Better formatting of conditional expressions.

In conditional expressions, if the condition is split over multiple
lines, also break before both operands.

This prevents formattings like:

  aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa ==
      aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa ? b : c;

Which are bad, because they suggestion incorrect operator precedence:

  aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa ==
      (aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa ? b : c);

This lead to the discovery that the expression parser incorrectly
handled conditional operators and that it could also handle semicolons
(which in turn reduced the amount of special casing for for-loops). As a
side-effect, we can now apply the bin-packing configuration to the
sections of for-loops.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@175973 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 74 insertions, 53 deletions

diff --git a/lib/Format/Format.cpp b/lib/Format/Format.cpp
index 880be39b1c..d8784c126e 100644
--- a/lib/Format/Format.cpp
+++ b/lib/Format/Format.cpp
@@ -330,8 +330,7 @@ private:
         : Indent(Indent), LastSpace(LastSpace), FirstLessLess(0),
           BreakBeforeClosingBrace(false), QuestionColumn(0),
           AvoidBinPacking(AvoidBinPacking), BreakBeforeParameter(false),
-          HasMultiParameterLine(HasMultiParameterLine), ColonPos(0),
-          BreakBeforeThirdOperand(false) {}
+          HasMultiParameterLine(HasMultiParameterLine), ColonPos(0) {}
 
     /// \brief The position to which a specific parenthesis level needs to be
     /// indented.
@@ -374,9 +373,6 @@ private:
     /// \brief The position of the colon in an ObjC method declaration/call.
     unsigned ColonPos;
 
-    /// \brief Break before third operand in ternary expression.
-    bool BreakBeforeThirdOperand;
-
     bool operator<(const ParenState &Other) const {
       if (Indent != Other.Indent)
         return Indent < Other.Indent;
@@ -396,8 +392,6 @@ private:
         return HasMultiParameterLine;
       if (ColonPos != Other.ColonPos)
         return ColonPos < Other.ColonPos;
-      if (BreakBeforeThirdOperand != Other.BreakBeforeThirdOperand)
-        return BreakBeforeThirdOperand;
       return false;
     }
   };
@@ -523,13 +517,11 @@ private:
       }
 
       if (Current.is(tok::question))
-        State.Stack.back().BreakBeforeThirdOperand = true;
-      if (Previous.is(tok::comma) && !State.Stack.back().AvoidBinPacking)
+        State.Stack.back().BreakBeforeParameter = true;
+      if ((Previous.is(tok::comma) || Previous.is(tok::semi)) &&
+          !State.Stack.back().AvoidBinPacking)
         State.Stack.back().BreakBeforeParameter = false;
 
-      if (RootToken.is(tok::kw_for))
-        State.LineContainsContinuedForLoopSection = Previous.isNot(tok::semi);
-
       if (!DryRun) {
         unsigned NewLines =
             std::max(1u, std::min(Current.FormatTok.NewlinesBefore,
@@ -546,9 +538,27 @@ private:
       State.StartOfLineLevel = State.ParenLevel;
       if (Current.is(tok::colon) && Current.Type != TT_ConditionalExpr)
         State.Stack.back().Indent += 2;
+
+      // Any break on this level means that the parent level has been broken
+      // and we need to avoid bin packing there.
+      for (unsigned i = 0, e = State.Stack.size() - 1; i != e; ++i) {
+        State.Stack[i].BreakBeforeParameter = true;
+      }
+      // If we break after {, we should also break before the corresponding }.
+      if (Previous.is(tok::l_brace))
+        State.Stack.back().BreakBeforeClosingBrace = true;
+
+      if (State.Stack.back().AvoidBinPacking) {
+        // If we are breaking after '(', '{', '<', this is not bin packing
+        // unless AllowAllParametersOfDeclarationOnNextLine is false.
+        if ((Previous.isNot(tok::l_paren) && Previous.isNot(tok::l_brace) &&
+             Previous.Type != TT_TemplateOpener) ||
+            (!Style.AllowAllParametersOfDeclarationOnNextLine &&
+             Line.MustBeDeclaration))
+          State.Stack.back().BreakBeforeParameter = true;
+      }
     } else {
-      if (Current.is(tok::equal) &&
-          (RootToken.is(tok::kw_for) || State.ParenLevel == 0))
+      if (Current.is(tok::equal))
         State.VariablePos = State.Column - Previous.FormatTok.TokenLength;
 
       unsigned Spaces = State.NextToken->SpacesRequiredBefore;
@@ -601,30 +611,6 @@ private:
         State.Stack.back().LastSpace = State.Column;
     }
 
