fix: insert auto-imports after header comments

Fixes rust-lang#8607.

This commit changes the auto-import functionality and causes it to add
imports after any leading comments, which are commonly license headers.
This does not affect comments on items as they're considered part of the
item itself and not separate.

Author: repnop

crates/ide_db/src/helpers/insert_use.rs

@@ -401,7 +401,7 @@ fn insert_use_(
         .children_with_tokens()
         .filter(|child| match child {
             NodeOrToken::Node(node) => is_inner_attribute(node.clone()),
-            NodeOrToken::Token(token) => is_inner_comment(token.clone()),
+            NodeOrToken::Token(token) => is_comment(token.clone()),
         })
         .last()
     {
@@ -440,7 +440,6 @@ fn is_inner_attribute(node: SyntaxNode) -> bool {
     ast::Attr::cast(node).map(|attr| attr.kind()) == Some(ast::AttrKind::Inner)
 }
 
-fn is_inner_comment(token: SyntaxToken) -> bool {
-    ast::Comment::cast(token).and_then(|comment| comment.kind().doc)
-        == Some(ast::CommentPlacement::Inner)
+fn is_comment(token: SyntaxToken) -> bool {
+    ast::Comment::cast(token).is_some()
 }

crates/ide_db/src/helpers/insert_use/tests.rs

@@ -390,6 +390,30 @@ use foo::bar::Baz;"#,
     );
 }
 
+#[test]
+fn inserts_after_single_line_comments() {
+    check_none(
+        "foo::bar::Baz",
+        "// Represents a possible license header and/or general module comments",
+        r#"// Represents a possible license header and/or general module comments
+
+use foo::bar::Baz;"#,
+    );
+}
+
+#[test]
+fn inserts_before_single_line_item_comments() {
+    check_none(
+        "foo::bar::Baz",
+        r#"// Represents a comment about a function
+fn foo() {}"#,
+        r#"use foo::bar::Baz;
+
+// Represents a comment about a function
+fn foo() {}"#,
+    );
+}
+
 #[test]
 fn inserts_after_multiline_inner_comments() {
     check_none(