Show type parameters like From<&str> in mutant names

Fixes #445

NEWS.md

@@ -1,5 +1,9 @@
 # cargo-mutants changelog
 
+## Unreleased
+
+- Changed: Show more type parameters in mutant names, like `impl From<&str> for Foo` rather than `impl From for Foo`.
+
 ## 25.0.0
 
 - Better estimation of time remaining, based on the time taken to test mutants so far, excluding the time for the baseline.
@@ -22,6 +26,8 @@
 
 - New: `--skip-calls=NAME,NAME` on the command line or `skip_calls = [NAMES..]` in `.cargo/mutants.toml` allows configuring other functions whose calls should never be mutated.
 
+- Changed: The mutant name for trait impls now includes the path of the trait as it occurs in the source file: for example `impl fmt::Display for Foo`.
+
 ## 24.11.0
 
 - New: `--test-workspace` and `--test-package` arguments and config options support projects whose tests live in a different package.

src/visit.rs

@@ -462,8 +462,7 @@ impl<'ast> Visit<'ast> for DiscoveryVisitor<'_> {
                 // Can't think of how to generate a viable different default.
                 return;
             }
-            format!("<impl {trait} for {type_name}>", trait = trait_path.segments.last().unwrap().ident)
-            // TODO: trait = trait_path.to_pretty_string()) and update tests to match
+            format!("<impl {trait} for {type_name}>", trait = trait_path.to_pretty_string())
         } else {
             type_name
         };
@@ -818,6 +817,7 @@ fn find_path_attribute(attrs: &[Attribute]) -> std::result::Result<Option<Utf8Pa
 mod test {
     use indoc::indoc;
     use itertools::Itertools;
+    use pretty_assertions::assert_eq;
     use test_log::test;
 
     use crate::test_util::copy_of_testdata;
@@ -1026,7 +1026,7 @@ mod test {
         let mutants = mutate_source_str(
             indoc! {"
                 fn main() {
-                    let mut v = V::new();
+                    let mut v = v::new();
                     v.dont_touch_this(2 + 3);
                 }
             "},
@@ -1042,4 +1042,46 @@ mod test {
             0
         );
     }
+
+    #[test]
+    fn mutant_name_includes_type_parameters() {
+        // From https://github.com/sourcefrog/cargo-mutants/issues/334
+        let options = Options::from_arg_strs(["mutants"]);
+        let mutants = mutate_source_str(
+            indoc! {r#"
+            impl AsRef<str> for Apath {
+                fn as_ref(&self) -> &str {
+                    &self.0
+                }
+            }
+
+            impl From<Apath> for String {
+                fn from(a: Apath) -> String {
+                    a.0
+                }
+            }
+
+            impl<'a> From<&'a str> for Apath {
+                fn from(s: &'a str) -> Apath {
+                    assert!(Apath::is_valid(s), "invalid apath: {s:?}");
+                    Apath(s.to_string())
+                }
+            }
+            "#},
+            &options,
+        )
+        .unwrap();
+        dbg!(&mutants);
+        let mutant_names = mutants.iter().map(|m| m.name(false) + "\n").join("");
+        assert_eq!(
+            mutant_names,
+            indoc! {r#"
+                src/main.rs: replace <impl AsRef<str> for Apath>::as_ref -> &str with ""
+                src/main.rs: replace <impl AsRef<str> for Apath>::as_ref -> &str with "xyzzy"
+                src/main.rs: replace <impl From<Apath> for String>::from -> String with String::new()
+                src/main.rs: replace <impl From<Apath> for String>::from -> String with "xyzzy".into()
+                src/main.rs: replace <impl From<&'a str> for Apath>::from -> Apath with Default::default()
+            "#}
+        );
+    }
 }

