	Speedup
fn($x)(42)	64ms	5ms	12.8x
fn($x)(3.14)	64ms	7ms	9.1x
fn($x)(true)	64ms	6ms	10.7x
fn($x)(-42)	64ms	5ms	12.8x
fn($x)(1===2)	64ms	6ms	10.7x
fn($x)("a"."b")	64ms	7ms	9.1x
fn(int $x)(42)	76ms	5ms	15.2x

What's Changed

Phase 1: Type Declaration Inference

PHP type hints on closure parameters are used to generate native C++ types:

$fn = fn(int $a) => $a + 1;    // php::Int a
$fn = fn(float $a) => $a * 2;  // php::Float a
$fn = fn(bool $a) => !$a;      // php::Bool a
$fn = fn(string $a) => $a;     // php::Str a
$fn = fn(array $a) => $a;      // php::Array a

Phase 2: Call-Site Literal Inference

When a closure is called exactly once with literal arguments, the parameter type is inferred:

$fn = fn($x) => $x + 1;
$fn(42);        // php::Int x
$fn(-3.14);     // php::Float x
$fn(true);      // php::Bool x
$fn([1, 2, 3]); // php::Array x

Edge Cases Handled

• Unary operators: -42 → php::Int, +3.14 → php::Float
• Boolean expressions: 1 === 2, true || false, $obj instanceof Foo → php::Bool
• String concatenation: "hello" . "world" → php::Str (both operands must be strings)
• Multiple call sites: Falls back to php::Var when types conflict across calls

Bug Fix

Fixed a variable name collision in Translator.php where the foreach loop variable $name overwrote the function's native C++ name, causing incorrect output for functions with closures.

Files Changed

File	Changes
src/Analysis/LocalClosureAnalyzer.php	+100/-2 — inferParamTypes(), detectArgType(), call-site tracking
src/Generator/ClosureGenerator.php	+36/-2 — Use inferred types, skip redundant type checks
src/Translator.php	+6/-1 — Wire analyzer output, fix $name collision
phpunit/code/closure-param-type.php	+113 — 17 test scenarios
phpunit/src/ClosureParamTypeTest.php	+110 — 6 unit tests
phpunit/src/LocalClosureCodegenTest.php	+2/-1 — Updated assertion
tests/compiler/closure/closure-param-type-inference.phpt	+81 — Integration test

Test Coverage

OK (6 tests, 20 assertions)

• testTypeHintParametersUseNativeCppTypes — Verifies type-hinted params generate native types
• testCallSiteInferredParametersUseNativeCppTypes — Verifies literal call-site inference
• testMultiCallClosureRemainsPhpVar — Verifies fallback to php::Var for multiple calls
• testUnaryMinusInfersNativeType — Verifies -42 → php::Int, -3.14 → php::Float
• testBooleanExpressionsInferBoolType — Verifies comparison/logical ops → php::Bool
• testConcatStringInference — Verifies string concat → php::Str

[yuan-dian]

Close, wait for all problems to be solved and resubmit PR.