4 files changed, 94 insertions, 28 deletions

diff --git a/crates/ra_hir_ty/src/display.rs b/crates/ra_hir_ty/src/display.rs
index f5edaea8c..b9c4d2e89 100644
--- a/crates/ra_hir_ty/src/display.rs
+++ b/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,
@@ -303,37 +309,40 @@ 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() {
-                        match self
-                            .ctor
-                            .as_generic_def()
-                            .map(|generic_def_id| f.db.generic_defaults(generic_def_id))
-                            .filter(|defaults| !defaults.is_empty())
-                        {
-                            None => self.parameters.0.as_ref(),
-                            Some(default_parameters) => {
-                                for (i, parameter) in self.parameters.iter().enumerate() {
-                                    match (parameter, default_parameters.get(i)) {
-                                        (&Ty::Unknown, _) | (_, None) => {
-                                            non_default_parameters.push(parameter.clone())
-                                        }
-                                        (_, Some(default_parameter))
-                                            if parameter != default_parameter =>
-                                        {
-                                            non_default_parameters.push(parameter.clone())
+                    let parameters_to_write =
+                        if f.display_target.is_source_code() || f.omit_verbose_types() {
+                            match self
+                                .ctor
+                                .as_generic_def()
+                                .map(|generic_def_id| f.db.generic_defaults(generic_def_id))
+                                .filter(|defaults| !defaults.is_empty())
+                            {
+                                None => self.parameters.0.as_ref(),
+                                Some(default_parameters) => {
+                                    for (i, parameter) in self.parameters.iter().enumerate() {
+                                        match (parameter, default_parameters.get(i)) {
+                                            (&Ty::Unknown, _) | (_, None) => {
+                                                non_default_parameters.push(parameter.clone())
+                                            }
+                                            (_, Some(default_parameter))
+                                                if parameter != default_parameter =>
+                                            {
+                                                non_default_parameters.push(parameter.clone())
+                                            }
+                                            _ => (),
                                         }
-                                        _ => (),
                                     }
+                                    &non_default_parameters
                                 }
-                                &non_default_parameters
                             }
-                        }
-                    } else {
-                        self.parameters.0.as_ref()
-                    };
-                    write!(f, "<")?;
-                    f.write_joined(parameters_to_write, ", ")?;
-                    write!(f, ">")?;
+                        } 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) => {
diff --git a/crates/ra_hir_ty/src/op.rs b/crates/ra_hir_ty/src/op.rs
index 54e2bd05a..0870874fc 100644
--- a/crates/ra_hir_ty/src/op.rs
+++ b/crates/ra_hir_ty/src/op.rs
@@ -30,7 +30,8 @@ pub(super) fn binary_op_return_ty(op: BinaryOp, lhs_ty: Ty, rhs_ty: Ty) -> Ty {
 pub(super) fn binary_op_rhs_expectation(op: BinaryOp, lhs_ty: Ty) -> Ty {
     match op {
         BinaryOp::LogicOp(..) => Ty::simple(TypeCtor::Bool),
-        BinaryOp::Assignment { op: None } | BinaryOp::CmpOp(CmpOp::Eq { .. }) => match lhs_ty {
+        BinaryOp::Assignment { op: None } => lhs_ty,
+        BinaryOp::CmpOp(CmpOp::Eq { .. }) => match lhs_ty {
             Ty::Apply(ApplicationTy { ctor, .. }) => match ctor {
                 TypeCtor::Int(..)
                 | TypeCtor::Float(..)
diff --git a/crates/ra_hir_ty/src/tests/display_source_code.rs b/crates/ra_hir_ty/src/tests/display_source_code.rs
index ca1748615..4088b1d22 100644
--- a/crates/ra_hir_ty/src/tests/display_source_code.rs
+++ b/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));
+}
diff --git a/crates/ra_hir_ty/src/tests/simple.rs b/crates/ra_hir_ty/src/tests/simple.rs
index 3820175f6..322838f02 100644
--- a/crates/ra_hir_ty/src/tests/simple.rs
+++ b/crates/ra_hir_ty/src/tests/simple.rs
@@ -1787,3 +1787,32 @@ fn main() {
     "###
     )
 }
+
+#[test]
+fn infer_generic_from_later_assignment() {
+    assert_snapshot!(
+        infer(r#"
+enum Option<T> { Some(T), None }
+use Option::*;
+
+fn test() {
+    let mut end = None;
+    loop {
+        end = Some(true);
+    }
+}
+"#),
+        @r###"
+    60..130 '{     ...   } }': ()
+    70..77 'mut end': Option<bool>
+    80..84 'None': Option<bool>
+    90..128 'loop {...     }': !
+    95..128 '{     ...     }': ()
+    105..108 'end': Option<bool>
+    105..121 'end = ...(true)': ()
+    111..115 'Some': Some<bool>(bool) -> Option<bool>
+    111..121 'Some(true)': Option<bool>
+    116..120 'true': bool
+    "###
+    );
+}