gccrs: Fix cast rules logic to try simple casts then fall back to coercions#3900
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This case:
let i = 1;
let j = i as i64;
'i' is meant to default to i32 but the inference was making both of these
i64 because the code was prefering coercion logic which can end up with a
default unify which causes the ?integer to unify with i64 making them both
i64.
But all we need to do is allow the simple cast rules to run first then
fallback to coercions but special consideration has to be made to ensure
that if there are dyn objects needed then this needs a unsize coercion, but
also we need to ensure the underlying types are a valid simple cast too
otherwise these also need to fallback to the coercion code.
Fixes #2680
gcc/rust/ChangeLog:
* typecheck/rust-casts.cc (TypeCastRules::resolve): optional emit_error flag
(TypeCastRules::check): try the simple cast rules then fallback to coercions
(TypeCastRules::check_ptr_ptr_cast): ensure the underlying's
(TypeCastRules::emit_cast_error): make this a static helper
* typecheck/rust-casts.h: new emit_error prototype
gcc/testsuite/ChangeLog:
* rust/compile/issue-2680.rs: New test.
Signed-off-by: Philip Herron <herron.philip@googlemail.com>
philberty
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This case:
'i' is meant to default to i32 but the inference was making both of these i64 because the code was prefering coercion logic which can end up with a default unify which causes the ?integer to unify with i64 making them both i64.
But all we need to do is allow the simple cast rules to run first then fallback to coercions but special consideration has to be made to ensure that if there are dyn objects needed then this needs a unsize coercion, but also we need to ensure the underlying types are a valid simple cast too otherwise these also need to fallback to the coercion code.
Fixes #2680
gcc/rust/ChangeLog:
gcc/testsuite/ChangeLog: