Merge #11220

11220: Turbo fish assist: don't include lifetime parameters r=Veykril a=Vannevelj

Fixes #11219

The issue talks about three different types of params: type, const & lifetime. I wasn't entirely sure which ones are intended to be included here so I've gone for the type & const params (i.e. exclude lifetime).

I've added a test case for both a lifetime param and a const param. I'm still making my way through the rust book (chapter 7, yay) so I'm not too sure yet what these are but my testing shows that this approach generates code that compiles.

Co-authored-by: Jeroen Vannevel <jer_vannevel@outlook.com>

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::{
@@ -77,8 +78,12 @@ 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(",");
+    let number_of_arguments = generics
+        .iter()
+        .filter(|param| {
+            matches!(param, hir::GenericParam::TypeParam(_) | hir::GenericParam::ConstParam(_))
+        })
+        .count();
 
     acc.add(
         AssistId("add_turbo_fish", AssistKind::RefactorRewrite),
@@ -86,10 +91,11 @@ pub(crate) fn add_turbo_fish(acc: &mut Assists, ctx: &AssistContext) -> Option<(
         ident.text_range(),
         |builder| match ctx.config.snippet_cap {
             Some(cap) => {
-                let snip = format!("::<${{0:{}}}>", fish_head);
+                let snip = format!("::<{}>", get_snippet_fish_head(number_of_arguments));
                 builder.insert_snippet(cap, ident.text_range().end(), snip)
             }
             None => {
+                let fish_head = std::iter::repeat("_").take(number_of_arguments).format(", ");
                 let snip = format!("::<{}>", fish_head);
                 builder.insert(ident.text_range().end(), snip);
             }
@@ -97,6 +103,17 @@ pub(crate) fn add_turbo_fish(acc: &mut Assists, ctx: &AssistContext) -> Option<(
     )
 }
 
+/// This will create a snippet string with tabstops marked
+fn get_snippet_fish_head(number_of_arguments: usize) -> String {
+    let mut fish_head = (1..number_of_arguments)
+        .format_with("", |i, f| f(&format_args!("${{{}:_}}, ", i)))
+        .to_string();
+
+    // tabstop 0 is a special case and always the last one
+    fish_head.push_str("${0:_}");
+    fish_head
+}
+
 #[cfg(test)]
 mod tests {
     use crate::tests::{check_assist, check_assist_by_label, check_assist_not_applicable};
@@ -135,7 +152,7 @@ fn main() {
             r#"
 fn make<T, A>() -> T {}
 fn main() {
-    make::<${0:_,_}>();
+    make::<${1:_}, ${0:_}>();
 }
 "#,
         );
@@ -154,7 +171,7 @@ fn main() {
             r#"
 fn make<T, A, B, C, D, E, F>() -> T {}
 fn main() {
-    make::<${0:_,_,_,_,_,_,_}>();
+    make::<${1:_}, ${2:_}, ${3:_}, ${4:_}, ${5:_}, ${6:_}, ${0:_}>();
 }
 "#,
         );
@@ -339,4 +356,42 @@ fn main() {
             "Add `: _` before assignment operator",
         );
     }
+
+    #[test]
+    fn add_turbo_fish_function_lifetime_parameter() {
+        check_assist(
+            add_turbo_fish,
+            r#"
+fn make<'a, T, A>(t: T, a: A) {}
+fn main() {
+    make$0(5, 2);
+}
+"#,
+            r#"
+fn make<'a, T, A>(t: T, a: A) {}
+fn main() {
+    make::<${1:_}, ${0:_}>(5, 2);
+}
+"#,
+        );
+    }
+
+    #[test]
+    fn add_turbo_fish_function_const_parameter() {
+        check_assist(
+            add_turbo_fish,
+            r#"
+fn make<T, const N: usize>(t: T) {}
+fn main() {
+    make$0(3);
+}
+"#,
+            r#"
+fn make<T, const N: usize>(t: T) {}
+fn main() {
+    make::<${1:_}, ${0:_}>(3);
+}
+"#,
+        );
+    }
 }