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Improve the error when an opaque type captures ReEmtpty

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This commit is contained in:
Matthew Jasper 2020-05-19 20:18:39 +01:00
parent 33f90f213d
commit 187bfb333b
1 changed files with 15 additions and 2 deletions
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17
src/librustc_infer/infer/error_reporting/mod.rs
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@ -297,7 +297,18 @@ pub fn unexpected_hidden_region_diagnostic(
);
// Explain the region we are capturing.
if let ty::ReEarlyBound(_) | ty::ReFree(_) | ty::ReStatic | ty::ReEmpty(_) = hidden_region {
match hidden_region {
ty::ReEmpty(ty::UniverseIndex::ROOT) => {
// All lifetimes shorter than the function body are `empty` in
// lexical region resolution. The default explanation of "an empty
// lifetime" isn't really accurate here.
let message = format!(
"hidden type `{}` captures lifetime smaller than the function body",
hidden_ty
);
err.span_note(span, &message);
}
ty::ReEarlyBound(_) | ty::ReFree(_) | ty::ReStatic | ty::ReEmpty(_) => {
// Assuming regionck succeeded (*), we ought to always be
// capturing *some* region from the fn header, and hence it
// ought to be free. So under normal circumstances, we will go
@ -313,7 +324,8 @@ pub fn unexpected_hidden_region_diagnostic(
hidden_region,
"",
);
} else {
}
_ => {
// Ugh. This is a painful case: the hidden region is not one
// that we can easily summarize or explain. This can happen
// in a case like
@ -358,6 +370,7 @@ pub fn unexpected_hidden_region_diagnostic(
);
}
}
}
err
}