tests/snapshots/list__list_mutants_in_all_trees_as_json.snap

@@ -6628,7 +6628,7 @@ expression: buf
   {
     "file": "src/methods.rs",
     "function": {
-      "function_name": "<impl Display for Foo>::fmt",
+      "function_name": "<impl fmt::Display for Foo>::fmt",
       "return_type": "-> fmt::Result",
       "span": {
         "end": {
@@ -6658,7 +6658,7 @@ expression: buf
   {
     "file": "src/methods.rs",
     "function": {
-      "function_name": "<impl Debug for &Foo>::fmt",
+      "function_name": "<impl fmt::Debug for &Foo>::fmt",
       "return_type": "-> fmt::Result",
       "span": {
         "end": {
@@ -9842,5 +9842,3 @@ expression: buf
   }
 ]
 ```
-
-

tests/snapshots/list__list_mutants_in_all_trees_as_text.snap

@@ -426,8 +426,8 @@ src/inside_mod.rs:4:13: replace outer::inner::name -> &'static str with "xyzzy"
 src/methods.rs:17:9: replace Foo::double with ()
 src/methods.rs:17:16: replace *= with += in Foo::double
 src/methods.rs:17:16: replace *= with /= in Foo::double
-src/methods.rs:23:9: replace <impl Display for Foo>::fmt -> fmt::Result with Ok(Default::default())
-src/methods.rs:29:9: replace <impl Debug for &Foo>::fmt -> fmt::Result with Ok(Default::default())
+src/methods.rs:23:9: replace <impl fmt::Display for Foo>::fmt -> fmt::Result with Ok(Default::default())
+src/methods.rs:29:9: replace <impl fmt::Debug for &Foo>::fmt -> fmt::Result with Ok(Default::default())
 src/nested_function.rs:2:5: replace has_nested -> u32 with 0
 src/nested_function.rs:2:5: replace has_nested -> u32 with 1
 src/nested_function.rs:3:9: replace has_nested::inner -> u32 with 0
@@ -545,5 +545,3 @@ main2/src/main.rs:10:5: replace triple_3 -> i32 with 0
 main2/src/main.rs:10:5: replace triple_3 -> i32 with 1
 main2/src/main.rs:10:5: replace triple_3 -> i32 with -1
 ```
-
-

tests/snapshots/main__well_tested_tree_check_only.snap

@@ -24,8 +24,8 @@ ok       src/inside_mod.rs:4:13: replace outer::inner::name -> &'static str with
 ok       src/methods.rs:17:9: replace Foo::double with ()
 ok       src/methods.rs:17:16: replace *= with += in Foo::double
 ok       src/methods.rs:17:16: replace *= with /= in Foo::double
-ok       src/methods.rs:23:9: replace <impl Display for Foo>::fmt -> fmt::Result with Ok(Default::default())
-ok       src/methods.rs:29:9: replace <impl Debug for &Foo>::fmt -> fmt::Result with Ok(Default::default())
+ok       src/methods.rs:23:9: replace <impl fmt::Display for Foo>::fmt -> fmt::Result with Ok(Default::default())
+ok       src/methods.rs:29:9: replace <impl fmt::Debug for &Foo>::fmt -> fmt::Result with Ok(Default::default())
 ok       src/nested_function.rs:2:5: replace has_nested -> u32 with 0
 ok       src/nested_function.rs:2:5: replace has_nested -> u32 with 1
 ok       src/nested_function.rs:3:9: replace has_nested::inner -> u32 with 0

tests/snapshots/main__well_tested_tree_finds_no_problems.snap

@@ -24,8 +24,8 @@ caught   src/inside_mod.rs:4:13: replace outer::inner::name -> &'static str with
 caught   src/methods.rs:17:9: replace Foo::double with ()
 caught   src/methods.rs:17:16: replace *= with += in Foo::double
 caught   src/methods.rs:17:16: replace *= with /= in Foo::double
-caught   src/methods.rs:23:9: replace <impl Display for Foo>::fmt -> fmt::Result with Ok(Default::default())
-caught   src/methods.rs:29:9: replace <impl Debug for &Foo>::fmt -> fmt::Result with Ok(Default::default())
+caught   src/methods.rs:23:9: replace <impl fmt::Display for Foo>::fmt -> fmt::Result with Ok(Default::default())
+caught   src/methods.rs:29:9: replace <impl fmt::Debug for &Foo>::fmt -> fmt::Result with Ok(Default::default())
 caught   src/nested_function.rs:2:5: replace has_nested -> u32 with 0
 caught   src/nested_function.rs:2:5: replace has_nested -> u32 with 1
 caught   src/nested_function.rs:3:9: replace has_nested::inner -> u32 with 0

