Omit default types in HirDisplay SourceCode mode

crates/ra_assists/src/handlers/add_explicit_type.rs

@@ -209,7 +209,7 @@ struct Test<K, T = u8> {
 }
 
 fn main() {
-    let test<|>: Test<i32, u8> = Test { t: 23, k: 33 };
+    let test<|>: Test<i32> = Test { t: 23, k: 33 };
 }"#,
         );
     }

crates/ra_hir_ty/src/display.rs

@@ -136,6 +136,12 @@ enum DisplayTarget {
     SourceCode { module_id: ModuleId },
 }
 
+impl DisplayTarget {
+    fn is_source_code(&self) -> bool {
+        matches!(self, Self::SourceCode {..})
+    }
+}
+
 #[derive(Debug)]
 pub enum DisplaySourceCodeError {
     PathNotFound,
@@ -303,7 +309,8 @@ impl HirDisplay for ApplicationTy {
 
                 if self.parameters.len() > 0 {
                     let mut non_default_parameters = Vec::with_capacity(self.parameters.len());
-                    let parameters_to_write = if f.omit_verbose_types() {
+                    let parameters_to_write =
+                        if f.display_target.is_source_code() || f.omit_verbose_types() {
                             match self
                                 .ctor
                                 .as_generic_def()
@@ -331,11 +338,13 @@ impl HirDisplay for ApplicationTy {
                         } else {
                             self.parameters.0.as_ref()
                         };
+                    if !parameters_to_write.is_empty() {
                         write!(f, "<")?;
                         f.write_joined(parameters_to_write, ", ")?;
                         write!(f, ">")?;
                     }
                 }
+            }
             TypeCtor::AssociatedType(type_alias) => {
                 let trait_ = match type_alias.lookup(f.db.upcast()).container {
                     AssocContainerId::TraitId(it) => it,

crates/ra_hir_ty/src/tests/display_source_code.rs

@@ -21,3 +21,30 @@ fn bar() {
     );
     assert_eq!("foo::Foo", displayed_source_at_pos(&db, pos));
 }
+
+#[test]
+fn omit_default_type_parameters() {
+    let (db, pos) = TestDB::with_position(
+        r"
+        //- /main.rs
+        struct Foo<T = u8> { t: T }
+        fn main() {
+            let foo = Foo { t: 5 };
+            foo<|>;
+        }
+        ",
+    );
+    assert_eq!("Foo", displayed_source_at_pos(&db, pos));
+
+    let (db, pos) = TestDB::with_position(
+        r"
+        //- /main.rs
+        struct Foo<K, T = u8> { k: K, t: T }
+        fn main() {
+            let foo = Foo { k: 400, t: 5 };
+            foo<|>;
+        }
+        ",
+    );
+    assert_eq!("Foo<i32>", displayed_source_at_pos(&db, pos));
+}