Check for proc macros from within explicit_deref_methods and do not lint on proc macro expansions (#15628)

Adds a `is_from_proc_macro(...,...)` check to the
`explicit_deref_methods` lint.

Note that this is my first contribution to clippy and i am not 100% sure
that this is how such bugs are intended to be fixed, so please be kind
with any feedback, I appreciate that a lot! Thanks!

changelog: [`explicit_deref_methods`]: no longer triggers from within
proc macro expansions

fixes #15168

Author: Alexendoo

clippy_lints/src/dereference.rs

@@ -3,7 +3,8 @@ use clippy_utils::source::{snippet_with_applicability, snippet_with_context};
 use clippy_utils::sugg::has_enclosing_paren;
 use clippy_utils::ty::{adjust_derefs_manually_drop, implements_trait, is_manually_drop, peel_and_count_ty_refs};
 use clippy_utils::{
-    DefinedTy, ExprUseNode, expr_use_ctxt, get_parent_expr, is_block_like, is_lint_allowed, path_to_local,
+    DefinedTy, ExprUseNode, expr_use_ctxt, get_parent_expr, is_block_like, is_from_proc_macro, is_lint_allowed,
+    path_to_local,
 };
 use rustc_ast::util::parser::ExprPrecedence;
 use rustc_data_structures::fx::FxIndexMap;
@@ -260,6 +261,13 @@ impl<'tcx> LateLintPass<'tcx> for Dereferencing<'tcx> {
         };
         self.skip_expr = skip_expr;
 
+        if is_from_proc_macro(cx, expr) {
+            if let Some((state, data)) = self.state.take() {
+                report(cx, expr, state, data, cx.typeck_results());
+            }
+            return;
+        }
+
         match (self.state.take(), kind) {
             (None, kind) => {
                 let expr_ty = typeck.expr_ty(expr);

tests/ui/explicit_deref_methods.fixed

@@ -1,3 +1,4 @@
+//@aux-build:proc_macros.rs
 #![warn(clippy::explicit_deref_methods)]
 #![allow(unused_variables, unused_must_use)]
 #![allow(
@@ -14,6 +15,8 @@
 
 use std::ops::{Deref, DerefMut};
 
+extern crate proc_macros;
+
 fn concat(deref_str: &str) -> String {
     format!("{}bar", deref_str)
 }
@@ -121,6 +124,18 @@ fn main() {
     let b: &str = expr_deref!(&*a);
     //~^ explicit_deref_methods
 
+    proc_macros::external! {
+        let a: &mut String = &mut String::from("foo");
+        let b: &str = a.deref();
+    }
+
+    // Issue #15168
+    proc_macros::with_span! {
+        span
+        let a: &mut String = &mut String::from("foo");
+        let b: &str = a.deref();
+    }
+
     // The struct does not implement Deref trait
     #[derive(Copy, Clone)]
     struct NoLint(u32);

tests/ui/explicit_deref_methods.rs

@@ -1,3 +1,4 @@
+//@aux-build:proc_macros.rs
 #![warn(clippy::explicit_deref_methods)]
 #![allow(unused_variables, unused_must_use)]
 #![allow(
@@ -14,6 +15,8 @@
 
 use std::ops::{Deref, DerefMut};
 
+extern crate proc_macros;
+
 fn concat(deref_str: &str) -> String {
     format!("{}bar", deref_str)
 }
@@ -121,6 +124,18 @@ fn main() {
     let b: &str = expr_deref!(a.deref());
     //~^ explicit_deref_methods
 
