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

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Sep 23, 2025
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Check for proc macros from within explicit_deref_methods and do not lint on proc macro expansions #15628

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e513ecc
Fix `explicit_deref_methods` triggering from within proc macros
JustusFluegel Sep 7, 2025
3e65620
Add tests for `explicit_deref_methods` lints from within proc macros
JustusFluegel Sep 7, 2025
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10 changes: 9 additions & 1 deletion clippy_lints/src/dereference.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand Down Expand Up @@ -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);
Expand Down
15 changes: 15 additions & 0 deletions tests/ui/explicit_deref_methods.fixed
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Original file line number Diff line number Diff line change
@@ -1,3 +1,4 @@
//@aux-build:proc_macros.rs
#![warn(clippy::explicit_deref_methods)]
#![allow(unused_variables, unused_must_use)]
#![allow(
Expand All @@ -14,6 +15,8 @@

use std::ops::{Deref, DerefMut};

extern crate proc_macros;

fn concat(deref_str: &str) -> String {
format!("{}bar", deref_str)
}
Expand Down Expand Up @@ -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);
Expand Down
15 changes: 15 additions & 0 deletions tests/ui/explicit_deref_methods.rs
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Original file line number Diff line number Diff line change
@@ -1,3 +1,4 @@
//@aux-build:proc_macros.rs
#![warn(clippy::explicit_deref_methods)]
#![allow(unused_variables, unused_must_use)]
#![allow(
Expand All @@ -14,6 +15,8 @@

use std::ops::{Deref, DerefMut};

extern crate proc_macros;

fn concat(deref_str: &str) -> String {
format!("{}bar", deref_str)
}
Expand Down Expand Up @@ -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);
Expand Down
26 changes: 13 additions & 13 deletions tests/ui/explicit_deref_methods.stderr
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Original file line number Diff line number Diff line change
@@ -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`
Expand All @@ -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)`
Expand Down