2 files changed, 275 insertions, 15 deletions

diff --git a/crates/assists/src/handlers/qualify_path.rs b/crates/assists/src/handlers/qualify_path.rs
index f436bdbbf..d5bc4e574 100644
--- a/crates/assists/src/handlers/qualify_path.rs
+++ b/crates/assists/src/handlers/qualify_path.rs
@@ -56,12 +56,14 @@ pub(crate) fn qualify_path(acc: &mut Assists, ctx: &AssistContext) -> Option<()>
         ImportCandidate::QualifierStart(_) => {
             mark::hit!(qualify_path_qualifier_start);
             let path = ast::Path::cast(import_assets.syntax_under_caret().clone())?;
-            let segment = path.segment()?;
-            QualifyCandidate::QualifierStart(segment)
+            let (prev_segment, segment) = (path.qualifier()?.segment()?, path.segment()?);
+            QualifyCandidate::QualifierStart(segment, prev_segment.generic_arg_list())
         }
         ImportCandidate::UnqualifiedName(_) => {
             mark::hit!(qualify_path_unqualified_name);
-            QualifyCandidate::UnqualifiedName
+            let path = ast::Path::cast(import_assets.syntax_under_caret().clone())?;
+            let generics = path.segment()?.generic_arg_list();
+            QualifyCandidate::UnqualifiedName(generics)
         }
         ImportCandidate::TraitAssocItem(_) => {
             mark::hit!(qualify_path_trait_assoc_item);
@@ -96,22 +98,25 @@ pub(crate) fn qualify_path(acc: &mut Assists, ctx: &AssistContext) -> Option<()>
 }
 
 enum QualifyCandidate<'db> {
-    QualifierStart(ast::PathSegment),
-    UnqualifiedName,
+    QualifierStart(ast::PathSegment, Option<ast::GenericArgList>),
+    UnqualifiedName(Option<ast::GenericArgList>),
     TraitAssocItem(ast::Path, ast::PathSegment),
     TraitMethod(&'db RootDatabase, ast::MethodCallExpr),
 }
 