+    proc_macros::external! {
+        let a: &mut String = &mut String::from("foo");
+        let b: &str = a.deref();
+    }
+
+    // Issue #15168
+    proc_macros::with_span! {
+        span
+        let a: &mut String = &mut String::from("foo");
+        let b: &str = a.deref();
+    }
+
     // The struct does not implement Deref trait
     #[derive(Copy, Clone)]
     struct NoLint(u32);

tests/ui/explicit_deref_methods.stderr

@@ -1,5 +1,5 @@
 error: explicit `deref` method call
-  --> tests/ui/explicit_deref_methods.rs:55:19
+  --> tests/ui/explicit_deref_methods.rs:58:19
    |
 LL |     let b: &str = a.deref();
    |                   ^^^^^^^^^ help: try: `&*a`
@@ -8,73 +8,73 @@ LL |     let b: &str = a.deref();
    = help: to override `-D warnings` add `#[allow(clippy::explicit_deref_methods)]`
 
 error: explicit `deref_mut` method call
-  --> tests/ui/explicit_deref_methods.rs:58:23
+  --> tests/ui/explicit_deref_methods.rs:61:23
    |
 LL |     let b: &mut str = a.deref_mut();
    |                       ^^^^^^^^^^^^^ help: try: `&mut **a`
 
 error: explicit `deref` method call
-  --> tests/ui/explicit_deref_methods.rs:62:39
+  --> tests/ui/explicit_deref_methods.rs:65:39
    |
 LL |     let b: String = format!("{}, {}", a.deref(), a.deref());
    |                                       ^^^^^^^^^ help: try: `&*a`
 
 error: explicit `deref` method call
-  --> tests/ui/explicit_deref_methods.rs:62:50
+  --> tests/ui/explicit_deref_methods.rs:65:50
    |
 LL |     let b: String = format!("{}, {}", a.deref(), a.deref());
    |                                                  ^^^^^^^^^ help: try: `&*a`
 
 error: explicit `deref` method call
-  --> tests/ui/explicit_deref_methods.rs:66:20
+  --> tests/ui/explicit_deref_methods.rs:69:20
    |
 LL |     println!("{}", a.deref());
    |                    ^^^^^^^^^ help: try: `&*a`
 
 error: explicit `deref` method call
-  --> tests/ui/explicit_deref_methods.rs:70:11
+  --> tests/ui/explicit_deref_methods.rs:73:11
    |
 LL |     match a.deref() {
    |           ^^^^^^^^^ help: try: `&*a`
 
 error: explicit `deref` method call
-  --> tests/ui/explicit_deref_methods.rs:75:28
+  --> tests/ui/explicit_deref_methods.rs:78:28
    |
 LL |     let b: String = concat(a.deref());
    |                            ^^^^^^^^^ help: try: `&*a`
 
 error: explicit `deref` method call
-  --> tests/ui/explicit_deref_methods.rs:78:13
+  --> tests/ui/explicit_deref_methods.rs:81:13
    |
 LL |     let b = just_return(a).deref();
    |             ^^^^^^^^^^^^^^^^^^^^^^ help: try: `just_return(a)`
 
 error: explicit `deref` method call
-  --> tests/ui/explicit_deref_methods.rs:81:28
+  --> tests/ui/explicit_deref_methods.rs:84:28
    |
 LL |     let b: String = concat(just_return(a).deref());
    |                            ^^^^^^^^^^^^^^^^^^^^^^ help: try: `just_return(a)`
 
 error: explicit `deref` method call
-  --> tests/ui/explicit_deref_methods.rs:121:31
+  --> tests/ui/explicit_deref_methods.rs:124:31
    |
 LL |     let b: &str = expr_deref!(a.deref());
    |                               ^^^^^^^^^ help: try: `&*a`
 
 error: explicit `deref` method call
-  --> tests/ui/explicit_deref_methods.rs:139:14
+  --> tests/ui/explicit_deref_methods.rs:154:14
    |
 LL |     let _ = &Deref::deref(&"foo");
    |              ^^^^^^^^^^^^^^^^^^^^ help: try: `*&"foo"`
 
 error: explicit `deref_mut` method call
-  --> tests/ui/explicit_deref_methods.rs:141:14
+  --> tests/ui/explicit_deref_methods.rs:156:14
    |
 LL |     let _ = &DerefMut::deref_mut(&mut x);
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `&mut **&mut x`
 
 error: explicit `deref_mut` method call
-  --> tests/ui/explicit_deref_methods.rs:142:14
+  --> tests/ui/explicit_deref_methods.rs:157:14
    |
 LL |     let _ = &DerefMut::deref_mut((&mut &mut x).deref_mut());
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `&mut ***(&mut &mut x)`