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test: reproduce rustfix panic on overlapping suggestions #16705

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epage merged 1 commit into from
Mar 16, 2026
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test: reproduce rustfix panic on overlapping suggestions #16705

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139 changes: 139 additions & 0 deletions tests/testsuite/fix_n_times.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -45,6 +45,8 @@ enum Step {
Error = b'e',
/// Emits one suggested fix and an error.
OneFixError = b'f',
/// Emits one diagnostic with two exclusive, overlapping suggestions.
TwoFixExclusive = b'x',
}

/// Verifies `cargo fix` behavior based on the given sequence of behaviors for
Expand Down Expand Up @@ -139,6 +141,9 @@ fn main() {
output_message("error", successful_count + 2);
std::process::exit(1);
}
b'x' => {
output_exclusive_suggestions(successful_count + 1);
}
_ => panic!("unexpected sequence"),
}
}
Expand Down Expand Up @@ -256,6 +261,112 @@ fn output_message(level: &str, count: usize) {
.replace("\n", "");
eprintln!("{json}");
}

fn output_exclusive_suggestions(count: usize) {
let json = format!(
r#"{{
"$message_type": "diagnostic",
"message": "rustc fix shim exclusive comment {count}",
"code": null,
"level": "warning",
"spans":
[
{{
"file_name": "src/lib.rs",
"byte_start": 13,
"byte_end": 14,
"line_start": 1,
"line_end": 1,
"column_start": 14,
"column_end": 15,
"is_primary": true,
"text":
[
{{
"text": "// fix-count 0",
"highlight_start": 14,
"highlight_end": 15
}}
],
"label": "increase this number",
"suggested_replacement": null,
"suggestion_applicability": null,
"expansion": null
}}
],
"children":
[
{{
"message": "try this",
"code": null,
"level": "help",
"spans":
[
{{
"file_name": "src/lib.rs",
"byte_start": 13,
"byte_end": 14,
"line_start": 1,
"line_end": 1,
"column_start": 14,
"column_end": 15,
"is_primary": true,
"text":
[
{{
"text": "// fix-count 0",
"highlight_start": 14,
"highlight_end": 15
}}
],
"label": null,
"suggested_replacement": "{count}a",
"suggestion_applicability": "MachineApplicable",
"expansion": null
}}
],
"children": [],
"rendered": null
}},
{{
"message": "or try this",
"code": null,
"level": "help",
"spans":
[
{{
"file_name": "src/lib.rs",
"byte_start": 13,
"byte_end": 14,
"line_start": 1,
"line_end": 1,
"column_start": 14,
"column_end": 15,
"is_primary": true,
"text":
[
{{
"text": "// fix-count 0",
"highlight_start": 14,
"highlight_end": 15
}}
],
"label": null,
"suggested_replacement": "{count}b",
"suggestion_applicability": "MachineApplicable",
"expansion": null
}}
],
"children": [],
"rendered": null
}}
],
"rendered": "rustc fix shim exclusive comment {count}"
}}"#,
)
.replace("\n", "");
eprintln!("{json}");
}
"##,
)
.build();
Expand Down Expand Up @@ -472,3 +583,31 @@ rustc fix shim error count=2
"// fix-count 1",
);
}

#[cargo_test]
fn fix_exclusive_suggestions() {
// One diagnostic with two exclusive suggestions for the same span.
// Currently, rustfix fails with a generic `AlreadyReplaced` error
// ("cannot replace slice of data that was already replaced") when it
// encounters this.
expect_fix_runs_rustc_n_times(
&[Step::TwoFixExclusive],
|execs| {
execs.with_status(0);
},
str![[r#"
[CHECKING] foo v0.0.1 ([ROOT]/foo)
[ERROR] error applying suggestions
--> src/lib.rs
= cause: cannot replace slice of data that was already replaced
[HELP] to report this as a bug, open an issue at https://github.com/rust-lang/rust/issues, quoting the full output of this command
[HELP] to possibly apply more fixes, pass in the `--broken-code` flag
[FIXED] src/lib.rs (0 fixes)
[..]
[WARNING] `foo` (lib) generated 1 warning (run `cargo fix --lib -p foo` to apply 1 suggestion)
[FINISHED] `dev` profile [unoptimized + debuginfo] target(s) in [ELAPSED]s

"#]],
"// fix-count 0",
);
}