Cleanup; add comments

Author: simanerush

include/swift/IDE/CodeCompletionResult.h

@@ -214,6 +214,8 @@ enum class CompletionKind : uint8_t {
   ReturnStmtExpr,
   YieldStmtExpr,
   ForEachSequence,
+
+  /// The \c in keyword in a for-each loop.
   ForEachInKw,
   AfterPoundExpr,
   AfterPoundDirective,

include/swift/Parse/CodeCompletionCallbacks.h

@@ -137,7 +137,7 @@ class CodeCompletionCallbacks {
   /// -- no tokens provided by user.
   virtual void completeForEachSequenceBeginning(CodeCompletionExpr *E) {};
 
-  /// Add comment
+  /// Complete the \c in keyword in a for-each loop.
   virtual void completeForEachInKeyword(){};
 
   /// Complete a given expr-postfix.

lib/Parse/ParseStmt.cpp

@@ -2292,14 +2292,14 @@ ParserResult<Stmt> Parser::parseStmtForEach(LabeledStmtInfo LabelInfo) {
     diagnose(LBraceLoc, diag::expected_foreach_container);
     Container = makeParserErrorResult(new (Context) ErrorExpr(LBraceLoc));
   } else if (Tok.is(tok::code_complete)) {
+    // If there is no "in" keyword, suggest it. Otherwise, complete the
+    // sequence.
     if (InLoc.isInvalid()) {
-      // Write something to complete In
       if (CodeCompletion)
         CodeCompletion->completeForEachInKeyword();
       consumeToken(tok::code_complete);
       return makeParserCodeCompletionStatus();
     } else {
-      // Complete everything else
       Container =
           makeParserResult(new (Context) CodeCompletionExpr(Tok.getLoc()));
       Container.setHasCodeCompletionAndIsError();

test/IDE/complete_loop.swift

@@ -6,6 +6,7 @@
 // RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=LOOP_4 | %FileCheck %s -check-prefix=LOOP_4
 // RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=LOOP_5 | %FileCheck %s -check-prefix=LOOP_5
 // RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=LOOP_6 | %FileCheck %s -check-prefix=LOOP_6
+// RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=LOOP_7 | %FileCheck %s -check-prefix=LOOP_6
 
 class Gen {
 	func IntGen() -> Int { return 0 }
@@ -69,10 +70,13 @@ class C {
 // LOOP_5: Begin completions
 }
 
+// https://github.com/apple/swift/issues/58633
 do {
   for value #^LOOP_6^#
 }
+do {
+  for value #^LOOP_7^# 1..<7 {}
+}
 // LOOP_6: Begin completions, 1 items
 // LOOP_6-CHECK-NEXT: Keyword[in]/None:                   in; name=in
 // LOOP_6-CHECK-NEXT: End completions
-