55 lines
1.1 KiB
Rust
55 lines
1.1 KiB
Rust
use std::ops::{Deref, DerefMut};
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trait Happy {}
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struct LDM;
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impl Happy for &mut LDM {}
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struct Foo(LDM);
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struct Bar(Foo);
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struct Baz(Bar);
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impl Deref for Foo {
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type Target = LDM;
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fn deref(&self) -> &Self::Target {
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&self.0
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}
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}
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impl Deref for Bar {
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type Target = Foo;
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fn deref(&self) -> &Self::Target {
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&self.0
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}
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}
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impl Deref for Baz {
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type Target = Bar;
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fn deref(&self) -> &Self::Target {
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&self.0
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}
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}
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impl DerefMut for Foo {
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fn deref_mut(&mut self) -> &mut Self::Target {
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&mut self.0
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}
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}
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impl DerefMut for Bar {
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fn deref_mut(&mut self) -> &mut Self::Target {
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&mut self.0
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}
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}
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impl DerefMut for Baz {
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fn deref_mut(&mut self) -> &mut Self::Target {
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&mut self.0
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}
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}
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fn foo<T>(_: T) where T: Happy {}
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fn main() {
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// Currently the compiler doesn't try to suggest dereferences for situations
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// where DerefMut involves. So this test is meant to ensure compiler doesn't
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// generate incorrect help message.
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let mut baz = Baz(Bar(Foo(LDM)));
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foo(&mut baz);
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//~^ ERROR the trait bound `&mut Baz: Happy` is not satisfied
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}
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