Fix completion snippet for reexported functions

Fixes #3356.

Author: flodiebold

crates/ra_ide/src/completion/complete_path.rs

@@ -784,4 +784,55 @@ mod tests {
         "###
         );
     }
+
+    #[test]
+    fn completes_reexported_items_under_correct_name() {
+        assert_debug_snapshot!(
+            do_reference_completion(
+                r"
+                fn foo() {
+                    self::m::<|>
+                }
+
+                mod m {
+                    pub use super::p::wrong_fn as right_fn;
+                    pub use super::p::WRONG_CONST as RIGHT_CONST;
+                    pub use super::p::WrongType as RightType;
+                }
+                mod p {
+                    fn wrong_fn() {}
+                    const WRONG_CONST: u32 = 1;
+                    struct WrongType {};
+                }
+                "
+            ),
+            @r###"
+        [
+            CompletionItem {
+                label: "RIGHT_CONST",
+                source_range: [57; 57),
+                delete: [57; 57),
+                insert: "RIGHT_CONST",
+                kind: Const,
+            },
+            CompletionItem {
+                label: "RightType",
+                source_range: [57; 57),
+                delete: [57; 57),
+                insert: "RightType",
+                kind: Struct,
+            },
+            CompletionItem {
+                label: "right_fn()",
+                source_range: [57; 57),
+                delete: [57; 57),
+                insert: "right_fn()$0",
+                kind: Function,
+                lookup: "right_fn",
+                detail: "fn wrong_fn()",
+            },
+        ]
+        "###
+        );
+    }
 }

crates/ra_ide/src/completion/presentation.rs

@@ -193,11 +193,10 @@ impl Completions {
         name: Option<String>,
         func: hir::Function,
     ) {
-        let func_name = func.name(ctx.db);
         let has_self_param = func.has_self_param(ctx.db);
         let params = func.params(ctx.db);
 
-        let name = name.unwrap_or_else(|| func_name.to_string());
+        let name = name.unwrap_or_else(|| func.name(ctx.db).to_string());
         let ast_node = func.source(ctx.db).value;
         let detail = function_label(&ast_node);
 
@@ -219,9 +218,9 @@ impl Completions {
         {
             tested_by!(inserts_parens_for_function_calls);
             let (snippet, label) = if params.is_empty() || has_self_param && params.len() == 1 {
-                (format!("{}()$0", func_name), format!("{}()", name))
+                (format!("{}()$0", name), format!("{}()", name))
             } else {
-                (format!("{}($0)", func_name), format!("{}(…)", name))
+                (format!("{}($0)", name), format!("{}(…)", name))
             };
             builder = builder.lookup_by(name).label(label).insert_snippet(snippet);
         }