Make generic const type mismatches not hide trait impls from the trait solver
This commit is contained in:
Oli Scherer
parent
366d112fa6
commit
9454b51b05
7 changed files with 80 additions and 31 deletions
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@ -165,9 +165,9 @@ impl<'tcx> InferCtxt<'tcx> {
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//
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// This probe is probably not strictly necessary but it seems better to be safe and not accidentally find
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// ourselves with a check to find bugs being required for code to compile because it made inference progress.
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let compatible_types = self.probe(|_| {
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self.probe(|_| {
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if a.ty() == b.ty() {
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return Ok(());
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return;
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}
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// We don't have access to trait solving machinery in `rustc_infer` so the logic for determining if the
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@ -177,32 +177,18 @@ impl<'tcx> InferCtxt<'tcx> {
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relation.param_env().and((a.ty(), b.ty())),
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&mut OriginalQueryValues::default(),
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);
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self.tcx.check_tys_might_be_eq(canonical).map_err(|_| {
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self.tcx.check_tys_might_be_eq(canonical).unwrap_or_else(|_| {
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// The error will only be reported later. If we emit an ErrorGuaranteed
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// here, then we will never get to the code that actually emits the error.
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self.tcx.dcx().delayed_bug(format!(
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"cannot relate consts of different types (a={a:?}, b={b:?})",
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))
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})
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));
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// We treat these constants as if they were of the same type, so that any
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// such constants being used in impls make these impls match barring other mismatches.
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// This helps with diagnostics down the road.
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});
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});
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// If the consts have differing types, just bail with a const error with
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// the expected const's type. Specifically, we don't want const infer vars
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// to do any type shapeshifting before and after resolution.
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if let Err(guar) = compatible_types {
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// HACK: equating both sides with `[const error]` eagerly prevents us
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// from leaving unconstrained inference vars during things like impl
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// matching in the solver.
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let a_error = ty::Const::new_error(self.tcx, guar, a.ty());
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if let ty::ConstKind::Infer(InferConst::Var(vid)) = a.kind() {
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return self.unify_const_variable(vid, a_error, relation.param_env());
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}
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let b_error = ty::Const::new_error(self.tcx, guar, b.ty());
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if let ty::ConstKind::Infer(InferConst::Var(vid)) = b.kind() {
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return self.unify_const_variable(vid, b_error, relation.param_env());
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}
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return Ok(if relation.a_is_expected() { a_error } else { b_error });
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}
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match (a.kind(), b.kind()) {
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(
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ty::ConstKind::Infer(InferConst::Var(a_vid)),
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@ -11,3 +11,4 @@ impl<const N: u64> Q for [u8; N] {
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}
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pub fn test() -> [u8; <[u8; 13] as Q>::ASSOC] { todo!() }
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//~^ ERROR: the constant `13` is not of type `u64`
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@ -1,9 +1,23 @@
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error: the constant `13` is not of type `u64`
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--> $DIR/bad-subst-const-kind.rs:13:24
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LL | pub fn test() -> [u8; <[u8; 13] as Q>::ASSOC] { todo!() }
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| ^^^^^^^^ expected `u64`, found `usize`
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note: required for `[u8; 13]` to implement `Q`
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--> $DIR/bad-subst-const-kind.rs:8:20
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LL | impl<const N: u64> Q for [u8; N] {
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| ------------ ^ ^^^^^^^
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| |
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| unsatisfied trait bound introduced here
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error[E0308]: mismatched types
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--> $DIR/bad-subst-const-kind.rs:8:31
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LL | impl<const N: u64> Q for [u8; N] {
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| ^ expected `usize`, found `u64`
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error: aborting due to 1 previous error
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error: aborting due to 2 previous errors
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For more information about this error, try `rustc --explain E0308`.
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@ -7,7 +7,10 @@ trait Q {
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impl<const N: u64> Q for [u8; N] {}
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//~^ ERROR not all trait items implemented
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//~| ERROR mismatched types
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pub fn q_user() -> [u8; <[u8; 13] as Q>::ASSOC] {}
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//~^ ERROR the constant `13` is not of type `u64`
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//~| ERROR mismatched types
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pub fn main() {}
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@ -7,6 +7,35 @@ LL | const ASSOC: usize;
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LL | impl<const N: u64> Q for [u8; N] {}
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ missing `ASSOC` in implementation
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error: aborting due to 1 previous error
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error: the constant `13` is not of type `u64`
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--> $DIR/type_mismatch.rs:12:26
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LL | pub fn q_user() -> [u8; <[u8; 13] as Q>::ASSOC] {}
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| ^^^^^^^^ expected `u64`, found `usize`
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note: required for `[u8; 13]` to implement `Q`
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--> $DIR/type_mismatch.rs:8:20
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LL | impl<const N: u64> Q for [u8; N] {}
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| ------------ ^ ^^^^^^^
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| |
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| unsatisfied trait bound introduced here
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For more information about this error, try `rustc --explain E0046`.
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error[E0308]: mismatched types
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--> $DIR/type_mismatch.rs:12:20
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LL | pub fn q_user() -> [u8; <[u8; 13] as Q>::ASSOC] {}
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| ------ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `[u8; <[u8; 13] as Q>::ASSOC]`, found `()`
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| |
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| implicitly returns `()` as its body has no tail or `return` expression
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error[E0308]: mismatched types
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--> $DIR/type_mismatch.rs:8:31
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LL | impl<const N: u64> Q for [u8; N] {}
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| ^ expected `usize`, found `u64`
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error: aborting due to 4 previous errors
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Some errors have detailed explanations: E0046, E0308.
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For more information about an error, try `rustc --explain E0046`.
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@ -8,5 +8,6 @@ struct S<const L: usize>;
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impl<const N: i32> Copy for S<N> {}
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//~^ ERROR the constant `N` is not of type `usize`
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impl<const M: usize> Copy for S<M> {}
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//~^ ERROR: conflicting implementations of trait `Copy` for type `S<_>`
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fn main() {}
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@ -1,14 +1,29 @@
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error[E0119]: conflicting implementations of trait `Copy` for type `S<_>`
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--> $DIR/bad-const-wf-doesnt-specialize.rs:10:1
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LL | impl<const N: i32> Copy for S<N> {}
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| -------------------------------- first implementation here
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LL |
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LL | impl<const M: usize> Copy for S<M> {}
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `S<_>`
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error: the constant `N` is not of type `usize`
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--> $DIR/bad-const-wf-doesnt-specialize.rs:8:29
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LL | impl<const N: i32> Copy for S<N> {}
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| ^^^^ expected `usize`, found `i32`
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note: required by a bound in `S`
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--> $DIR/bad-const-wf-doesnt-specialize.rs:6:10
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note: required for `S<N>` to implement `Clone`
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--> $DIR/bad-const-wf-doesnt-specialize.rs:5:10
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LL | #[derive(Clone)]
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| ^^^^^
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LL | struct S<const L: usize>;
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| ^^^^^^^^^^^^^^ required by this bound in `S`
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| ----- unsatisfied trait bound introduced in this `derive` macro
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note: required by a bound in `Copy`
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--> $SRC_DIR/core/src/marker.rs:LL:COL
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= note: this error originates in the derive macro `Clone` (in Nightly builds, run with -Z macro-backtrace for more info)
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error: aborting due to 1 previous error
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error: aborting due to 2 previous errors
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For more information about this error, try `rustc --explain E0119`.
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