Merge #11136

11136: Turbo fish assist supports multiple type arguments r=matklad a=Vannevelj

This fixes #11135 (changelog: bug).

I've only started using Rust a few days ago but saw this issue on the top of the list when I looked at this repo. I based myself on [this blog post](https://techblog.tonsser.com/posts/what-is-rusts-turbofish) to understand what a "turbo fish" is so let me know if I missed anything.

Co-authored-by: Jeroen Vannevel <[email protected]>

Author: bors[bot]

crates/ide_assists/src/handlers/add_turbo_fish.rs

@@ -1,4 +1,5 @@
 use ide_db::defs::{Definition, NameRefClass};
+use itertools::Itertools;
 use syntax::{ast, AstNode, SyntaxKind, T};
 
 use crate::{
@@ -77,13 +78,22 @@ pub(crate) fn add_turbo_fish(acc: &mut Assists, ctx: &AssistContext) -> Option<(
         }
     }
 
+    let number_of_arguments = generics.len();
+    let fish_head = std::iter::repeat("_").take(number_of_arguments).collect_vec().join(",");
+
     acc.add(
         AssistId("add_turbo_fish", AssistKind::RefactorRewrite),
         "Add `::<>`",
         ident.text_range(),
         |builder| match ctx.config.snippet_cap {
-            Some(cap) => builder.insert_snippet(cap, ident.text_range().end(), "::<${0:_}>"),
-            None => builder.insert(ident.text_range().end(), "::<_>"),
+            Some(cap) => {
+                let snip = format!("::<${{0:{}}}>", fish_head);
+                builder.insert_snippet(cap, ident.text_range().end(), snip)
+            }
+            None => {
+                let snip = format!("::<{}>", fish_head);
+                builder.insert(ident.text_range().end(), snip);
+            }
         },
     )
 }
@@ -113,6 +123,44 @@ fn main() {
         );
     }
 
+    #[test]
+    fn add_turbo_fish_function_multiple_generic_types() {
+        check_assist(
+            add_turbo_fish,
+            r#"
+fn make<T, A>() -> T {}
+fn main() {
+    make$0();
+}
+"#,
+            r#"
+fn make<T, A>() -> T {}
+fn main() {
+    make::<${0:_,_}>();
+}
+"#,
+        );
+    }
+
+    #[test]
+    fn add_turbo_fish_function_many_generic_types() {
+        check_assist(
+            add_turbo_fish,
+            r#"
+fn make<T, A, B, C, D, E, F>() -> T {}
+fn main() {
+    make$0();
+}
+"#,
+            r#"
+fn make<T, A, B, C, D, E, F>() -> T {}
+fn main() {
+    make::<${0:_,_,_,_,_,_,_}>();
+}
+"#,
+        );
+    }
+
     #[test]
     fn add_turbo_fish_after_call() {
         cov_mark::check!(add_turbo_fish_after_call);