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Improve suggestion for unit Option/Result at the end of a block.

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This commit is contained in:
Mara Bos 2021-11-04 17:56:04 +01:00
parent 483cff7ed3
commit 453e2423e6
1 changed files with 45 additions and 0 deletions
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45
compiler/rustc_typeck/src/check/demand.rs
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@ -199,6 +199,51 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
return;
}
// If the expression is of type () and it's the return expression of a block,
// we suggest adding a separate return expression instead.
// (To avoid things like suggesting `Ok(while .. { .. })`.)
if expr_ty.is_unit() {
if let Some(hir::Node::Block(&hir::Block {
span: block_span, expr: Some(e), ..
})) = self.tcx.hir().find(self.tcx.hir().get_parent_node(expr.hir_id))
{
if e.hir_id == expr.hir_id {
if let Some(span) = expr.span.find_ancestor_inside(block_span) {
let return_suggestions =
if self.tcx.is_diagnostic_item(sym::Result, expected_adt.did) {
vec!["Ok(())".to_string()]
} else if self.tcx.is_diagnostic_item(sym::Option, expected_adt.did)
{
vec!["None".to_string(), "Some(())".to_string()]
} else {
return;
};
if let Some(indent) =
self.tcx.sess.source_map().indentation_before(span.shrink_to_lo())
{
// Add a semicolon, except after `}`.
let semicolon =
match self.tcx.sess.source_map().span_to_snippet(span) {
Ok(s) if s.ends_with('}') => "",
_ => ";",
};
err.multipart_suggestions(
"try adding an expression at the end of the block",
return_suggestions.into_iter().map(|r| {
vec![(
span.shrink_to_hi(),
format!("{}\n{}{}", semicolon, indent, r),
)]
}),
Applicability::MaybeIncorrect,
);
}
return;
}
}
}
}
let mut compatible_variants = expected_adt
.variants
.iter()