Also include calls to ::default via non-Default types

Author: Henri Lunnikivi

clippy_lints/src/field_reassign_with_default.rs

@@ -91,43 +91,39 @@ impl LateLintPass<'_> for FieldReassignWithDefault {
                 let stmt = &block.stmts[stmt_idx];
 
                 if let StmtKind::Local(preceding_local) = &stmt.kind {
-                    if let Some(ty) = &preceding_local.ty {
-
-                        // if all fields of the struct are not assigned, add `.. Default::default()` to the suggestion.
-                        let ext_with_default = !fields_of_type(&binding_type).iter().all(|field| assigned_fields.contains_key(&field.name));
-
-                        let ty_snippet = snippet(cx, ty.span, "_");
-
-                        let field_list = assigned_fields
-                            .into_iter()
-                            .map(|(field, value)| format!("{}: {}", field, value))
-                            .collect::<Vec<String>>()
-                            .join(", ");
-
-                        let sugg = if ext_with_default {
-                            format!("{} {{ {}, ..Default::default() }}", ty_snippet, field_list)
-                        } else {
-                            format!("{} {{ {} }}", ty_snippet, field_list)
-                        };
-
-                        // span lint once per statement that binds default
-                        span_lint_and_note(
-                            cx,
-                            FIELD_REASSIGN_WITH_DEFAULT,
-                            first_assign.unwrap_or_else(|| unreachable!()).span,
-                            "field assignment outside of initializer for an instance created with Default::default()",
-                            Some(preceding_local.span),
-                            &format!("consider initializing the variable with `{}`", sugg),
-                        );
 
-                    }
+                    // if all fields of the struct are not assigned, add `.. Default::default()` to the suggestion.
+                    let ext_with_default = !fields_of_type(&binding_type).iter().all(|field| assigned_fields.contains_key(&field.name));
+
+                    let field_list = assigned_fields
+                        .into_iter()
+                        .map(|(field, value)| format!("{}: {}", field, value))
+                        .collect::<Vec<String>>()
+                        .join(", ");
+
+                    let sugg = if ext_with_default {
+                        format!("{} {{ {}, ..Default::default() }}", binding_type, field_list)
+                    } else {
+                        format!("{} {{ {} }}", binding_type, field_list)
+                    };
+
+                    // span lint once per statement that binds default
+                    span_lint_and_note(
+                        cx,
+                        FIELD_REASSIGN_WITH_DEFAULT,
+                        first_assign.unwrap_or_else(|| unreachable!()).span,
+                        "field assignment outside of initializer for an instance created with Default::default()",
+                        Some(preceding_local.span),
+                        &format!("consider initializing the variable with `{}`", sugg),
+                    );
+
                 }
             }
         }
     }
 }
 
-/// Returns the indices, identifiers and types of bindings set as `Default::default()`.
+/// Returns the block indices, identifiers and types of bindings set as `Default::default()`.
 fn enumerate_bindings_using_default<'cx, 'hir>(cx: &LateContext<'cx>, block: &Block<'hir>) -> Vec<(usize, Symbol, &'cx TyS<'cx>)> {
     block
         .stmts

tests/ui/field_reassign_with_default.rs

@@ -62,4 +62,8 @@ fn main() {
     a.i = 42;
     a.j = 43;
     a.j = 44;
+
+    // wrong, produces fourth error in stderr
+    let mut a = A::default();
+    a.i = 42;
 }

tests/ui/field_reassign_with_default.stderr

@@ -35,5 +35,17 @@ note: consider initializing the variable with `A { i: 42, j: 44 }`
 LL |     let mut a: A = Default::default();
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 3 previous errors
+error: field assignment outside of initializer for an instance created with Default::default()
+  --> $DIR/field_reassign_with_default.rs:68:5
+   |
+LL |     a.i = 42;
+   |     ^^^^^^^^^
+   |
+note: consider initializing the variable with `A { i: 42, ..Default::default() }`
+  --> $DIR/field_reassign_with_default.rs:67:5
+   |
+LL |     let mut a = A::default();
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 4 previous errors