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Rollup merge of #90930 - Nilstrieb:fix-non-const-value-ice, r=estebank

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Fix `non-constant value` ICE (#90878)

This also fixes the same suggestion, which was kind of broken, because it just searched for the last occurence of `const` to replace with a `let`. This works great in some cases, but when there is no const and a leading space to the file, it doesn't work and panic with overflow because it thought that it had found a const.

I also changed the suggestion to only trigger if the `const` and the non-constant value are on the same line, because if they aren't, the suggestion is very likely to be wrong.

Also don't trigger the suggestion if the found `const` is on line 0, because that triggers the ICE.

Asking Esteban to review since he was the last one to change the relevant code.

r? ``@estebank``

Fixes #90878
This commit is contained in:
Matthias Krüger 2021-11-20 10:21:14 +01:00 • committed by GitHub
commit 79935714f3
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11 changed files with 125 additions and 3 deletions
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16
compiler/rustc_resolve/src/diagnostics.rs
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@ -450,12 +450,24 @@ impl<'a> Resolver<'a> {
// let foo =...
// ^^^ given this Span
// ------- get this Span to have an applicable suggestion
// edit:
// only do this if the const and usage of the non-constant value are on the same line
// the further the two are apart, the higher the chance of the suggestion being wrong
// also make sure that the pos for the suggestion is not 0 (ICE #90878)
let sp =
self.session.source_map().span_extend_to_prev_str(ident.span, current, true);
if sp.lo().0 == 0 {
let pos_for_suggestion = sp.lo().0.saturating_sub(current.len() as u32);
if sp.lo().0 == 0
|| pos_for_suggestion == 0
|| self.session.source_map().is_multiline(sp)
{
err.span_label(ident.span, &format!("this would need to be a `{}`", sugg));
} else {
let sp = sp.with_lo(BytePos(sp.lo().0 - current.len() as u32));
let sp = sp.with_lo(BytePos(pos_for_suggestion));
err.span_suggestion(
sp,
&format!("consider using `{}` instead of `{}`", sugg, current),