[CodeCompletion] Use CodeCompletionExpr as a value of dictionary literal

When a completion happens in a key position and the value expression
is missing. This allows type checker to use TypeVariable so it increases
the chance to type check them successfully.

Author: rintaro

lib/Parse/ParseExpr.cpp

@@ -3525,8 +3525,14 @@ Parser::parseExprCollectionElement(Optional<bool> &isDictionary) {
   // Parse the value.
   auto Value = parseExpr(diag::expected_value_in_dictionary_literal);
 
-  if (Value.isNull())
-    Value = makeParserResult(Value, new (Context) ErrorExpr(PreviousLoc));
+  if (Value.isNull()) {
+    if (!Element.hasCodeCompletion()) {
+      Value = makeParserResult(Value, new (Context) ErrorExpr(PreviousLoc));
+    } else {
+      Value = makeParserResult(Value,
+                               new (Context) CodeCompletionExpr(PreviousLoc));
+    }
+  }
 
   // Make a tuple of Key Value pair.
   return makeParserResult(

test/IDE/complete_expr_postfix_begin.swift

@@ -64,10 +64,10 @@
 // RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=IN_FOR_EACH_5 | %FileCheck %s -check-prefix=IN_FOR_EACH_1
 // RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=IN_FOR_EACH_6 | %FileCheck %s -check-prefix=IN_FOR_EACH_2
 // RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=IN_FOR_EACH_7 | %FileCheck %s -check-prefix=IN_FOR_EACH_1
-// RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=IN_FOR_EACH_8 | %FileCheck %s -check-prefix=IN_FOR_EACH_1
+// RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=IN_FOR_EACH_8 | %FileCheck %s -check-prefix=IN_FOR_EACH_4
 // RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=IN_FOR_EACH_9 | %FileCheck %s -check-prefix=IN_FOR_EACH_4
 // RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=IN_FOR_EACH_10 | %FileCheck %s -check-prefix=IN_FOR_EACH_1
-// RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=IN_FOR_EACH_11 | %FileCheck %s -check-prefix=IN_FOR_EACH_1
+// RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=IN_FOR_EACH_11 | %FileCheck %s -check-prefix=IN_FOR_EACH_2
 // RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=IN_FOR_EACH_12 | %FileCheck %s -check-prefix=IN_FOR_EACH_2
 
 // RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=DEPRECATED_1 | %FileCheck %s -check-prefix=DEPRECATED_1

test/IDE/complete_unresolved_members.swift

@@ -51,7 +51,8 @@
 // RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=UNRESOLVED_40 | %FileCheck %s -check-prefix=UNRESOLVED_3
 // RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=UNRESOLVED_41 | %FileCheck %s -check-prefix=UNRESOLVED_3
 // RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=UNRESOLVED_42 | %FileCheck %s -check-prefix=UNRESOLVED_3
-// RUN-FIXME: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=UNRESOLVED_43 | %FileCheck %s -check-prefix=UNRESOLVED_3
+// RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=UNRESOLVED_43 | %FileCheck %s -check-prefix=UNRESOLVED_3
+// RUN-FIXME: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=UNRESOLVED_44 | %FileCheck %s -check-prefix=UNRESOLVED_3
 
 // RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=ENUM_AVAIL_1 | %FileCheck %s -check-prefix=ENUM_AVAIL_1
 // RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=OPTIONS_AVAIL_1 | %FileCheck %s -check-prefix=OPTIONS_AVAIL_1
@@ -397,7 +398,8 @@ let _: [SomeEnum1:SomeOptions1] = [.#^UNRESOLVED_39^#]
 let _: [SomeEnum1:SomeOptions1] = [.#^UNRESOLVED_40^#:]
 let _: [SomeEnum1:SomeEnum3] = [.South:.Payload(.South), .South: .Payload(.#^UNRESOLVED_41^#)]
 let _: [SomeEnum3:SomeEnum1] = [.Payload(.South):.South, .Payload(.#^UNRESOLVED_42^#):.South]
-let _: [SomeEnum3:SomeEnum1] = [.Payload(.South):.South, .Payload(.#^UNRESOLVED_43^#)]
+let _: [SomeEnum3:SomeEnum1] = [.Payload(.South):.South, .Payload(.#^UNRESOLVED_43^#):]
+let _: [SomeEnum3:SomeEnum1] = [.Payload(.South):.South, .Payload(.#^UNRESOLVED_44^#)]
 
 func testAvail1(_ x: EnumAvail1) {
   testAvail1(.#^ENUM_AVAIL_1^#)