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coverage: Don't underflow column number #97368

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Apr 26, 2023
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coverage: Don't underflow column number #97368

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2 changes: 1 addition & 1 deletion compiler/rustc_mir_transform/src/coverage/mod.rs
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Original file line number Diff line number Diff line change
@@ -515,7 +515,7 @@ fn make_code_region(
// Extend an empty span by one character so the region will be counted.
let CharPos(char_pos) = start_col;
if span.hi() == body_span.hi() {
start_col = CharPos(char_pos - 1);
start_col = CharPos(char_pos.saturating_sub(1));
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@wesleywiser wesleywiser May 24, 2022 •
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I'm wondering if we should fix the rest of this function to use saturating math since it's not much code? Specifically, can we also fix the addition on lines 520, 531 and 533?

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@tmandry - Do you mind doing that, if you agree it's worth it?

Sorry for the bug, but I thought lookup_file_pos() should never return less than 1. Maybe I misunderstood or the implementation changed, but that's not something the compiler would have enforced of course, so this is a good fix. Thanks.

} else {
end_col = CharPos(char_pos + 1);
}