Implement #[define_opaque] attribute for functions.

Author: oli-obk

clippy_utils/src/ast_utils/mod.rs

@@ -364,13 +364,15 @@ pub fn eq_item_kind(l: &ItemKind, r: &ItemKind) -> bool {
                 generics: lg,
                 contract: lc,
                 body: lb,
+                define_opaque: _,
             }),
             Fn(box ast::Fn {
                 defaultness: rd,
                 sig: rf,
                 generics: rg,
                 contract: rc,
                 body: rb,
+                define_opaque: _,
             }),
         ) => {
             eq_defaultness(*ld, *rd)
@@ -502,13 +504,15 @@ pub fn eq_foreign_item_kind(l: &ForeignItemKind, r: &ForeignItemKind) -> bool {
                 generics: lg,
                 contract: lc,
                 body: lb,
+                define_opaque: _,
             }),
             Fn(box ast::Fn {
                 defaultness: rd,
                 sig: rf,
                 generics: rg,
                 contract: rc,
                 body: rb,
+                define_opaque: _,
             }),
         ) => {
             eq_defaultness(*ld, *rd)
@@ -567,13 +571,15 @@ pub fn eq_assoc_item_kind(l: &AssocItemKind, r: &AssocItemKind) -> bool {
                 generics: lg,
                 contract: lc,
                 body: lb,
+                define_opaque: _,
             }),
             Fn(box ast::Fn {
                 defaultness: rd,
                 sig: rf,
                 generics: rg,
                 contract: rc,
                 body: rb,
+                define_opaque: _,
             }),
         ) => {
             eq_defaultness(*ld, *rd)

tests/ui/crashes/ice-10972-tait.rs

@@ -192,6 +192,7 @@ impl Atpit for () {
 
 type Tait = impl DerefMut;
 //~^ implied_bounds_in_impls
+#[define_opaque(Tait)]
 fn define() -> Tait {
     &mut [] as &mut [()]
 }

tests/ui/implied_bounds_in_impls.fixed

@@ -192,6 +192,7 @@ impl Atpit for () {
 
 type Tait = impl Deref + DerefMut;
 //~^ implied_bounds_in_impls
+#[define_opaque(Tait)]
 fn define() -> Tait {
     &mut [] as &mut [()]
 }

tests/ui/implied_bounds_in_impls.rs

@@ -207,6 +207,7 @@ mod msrv {
 mod with_ty_alias {
     type Foo = impl std::fmt::Debug;
 
+    #[define_opaque(Foo)]
     fn foo(_: Foo) {
         let _: Foo = 1;
     }

tests/ui/missing_const_for_fn/cant_be_const.rs

@@ -17,6 +17,7 @@ mod issue10041 {
     struct Bomb2;
 
     impl Bomb2 {
+        #[define_opaque(X)]
         pub fn new() -> X {
             //~^ ERROR: overflow evaluating the requirement
             0i32

tests/ui/new_ret_no_self_overflow.rs

@@ -1,5 +1,5 @@
 error[E0275]: overflow evaluating the requirement `<i32 as std::ops::Add>::Output == issue10041::X`
-  --> tests/ui/new_ret_no_self_overflow.rs:20:25
+  --> tests/ui/new_ret_no_self_overflow.rs:21:25
    |
 LL |         pub fn new() -> X {
    |                         ^