Compiler: Return type declarations on user functions (VM + JIT)

[PurHur]

Problem

Modern PHP web code uses return types:

function slug(string $s): string { ... }

#55 covers non-void returns in JIT; this issue adds declared return type checking/coercion per strict_types (#156).

Goal

Honor : return types on user functions in VM; JIT emits typed returns where possible.

Tasks

• Read return type from PHPCfg\Func in compileFunction
• VM: coerce/check return value at TYPE_RETURN
• JIT: use declared type for LLVM return value
• PHPT: valid/invalid returns with strict_types=1
• Void return (): void explicit

Acceptance criteria

Returning wrong type throws TypeError when strict_types enabled.

Dependencies

• Language: JIT support for non-void function return types #55 non-void JIT returns
• Language: declare(strict_types=1) enforcement in VM #156 strict_types

Files

• lib/Compiler.php, lib/VM.php, lib/JIT.php