mathieu/os-rust
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

Rollup merge of #78249 - lcnr:ct-infer-origin, r=varkor

Browse source 
improve const infer error

For type inference we probably have to be careful about subtyping and stuff but considering that subtyping shouldn't be relevant for constants I don't really see a reason why we may not want to reuse the const origin here.

r? `@varkor`
This commit is contained in:
Jonas Schievink 2020-10-24 14:12:06 +02:00 • committed by GitHub
commit 77cd5b5485
No known key found for this signature in database
GPG key ID: 4AEE18F83AFDEB23
2 changed files with 9 additions and 18 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

25
compiler/rustc_middle/src/infer/unify_key.rs
View file

@ -175,19 +175,15 @@ impl<'tcx> UnifyKey for ty::ConstVid<'tcx> {
impl<'tcx> UnifyValue for ConstVarValue<'tcx> {
type Error = (&'tcx ty::Const<'tcx>, &'tcx ty::Const<'tcx>);
fn unify_values(value1: &Self, value2: &Self) -> Result<Self, Self::Error> {
let (val, span) = match (value1.val, value2.val) {
fn unify_values(&value1: &Self, &value2: &Self) -> Result<Self, Self::Error> {
Ok(match (value1.val, value2.val) {
(ConstVariableValue::Known { .. }, ConstVariableValue::Known { .. }) => {
bug!("equating two const variables, both of which have known values")
}
// If one side is known, prefer that one.
(ConstVariableValue::Known { .. }, ConstVariableValue::Unknown { .. }) => {
(value1.val, value1.origin.span)
}
(ConstVariableValue::Unknown { .. }, ConstVariableValue::Known { .. }) => {
(value2.val, value2.origin.span)
}
(ConstVariableValue::Known { .. }, ConstVariableValue::Unknown { .. }) => value1,
(ConstVariableValue::Unknown { .. }, ConstVariableValue::Known { .. }) => value2,
// If both sides are *unknown*, it hardly matters, does it?
(
@ -200,16 +196,11 @@ impl<'tcx> UnifyValue for ConstVarValue<'tcx> {
// universe is the minimum of the two universes, because that is
// the one which contains the fewest names in scope.
let universe = cmp::min(universe1, universe2);
(ConstVariableValue::Unknown { universe }, value1.origin.span)
ConstVarValue {
val: ConstVariableValue::Unknown { universe },
origin: value1.origin,
}
}
};
Ok(ConstVarValue {
origin: ConstVariableOrigin {
kind: ConstVariableOriginKind::ConstInference,
span: span,
},
val,
})
}
}

2
src/test/ui/const-generics/infer/issue-77092.stderr
View file

@ -2,7 +2,7 @@ error[E0282]: type annotations needed
--> $DIR/issue-77092.rs:13:26
|
LL | println!("{:?}", take_array_from_mut(&mut arr, i));
| ^^^^^^^^^^^^^^^^^^^ cannot infer the value of the constant `{_: usize}`
| ^^^^^^^^^^^^^^^^^^^ cannot infer the value of const parameter `N` declared on the function `take_array_from_mut`
error: aborting due to previous error