-    // If we break after an {, we should also break before the corresponding }.
-    if (Newline && Previous.is(tok::l_brace))
-      State.Stack.back().BreakBeforeClosingBrace = true;
-
-    if (State.Stack.back().AvoidBinPacking && Newline &&
-        (Line.First.isNot(tok::kw_for) || State.ParenLevel != 1)) {
-      // If we are breaking after '(', '{', '<', this is not bin packing unless
-      // AllowAllParametersOfDeclarationOnNextLine is false.
-      if ((Previous.isNot(tok::l_paren) && Previous.isNot(tok::l_brace) &&
-           Previous.Type != TT_TemplateOpener) ||
-          (!Style.AllowAllParametersOfDeclarationOnNextLine &&
-           Line.MustBeDeclaration))
-        State.Stack.back().BreakBeforeParameter = true;
-    }
-
-    if (Newline) {
-      // Any break on this level means that the parent level has been broken
-      // and we need to avoid bin packing there.
-      for (unsigned i = 0, e = State.Stack.size() - 1; i != e; ++i) {
-        if (Line.First.isNot(tok::kw_for) || i != 1)
-          State.Stack[i].BreakBeforeParameter = true;
-      }
-    }
-
     return moveStateToNextToken(State, DryRun);
   }
 
@@ -650,6 +636,7 @@ private:
     for (unsigned i = 0, e = Current.FakeLParens; i != e; ++i) {
       ParenState NewParenState = State.Stack.back();
       NewParenState.Indent = std::max(State.Column, State.Stack.back().Indent);
+      NewParenState.BreakBeforeParameter = false;
       State.Stack.push_back(NewParenState);
     }
 
@@ -907,7 +894,10 @@ private:
     if (State.NextToken->Parent->is(tok::semi) &&
         State.LineContainsContinuedForLoopSection)
       return true;
-    if (State.NextToken->Parent->is(tok::comma) &&
+    if ((State.NextToken->Parent->is(tok::comma) ||
+         State.NextToken->Parent->is(tok::semi) ||
+         State.NextToken->is(tok::question) ||
+         State.NextToken->Type == TT_ConditionalExpr) &&
         State.Stack.back().BreakBeforeParameter &&
         !isTrailingComment(*State.NextToken) &&
         State.NextToken->isNot(tok::r_paren) &&
@@ -923,9 +913,6 @@ private:
          (State.NextToken->Parent->ClosesTemplateDeclaration &&
           State.ParenLevel == 0)))
       return true;
-    if (State.NextToken->is(tok::colon) &&
-        State.Stack.back().BreakBeforeThirdOperand)
-      return true;
     return false;
   }
 
diff --git a/lib/Format/TokenAnnotator.cpp b/lib/Format/TokenAnnotator.cpp
index 80780185c0..b7f43d52ed 100644
--- a/lib/Format/TokenAnnotator.cpp
+++ b/lib/Format/TokenAnnotator.cpp
@@ -724,7 +724,7 @@ public:
   ExpressionParser(AnnotatedLine &Line) : Current(&Line.First) {}
 
   /// \brief Parse expressions with the given operatore precedence.
-  void parse(prec::Level Precedence = prec::Unknown) {
+  void parse(int Precedence = 0) {
     if (Precedence > prec::PointerToMember || Current == NULL)
       return;
 
@@ -740,18 +740,27 @@ public:
     AnnotatedToken *Start = Current;
     bool OperatorFound = false;
 
-    while (Current != NULL) {
+    while (Current) {
       // Consume operators with higher precedence.
       parse(prec::Level(Precedence + 1));
 
