[AST] Make sure that if a TupleExpr is created with element names but not name locations, it is marked implicit as appropriate

Fixes a crash for SourceEntityWalker which assumed that a non-implicit TupleExpr has source locations for its name elements.

Fixes SR-6517, rdar://35830880

Author: akyrtzi

lib/AST/ASTDumper.cpp

@@ -1917,6 +1917,11 @@ class PrintExpr : public ExprVisitor<PrintExpr> {
   }
   void visitDictionaryExpr(DictionaryExpr *E) {
     printCommon(E, "dictionary_expr");
+    if (auto semaE = E->getSemanticExpr()) {
+      OS << '\n';
+      printRec(semaE);
+      return;
+    }
     for (auto elt : E->getElements()) {
       OS << '\n';
       printRec(elt);

lib/AST/Expr.cpp

@@ -1197,7 +1197,7 @@ packSingleArgument(ASTContext &ctx, SourceLoc lParenLoc, ArrayRef<Expr *> args,
 
     auto arg = TupleExpr::create(ctx, lParenLoc, args, argLabels, argLabelLocs,
                                  rParenLoc, /*HasTrailingClosure=*/false,
-                                 /*Implicit=*/false);
+                                 implicit);
     computeSingleArgumentType(ctx, arg, implicit, getType);
     return arg;
   }
@@ -1454,6 +1454,16 @@ TupleExpr *TupleExpr::create(ASTContext &ctx,
                              SourceLoc RParenLoc, bool HasTrailingClosure, 
                              bool Implicit, Type Ty) {
   assert(!Ty || isa<TupleType>(Ty.getPointer()));
+  auto hasNonEmptyIdentifier = [](ArrayRef<Identifier> Ids) -> bool {
+    for (auto ident : Ids) {
+      if (!ident.empty())
+        return true;
+    }
+    return false;
+  };
+  assert((Implicit || ElementNames.size() == ElementNameLocs.size() ||
+          (!hasNonEmptyIdentifier(ElementNames) && ElementNameLocs.empty())) &&
+         "trying to create non-implicit tuple-expr without name locations");
 
   size_t size =
       totalSizeToAlloc<Expr *, Identifier, SourceLoc>(SubExprs.size(),

lib/Sema/CSApply.cpp

@@ -2829,7 +2829,7 @@ namespace {
                               { },
                               expr->getRBracketLoc(),
                               /*HasTrailingClosure=*/false,
-                              /*Implicit=*/false,
+                              /*Implicit=*/true,
                               argType);
 
       cs.cacheExprTypes(arg);

test/Index/invalid_code.swift

@@ -2,3 +2,13 @@
 
 // CHECK: [[@LINE+1]]:8 | struct/Swift | Int | {{.*}} | Ref | rel: 0
 var _: Int { get { return 1 } }
+
+class CrashTest {
+  var something = 0
+  func returnSelf(_ h: [AnyHashable: Any?]) -> CrashTest {
+    return self
+  }
+  init() { }
+}
+// CHECK: [[@LINE+1]]:13 | instance-method/Swift | returnSelf
+CrashTest().returnSelf(["": 0]).something()