Auto merge of #10813 - y21:issue10755, r=xFrednet

[`default_constructed_unit_structs`]: do not lint on type alias paths

Fixes #10755.

Type aliases cannot be used as a constructor, so this lint should not trigger in those cases.
I also changed `clippy_utils::is_ty_alias` to also consider associated types since [they kinda are type aliases too](48ec50ae39/compiler/rustc_resolve/src/late/diagnostics.rs (L1520)).

changelog: [`default_constructed_unit_structs`]: do not lint on type alias paths

tests/ui/default_constructed_unit_structs.fixed

@@ -101,6 +101,28 @@ struct EmptyStruct {}
 #[non_exhaustive]
 struct NonExhaustiveStruct;
 
+mod issue_10755 {
+    struct Sqlite {}
+
+    trait HasArguments<'q> {
+        type Arguments;
+    }
+
+    impl<'q> HasArguments<'q> for Sqlite {
+        type Arguments = std::marker::PhantomData<&'q ()>;
+    }
+
+    type SqliteArguments<'q> = <Sqlite as HasArguments<'q>>::Arguments;
+
+    fn foo() {
+        // should not lint
+        // type alias cannot be used as a constructor
+        let _ = <Sqlite as HasArguments>::Arguments::default();
+
+        let _ = SqliteArguments::default();
+    }
+}
+
 fn main() {
     // should lint
     let _ = PhantomData::<usize>;

tests/ui/default_constructed_unit_structs.rs

@@ -101,6 +101,28 @@ struct EmptyStruct {}
 #[non_exhaustive]
 struct NonExhaustiveStruct;
 
+mod issue_10755 {
+    struct Sqlite {}
+
+    trait HasArguments<'q> {
+        type Arguments;
+    }
+
+    impl<'q> HasArguments<'q> for Sqlite {
+        type Arguments = std::marker::PhantomData<&'q ()>;
+    }
+
+    type SqliteArguments<'q> = <Sqlite as HasArguments<'q>>::Arguments;
+
+    fn foo() {
+        // should not lint
+        // type alias cannot be used as a constructor
+        let _ = <Sqlite as HasArguments>::Arguments::default();
+
+        let _ = SqliteArguments::default();
+    }
+}
+
 fn main() {
     // should lint
     let _ = PhantomData::<usize>::default();

tests/ui/default_constructed_unit_structs.stderr

@@ -13,25 +13,25 @@ LL |             inner: PhantomData::default(),
    |                               ^^^^^^^^^^^ help: remove this call to `default`
 
 error: use of `default` to create a unit struct
-  --> $DIR/default_constructed_unit_structs.rs:106:33
+  --> $DIR/default_constructed_unit_structs.rs:128:33
    |
 LL |     let _ = PhantomData::<usize>::default();
    |                                 ^^^^^^^^^^^ help: remove this call to `default`
 
 error: use of `default` to create a unit struct
-  --> $DIR/default_constructed_unit_structs.rs:107:42
+  --> $DIR/default_constructed_unit_structs.rs:129:42
    |
 LL |     let _: PhantomData<i32> = PhantomData::default();
    |                                          ^^^^^^^^^^^ help: remove this call to `default`
 
 error: use of `default` to create a unit struct
-  --> $DIR/default_constructed_unit_structs.rs:108:55
+  --> $DIR/default_constructed_unit_structs.rs:130:55
    |
 LL |     let _: PhantomData<i32> = std::marker::PhantomData::default();
    |                                                       ^^^^^^^^^^^ help: remove this call to `default`
 
 error: use of `default` to create a unit struct
-  --> $DIR/default_constructed_unit_structs.rs:109:23
+  --> $DIR/default_constructed_unit_structs.rs:131:23
    |
 LL |     let _ = UnitStruct::default();
    |                       ^^^^^^^^^^^ help: remove this call to `default`