Auto merge of #12736 - UlazkaMateusz:fix-type_complexity_duplicate_errors, r=xFrednet

[`type_complexity`]: Fix duplicate errors

Relates to #12379

Following message was duplicated:
```
LL |     fn def_method(&self, p: Vec<Vec<Box<(u32, u32, u32, u32)>>>) {}
   |                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`

error: very complex type used. Consider factoring parts into `type` definitions
  --> tests/ui/type_complexity.rs:55:15
```

Methods `check_trait_item` and `check_fn` were both checking method named def_method.
Now `check_trait_item` only checks methods without body.

---
changelog: [`type_complexity`]: Fix duplicate diagnostics

Author: bors

Diff for: clippy_lints/src/types/mod.rs

@@ -12,8 +12,8 @@ mod vec_box;
 use rustc_hir as hir;
 use rustc_hir::intravisit::FnKind;
 use rustc_hir::{
-    Body, FnDecl, FnRetTy, GenericArg, ImplItem, ImplItemKind, Item, ItemKind, LetStmt, MutTy, QPath, TraitItem,
-    TraitItemKind, TyKind,
+    Body, FnDecl, FnRetTy, GenericArg, ImplItem, ImplItemKind, Item, ItemKind, LetStmt, MutTy, QPath, TraitFn,
+    TraitItem, TraitItemKind, TyKind,
 };
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::impl_lint_pass;
@@ -420,7 +420,13 @@ impl<'tcx> LateLintPass<'tcx> for Types {
             TraitItemKind::Const(ty, _) | TraitItemKind::Type(_, Some(ty)) => {
                 self.check_ty(cx, ty, context);
             },
-            TraitItemKind::Fn(ref sig, _) => self.check_fn_decl(cx, sig.decl, context),
+            TraitItemKind::Fn(ref sig, trait_method) => {
+                // Check only methods without body
+                // Methods with body are covered by check_fn.
+                if let TraitFn::Required(_) = trait_method {
+                    self.check_fn_decl(cx, sig.decl, context);
+                }
+            },
             TraitItemKind::Type(..) => (),
         }
     }

Diff for: tests/ui/type_complexity.rs

@@ -1,5 +1,3 @@
-//@compile-flags: -Zdeduplicate-diagnostics=yes
-
 #![warn(clippy::all)]
 #![allow(unused, clippy::needless_pass_by_value, clippy::vec_box, clippy::useless_vec)]
 #![feature(associated_type_defaults)]

Diff for: tests/ui/type_complexity.stderr

@@ -1,5 +1,5 @@
 error: very complex type used. Consider factoring parts into `type` definitions
-  --> tests/ui/type_complexity.rs:9:12
+  --> tests/ui/type_complexity.rs:7:12
    |
 LL | const CST: (u32, (u32, (u32, (u32, u32)))) = (0, (0, (0, (0, 0))));
    |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -8,85 +8,85 @@ LL | const CST: (u32, (u32, (u32, (u32, u32)))) = (0, (0, (0, (0, 0))));
    = help: to override `-D warnings` add `#[allow(clippy::type_complexity)]`
 
 error: very complex type used. Consider factoring parts into `type` definitions
-  --> tests/ui/type_complexity.rs:12:12
+  --> tests/ui/type_complexity.rs:10:12
    |
 LL | static ST: (u32, (u32, (u32, (u32, u32)))) = (0, (0, (0, (0, 0))));
    |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: very complex type used. Consider factoring parts into `type` definitions
-  --> tests/ui/type_complexity.rs:16:8
+  --> tests/ui/type_complexity.rs:14:8
    |
 LL |     f: Vec<Vec<Box<(u32, u32, u32, u32)>>>,
    |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: very complex type used. Consider factoring parts into `type` definitions
-  --> tests/ui/type_complexity.rs:20:11
+  --> tests/ui/type_complexity.rs:18:11
    |
 LL | struct Ts(Vec<Vec<Box<(u32, u32, u32, u32)>>>);
    |           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: very complex type used. Consider factoring parts into `type` definitions
-  --> tests/ui/type_complexity.rs:24:11
+  --> tests/ui/type_complexity.rs:22:11
    |
 LL |     Tuple(Vec<Vec<Box<(u32, u32, u32, u32)>>>),
    |           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: very complex type used. Consider factoring parts into `type` definitions
-  --> tests/ui/type_complexity.rs:26:17
+  --> tests/ui/type_complexity.rs:24:17
    |
 LL |     Struct { f: Vec<Vec<Box<(u32, u32, u32, u32)>>> },
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: very complex type used. Consider factoring parts into `type` definitions
-  --> tests/ui/type_complexity.rs:31:14
+  --> tests/ui/type_complexity.rs:29:14
    |
 LL |     const A: (u32, (u32, (u32, (u32, u32)))) = (0, (0, (0, (0, 0))));
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: very complex type used. Consider factoring parts into `type` definitions
-  --> tests/ui/type_complexity.rs:33:30
+  --> tests/ui/type_complexity.rs:31:30
    |
 LL |     fn impl_method(&self, p: Vec<Vec<Box<(u32, u32, u32, u32)>>>) {}
    |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: very complex type used. Consider factoring parts into `type` definitions
-  --> tests/ui/type_complexity.rs:38:14
+  --> tests/ui/type_complexity.rs:36:14
    |
 LL |     const A: Vec<Vec<Box<(u32, u32, u32, u32)>>>;
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: very complex type used. Consider factoring parts into `type` definitions
-  --> tests/ui/type_complexity.rs:40:14
+  --> tests/ui/type_complexity.rs:38:14
    |
 LL |     type B = Vec<Vec<Box<(u32, u32, u32, u32)>>>;
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: very complex type used. Consider factoring parts into `type` definitions
-  --> tests/ui/type_complexity.rs:42:25
+  --> tests/ui/type_complexity.rs:40:25
    |
 LL |     fn method(&self, p: Vec<Vec<Box<(u32, u32, u32, u32)>>>);
    |                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: very complex type used. Consider factoring parts into `type` definitions
-  --> tests/ui/type_complexity.rs:44:29
+  --> tests/ui/type_complexity.rs:42:29
    |
 LL |     fn def_method(&self, p: Vec<Vec<Box<(u32, u32, u32, u32)>>>) {}
    |                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: very complex type used. Consider factoring parts into `type` definitions
-  --> tests/ui/type_complexity.rs:57:15
+  --> tests/ui/type_complexity.rs:55:15
    |
 LL | fn test1() -> Vec<Vec<Box<(u32, u32, u32, u32)>>> {
    |               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: very complex type used. Consider factoring parts into `type` definitions
-  --> tests/ui/type_complexity.rs:62:14
+  --> tests/ui/type_complexity.rs:60:14
    |
 LL | fn test2(_x: Vec<Vec<Box<(u32, u32, u32, u32)>>>) {}
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: very complex type used. Consider factoring parts into `type` definitions
-  --> tests/ui/type_complexity.rs:66:13
+  --> tests/ui/type_complexity.rs:64:13
    |
 LL |     let _y: Vec<Vec<Box<(u32, u32, u32, u32)>>> = vec![];
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^