Filter out LHS from macro expansion

Author: bluebear94

clippy_lints/src/default_box_assignments.rs

@@ -38,6 +38,7 @@ declare_lint_pass!(DefaultBoxAssignments => [DEFAULT_BOX_ASSIGNMENTS]);
 impl LateLintPass<'_> for DefaultBoxAssignments {
     fn check_expr(&mut self, cx: &LateContext<'_>, expr: &'_ Expr<'_>) {
         if let ExprKind::Assign(lhs, rhs, _) = &expr.kind
+            && !lhs.span.from_expansion()
             && !rhs.span.from_expansion()
         {
             let lhs_ty = cx.typeck_results().expr_ty(lhs);

tests/ui/default_box_assignments.fixed

@@ -27,6 +27,12 @@ macro_rules! create_zero_box {
     };
 }
 
+macro_rules! same {
+    ($v:ident) => {
+        $v
+    };
+}
+
 fn main() {
     let mut b = Box::new(1u32);
     *b = Default::default();
@@ -38,9 +44,10 @@ fn main() {
     *b = Default::default();
     *b = u32::default();
 
-    // No lint for call originating in macro
+    // No lint if either LHS or RHS originates in macro
     b = create_default!();
     b = create_zero_box!();
+    same!(b) = Default::default();
 
     *b = 5;
     //~^ default_box_assignments

tests/ui/default_box_assignments.rs

@@ -27,6 +27,12 @@ macro_rules! create_zero_box {
     };
 }
 
+macro_rules! same {
+    ($v:ident) => {
+        $v
+    };
+}
+
 fn main() {
     let mut b = Box::new(1u32);
     b = Default::default();
@@ -38,9 +44,10 @@ fn main() {
     *b = Default::default();
     *b = u32::default();
 
-    // No lint for call originating in macro
+    // No lint if either LHS or RHS originates in macro
     b = create_default!();
     b = create_zero_box!();
+    same!(b) = Default::default();
 
     b = Box::new(5);
     //~^ default_box_assignments

tests/ui/default_box_assignments.stderr

@@ -17,23 +17,23 @@ LL |     *b = Box::new(t);
    = note: this creates a needless allocation
 
 error: creating a new box with default content
-  --> tests/ui/default_box_assignments.rs:32:5
+  --> tests/ui/default_box_assignments.rs:38:5
    |
 LL |     b = Default::default();
    |     ^^^^^^^^^^^^^^^^^^^^^^ help: replace existing content with default instead: `*b = Default::default()`
    |
    = note: this creates a needless allocation
 
 error: creating a new box with default content
-  --> tests/ui/default_box_assignments.rs:34:5
+  --> tests/ui/default_box_assignments.rs:40:5
    |
 LL |     b = Box::default();
    |     ^^^^^^^^^^^^^^^^^^ help: replace existing content with default instead: `*b = Default::default()`
    |
    = note: this creates a needless allocation
 
 error: creating a new box
-  --> tests/ui/default_box_assignments.rs:45:5
+  --> tests/ui/default_box_assignments.rs:52:5
    |
 LL |     b = Box::new(5);
    |     ^^^^^^^^^^^^^^^ help: replace existing content with inner value instead: `*b = 5`