Fix complete after extern, add crate completion

Example
---
```rust
extern "C" $0
```

**Before this PR**

Can't be completion

**After this PR**

```text
kw async
kw const
kw enum
kw fn
kw impl
kw impl for
kw mod
kw pub
kw pub(crate)
kw pub(super)
kw static
kw struct
kw trait
kw type
kw union
kw unsafe
kw use
```

---

```rust
extern $0
```

**Before this PR**

Can't be completion

**After this PR**

```rust
extern crate $0;
```

Author: A4-Tacks

src/tools/rust-analyzer/crates/ide-completion/src/completions/item_list.rs

@@ -87,6 +87,9 @@ fn add_keywords(acc: &mut Completions, ctx: &CompletionContext<'_>, kind: Option
     let in_block = kind.is_none();
 
     let no_vis_qualifiers = ctx.qualifier_ctx.vis_node.is_none();
+    let no_abi_qualifiers = ctx.qualifier_ctx.abi_node.is_none();
+    let has_extern_kw =
+        ctx.qualifier_ctx.abi_node.as_ref().is_some_and(|it| it.string_token().is_none());
     let has_unsafe_kw = ctx.qualifier_ctx.unsafe_tok.is_some();
     let has_async_kw = ctx.qualifier_ctx.async_tok.is_some();
     let has_safe_kw = ctx.qualifier_ctx.safe_tok.is_some();
@@ -118,7 +121,7 @@ fn add_keywords(acc: &mut Completions, ctx: &CompletionContext<'_>, kind: Option
             }
         }
 
-        if !has_async_kw && no_vis_qualifiers && in_item_list {
+        if !has_async_kw && no_vis_qualifiers && no_abi_qualifiers && in_item_list {
             add_keyword("extern", "extern $0");
         }
 
@@ -159,11 +162,14 @@ fn add_keywords(acc: &mut Completions, ctx: &CompletionContext<'_>, kind: Option
         add_keyword("static", "static $1: $2;");
     } else {
         if !in_inherent_impl {
-            if !in_trait {
+            if !in_trait && no_abi_qualifiers {
                 add_keyword("extern", "extern $0");
             }
             add_keyword("type", "type $0");
         }
+        if has_extern_kw {
+            add_keyword("crate", "crate $0;");
+        }
 
         add_keyword("fn", "fn $1($2) {\n    $0\n}");
         add_keyword("unsafe", "unsafe $0");

src/tools/rust-analyzer/crates/ide-completion/src/context.rs

@@ -53,6 +53,7 @@ pub(crate) struct QualifierCtx {
     pub(crate) unsafe_tok: Option<SyntaxToken>,
     pub(crate) safe_tok: Option<SyntaxToken>,
     pub(crate) vis_node: Option<ast::Visibility>,
+    pub(crate) abi_node: Option<ast::Abi>,
 }
 
 impl QualifierCtx {
@@ -61,6 +62,7 @@ impl QualifierCtx {
             && self.unsafe_tok.is_none()
             && self.safe_tok.is_none()
             && self.vis_node.is_none()
+            && self.abi_node.is_none()
     }
 }
 

src/tools/rust-analyzer/crates/ide-completion/src/context/analysis.rs

@@ -1628,6 +1628,7 @@ fn classify_name_ref<'db>(
                     }
                 }
                 qualifier_ctx.vis_node = error_node.children().find_map(ast::Visibility::cast);
+                qualifier_ctx.abi_node = error_node.children().find_map(ast::Abi::cast);
             }
 
             if let PathKind::Item { .. } = path_ctx.kind

src/tools/rust-analyzer/crates/ide-completion/src/tests/item_list.rs

@@ -176,6 +176,105 @@ fn after_visibility_unsafe() {
     );
 }
 
+#[test]
+fn after_abi() {
+    check_with_base_items(
+        r#"extern "C" $0"#,
+        expect![[r#"
+            kw async
+            kw const
+            kw enum
+            kw fn
+            kw impl
+            kw impl for
+            kw mod
+            kw pub
+            kw pub(crate)
+            kw pub(super)
+            kw static
+            kw struct
+            kw trait
+            kw type
+            kw union
+            kw unsafe
+            kw use
+        "#]],
+    );
+    check_with_base_items(
+        r#"extern "C" f$0"#,
+        expect![[r#"
+            kw async
+            kw const
+            kw enum
+            kw fn
+            kw impl
+            kw impl for
+            kw mod
+            kw pub
+            kw pub(crate)
+            kw pub(super)
+            kw static
+            kw struct
+            kw trait
+            kw type
+            kw union
+            kw unsafe
+            kw use
+        "#]],
+    );
+}
+
+#[test]
+fn after_extern_token() {
+    check_with_base_items(
+        r#"extern $0"#,
+        expect![[r#"
+            kw async
+            kw const
+            kw crate
+            kw enum
+            kw fn
+            kw impl
+            kw impl for
+            kw mod
+            kw pub
+            kw pub(crate)
+            kw pub(super)
+            kw static
+            kw struct
+            kw trait
+            kw type
+            kw union
+            kw unsafe
+            kw use
+        "#]],
+    );
+    check_with_base_items(
+        r#"extern cr$0"#,
+        expect![[r#"
+            kw async
+            kw const
+            kw crate
+            kw enum
+            kw fn
+            kw impl
+            kw impl for
+            kw mod
+            kw pub
+            kw pub(crate)
+            kw pub(super)
+            kw static
+            kw struct
+            kw trait
+            kw type
+            kw union
+            kw unsafe
+            kw use
+        "#]],
+    );
+    check_edit("crate", "extern $0", "extern crate $0;");
+}
+
 #[test]
 fn in_impl_assoc_item_list() {
     check_with_base_items(