Add temprary fix for complete tuple structs

By rust-lang/rust#49718, ExprKind::TupField
was removed. This commit includes a temorary fix and a tests for this
removal.

src/racer/typeinf.rs

@@ -217,13 +217,27 @@ fn get_type_of_for_expr(m: &Match, msrc: Src, session: &Session) -> Option<core:
 }
 
 pub fn get_struct_field_type(fieldname: &str, structmatch: &Match, session: &Session) -> Option<core::Ty> {
-    assert!(structmatch.mtype == core::MatchType::Struct);
+    // temporary fix for https://github.com/rust-lang-nursery/rls/issues/783
+    if structmatch.mtype != core::MatchType::Struct {
+        warn!("get_struct_filed_type is called for {:?}", structmatch.mtype);
+        return None;
+    }
+
+    debug!("[get_struct_filed_type]{}, {:?}", fieldname, structmatch);
 
     let src = session.load_file(&structmatch.filepath);
 
     let opoint = scopes::expect_stmt_start(src.as_src(), structmatch.point);
     let structsrc = scopes::end_of_next_scope(&src[opoint..]);
 
+    // HACK: if scopes::end_of_next_scope returns empty struct, it's maybe tuple struct
+    // TODO: remove this hack
+    let structsrc = if structsrc == "" {
+        (*get_first_stmt(src.as_src().from(opoint))).to_owned()
+    } else {
+        structsrc.to_owned()
+    };
+
     let fields = ast::parse_struct_fields(structsrc.to_owned(), Scope::from_match(structmatch));
     for (field, _, ty) in fields {
         if fieldname == field {

tests/system.rs

@@ -4256,3 +4256,20 @@ fn main {
         assert_eq!(doc_str, got.docs);
     })
 }
+
+#[test]
+fn completes_methods_for_tuple_struct() {
+    let _lock = sync!();
+    let src = r"
+        fn main() {
+            struct A(i32, Vec<i32>);
+            let mut a = A(0, vec![3, 4]);
+            a.1.appen~
+        }
+    ";
+    assert!(
+        get_all_completions(src, None)
+            .into_iter()
+            .any(|ma| ma.matchstr == "append")
+    );
+}