+      int CurrentPrecedence = 0;
+      if (Current) {
+        if (Current->Type == TT_ConditionalExpr)
+          CurrentPrecedence = 1 + (int) prec::Conditional;
+        else if (Current->is(tok::semi))
+          CurrentPrecedence = 1;
+        else if (Current->Type == TT_BinaryOperator || Current->is(tok::comma))
+          CurrentPrecedence = 1 + (int) getPrecedence(*Current);
+      }
+
       // At the end of the line or when an operator with higher precedence is
       // found, insert fake parenthesis and return.
-      if (Current == NULL || Current->is(tok::semi) || closesScope(*Current) ||
-          ((Current->Type == TT_BinaryOperator || Current->is(tok::comma)) &&
-           getPrecedence(*Current) < Precedence)) {
+      if (Current == NULL || closesScope(*Current) ||
+          (CurrentPrecedence != 0 && CurrentPrecedence < Precedence)) {
         if (OperatorFound) {
           ++Start->FakeLParens;
-          if (Current != NULL)
+          if (Current)
             ++Current->Parent->FakeRParens;
         }
         return;
@@ -759,14 +768,21 @@ public:
 
       // Consume scopes: (), [], <> and {}
       if (opensScope(*Current)) {
-        while (Current != NULL && !closesScope(*Current)) {
+        AnnotatedToken *Left = Current;
+        while (Current && !closesScope(*Current)) {
           next();
           parse();
         }
+        // Remove fake parens that just duplicate the real parens.
+        if (Current && Left->Children[0].FakeLParens > 0 &&
+            Current->Parent->FakeRParens > 0) {
+          --Left->Children[0].FakeLParens;
+          --Current->Parent->FakeRParens;
+        }
         next();
       } else {
         // Operator found.
-        if (getPrecedence(*Current) == Precedence)
+        if (CurrentPrecedence == Precedence)
           OperatorFound = true;
 
         next();
diff --git a/unittests/Format/FormatTest.cpp b/unittests/Format/FormatTest.cpp
index daaeca3fa0..2f8097c612 100644
--- a/unittests/Format/FormatTest.cpp
+++ b/unittests/Format/FormatTest.cpp
@@ -306,6 +306,11 @@ TEST_F(FormatTest, FormatsForLoop) {
       "                                           aaaaaaaaaaaaaaaa);\n"
       "     aaaaaaaaaaa++, bbbbbbbbbbbbbbbbb++) {\n"
       "}");
+  verifyGoogleFormat(
+      "for (std::vector<UnwrappedLine>::iterator I = UnwrappedLines.begin(),\n"
+      "                                          E = UnwrappedLines.end();\n"
+      "     I != E;\n"
+      "     ++I) {\n}");
 }
 
 TEST_F(FormatTest, RangeBasedForLoops) {
@@ -1397,9 +1402,14 @@ TEST_F(FormatTest, BreaksConditionalExpressions) {
   verifyFormat("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\n"
                "    ? aaaaaaaaaaaaaaaaaaaaaaaaaaa\n"
                "    : aaaaaaaaaaaaaaaaaaaaaaaaaaa;");
-
-  // FIXME: The trailing third parameter here is kind of hidden. Prefer putting
-  // it on the next line.
+  verifyFormat(
+      "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa == aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\n"
+      "    ? aaaaaaaaaaaaaaa\n"
+      "    : aaaaaaaaaaaaaaa;");
+  verifyFormat("f(aaaaaaaaaaaaaaaa == // force break\n"
+               "  aaaaaaaaa\n"
+               "      ? b\n"
+               "      : c);");
   verifyFormat(
       "unsigned Indent =\n"
       "    format(TheLine.First, IndentForLevel[TheLine.Level] >= 0\n"
@@ -1408,6 +1418,14 @@ TEST_F(FormatTest, BreaksConditionalExpressions) {
       "           TheLine.InPPDirective, PreviousEndOfLineColumn);",
       getLLVMStyleWithColumns(70));
 
+  verifyGoogleFormat(
+      "void f() {\n"
+      "  g(aaa,\n"
+      "    aaaaaaaaaa == aaaaaaaaaa ? aaaa : aaaaa,\n"
+      "    aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa == aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\n"
+      "        ? aaaaaaaaaaaaaaa\n"
+      "        : aaaaaaaaaaaaaaa);\n"
+      "}");
 }
 
 TEST_F(FormatTest, DeclarationsOfMultipleVariables) {