ICE: "attempt to add with overflow" in error emitter when building clippy_utils lib #94171
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C-bug
Category: This is a bug.
I-ICE
Issue: The compiler panicked, giving an Internal Compilation Error (ICE) ❄️
requires-debug-assertions
This issue requires a build of rustc or tooling with debug-assertions in some way
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matthiaskrgr
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I-ICE
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Run into this while fuzzing, here is a minimized test case: fn L(]{match
(; {`Note that you need rustc with debug assertions enabled. Reproduced in nightly 2022-02-25. |
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Another test case: #[B=L(E:..,B=;
,t |
matthiaskrgr
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OP and #94171 (comment) seem to be fixed on latest master (ae4d89d). #94171 (comment) now outputs "Span must not be empty and have no suggestion" backtrace |
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I can confirm that both of my examples have been fixed on latest master (b652d9a) so this issue can be closed. |
matthiaskrgr
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May 21, 2023
…piler-errors Fix overflow in error emitter Fix rust-lang#109854 Close rust-lang#94171 (was already fixed before but missing test) This bug happens when a multipart suggestion spans more than one line. The fix is to update the `acc` variable, which didn't handle the case when the text to remove spans multiple lines but the text to add spans only one line. Also, use `usize::try_from` instead of `as usize` to detect overflows earlier in the future, and point to the source of the overflow (the original issue points to a different place where this value is used, not where the overflow had happened). And finally add an `if start != end` check to avoid doing any extra work in case of empty ranges. Long explanation: Given this test case: ```rust fn generate_setter() { String::with_capacity( //~^ ERROR this function takes 1 argument but 3 arguments were supplied generate_setter, r#" pub(crate) struct Person<T: Clone> {} "#, r#""#, ); } ``` The compiler will try to convert that code into the following: ```rust fn generate_setter() { String::with_capacity( //~^ ERROR this function takes 1 argument but 3 arguments were supplied /* usize */, ); } ``` So it creates a suggestion with 3 separate parts: ``` // Replace "generate_setter" with "/* usize */" SubstitutionPart { span: fuzz_input.rs:4:5: 4:20 (#0), snippet: "/* usize */" } // Remove second arg (multiline string) SubstitutionPart { span: fuzz_input.rs:4:20: 7:3 (#0), snippet: "" } // Remove third arg (r#""#) SubstitutionPart { span: fuzz_input.rs:7:3: 8:11 (#0), snippet: "" } ``` Each of this parts gets a separate `SubstitutionHighlight` (this marks the relevant text green in a terminal, the values are 0-indexed so `start: 4` means column 5): ``` SubstitutionHighlight { start: 4, end: 15 } SubstitutionHighlight { start: 15, end: 15 } SubstitutionHighlight { start: 18446744073709551614, end: 18446744073709551614 } ``` The 2nd and 3rd suggestion are empty (start = end) because they only remove text, so there are no additions to highlight. But the 3rd span has overflowed because the compiler assumes that the 3rd suggestion is on the same line as the first suggestion. The 2nd span starts at column 20 and the highlight starts at column 16 (15+1), so that suggestion is good. But since the 3rd span starts at column 3, the result is `3 - 4`, or column -1, which turns into -2 with 0-indexed, and that's equivalent to `18446744073709551614 as isize`. With this fix, the resulting `SubstitutionHighlight` are: ``` SubstitutionHighlight { start: 4, end: 15 } SubstitutionHighlight { start: 15, end: 15 } SubstitutionHighlight { start: 15, end: 15 } ``` As expected. I guess ideally we shouldn't emit empty highlights when removing text, but I am too scared to change that.
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code is from clippy:
⚠️ you need rustc build with debug assertions ⚠️
./src/tools/clippy/clippy_utils/src/lib.rsMeta
rustc --version --verbose:Error output
rustc ./src/tools/clippy/clippy_utils/src/lib.rs --crate-type lib -Wsingle-use-lifetimesBacktrace
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