Fix macro issues with field_reassign_with_default

Author: phansch

clippy_lints/src/default.rs

@@ -8,6 +8,7 @@ use rustc_errors::Applicability;
 use rustc_hir::def::Res;
 use rustc_hir::{Block, Expr, ExprKind, PatKind, QPath, Stmt, StmtKind};
 use rustc_lint::{LateContext, LateLintPass};
+use rustc_middle::lint::in_external_macro;
 use rustc_middle::ty;
 use rustc_session::{declare_tool_lint, impl_lint_pass};
 use rustc_span::symbol::{Ident, Symbol};
@@ -120,6 +121,8 @@ impl LateLintPass<'_> for Default {
                 // only take `let ...` statements
                 if let StmtKind::Local(local) = stmt.kind;
                 if let Some(expr) = local.init;
+                if !any_parent_is_automatically_derived(cx.tcx, expr.hir_id);
+                if !in_external_macro(cx.tcx.sess, expr.span);
                 // only take bindings to identifiers
                 if let PatKind::Binding(_, binding_id, ident, _) = local.pat.kind;
                 // only when assigning `... = Default::default()`

tests/ui/auxiliary/macro_rules.rs

@@ -94,3 +94,19 @@ macro_rules! large_enum_variant {
         }
     };
 }
+
+#[macro_export]
+macro_rules! field_reassign_with_default {
+    () => {
+        #[derive(Default)]
+        struct A {
+            pub i: i32,
+            pub j: i64,
+        }
+        fn lint() {
+            let mut a: A = Default::default();
+            a.i = 42;
+            a;
+        }
+    };
+}

tests/ui/auxiliary/proc_macro_derive.rs

@@ -4,6 +4,7 @@
 #![crate_type = "proc-macro"]
 #![feature(repr128, proc_macro_quote)]
 #![allow(incomplete_features)]
+#![allow(clippy::field_reassign_with_default)]
 #![allow(clippy::eq_op)]
 
 extern crate proc_macro;
@@ -23,3 +24,20 @@ pub fn derive(_: TokenStream) -> TokenStream {
     };
     output
 }
+
+#[proc_macro_derive(FieldReassignWithDefault)]
+pub fn derive_foo(_input: TokenStream) -> TokenStream {
+    quote! {
+        #[derive(Default)]
+        struct A {
+            pub i: i32,
+            pub j: i64,
+        }
+        #[automatically_derived]
+        fn lint() {
+            let mut a: A = Default::default();
+            a.i = 42;
+            a;
+        }
+    }
+}

tests/ui/field_reassign_with_default.rs

@@ -1,5 +1,18 @@
+// aux-build:proc_macro_derive.rs
+// aux-build:macro_rules.rs
+
 #![warn(clippy::field_reassign_with_default)]
 
+#[macro_use]
+extern crate proc_macro_derive;
+#[macro_use]
+extern crate macro_rules;
+
+// Don't lint on derives that derive `Default`
+// See https://github.com/rust-lang/rust-clippy/issues/6545
+#[derive(FieldReassignWithDefault)]
+struct DerivedStruct;
+
 #[derive(Default)]
 struct A {
     i: i32,
@@ -120,6 +133,9 @@ fn main() {
     // don't expand macros in the suggestion (#6522)
     let mut a: C = C::default();
     a.i = vec![1];
+
+    // Don't lint in external macros
+    field_reassign_with_default!();
 }
 
