fix(test): improve mutants coverage

Author: andogq

src/main.rs

@@ -438,5 +438,65 @@ mod test {
                 10
             );
         }
+
+        #[test]
+        #[should_panic(expected = "Type")]
+        fn trait_impl_mismatch() {
+            run(r#"trait MyTrait {
+                fn some_method() -> Self;
+            }
+
+            impl MyTrait for u8 {
+                fn some_method(parameter: bool) -> Self {
+                    10
+                }
+            }
+
+            fn main() -> u8 {
+                <u8 as MyTrait>::some_method()
+            }"#);
+        }
+
+        #[test]
+        #[should_panic(expected = "type must implement trait")]
+        fn trait_not_implemented() {
+            run(r#"trait MyTrait {
+                fn some_method() -> Self;
+            }
+
+            fn main() -> u8 {
+                <u8 as MyTrait>::some_method()
+            }"#);
+        }
+
+        #[test]
+        fn complex_path_usage() {
+            assert_eq!(
+                run(r#"trait MyTrait {
+                        fn some_method() -> Self;
+                    }
+
+                    impl MyTrait for u8 {
+                        fn some_method() -> Self {
+                            10
+                        }
+                    }
+
+                    fn fallback() -> u8 {
+                        3
+                    }
+
+                    fn main() -> u8 {
+                        let get_num = if true {
+                            <u8 as MyTrait>::some_method
+                        } else {
+                            fallback
+                        };
+
+                        get_num()
+                    }"#),
+                10
+            );
+        }
     }
 }

src/passes/hir_gen.rs

@@ -561,6 +561,7 @@ impl FunctionCtx {
         dead_code,
         reason = "tracking current trait may be useful for diagnostics"
     )]
+    #[mutants::skip(reason = "dead code")]
     fn current_trait(&self) -> Option<TraitId> {
         match self {
             Self::TraitMethod { current_trait, .. } => Some(*current_trait),
@@ -573,6 +574,7 @@ impl FunctionCtx {
         dead_code,
         reason = "tracking current method may be useful for diagnostics"
     )]
+    #[mutants::skip(reason = "dead code")]
     fn current_trait_method(&self) -> Option<TraitMethodId> {
         match self {
             Self::TraitMethod { method, .. } => Some(*method),

src/util/scopes.rs

@@ -39,6 +39,7 @@ impl<B: BindingKind> PartialEq for BindingId<B> {
 }
 impl<B: BindingKind> Eq for BindingId<B> {}
 impl<B: BindingKind> Hash for BindingId<B> {
+    #[mutants::skip(reason = "tests don't cover hashing")]
     fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
         self.id.hash(state);
     }
@@ -71,17 +72,6 @@ impl<B: BindingKind> Binding<B> {
         }
     }
 }
-impl<B: BindingKind> TryFrom<ErasedBinding> for Binding<B> {
-    type Error = ErasedBinding;
-
-    fn try_from(binding: ErasedBinding) -> Result<Self, Self::Error> {
-        if binding.kind == B::get_marker() {
-            return Err(binding);
-        }
-
-        Ok(Self::new(binding.string))
-    }
-}
 
 /// Type-erased version of [`Binding`], using [`BindingKindMarker`] instead of a generic.
 #[derive(Clone, Debug, Hash, PartialEq, Eq)]