feat(closure): closure parameter type narrowing from call-site literals

[yuan-dian]

Summary

Infer closure parameter types from call-site literal arguments to generate native C++ types instead of php::Var. When all call sites pass the same literal type, the lambda signature uses the native type directly, eliminating runtime type checks.

Performance

Scenario	Before	After	Speedup
fn($x)(3.14) float	28ms	4ms	7x
fn($x)("hello") string	140ms	22ms	6x
fn($x)(true) bool	10ms	3ms	3x
fn($x)(42) int	6ms	3ms	2x
fn($x)($i) variable	35ms	35ms	no change
fn($x)([1,2,3]) array	360ms	360ms	no change

Changes

Core Logic:

• LocalClosureAnalyzer.php: Track call sites per candidate, inferParamTypes() detects int/float/string/bool/array literals, unary ops, boolean expressions, string concatenation, cast expressions, and ConstFetch
• ClosureGenerator.php: Use inferred types in lambda signatures, skip type checks when effectiveType is native, add newClosureWithParameters for closures with type checks
• Translator.php: Wire inferParamTypes() into candidate processing
• FunctionContext.php: Document callSites and inferredParamTypes keys

Tests:

• ClosureParamTypeTest.php: 22 unit tests covering type declarations, call-site literals, multi-call fallback, unary ops, boolean expressions, string concatenation, cast expressions, goto, nested functions, and class method guard
• closure-param-type.php: Test fixture with 20+ scenarios
• closure-param-type-class.php: Class method guard test
• closure-param-type-inference.phpt: End-to-end integration test

How It Works

1. Analysis phase: LocalClosureAnalyzer tracks all call sites for each closure candidate and infers parameter types from literal arguments
2. Code generation: If all call sites pass the same type (or type declaration exists), the lambda uses native C++ type (e.g., php::Int, php::Float) instead of php::Var
3. Fallback: Multiple call sites with different types → php::Var + runtime type check (unchanged behavior)

Scope

• ✅ Scalar type declarations (int, float, string, bool)
• ✅ Array type declarations
• ✅ Call-site literal inference (all scalar types + array)
• ✅ Unary expressions (-42, +42)
• ✅ Boolean expressions (===, ||, instanceof)
• ✅ String concatenation ("hello" . "world")
• ✅ Cast expressions ((int)"42")
• ✅ ConstFetch (true, false)
• ✅ FuncCall (count, strlen, sizeof)
• ❌ Class method closures (guard: stays as Zend closure)
• ❌ Closures with goto (invalidated)
• ❌ Closures with nested functions (invalidated)

Safety

• No behavior change for existing code
• Multi-call closures with different types fall back to php::Var
• Class method closures remain as Zend closures
• Closures with goto/labels are invalidated
• 60 closure tests pass, full test suite 1987 tests (8 pre-existing failures unchanged)