Fix closure with block body followed by method call (issue #4050)#6900
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Fix closure with block body followed by method call (issue #4050)#6900tao501 wants to merge 1 commit into
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…4050) In src/chains.rs should_add_parens(), closures with block bodies were not getting parentheses when followed by method calls, causing rustfmt to change program semantics. This adds ast::ExprKind::Block(..) => true to the closure match to ensure block-bodied closures get proper parenthesization.
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Description
Fix for rustfmt issue #4050: "Rustfmt changes meaning of closure, also not idempotent"
Problem
When a closure with a block body is followed by a method call (e.g.,
|| { ... }().to_string()), rustfmt incorrectly formats it as:This changes the program's semantics from
((|| {...}())..to_string())to|| {({...}()..to_string());}.Root Cause
In
src/chains.rs, theshould_add_parens()function returnsfalsefor closures with block bodies, so the chain formatter doesn't add the necessary parentheses around the closure call before the method call.Fix
Added
ast::ExprKind::Block(..) => trueto the closure match inshould_add_parens(), ensuring that closures with block bodies get parenthesized when followed by method calls.This produces the correct output:
Closes #4050