clang-format: Handle "if constexpr".

c++1z adds the following constructions to the language:

  if constexpr (cond)
    statement1;
  else if constexpr (cond)
    statement2;
  else if constexpr (cond)
    statement3;
  else
    statement4;

A first version of this was proposed in reviews.llvm.org/D26953 by
Francis Visoiu Mistrih, but never commited. This patch additionally
fixes the behavior when allowing short if statements on a single line
and was authored by Jacob Bandes-Storch. Thank you to both authors.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@305666 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 68 insertions, 0 deletions

diff --git a/unittests/Format/FormatTest.cpp b/unittests/Format/FormatTest.cpp
index f493717103..e6cd617abd 100644
--- a/unittests/Format/FormatTest.cpp
+++ b/unittests/Format/FormatTest.cpp
@@ -341,6 +341,18 @@ TEST_F(FormatTest, FormatIfWithoutCompoundStatement) {
   verifyFormat("if (true)\n  f();\ng();");
   verifyFormat("if (a)\n  if (b)\n    if (c)\n      g();\nh();");
   verifyFormat("if (a)\n  if (b) {\n    f();\n  }\ng();");
+  verifyFormat("if constexpr (true)\n"
+               "  f();\ng();");
+  verifyFormat("if constexpr (a)\n"
+               "  if constexpr (b)\n"
+               "    if constexpr (c)\n"
+               "      g();\n"
+               "h();");
+  verifyFormat("if constexpr (a)\n"
+               "  if constexpr (b) {\n"
+               "    f();\n"
+               "  }\n"
+               "g();");
 
   FormatStyle AllowsMergedIf = getLLVMStyle();
   AllowsMergedIf.AlignEscapedNewlines = FormatStyle::ENAS_Left;
@@ -423,9 +435,11 @@ TEST_F(FormatTest, FormatShortBracedStatements) {
   AllowSimpleBracedStatements.AllowShortLoopsOnASingleLine = true;
 
   verifyFormat("if (true) {}", AllowSimpleBracedStatements);
+  verifyFormat("if constexpr (true) {}", AllowSimpleBracedStatements);
   verifyFormat("while (true) {}", AllowSimpleBracedStatements);
   verifyFormat("for (;;) {}", AllowSimpleBracedStatements);
   verifyFormat("if (true) { f(); }", AllowSimpleBracedStatements);
+  verifyFormat("if constexpr (true) { f(); }", AllowSimpleBracedStatements);
   verifyFormat("while (true) { f(); }", AllowSimpleBracedStatements);
   verifyFormat("for (;;) { f(); }", AllowSimpleBracedStatements);
   verifyFormat("if (true) { //\n"
@@ -496,6 +510,19 @@ TEST_F(FormatTest, ParseIfElse) {
                "else {\n"
                "  i();\n"
                "}");
+  verifyFormat("if (true)\n"
+               "  if constexpr (true)\n"
+               "    if (true) {\n"
+               "      if constexpr (true)\n"
+               "        f();\n"
+               "    } else {\n"
+               "      g();\n"
+               "    }\n"
+               "  else\n"
+               "    h();\n"
+               "else {\n"
+               "  i();\n"
+               "}");
   verifyFormat("void f() {\n"
                "  if (a) {\n"
                "  } else {\n"
@@ -511,6 +538,12 @@ TEST_F(FormatTest, ElseIf) {
                "  g();\n"
                "else\n"
                "  h();");
+  verifyFormat("if constexpr (a)\n"
+               "  f();\n"
+               "else if constexpr (b)\n"
+               "  g();\n"
+               "else\n"
+               "  h();");
   verifyFormat("if (a) {\n"
                "  f();\n"
                "}\n"
@@ -528,6 +561,11 @@ TEST_F(FormatTest, ElseIf) {
                "    aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa) {\n"
                "}",
                getLLVMStyleWithColumns(62));
+  verifyFormat("if (a) {\n"
+               "} else if constexpr (\n"
+               "    aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa) {\n"
+               "}",
+               getLLVMStyleWithColumns(62));
 }
 
 TEST_F(FormatTest, FormatsForLoop) {
@@ -2506,6 +2544,9 @@ TEST_F(FormatTest, LineBreakingInBinaryExpressions) {
   verifyFormat("if ((aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa ||\n"
                "     bbbbbbbbbbbbbbbbbb) && // aaaaaaaaaaaaaaaa\n"
                "    cccccc) {\n}");
+  verifyFormat("if constexpr ((aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa ||\n"
+               "               bbbbbbbbbbbbbbbbbb) && // aaaaaaaaaaa\n"
+               "              cccccc) {\n}");
   verifyFormat("b = a &&\n"
                "    // Comment\n"
                "    b.c && d;");
@@ -6627,6 +6668,10 @@ TEST_F(FormatTest, MergeHandlingInTheFaceOfPreprocessorDirectives) {
                "  if (true) continue;\n"
                "}",
                ShortMergedIf);
+  ShortMergedIf.ColumnLimit = 33;
+  verifyFormat("#define A \\\n"
+               "  if constexpr (true) return 42;",
+               ShortMergedIf);
   ShortMergedIf.ColumnLimit = 29;
   verifyFormat("#define A                   \\\n"
                "  if (aaaaaaaaaa) return 1; \\\n"
@@ -6638,6 +6683,11 @@ TEST_F(FormatTest, MergeHandlingInTheFaceOfPreprocessorDirectives) {
                "    return 1;     \\\n"
                "  return 2;",
                ShortMergedIf);
+  verifyFormat("#define A                \\\n"
+               "  if constexpr (aaaaaaa) \\\n"
+               "    return 1;            \\\n"
+               "  return 2;",
+               ShortMergedIf);
 }
 
 TEST_F(FormatTest, FormatStarDependingOnContext) {
@@ -8847,11 +8897,24 @@ TEST_F(FormatTest, AllmanBraceBreaking) {
                BreakBeforeBraceShortIfs);
   verifyFormat("void f(bool b)\n"
                "{\n"
+               "  if constexpr (b)\n"
+               "  {\n"
+               "    return;\n"
+               "  }\n"
+               "}\n",
+               BreakBeforeBraceShortIfs);
+  verifyFormat("void f(bool b)\n"
+               "{\n"
                "  if (b) return;\n"
                "}\n",
                BreakBeforeBraceShortIfs);
   verifyFormat("void f(bool b)\n"
                "{\n"
+               "  if constexpr (b) return;\n"
+               "}\n",
+               BreakBeforeBraceShortIfs);
+  verifyFormat("void f(bool b)\n"
+               "{\n"
                "  while (b)\n"
                "  {\n"
                "    return;\n"
@@ -10098,6 +10161,11 @@ TEST_F(FormatTest, FormatsLambdas) {
                "      doo_dah();\n"
                "    })) {\n"
                "}");
+  verifyFormat("if constexpr (blah_blah(whatever, whatever, [] {\n"
+               "                doo_dah();\n"
+               "                doo_dah();\n"
+               "              })) {\n"
+               "}");
   verifyFormat("auto lambda = []() {\n"
                "  int a = 2\n"
                "#if A\n"