Proposal: Make match expression a constant expression (when parts are constant) #5951
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I'd forgotten to check if this was part of the original RFC. It seems like constant expressions using match can be thought of as a much more concise form than chained ternary operators. It's already possible for constant expressions to throw, e.g. - Undeclared constants. - Wrong operands for unary or binary operators.
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I don't really see a usefulness for match in constant expression context, but I'd be okay with allowing it for the sake of consistency. You should probably start an internals thread about this, to decide which version to target. |
Zend/tests/match/044.phpt
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| // Here, this test uses strtolower because the locale dependence and change to the string |
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Oops, got sidetracked checking if constant expressions were proposed before and forgot to update this.
On second thought, I don't think I'll use this often enough to justify working on this. Both of the alternatives aren't perfect, but I'd probably still vote yes on either of them if someone else started the RFC process for them (e.g. based on this code)
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| @@ -654,6 +654,51 @@ ZEND_API int ZEND_FASTCALL zend_ast_evaluate(zval *result, zend_ast *ast, zend_c | |||
| zval_ptr_dtor_nogc(&op1); | |||
| } | |||
| break; | |||
| case ZEND_AST_MATCH: | |||
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zend_const_expr_to_zval would also benefit from being updated to support ZEND_AST_MATCH, but it'd only matter if this were to be supported in constant expressions
Motivations: This would be potentially useful for class constant and static variable declarations that would previously need to use
(some_value === b ? c : (some_value === d || some_value === d2 ? e : f))instead ofmatch (some_value) { b => c, d, d2 => e, default => f}I'd forgotten to check if this was part of the original RFC earlier.
It seems like constant expressions using match can be thought of as a much
more concise form of conditional than chained ternary(a?b:c) operators.
It's already possible for constant expressions to throw, e.g.
(But the UnhandledMatchError would be new,)
@nikic @iluuu1994 - thoughts on allowing this for PHP 8.0 or 8.1? I'd personally assumed this would be an implementation oversight since I don't remember seeing constant expressions discussed (it was a large PR)
Prior to this proposed change, the error message was always
Constant expression contains invalid operations