Rudimentarily autocomplete tuple struct field access

Author: robojumper

crates/ra_ide_api/src/completion/complete_dot.rs

@@ -184,4 +184,26 @@ mod tests {
             ",
         );
     }
+
+    #[test]
+    fn test_tuple_field_inference() {
+        check_ref_completion(
+            "tuple_field_inference",
+            r"
+            pub struct S;
+            impl S {
+                pub fn blah(&self) {}
+            }
+
+            struct T(S);
+
+            impl T {
+                fn foo(&self) {
+                    // FIXME: This doesn't work without the trailing `a` as `0.` is a float
+                    self.0.a<|>
+                }
+            }
+            ",
+        );
+    }
 }

crates/ra_ide_api/src/completion/snapshots/completion_item__tuple_field_inference.snap

@@ -0,0 +1,16 @@
+---
+created: "2019-04-05T23:00:18.283812700Z"
+creator: insta@0.7.4
+source: crates/ra_ide_api/src/completion/completion_item.rs
+expression: kind_completions
+---
+[
+    CompletionItem {
+        label: "blah",
+        source_range: [299; 300),
+        delete: [299; 300),
+        insert: "blah()$0",
+        kind: Method,
+        detail: "pub fn blah(&self)"
+    }
+]