More orthogonal path editing

crates/ra_assists/src/ast_transform.rs

@@ -2,7 +2,7 @@
 use rustc_hash::FxHashMap;
 
 use hir::{db::HirDatabase, InFile, PathResolution};
-use ra_syntax::ast::{self, make, AstNode};
+use ra_syntax::ast::{self, AstNode};
 
 pub trait AstTransform<'a> {
     fn get_substitution(
@@ -134,11 +134,18 @@ fn get_substitution_inner(
         match resolution {
             PathResolution::Def(def) => {
                 let found_path = from.find_use_path(self.db, def)?;
-                let args = p
+                let mut path = path_to_ast(found_path);
+
+                let type_args = p
                     .segment()
                     .and_then(|s| s.type_arg_list())
                     .map(|arg_list| apply(self, node.with_value(arg_list)));
-                Some(make::path_with_type_arg_list(path_to_ast(found_path), args).syntax().clone())
+                if let Some(type_args) = type_args {
+                    let last_segment = path.segment().unwrap();
+                    path = path.with_segment(last_segment.with_type_args(type_args))
+                }
+
+                Some(path.syntax().clone())
             }
             PathResolution::Local(_)
             | PathResolution::TypeParam(_)

crates/ra_syntax/src/ast/edit.rs

@@ -207,6 +207,48 @@ pub fn remove_bounds(&self) -> ast::TypeParam {
     }
 }
 
+impl ast::Path {
+    #[must_use]
+    pub fn with_segment(&self, segment: ast::PathSegment) -> ast::Path {
+        if let Some(old) = self.segment() {
+            return replace_children(
+                self,
+                single_node(old.syntax().clone()),
+                iter::once(segment.syntax().clone().into()),
+            );
+        }
+        self.clone()
+    }
+}
+
+impl ast::PathSegment {
+    #[must_use]
+    pub fn with_type_args(&self, type_args: ast::TypeArgList) -> ast::PathSegment {
+        self._with_type_args(type_args, false)
+    }
+
+    #[must_use]
+    pub fn with_turbo_fish(&self, type_args: ast::TypeArgList) -> ast::PathSegment {
+        self._with_type_args(type_args, true)
+    }
+
+    fn _with_type_args(&self, type_args: ast::TypeArgList, turbo: bool) -> ast::PathSegment {
+        if let Some(old) = self.type_arg_list() {
+            return replace_children(
+                self,
+                single_node(old.syntax().clone()),
+                iter::once(type_args.syntax().clone().into()),
+            );
+        }
+        let mut to_insert: ArrayVec<[SyntaxElement; 2]> = ArrayVec::new();
+        if turbo {
+            to_insert.push(make::token(T![::]).into());
+        }
+        to_insert.push(type_args.syntax().clone().into());
+        insert_children(self, InsertPosition::Last, to_insert)
+    }
+}
+
 #[must_use]
 pub fn strip_attrs_and_docs<N: ast::AttrsOwner>(node: &N) -> N {
     N::cast(strip_attrs_and_docs_inner(node.syntax().clone())).unwrap()

crates/ra_syntax/src/ast/make.rs

@@ -2,7 +2,7 @@
 //! of smaller pieces.
 use itertools::Itertools;
 
-use crate::{algo, ast, AstNode, SourceFile, SyntaxKind, SyntaxToken};
+use crate::{ast, AstNode, SourceFile, SyntaxKind, SyntaxToken};
 
 pub fn name(text: &str) -> ast::Name {
     ast_from_text(&format!("mod {};", text))
@@ -21,20 +21,6 @@ pub fn path_qualified(qual: ast::Path, name_ref: ast::NameRef) -> ast::Path {
 fn path_from_text(text: &str) -> ast::Path {
     ast_from_text(text)
 }
-pub fn path_with_type_arg_list(path: ast::Path, args: Option<ast::TypeArgList>) -> ast::Path {
-    if let Some(args) = args {
-        let syntax = path.syntax();
-        // FIXME: remove existing type args
-        let new_syntax = algo::insert_children(
-            syntax,
-            crate::algo::InsertPosition::Last,
-            &mut Some(args).into_iter().map(|n| n.syntax().clone().into()),
-        );
-        ast::Path::cast(new_syntax).unwrap()
-    } else {
-        path
-    }
-}
 
 pub fn record_field(name: ast::NameRef, expr: Option<ast::Expr>) -> ast::RecordField {
     return match expr {
@@ -201,7 +187,7 @@ pub mod tokens {
     use once_cell::sync::Lazy;
 
     pub(super) static SOURCE_FILE: Lazy<Parse<SourceFile>> =
-        Lazy::new(|| SourceFile::parse("const C: () = (1 != 1, 2 == 2)\n;"));
+        Lazy::new(|| SourceFile::parse("const C: <()>::Item = (1 != 1, 2 == 2)\n;"));
 
     pub fn comma() -> SyntaxToken {
         SOURCE_FILE