 impl QualifyCandidate<'_> {
     fn qualify(&self, mut replacer: impl FnMut(String), import: hir::ModPath, item: hir::ItemInNs) {
+        let import = mod_path_to_ast(&import);
         match self {
-            QualifyCandidate::QualifierStart(segment) => {
-                let import = mod_path_to_ast(&import);
-                replacer(format!("{}::{}", import, segment));
+            QualifyCandidate::QualifierStart(segment, generics) => {
+                let generics = generics.as_ref().map_or_else(String::new, ToString::to_string);
+                replacer(format!("{}{}::{}", import, generics, segment));
+            }
+            QualifyCandidate::UnqualifiedName(generics) => {
+                let generics = generics.as_ref().map_or_else(String::new, ToString::to_string);
+                replacer(format!("{}{}", import.to_string(), generics));
             }
-            QualifyCandidate::UnqualifiedName => replacer(mod_path_to_ast(&import).to_string()),
             QualifyCandidate::TraitAssocItem(qualifier, segment) => {
-                let import = mod_path_to_ast(&import);
                 replacer(format!("<{} as {}>::{}", qualifier, import, segment));
             }
             &QualifyCandidate::TraitMethod(db, ref mcall_expr) => {
@@ -124,25 +129,27 @@ impl QualifyCandidate<'_> {
         db: &RootDatabase,
         mcall_expr: &ast::MethodCallExpr,
         mut replacer: impl FnMut(String),
-        import: hir::ModPath,
+        import: ast::Path,
         item: hir::ItemInNs,
     ) -> Option<()> {
         let receiver = mcall_expr.receiver()?;
         let trait_method_name = mcall_expr.name_ref()?;
+        let generics =
+            mcall_expr.generic_arg_list().as_ref().map_or_else(String::new, ToString::to_string);
         let arg_list = mcall_expr.arg_list().map(|arg_list| arg_list.args());
         let trait_ = item_as_trait(item)?;
         let method = find_trait_method(db, trait_, &trait_method_name)?;
         if let Some(self_access) = method.self_param(db).map(|sp| sp.access(db)) {
-            let import = mod_path_to_ast(&import);
             let receiver = match self_access {
                 hir::Access::Shared => make::expr_ref(receiver, false),
                 hir::Access::Exclusive => make::expr_ref(receiver, true),
                 hir::Access::Owned => receiver,
             };
             replacer(format!(
-                "{}::{}{}",
+                "{}::{}{}{}",
                 import,
                 trait_method_name,
+                generics,
                 match arg_list.clone() {
                     Some(args) => make::arg_list(iter::once(receiver).chain(args)),
                     None => make::arg_list(iter::once(receiver)),
@@ -1045,4 +1052,153 @@ fn main() {
 ",
         );
     }
+
+    #[test]
+    fn keep_generic_annotations() {
+        check_assist(
+            qualify_path,
+            r"
+//- /lib.rs crate:dep
+pub mod generic { pub struct Thing<'a, T>(&'a T); }
+
+//- /main.rs crate:main deps:dep
+fn foo() -> Thin<|>g<'static, ()> {}
+
+fn main() {}
+",
+            r"
+fn foo() -> dep::generic::Thing<'static, ()> {}
+
+fn main() {}
+",
+        );
+    }
+
+    #[test]
+    fn keep_generic_annotations_leading_colon() {
+        check_assist(
+            qualify_path,
+            r"
+//- /lib.rs crate:dep
+pub mod generic { pub struct Thing<'a, T>(&'a T); }
+
+//- /main.rs crate:main deps:dep
+fn foo() -> Thin<|>g::<'static, ()> {}
+
+fn main() {}
+",
+            r"
+fn foo() -> dep::generic::Thing::<'static, ()> {}
+
+fn main() {}
+",
+        );
+    }
+
+    #[test]
+    fn associated_struct_const_generic() {
+        check_assist(
+            qualify_path,
+            r"
+            mod test_mod {
+                pub struct TestStruct<T> {}
+                impl<T> TestStruct<T> {
+                    const TEST_CONST: u8 = 42;
+                }
+            }
+
+            fn main() {
+                TestStruct::<()>::TEST_CONST<|>
+            }
+            ",
+            r"
+            mod test_mod {
+                pub struct TestStruct<T> {}
+                impl<T> TestStruct<T> {
+                    const TEST_CONST: u8 = 42;
+                }
+            }
+
+            fn main() {
+                test_mod::TestStruct::<()>::TEST_CONST
+            }
+            ",
+        );
+    }
+
+    #[test]
+    fn associated_trait_const_generic() {
+        check_assist(
+            qualify_path,
+            r"
+            mod test_mod {
+                pub trait TestTrait {
+                    const TEST_CONST: u8;
+                }
+                pub struct TestStruct<T> {}
+                impl<T> TestTrait for TestStruct<T> {
+                    const TEST_CONST: u8 = 42;
+                }
+            }
+
+            fn main() {
+                test_mod::TestStruct::<()>::TEST_CONST<|>
+            }
+            ",
+            r"
+            mod test_mod {
+                pub trait TestTrait {
+                    const TEST_CONST: u8;
+                }
+                pub struct TestStruct<T> {}
+                impl<T> TestTrait for TestStruct<T> {
+                    const TEST_CONST: u8 = 42;
+                }
+            }
+
+            fn main() {
+                <test_mod::TestStruct::<()> as test_mod::TestTrait>::TEST_CONST
+            }
+            ",
+        );
+    }
+
+    #[test]
+    fn trait_method_generic() {
+        check_assist(
+            qualify_path,
+            r"
+            mod test_mod {
+                pub trait TestTrait {
+                    fn test_method<T>(&self);
+                }
+                pub struct TestStruct {}
+                impl TestTrait for TestStruct {
+                    fn test_method<T>(&self) {}
+                }
+            }
+
+            fn main() {
+                let test_struct = test_mod::TestStruct {};
+                test_struct.test_meth<|>od::<()>()
+            }
+            ",
+            r"
+            mod test_mod {
+                pub trait TestTrait {
+                    fn test_method<T>(&self);
+                }
+                pub struct TestStruct {}
+                impl TestTrait for TestStruct {
+                    fn test_method<T>(&self) {}
+                }
+            }
+
+            fn main() {
+                let test_struct = test_mod::TestStruct {};
+                test_mod::TestTrait::test_method::<()>(&test_struct)
+            }
+            ",
+        );
+    }
 }
diff --git a/crates/ide/src/inlay_hints.rs b/crates/ide/src/inlay_hints.rs
index adb93efd7..ac704ae21 100644
--- a/crates/ide/src/inlay_hints.rs
+++ b/crates/ide/src/inlay_hints.rs
@@ -1,6 +1,6 @@
 use assists::utils::FamousDefs;
 use either::Either;
-use hir::{known, HirDisplay, Semantics};
+use hir::{known, Callable, HirDisplay, Semantics};
 use ide_db::RootDatabase;
 use stdx::to_lower_snake_case;
 use syntax::{
@@ -170,7 +170,7 @@ fn get_param_name_hints(
             };
             Some((param_name, arg))
         })
-        .filter(|(param_name, arg)| should_show_param_name_hint(sema, &callable, &param_name, &arg))
+        .filter(|(param_name, arg)| should_show_param_name_hint(sema, &callable, param_name, &arg))
         .map(|(param_name, arg)| InlayHint {
             range: arg.syntax().text_range(),
             kind: InlayKind::ParameterHint,
@@ -334,9 +334,11 @@ fn should_show_param_name_hint(
         | hir::CallableKind::TupleEnumVariant(_)
         | hir::CallableKind::Closure => None,
     };
+
     if param_name.is_empty()
         || Some(param_name) == fn_name.as_ref().map(|s| s.trim_start_matches('_'))
         || is_argument_similar_to_param_name(sema, argument, param_name)
+        || is_param_name_similar_to_fn_name(param_name, callable, fn_name.as_ref())
         || param_name.starts_with("ra_fixture")
     {
         return false;
@@ -364,6 +366,26 @@ fn is_argument_similar_to_param_name(
     }
 }
 
