Elide provably-passing return type checks at compile time - #23305
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Without the opcache optimizer every 'return <expr>;' in a typed function executes ZEND_VERIFY_RETURN_TYPE. Skip emitting it when the check provably always passes: - expressions whose opcode always produces a specific type accepted by the return type: comparisons, instanceof, isset/empty and boolean operators produce bool; concatenation produces string; - 'return $this->prop;' where the property is declared in the class being compiled and its type is a subtype of the return type. Property types are invariant under inheritance, and typed property reads always yield conforming values: uninitialized reads throw before the return, and __get()/get-hook results are verified against the property type. Only same-class declarations are visible during method compilation, which keeps the proof local. Closures are excluded (Closure::bind can rebind scopes), as are by-ref returns, generators, union/intersection property types and context-dependent return types (static, callable). Coercion semantics are preserved by requiring the value type set to be a subset of the return type set (e.g. an int property returned as float still emits the check). Getter-style code drops one opcode per return; 'return $x === null;' style predicates drop the check entirely.
staabm
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Aug 16, 2026
Without the opcache optimizer every 'return <expr>;' in a typed function executes ZEND_VERIFY_RETURN_TYPE. Skip emitting it when the check provably always passes: - expressions whose opcode always produces a specific type accepted by the return type: comparisons, instanceof, isset/empty and boolean operators produce bool; concatenation produces string; - 'return $this->prop;' where the property is declared in the class being compiled and its type is a subtype of the return type. Property types are invariant under inheritance, and typed property reads always yield conforming values: uninitialized reads throw before the return, and __get()/get-hook results are verified against the property type. Only same-class declarations are visible during method compilation, which keeps the proof local. Closures are excluded (Closure::bind can rebind scopes), as are by-ref returns, generators, union/intersection property types and context-dependent return types (static, callable). Coercion semantics are preserved by requiring the value type set to be a subset of the return type set (e.g. an int property returned as float still emits the check). Getter-style code drops one opcode per return; 'return $x === null;' style predicates drop the check entirely.
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disclaimer: this change was generated by claude opus. I have little experience with php-src development
Without the opcache optimizer every 'return ;' in a typed function executes ZEND_VERIFY_RETURN_TYPE. Skip emitting it when the check provably always passes:
Closures are excluded (Closure::bind can rebind scopes), as are by-ref returns, generators, union/intersection property types and context-dependent return types (static, callable). Coercion semantics are preserved by requiring the value type set to be a subset of the return type set (e.g. an int property returned as float still emits the check).
Getter-style code drops one opcode per return; 'return $x === null;' style predicates drop the check entirely.
before PR
after PR
using return_type_check_elision_repro.php