[CodeCompletion] Fix completion after unspaced binary operator

We were miscalculating 'isRightBound' when the RHS was a code-completion
token leading to missing completions in unspaced binary expressions
  1+<here>
  1...<here>

rdar://problem/24278699

Author: benlangmuir

lib/Parse/Lexer.cpp

@@ -594,14 +594,21 @@ static bool isLeftBound(const char *tokBegin, const char *bufferBegin) {
 
 /// Is the operator ending at the given character (actually one past the end)
 /// "right-bound"?
-static bool isRightBound(const char *tokEnd, bool isLeftBound) {
+///
+/// The code-completion point is considered right-bound.
+static bool isRightBound(const char *tokEnd, bool isLeftBound,
+                         const char *codeCompletionPtr) {
   switch (*tokEnd) {
   case ' ': case '\r': case '\n': case '\t': // whitespace
   case ')': case ']': case '}':              // closing delimiters
   case ',': case ';': case ':':              // expression separators
-  case '\0':                                 // whitespace / last char in file
     return false;
 
+  case '\0':
+    if (tokEnd == codeCompletionPtr)         // code-completion
+      return true;
+    return false;                            // whitespace / last char in file
+
   case '.':
     // Prefer the '^' in "x^.y" to be a postfix op, not binary, but the '^' in
     // "^.y" to be a prefix op, not binary.
@@ -637,7 +644,7 @@ void Lexer::lexOperatorIdentifier() {
   // It's binary if either both sides are bound or both sides are not bound.
   // Otherwise, it's postfix if left-bound and prefix if right-bound.
   bool leftBound = isLeftBound(TokStart, BufferStart);
-  bool rightBound = isRightBound(CurPtr, leftBound);
+  bool rightBound = isRightBound(CurPtr, leftBound, CodeCompletionPtr);
 
   // Match various reserved words.
   if (CurPtr-TokStart == 1) {
@@ -669,17 +676,16 @@ void Lexer::lexOperatorIdentifier() {
       const char *AfterHorzWhitespace = CurPtr;
       while (*AfterHorzWhitespace == ' ' || *AfterHorzWhitespace == '\t')
         ++AfterHorzWhitespace;
-      
-      // First, when we are code completing "x.<ESC>", then make sure to return
+
+      // First, when we are code completing "x. <ESC>", then make sure to return
       // a tok::period, since that is what the user is wanting to know about.
-      // FIXME: isRightBound should consider this to be right bound.
       if (*AfterHorzWhitespace == '\0' &&
           AfterHorzWhitespace == CodeCompletionPtr) {
         diagnose(TokStart, diag::expected_member_name);
         return formToken(tok::period, TokStart);
       }
-      
-      if (isRightBound(AfterHorzWhitespace, leftBound) &&
+
+      if (isRightBound(AfterHorzWhitespace, leftBound, CodeCompletionPtr) &&
           // Don't consider comments to be this.  A leading slash is probably
           // either // or /* and most likely occurs just in our testsuite for
           // expected-error lines.

lib/Parse/ParseStmt.cpp

@@ -888,7 +888,8 @@ static void parseGuardedPattern(Parser &P, GuardedPattern &result,
     }
   }
   if (parsingContext == GuardedPatternContext::Case &&
-      P.Tok.is(tok::period) && P.peekToken().is(tok::code_complete)) {
+      P.Tok.isAny(tok::period_prefix, tok::period) &&
+      P.peekToken().is(tok::code_complete)) {
     setErrorResult();
     if (P.CodeCompletion) {
       P.consumeToken();

test/IDE/complete_expr_postfix_begin.swift

@@ -2,6 +2,8 @@
 // RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=EXPR_POSTFIX_BEGIN_2 | FileCheck %s -check-prefix=COMMON
 // RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=EXPR_POSTFIX_BEGIN_3 | FileCheck %s -check-prefix=COMMON
 // RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=EXPR_POSTFIX_BEGIN_4 | FileCheck %s -check-prefix=COMMON
+// RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=EXPR_POSTFIX_BEGIN_5 | FileCheck %s -check-prefix=COMMON
+// RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=EXPR_POSTFIX_BEGIN_6 | FileCheck %s -check-prefix=COMMON
 
 // RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=EXPR_POSTFIX_BEGIN_IGNORED_1 | FileCheck %s -check-prefix=COMMON
 // RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=EXPR_POSTFIX_BEGIN_IGNORED_2 | FileCheck %s -check-prefix=COMMON
@@ -125,6 +127,13 @@ func testExprPostfixBegin4(fooParam: FooStruct) {
   "\(#^EXPR_POSTFIX_BEGIN_4^#)"
 }
 
+func testExprPostfixBegin3(fooParam: FooStruct) {
+  1+#^EXPR_POSTFIX_BEGIN_5^#
+}
+func testExprPostfixBegin3(fooParam: FooStruct) {
+  for i in 1...#^EXPR_POSTFIX_BEGIN_6^#
+}
+
 //===--- Test that we sometimes ignore the expr-postfix.
 // In these cases, displaying '.instance*' completion results is technically
 // valid, but would be extremely surprising.