b6657a8ad4
HIR typeck tries to figure out which casts are trivial by doing them as coercions and seeing whether this works. Since HIR typeck is oblivious of lifetimes, this doesn't work for pointer casts that only change the lifetime of the pointee, which are, as borrowck will tell you, not trivial. This change makes it so that raw pointer casts are never considered trivial. This also incidentally fixes the "trivial cast" lint false positive on the same code. Unfortunately, "trivial cast" lints are now never emitted on raw pointer casts, even if they truly are trivial. This could be fixed by also doing the lint in borrowck for raw pointers specifically.
26 lines
739 B
Rust
26 lines
739 B
Rust
// unit-test: InstSimplify
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// compile-flags: -Zinline-mir
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#![crate_type = "lib"]
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#[inline(always)]
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fn generic_cast<T, U>(x: *const T) -> *const U {
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x as *const U
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}
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// EMIT_MIR casts.redundant.InstSimplify.diff
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pub fn redundant<'a, 'b: 'a>(x: *const &'a u8) -> *const &'a u8 {
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// CHECK-LABEL: fn redundant(
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// CHECK: inlined generic_cast
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// CHECK-NOT: as
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generic_cast::<&'a u8, &'b u8>(x) as *const &'a u8
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}
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// EMIT_MIR casts.roundtrip.InstSimplify.diff
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pub fn roundtrip(x: *const u8) -> *const u8 {
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// CHECK-LABEL: fn roundtrip(
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// CHECK: _4 = _1;
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// CHECK: _3 = move _4 as *mut u8 (PtrToPtr);
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// CHECK: _2 = move _3 as *const u8 (PointerCoercion(MutToConstPointer));
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x as *mut u8 as *const u8
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}
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