[IDE] Fix assertion hit when a function call has no argument labels.

rdar://27611931.

Author: akyrtzi

lib/AST/SourceEntityWalker.cpp

@@ -426,11 +426,13 @@ bool SemaAnnotator::passCallArgNames(Expr *Fn, TupleExpr *TupleE) {
 
   ArrayRef<Identifier> ArgNames = TupleE->getElementNames();
   ArrayRef<SourceLoc> ArgLocs = TupleE->getElementNameLocs();
-  assert(ArgNames.size() == ArgLocs.size());
   for (auto i : indices(ArgNames)) {
     Identifier Name = ArgNames[i];
+    if (Name.empty())
+      continue;
+
     SourceLoc Loc = ArgLocs[i];
-    if (Name.empty() || Loc.isInvalid())
+    if (Loc.isInvalid())
       continue;
 
     CharSourceRange Range{ Loc, Name.getLength() };

test/IDE/annotation.swift

@@ -328,3 +328,16 @@ func test_defer() {
     test_defer()
   }
 }
+
+func test_arg_tuple1(_: Int, _: Int) {}
+func test_arg_tuple2(p1: Int, _: Int) {}
+func test_arg_tuple3(_: Int, p2: Int) {}
+func test_arg_tuple4(p1: Int, p2: Int) {}
+// CHECK: <Func@[[@LINE-4]]:6>test_arg_tuple1</Func>(0,0)
+test_arg_tuple1(0,0)
+// CHECK: <Func@[[@LINE-5]]:6>test_arg_tuple2</Func>(<Func@[[@LINE-5]]:6#p1>p1</Func>:0,0)
+test_arg_tuple2(p1:0,0)
+// CHECK: <Func@[[@LINE-6]]:6>test_arg_tuple3</Func>(0,<Func@[[@LINE-6]]:6#p2>p2</Func>:0)
+test_arg_tuple3(0,p2:0)
+// CHECK: <Func@[[@LINE-7]]:6>test_arg_tuple4</Func>(<Func@[[@LINE-7]]:6#p1>p1</Func>:0,<Func@[[@LINE-7]]:6#p2>p2</Func>:0)
+test_arg_tuple4(p1:0,p2:0)