+fn is_param_name_similar_to_fn_name(
+    param_name: &str,
+    callable: &Callable,
+    fn_name: Option<&String>,
+) -> bool {
+    // if it's the only parameter, don't show it if:
+    // - is the same as the function name, or
+    // - the function ends with '_' + param_name
+
+    match (callable.n_params(), fn_name) {
+        (1, Some(function)) => {
+            function == param_name
+                || (function.len() > param_name.len()
+                    && function.ends_with(param_name)
+                    && function[..function.len() - param_name.len()].ends_with('_'))
+        }
+        _ => false,
+    }
+}
+
 fn is_enum_name_similar_to_param_name(
     sema: &Semantics<RootDatabase>,
     argument: &ast::Expr,
@@ -457,6 +479,88 @@ fn main() {
     }
 
     #[test]
+    fn param_name_similar_to_fn_name_still_hints() {
+        check_with_config(
+            InlayHintsConfig {
+                parameter_hints: true,
+                type_hints: false,
+                chaining_hints: false,
+                max_length: None,
+            },
+            r#"
+fn max(x: i32, y: i32) -> i32 { x + y }
+fn main() {
+    let _x = max(
+        4,
+      //^ x
+        4,
+      //^ y
+    );
+}"#,
+        );
+    }
+
+    #[test]
+    fn param_name_similar_to_fn_name() {
+        check_with_config(
+            InlayHintsConfig {
+                parameter_hints: true,
+                type_hints: false,
+                chaining_hints: false,
+                max_length: None,
+            },
+            r#"
+fn param_with_underscore(with_underscore: i32) -> i32 { with_underscore }
+fn main() {
+    let _x = param_with_underscore(
+        4,
+    );
+}"#,
+        );
+    }
+
+    #[test]
+    fn param_name_same_as_fn_name() {
+        check_with_config(
+            InlayHintsConfig {
+                parameter_hints: true,
+                type_hints: false,
+                chaining_hints: false,
+                max_length: None,
+            },
+            r#"
+fn foo(foo: i32) -> i32 { foo }
+fn main() {
+    let _x = foo(
+        4,
+    );
+}"#,
+        );
+    }
+
+    #[test]
+    fn never_hide_param_when_multiple_params() {
+        check_with_config(
+            InlayHintsConfig {
+                parameter_hints: true,
+                type_hints: false,
+                chaining_hints: false,
+                max_length: None,
+            },
+            r#"
+fn foo(bar: i32, baz: i32) -> i32 { bar + baz }
+fn main() {
+    let _x = foo(
+        4,
+      //^ bar
+        8,
+      //^ baz
+    );
+}"#,
+        );
+    }
+
+    #[test]
     fn hints_disabled() {
         check_with_config(
             InlayHintsConfig {