detect redundant nested match #13798
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| @@ -108,6 +108,28 @@ fn check_arm<'tcx>( | |||
| "the outer pattern can be modified to include the inner pattern", | |||
| ); | |||
| }); | |||
| } else if let Some(inner) = IfLetOrMatch::parse(cx, inner_expr) | |||
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The conditional branch added this time could have been written by nesting ifs together with the conditional branch above, but I have not done so for the sake of readability (the former condition is long).
| && let Some(inner_binding_id) = path_to_local(peel_ref_operators(cx, inner_scrutinee)) | ||
| && let Some(outer_binding_id) = path_to_local(peel_ref_operators(cx, outer_then_body)) | ||
| // check if the inner match can be collapsed into the outer match | ||
| && inner_binding_id == outer_binding_id |
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checks if the outer match and inner match refer to the same binding
| && let IfLetOrMatch::Match(inner_scrutinee, inner_arms, ..) = inner | ||
| && outer_pat.span.eq_ctxt(inner_scrutinee.span) | ||
| && let Some(inner_binding_id) = path_to_local(peel_ref_operators(cx, inner_scrutinee)) | ||
| && let Some(outer_binding_id) = path_to_local(peel_ref_operators(cx, outer_then_body)) |
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Isn't this pattern here unreachable, considering that outer_then_body will be the match expression and never a path to a local variable? The test that was added already gets a warning today and the linked issue doesn't have a warning with this change, so it would be nice to see a test case for what this changes/one that didn't warn before
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I think it would be better if this lint rewrote the nested match into a simply simpler match... I will update this explanation with code examples later.
fix #13773
matchstatements that refer to the same binding inside and outside can be combined.changelog: [
collapsible_match]: detect redundant nested match