Filter out rhs.span.from_expansion() at the start

Author: bluebear94

clippy_lints/src/default_box_assignments.rs

@@ -37,7 +37,9 @@ 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 {
+        if let ExprKind::Assign(lhs, rhs, _) = &expr.kind
+            && !rhs.span.from_expansion()
+        {
             let lhs_ty = cx.typeck_results().expr_ty(lhs);
 
             // No diagnostic for late-initialized locals
@@ -54,7 +56,6 @@ impl LateLintPass<'_> for DefaultBoxAssignments {
             if let Some(default_trait_id) = cx.tcx.get_diagnostic_item(sym::Default)
                 && implements_trait(cx, inner_ty, default_trait_id, &[])
                 && is_default_call(cx, rhs)
-                && !rhs.span.from_expansion()
             {
                 span_lint_and_then(
                     cx,

tests/ui/default_box_assignments.fixed

@@ -21,6 +21,12 @@ macro_rules! create_default {
     };
 }
 
+macro_rules! create_zero_box {
+    () => {
+        Box::new(0)
+    };
+}
+
 fn main() {
     let mut b = Box::new(1u32);
     *b = Default::default();
@@ -34,6 +40,7 @@ fn main() {
 
     // No lint for call originating in macro
     b = create_default!();
+    b = create_zero_box!();
 
     *b = 5;
     //~^ default_box_assignments

tests/ui/default_box_assignments.rs

@@ -21,6 +21,12 @@ macro_rules! create_default {
     };
 }
 
+macro_rules! create_zero_box {
+    () => {
+        Box::new(0)
+    };
+}
+
 fn main() {
     let mut b = Box::new(1u32);
     b = Default::default();
@@ -34,6 +40,7 @@ fn main() {
 
     // No lint for call originating in macro
     b = create_default!();
+    b = create_zero_box!();
 
     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:26:5
+  --> tests/ui/default_box_assignments.rs:32:5
    |
 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:28:5
+  --> tests/ui/default_box_assignments.rs:34:5
    |
 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:38:5
+  --> tests/ui/default_box_assignments.rs:45:5
    |
 LL |     b = Box::new(5);
    |     ^^^^^^^^^^^^^^^ help: replace existing content with inner value instead: `*b = 5`