Penalize tokens with a lower parenthesis level than the start of the line.

This prevents formattings like this (assuming "parameter" doesn't fit the line):
  bool f = someFunction() && someFunctionWithParam(
      parameter) && someOtherFunction();

Here, "parameter" - the start of line 2 - has a parenthesis level of 2, but
there are subsequent tokens ("&&" and "someOtherFunction") with a lower level.
This is bad for readability as "parameter" hides "someOtherFunction". With this
patch, this changes to:
  bool f = someFunction() &&
           someFunctionWithParam(parameter) &&
           someOtherFunction();

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@171038 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Format/Format.cpp

@@ -83,6 +83,7 @@ FormatStyle getGoogleStyle() {
 
 struct OptimizationParameters {
   unsigned PenaltyIndentLevel;
+  unsigned PenaltyLevelDecrease;
 };
 
 class UnwrappedLineFormatter {
@@ -95,6 +96,7 @@ public:
         Annotations(Annotations), Replaces(Replaces),
         StructuralError(StructuralError) {
     Parameters.PenaltyIndentLevel = 15;
+    Parameters.PenaltyLevelDecrease = 10;
   }
 
   void format() {
@@ -110,6 +112,7 @@ public:
     State.FirstLessLess.push_back(0);
     State.ForLoopVariablePos = 0;
     State.LineContainsContinuedForLoopSection = false;
+    State.StartOfLineLevel = 1;
 
     // The first token has already been indented and thus consumed.
     moveStateToNextToken(State);
@@ -155,6 +158,9 @@ private:
     /// \brief The number of tokens already consumed.
     unsigned ConsumedTokens;
 
+    /// \brief The parenthesis level of the first token on the current line.
+    unsigned StartOfLineLevel;
+
     /// \brief The position to which a specific parenthesis level needs to be
     /// indented.
     std::vector<unsigned> Indent;
@@ -186,6 +192,8 @@ private:
         return Other.ConsumedTokens > ConsumedTokens;
       if (Other.Column != Column)
         return Other.Column > Column;
+      if (Other.StartOfLineLevel != StartOfLineLevel)
+        return Other.StartOfLineLevel > StartOfLineLevel;
       if (Other.Indent.size() != Indent.size())
         return Other.Indent.size() > Indent.size();
       for (int i = 0, e = Indent.size(); i != e; ++i) {
@@ -247,6 +255,8 @@ private:
         State.Column = State.Indent[ParenLevel];
       }
 
+      State.StartOfLineLevel = ParenLevel + 1;
+
       if (Line.Tokens[0].Tok.is(tok::kw_for))
         State.LineContainsContinuedForLoopSection =
             Previous.Tok.isNot(tok::semi);
@@ -343,7 +353,7 @@ private:
       return Level;
 
     if (Right.Tok.is(tok::arrow) || Right.Tok.is(tok::period))
-      return 200;
+      return 50;
 
     return 3;
   }
@@ -375,6 +385,10 @@ private:
     if (NewLine) {
       CurrentPenalty += Parameters.PenaltyIndentLevel * State.Indent.size() +
           splitPenalty(State.ConsumedTokens - 1);
+    } else {
+      if (State.Indent.size() < State.StartOfLineLevel)
+        CurrentPenalty += Parameters.PenaltyLevelDecrease *
+                          (State.StartOfLineLevel - State.Indent.size());
     }
 
     addTokenToState(NewLine, true, State);

unittests/Format/FormatTest.cpp

@@ -379,8 +379,9 @@ TEST_F(FormatTest, FormatsFunctionDefinition) {
 
 TEST_F(FormatTest, FormatsAwesomeMethodCall) {
   verifyFormat(
-      "SomeLongMethodName(SomeReallyLongMethod(CallOtherReallyLongMethod(\n"
-      "    parameter, parameter, parameter)), SecondLongCall(parameter));");
+      "SomeLongMethodName(SomeReallyLongMethod(\n"
+      "    CallOtherReallyLongMethod(parameter, parameter, parameter)),\n"
+      "                   SecondLongCall(parameter));");
 }
 
 TEST_F(FormatTest, ConstructorInitializers) {
@@ -454,6 +455,13 @@ TEST_F(FormatTest, BreaksDesireably) {
       "       aaaaaaaaaaa(aaaaaaaaa) || aaaaaaaaaaaaaaaaaaaaaaa ||\n"
       "       aaaaaaaaaaaaaaaaaaaaaaaaa || aaaaaaaaaaaaaaaaaaaaaaa ||\n"
       "       (aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa);");
+
+  verifyFormat(
+      "{\n  {\n    {\n"
+      "      Annotation.SpaceRequiredBefore =\n"
+      "          Line.Tokens[i - 1].Tok.isNot(tok::l_paren) &&\n"
+      "          Line.Tokens[i - 1].Tok.isNot(tok::l_square);\n"
+      "    }\n  }\n}");
 }
 
 TEST_F(FormatTest, BreaksAccordingToOperatorPrecedence) {