tests/snapshots/main__well_tested_tree_finds_no_problems__caught.txt.snap

@@ -22,8 +22,8 @@ src/inside_mod.rs:4:13: replace outer::inner::name -> &'static str with "xyzzy"
 src/methods.rs:17:9: replace Foo::double with ()
 src/methods.rs:17:16: replace *= with += in Foo::double
 src/methods.rs:17:16: replace *= with /= in Foo::double
-src/methods.rs:23:9: replace <impl Display for Foo>::fmt -> fmt::Result with Ok(Default::default())
-src/methods.rs:29:9: replace <impl Debug for &Foo>::fmt -> fmt::Result with Ok(Default::default())
+src/methods.rs:23:9: replace <impl fmt::Display for Foo>::fmt -> fmt::Result with Ok(Default::default())
+src/methods.rs:29:9: replace <impl fmt::Debug for &Foo>::fmt -> fmt::Result with Ok(Default::default())
 src/nested_function.rs:2:5: replace has_nested -> u32 with 0
 src/nested_function.rs:2:5: replace has_nested -> u32 with 1
 src/nested_function.rs:3:9: replace has_nested::inner -> u32 with 0

tests/util/snapshots/list__util__list_mutants_json_well_tested.snap

@@ -606,7 +606,7 @@ expression: "String::from_utf8_lossy(&output.stdout)"
   {
     "file": "src/methods.rs",
     "function": {
-      "function_name": "<impl Display for Foo>::fmt",
+      "function_name": "<impl fmt::Display for Foo>::fmt",
       "return_type": "-> fmt::Result",
       "span": {
         "end": {
@@ -636,7 +636,7 @@ expression: "String::from_utf8_lossy(&output.stdout)"
   {
     "file": "src/methods.rs",
     "function": {
-      "function_name": "<impl Debug for &Foo>::fmt",
+      "function_name": "<impl fmt::Debug for &Foo>::fmt",
       "return_type": "-> fmt::Result",
       "span": {
         "end": {

tests/util/snapshots/list__util__list_mutants_well_tested.snap

@@ -22,8 +22,8 @@ src/inside_mod.rs:4:13: replace outer::inner::name -> &'static str with "xyzzy"
 src/methods.rs:17:9: replace Foo::double with ()
 src/methods.rs:17:16: replace *= with += in Foo::double
 src/methods.rs:17:16: replace *= with /= in Foo::double
-src/methods.rs:23:9: replace <impl Display for Foo>::fmt -> fmt::Result with Ok(Default::default())
-src/methods.rs:29:9: replace <impl Debug for &Foo>::fmt -> fmt::Result with Ok(Default::default())
+src/methods.rs:23:9: replace <impl fmt::Display for Foo>::fmt -> fmt::Result with Ok(Default::default())
+src/methods.rs:29:9: replace <impl fmt::Debug for &Foo>::fmt -> fmt::Result with Ok(Default::default())
 src/nested_function.rs:2:5: replace has_nested -> u32 with 0
 src/nested_function.rs:2:5: replace has_nested -> u32 with 1
 src/nested_function.rs:3:9: replace has_nested::inner -> u32 with 0

tests/util/snapshots/list__util__list_mutants_well_tested_exclude_name_filter.snap

@@ -22,8 +22,8 @@ src/inside_mod.rs:4:13: replace outer::inner::name -> &'static str with "xyzzy"
 src/methods.rs:17:9: replace Foo::double with ()
 src/methods.rs:17:16: replace *= with += in Foo::double
 src/methods.rs:17:16: replace *= with /= in Foo::double
-src/methods.rs:23:9: replace <impl Display for Foo>::fmt -> fmt::Result with Ok(Default::default())
-src/methods.rs:29:9: replace <impl Debug for &Foo>::fmt -> fmt::Result with Ok(Default::default())
+src/methods.rs:23:9: replace <impl fmt::Display for Foo>::fmt -> fmt::Result with Ok(Default::default())
+src/methods.rs:29:9: replace <impl fmt::Debug for &Foo>::fmt -> fmt::Result with Ok(Default::default())
 src/nested_function.rs:2:5: replace has_nested -> u32 with 0
 src/nested_function.rs:2:5: replace has_nested -> u32 with 1
 src/nested_function.rs:3:9: replace has_nested::inner -> u32 with 0