 mod m {

tests/ui/field_reassign_with_default.stderr

@@ -1,84 +1,84 @@
 error: field assignment outside of initializer for an instance created with Default::default()
-  --> $DIR/field_reassign_with_default.rs:35:5
+  --> $DIR/field_reassign_with_default.rs:48:5
    |
 LL |     a.i = 42;
    |     ^^^^^^^^^
    |
    = note: `-D clippy::field-reassign-with-default` implied by `-D warnings`
-note: consider initializing the variable with `A { i: 42, ..Default::default() }` and removing relevant reassignments
-  --> $DIR/field_reassign_with_default.rs:34:5
+note: consider initializing the variable with `main::A { i: 42, ..Default::default() }` and removing relevant reassignments
+  --> $DIR/field_reassign_with_default.rs:47:5
    |
 LL |     let mut a: A = Default::default();
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: field assignment outside of initializer for an instance created with Default::default()
-  --> $DIR/field_reassign_with_default.rs:75:5
+  --> $DIR/field_reassign_with_default.rs:88:5
    |
 LL |     a.j = 43;
    |     ^^^^^^^^^
    |
-note: consider initializing the variable with `A { j: 43, i: 42 }` and removing relevant reassignments
-  --> $DIR/field_reassign_with_default.rs:74:5
+note: consider initializing the variable with `main::A { j: 43, i: 42 }` and removing relevant reassignments
+  --> $DIR/field_reassign_with_default.rs:87:5
    |
 LL |     let mut a: A = Default::default();
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: field assignment outside of initializer for an instance created with Default::default()
-  --> $DIR/field_reassign_with_default.rs:80:5
+  --> $DIR/field_reassign_with_default.rs:93:5
    |
 LL |     a.i = 42;
    |     ^^^^^^^^^
    |
-note: consider initializing the variable with `A { i: 42, j: 44 }` and removing relevant reassignments
-  --> $DIR/field_reassign_with_default.rs:79:5
+note: consider initializing the variable with `main::A { i: 42, j: 44 }` and removing relevant reassignments
+  --> $DIR/field_reassign_with_default.rs:92:5
    |
 LL |     let mut a: A = Default::default();
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: field assignment outside of initializer for an instance created with Default::default()
-  --> $DIR/field_reassign_with_default.rs:86:5
+  --> $DIR/field_reassign_with_default.rs:99:5
    |
 LL |     a.i = 42;
    |     ^^^^^^^^^
    |
-note: consider initializing the variable with `A { i: 42, ..Default::default() }` and removing relevant reassignments
-  --> $DIR/field_reassign_with_default.rs:85:5
+note: consider initializing the variable with `main::A { i: 42, ..Default::default() }` and removing relevant reassignments
+  --> $DIR/field_reassign_with_default.rs:98:5
    |
 LL |     let mut a = A::default();
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: field assignment outside of initializer for an instance created with Default::default()
-  --> $DIR/field_reassign_with_default.rs:96:5
+  --> $DIR/field_reassign_with_default.rs:109:5
    |
 LL |     a.i = Default::default();
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-note: consider initializing the variable with `A { i: Default::default(), ..Default::default() }` and removing relevant reassignments
-  --> $DIR/field_reassign_with_default.rs:95:5
+note: consider initializing the variable with `main::A { i: Default::default(), ..Default::default() }` and removing relevant reassignments
+  --> $DIR/field_reassign_with_default.rs:108:5
    |
 LL |     let mut a: A = Default::default();
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: field assignment outside of initializer for an instance created with Default::default()
-  --> $DIR/field_reassign_with_default.rs:100:5
+  --> $DIR/field_reassign_with_default.rs:113:5
    |
 LL |     a.i = Default::default();
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-note: consider initializing the variable with `A { i: Default::default(), j: 45 }` and removing relevant reassignments
-  --> $DIR/field_reassign_with_default.rs:99:5
+note: consider initializing the variable with `main::A { i: Default::default(), j: 45 }` and removing relevant reassignments
+  --> $DIR/field_reassign_with_default.rs:112:5
    |
 LL |     let mut a: A = Default::default();
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: field assignment outside of initializer for an instance created with Default::default()
-  --> $DIR/field_reassign_with_default.rs:122:5
+  --> $DIR/field_reassign_with_default.rs:135:5
    |
 LL |     a.i = vec![1];
    |     ^^^^^^^^^^^^^^
    |
 note: consider initializing the variable with `C { i: vec![1], ..Default::default() }` and removing relevant reassignments
-  --> $DIR/field_reassign_with_default.rs:121:5
+  --> $DIR/field_reassign_with_default.rs:134:5
    |
 LL |     let mut a: C = C::default();
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^