clang-format: Prefer an additional line-break over hanging indent.

Don't allow the RHS of an operator to be split over multiple
lines unless there is a line-break right after the operator.

Before:
  if (aaaa && bbbbb || // break
                  cccc) {
  }

After:
  if (aaaa &&
      bbbbb || // break
          cccc) {
  }

In most cases, this seems to increase readability.

llvm-svn: 205527

clang/lib/Format/ContinuationIndenter.cpp

@@ -609,6 +609,18 @@ unsigned ContinuationIndenter::moveStateToNextToken(LineState &State,
           std::max(std::max(State.Column, NewParenState.Indent),
                    State.Stack.back().LastSpace);
 
+    // Don't allow the RHS of an operator to be split over multiple lines unless
+    // there is a line-break right after the operator.
+    // Exclude relational operators, as there, it is always more desirable to
+    // have the LHS 'left' of the RHS.
+    // FIXME: Implement this for '<<' and BreakBeforeBinaryOperators.
+    if (!Newline && Previous && Previous->Type == TT_BinaryOperator &&
+        !Previous->isOneOf(tok::lessless, tok::question, tok::colon) &&
+        Previous->getPrecedence() > prec::Assignment &&
+        Previous->getPrecedence() != prec::Relational &&
+        !Style.BreakBeforeBinaryOperators)
+      NewParenState.NoLineBreak = true;
+
     // Do not indent relative to the fake parentheses inserted for "." or "->".
     // This is a special case to make the following to statements consistent:
     //   OuterFunction(InnerFunctionCall( // break

clang/unittests/Format/FormatTest.cpp

@@ -2889,7 +2889,8 @@ TEST_F(FormatTest, ExpressionIndentation) {
                "            aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa +\n"
                "        bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb) {\n}");
   verifyFormat("if () {\n"
-               "} else if (aaaaa && bbbbb > // break\n"
+               "} else if (aaaaa &&\n"
+               "           bbbbb > // break\n"
                "               ccccc) {\n"
                "}");