Show only assoc type args in the correct arg pos

Author: xuhongxu96

crates/hir/src/lib.rs

@@ -41,6 +41,7 @@ use hir_def::{
     adt::{ReprKind, VariantData},
     body::{BodyDiagnostic, SyntheticSyntax},
     expr::{BindingAnnotation, LabelId, Pat, PatId},
+    generics::{TypeOrConstParamData, TypeParamProvenance},
     item_tree::ItemTreeNode,
     lang_item::LangItemTarget,
     nameres::{self, diagnostics::DefDiagnostic},
@@ -1707,6 +1708,22 @@ impl Trait {
     pub fn is_unsafe(&self, db: &dyn HirDatabase) -> bool {
         db.trait_data(self.id).is_unsafe
     }
+
+    pub fn type_parameters(&self, db: &dyn HirDatabase) -> Vec<TypeOrConstParamData> {
+        db.generic_params(GenericDefId::from(self.id))
+            .type_or_consts
+            .iter()
+            .filter(|(_, ty)| match ty {
+                TypeOrConstParamData::TypeParamData(ty)
+                    if ty.provenance != TypeParamProvenance::TypeParamList =>
+                {
+                    false
+                }
+                _ => true,
+            })
+            .map(|(_, ty)|ty.clone())
+            .collect()
+        }
 }
 
 impl HasVisibility for Trait {

crates/ide-completion/src/completions/type.rs

@@ -1,6 +1,7 @@
 //! Completion of names from the current scope in type position.
 
 use hir::{HirDisplay, ScopeDef};
+use itertools::Itertools;
 use syntax::{ast, AstNode};
 
 use crate::{
@@ -140,6 +141,18 @@ pub(crate) fn complete_type_path(
                     return;
                 }
                 TypeLocation::GenericArgList(Some(arg_list)) => {
+                    // the current token is in which generic arg
+                    let arg_pos = if let Some((pos, _)) =
+                        arg_list.generic_args().find_position(|arg| {
+                            arg.syntax()
+                                .descendants_with_tokens()
+                                .any(|t| t.as_token() == Some(&ctx.original_token))
+                        }) {
+                        pos
+                    } else {
+                        0
+                    };
+
                     match arg_list.generic_args().next() {
                         Some(ast::GenericArg::AssocTypeArg(_)) => {}
                         _ => {
@@ -167,7 +180,10 @@ pub(crate) fn complete_type_path(
                                                     acc.add_type_alias_with_eq(ctx, alias);
                                                 }
                                             });
-                                        return; // only AssocTypeArgs make sense
+
+                                        if arg_pos >= trait_.type_parameters(ctx.sema.db).len() {
+                                            return; // only AssocTypeArgs make sense
+                                        }
                                     }
                                 }
                             }

crates/ide-completion/src/tests/type_pos.rs

@@ -386,6 +386,39 @@ fn foo<'lt, T: Trait2<$0>, const CONST_PARAM: usize>(_: T) {}
     );
     check(
         r#"
+trait Trait1 {
+    type Super;
+}
+trait Trait2<T>: Trait1 {
+    type Foo;
+}
+
+fn foo<'lt, T: Trait2<$0>, const CONST_PARAM: usize>(_: T) {}
+"#,
+        expect![[r#"
+            ct CONST
+            cp CONST_PARAM
+            en Enum
+            ma makro!(…)            macro_rules! makro
+            md module
+            st Record
+            st Tuple
+            st Unit
+            tt Trait
+            tt Trait1
+            tt Trait2
+            ta Foo =  (as Trait2)   type Foo
+            ta Super =  (as Trait1) type Super
+            tp T
+            un Union
+            bt u32
+            kw crate::
+            kw self::
+            kw super::
+        "#]],
+    );
+    check(
+        r#"
 trait Trait2 {
     type Foo;
 }
@@ -460,11 +493,11 @@ fn func(_: Enum::$0) {}
 fn completes_associated_type_only() {
     check(
         r#"
-trait MyTrait {
+trait MyTrait<T> {
     type Item;
 };
 
-fn f(t: impl MyTrait<I$0
+fn f(t: impl MyTrait<u8,I$0
 "#,
         expect![[r#"
             ta Item =  (as MyTrait) type Item