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Mutate NonZero<T> generic return types #602

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9c6b890
Release 27.0.0
sourcefrog Mar 7, 2026
ec406c9
Mutate NonZero<T> generic return types
sourcefrog Feb 9, 2026
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2 changes: 1 addition & 1 deletion Cargo.lock
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2 changes: 1 addition & 1 deletion Cargo.toml
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Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
[package]
name = "cargo-mutants"
version = "27.0.0-pre"
version = "27.0.0"
edition = "2024"
authors = ["Martin Pool"]
license = "MIT"
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4 changes: 3 additions & 1 deletion NEWS.md
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Original file line number Diff line number Diff line change
@@ -1,6 +1,8 @@
# cargo-mutants changelog

## Unreleased
## 27.0.0

Released 2026-03-07.

- Changed: Command line values for `--file`, `--exclude`, `--examine-re`, and `--exclude-re` are now combined with, rather than replacing, values given in the configuration file, consistently with every other option that takes a list. (Use `--config=OTHER` or `--no-config` to avoid using values in the configuration.) Thanks to @sandersaares for pointing this out.

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80 changes: 79 additions & 1 deletion src/fnvalue.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -56,6 +56,33 @@ fn type_replacements(type_: &Type, error_exprs: &[Expr]) -> impl Iterator<Item =
]
} else if path_is_nonzero_unsigned(path) {
vec![quote! { 1.try_into().unwrap() }]
} else if let Some(inner_type) = match_first_type_arg(path, "NonZero") {
// NonZero<T> generic form (stabilized in Rust 1.79)
if let Type::Path(syn::TypePath {
path: inner_path, ..
}) = inner_type
{
if path_is_unsigned(inner_path) {
vec![quote! { 1.try_into().unwrap() }]
} else if path_is_signed(inner_path) {
vec![
quote! { 1.try_into().unwrap() },
quote! { (-1).try_into().unwrap() },
]
} else {
// Unknown T, assume it could be signed
vec![
quote! { 1.try_into().unwrap() },
quote! { (-1).try_into().unwrap() },
]
}
} else {
// T is not a simple path, assume it could be signed
vec![
quote! { 1.try_into().unwrap() },
quote! { (-1).try_into().unwrap() },
]
}
Comment on lines +72 to +85
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Copilot AI Mar 7, 2026

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The NonZero<T> branch repeats the same two-value vec![1.try_into()..., (-1).try_into()...] construction in multiple places. Consider extracting this into a small local variable/helper to reduce duplication and make future tweaks (e.g., additional candidate values) less error-prone.

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} else if path_is_float(path) {
vec![quote! { 0.0 }, quote! { 1.0 }, quote! { -1.0 }]
} else if path_ends_with(path, "Result") {
Expand Down Expand Up @@ -393,7 +420,6 @@ fn path_is_nonzero_signed(path: &Path) -> bool {
}

fn path_is_nonzero_unsigned(path: &Path) -> bool {
// TODO: Also NonZero<usize> etc.
if let Some(l) = path.segments.last().map(|p| p.ident.to_string()) {
matches!(
l.as_str(),
Expand Down Expand Up @@ -494,6 +520,58 @@ mod test {
);
}

#[test]
fn nonzero_generic_unsigned_replacements() {
check_replacements(
&parse_quote! { -> NonZero<u32> },
&[],
&["1.try_into().unwrap()"],
);

check_replacements(
&parse_quote! { -> NonZero<usize> },
&[],
&["1.try_into().unwrap()"],
);

check_replacements(
&parse_quote! { -> std::num::NonZero<u8> },
&[],
&["1.try_into().unwrap()"],
);
}

#[test]
fn nonzero_generic_signed_replacements() {
check_replacements(
&parse_quote! { -> NonZero<i32> },
&[],
&["1.try_into().unwrap()", "(-1).try_into().unwrap()"],
);

check_replacements(
&parse_quote! { -> NonZero<isize> },
&[],
&["1.try_into().unwrap()", "(-1).try_into().unwrap()"],
);

check_replacements(
&parse_quote! { -> std::num::NonZero<i64> },
&[],
&["1.try_into().unwrap()", "(-1).try_into().unwrap()"],
);
}

#[test]
fn nonzero_generic_unknown_type_replacements() {
// When T is not a recognized integer type, assume it could be signed.
check_replacements(
&parse_quote! { -> NonZero<T> },
&[],
&["1.try_into().unwrap()", "(-1).try_into().unwrap()"],
);
}

#[test]
fn unit_replacement() {
check_replacements(&parse_quote! { -> () }, &[], &["()"]);
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