Fix incorrect suggestion for macro expansion in deref_addrof lint

Author: ThibsG

clippy_lints/src/reference.rs

@@ -46,13 +46,19 @@ impl EarlyLintPass for DerefAddrOf {
             if !in_macro(addrof_target.span);
             then {
                 let mut applicability = Applicability::MachineApplicable;
+                let sugg = if e.span.from_expansion() {
+                    let snip = snippet_with_applicability(cx, e.span, "_", &mut applicability);
+                    snip.trim_start_matches(|c| c == '&' || c == '*').to_string()
+                } else {
+                    snippet_with_applicability(cx, addrof_target.span, "_", &mut applicability).to_string()
+                };
                 span_lint_and_sugg(
                     cx,
                     DEREF_ADDROF,
                     e.span,
                     "immediately dereferencing a reference",
                     "try this",
-                    format!("{}", snippet_with_applicability(cx, addrof_target.span, "_", &mut applicability)),
+                    sugg,
                     applicability,
                 );
             }

tests/ui/deref_addrof.fixed

@@ -1,4 +1,5 @@
 // run-rustfix
+#![warn(clippy::deref_addrof)]
 
 fn get_number() -> usize {
     10
@@ -10,7 +11,6 @@ fn get_reference(n: &usize) -> &usize {
 
 #[allow(clippy::many_single_char_names, clippy::double_parens)]
 #[allow(unused_variables, unused_parens)]
-#[warn(clippy::deref_addrof)]
 fn main() {
     let a = 10;
     let aref = &a;
@@ -37,3 +37,16 @@ fn main() {
 
     let b = *aref;
 }
+
+macro_rules! m {
+    ($visitor: expr) => {
+        $visitor
+    };
+}
+
+pub struct S;
+impl S {
+    pub fn f(&self) -> &Self {
+        m!(self)
+    }
+}

tests/ui/deref_addrof.rs

@@ -1,4 +1,5 @@
 // run-rustfix
+#![warn(clippy::deref_addrof)]
 
 fn get_number() -> usize {
     10
@@ -10,7 +11,6 @@ fn get_reference(n: &usize) -> &usize {
 
 #[allow(clippy::many_single_char_names, clippy::double_parens)]
 #[allow(unused_variables, unused_parens)]
-#[warn(clippy::deref_addrof)]
 fn main() {
     let a = 10;
     let aref = &a;
@@ -37,3 +37,16 @@ fn main() {
 
     let b = **&aref;
 }
+
+macro_rules! m {
+    ($visitor: expr) => {
+        *&$visitor
+    };
+}
+
+pub struct S;
+impl S {
+    pub fn f(&self) -> &Self {
+        m!(self)
+    }
+}

tests/ui/deref_addrof.stderr

@@ -48,5 +48,16 @@ error: immediately dereferencing a reference
 LL |     let b = **&aref;
    |              ^^^^^^ help: try this: `aref`
 
-error: aborting due to 8 previous errors
+error: immediately dereferencing a reference
+  --> $DIR/deref_addrof.rs:43:9
+   |
+LL |         *&$visitor
+   |         ^^^^^^^^^^ help: try this: `$visitor`
+...
+LL |         m!(self)
+   |         -------- in this macro invocation
+   |
+   = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: aborting due to 9 previous errors