Properly lint macro arguments for explicit_deref_methods

Author: Jarcho

clippy_lints/src/dereference.rs

@@ -105,7 +105,7 @@ impl<'tcx> LateLintPass<'tcx> for Dereferencing {
                 match kind {
                     RefOp::Method(target_mut)
                         if !is_allowed(cx, EXPLICIT_DEREF_METHODS, expr.hir_id)
-                            && is_linted_explicit_deref_position(parent, expr.hir_id) =>
+                            && is_linted_explicit_deref_position(parent, expr.hir_id, expr.span) =>
                     {
                         self.state = Some((
                             State::DerefMethod {
@@ -189,9 +189,9 @@ fn deref_method_same_type(result_ty: Ty<'tcx>, arg_ty: Ty<'tcx>) -> bool {
 
 // Checks whether the parent node is a suitable context for switching from a deref method to the
 // deref operator.
-fn is_linted_explicit_deref_position(parent: Option<Node<'_>>, child_id: HirId) -> bool {
+fn is_linted_explicit_deref_position(parent: Option<Node<'_>>, child_id: HirId, child_span: Span) -> bool {
     let parent = match parent {
-        Some(Node::Expr(e)) => e,
+        Some(Node::Expr(e)) if e.span.ctxt() == child_span.ctxt() => e,
         _ => return true,
     };
     match parent.kind {

tests/ui/explicit_deref_methods.fixed

@@ -76,6 +76,8 @@ fn main() {
     }
     let b: &str = expr_deref!(a);
 
+    let b: &str = expr_deref!(&*a);
+
     // The struct does not implement Deref trait
     #[derive(Copy, Clone)]
     struct NoLint(u32);

tests/ui/explicit_deref_methods.rs

@@ -76,6 +76,8 @@ fn main() {
     }
     let b: &str = expr_deref!(a);
 
+    let b: &str = expr_deref!(a.deref());
+
     // The struct does not implement Deref trait
     #[derive(Copy, Clone)]
     struct NoLint(u32);

tests/ui/explicit_deref_methods.stderr

@@ -66,5 +66,11 @@ error: explicit `deref` method call
 LL |     let b = opt_a.unwrap().deref();
    |             ^^^^^^^^^^^^^^^^^^^^^^ help: try this: `&*opt_a.unwrap()`
 
-error: aborting due to 11 previous errors
+error: explicit `deref` method call
+  --> $DIR/explicit_deref_methods.rs:79:31
+   |
+LL |     let b: &str = expr_deref!(a.deref());
+   |                               ^^^^^^^^^ help: try this: `&*a`
+
+error: aborting due to 12 previous errors