Index: clang/include/clang/Driver/Options.td
===================================================================
--- clang/include/clang/Driver/Options.td
+++ clang/include/clang/Driver/Options.td
@@ -274,10 +274,10 @@
 // Use this only when the option cannot be declared via BoolFOption.
 multiclass OptInFFlag<string name, string pos_prefix, string neg_prefix="",
                       string help="", list<OptionFlag> flags=[]> {
-  def f#NAME : Flag<["-"], "f"#name>, Flags<!listconcat([CC1Option], flags)>,
-               Group<f_Group>, HelpText<!strconcat(pos_prefix, help)>;
+  def f#NAME : Flag<["-"], "f"#name>, Flags<[CC1Option] # flags>,
+               Group<f_Group>, HelpText<pos_prefix # help>;
   def fno_#NAME : Flag<["-"], "fno-"#name>, Flags<flags>,
-                  Group<f_Group>, HelpText<!strconcat(neg_prefix, help)>;
+                  Group<f_Group>, HelpText<neg_prefix # help>;
 }
 
 // A boolean option which is opt-out in CC1. The negative option exists in CC1 and
@@ -286,9 +286,9 @@
 multiclass OptOutFFlag<string name, string pos_prefix, string neg_prefix,
                        string help="", list<OptionFlag> flags=[]> {
   def f#NAME : Flag<["-"], "f"#name>, Flags<flags>,
-               Group<f_Group>, HelpText<!strconcat(pos_prefix, help)>;
-  def fno_#NAME : Flag<["-"], "fno-"#name>, Flags<!listconcat([CC1Option], flags)>,
-                  Group<f_Group>, HelpText<!strconcat(neg_prefix, help)>;
+               Group<f_Group>, HelpText<pos_prefix # help>;
+  def fno_#NAME : Flag<["-"], "fno-"#name>, Flags<[CC1Option] # flags>,
+                  Group<f_Group>, HelpText<neg_prefix # help>;
 }
 
 // Creates a positive and negative flags where both of them are prefixed with
@@ -297,9 +297,9 @@
 multiclass SimpleMFlag<string name, string pos_prefix, string neg_prefix,
                        string help, OptionGroup opt_group = m_Group> {
   def m#NAME : Flag<["-"], "m"#name>, Group<opt_group>,
-    HelpText<!strconcat(pos_prefix, help)>;
+    HelpText<pos_prefix # help>;
   def mno_#NAME : Flag<["-"], "mno-"#name>, Group<opt_group>,
-    HelpText<!strconcat(neg_prefix, help)>;
+    HelpText<neg_prefix # help>;
 }
 
 //===----------------------------------------------------------------------===//
@@ -349,8 +349,8 @@
 class ApplySuffix<FlagDef flag, BothFlags suffix> {
   FlagDef Result
     = FlagDef<flag.Polarity, flag.Value,
-              !listconcat(flag.OptionFlags, suffix.OptionFlags),
-              !strconcat(flag.Help, suffix.Help), flag.ImpliedBy>;
+              flag.OptionFlags # suffix.OptionFlags,
+              flag.Help # suffix.Help, flag.ImpliedBy>;
 }
 
 // Definition of the command line flag with positive spelling, e.g. "-ffoo".
@@ -368,16 +368,16 @@
   : FlagDef<flag.Polarity, flag.Value, flag.OptionFlags, flag.Help,
             flag.ImpliedBy> {
   // Name of the TableGen record.
-  string RecordName = prefix#!cond(flag.Polarity : "", true : "no_")#name;
+  string RecordName = prefix # !if(flag.Polarity, "", "no_") # name;
 
   // Spelling of the flag.
-  string Spelling = prefix#!cond(flag.Polarity : "", true : "no-")#spelling;
+  string Spelling = prefix # !if(flag.Polarity, "", "no-") # spelling;
 
   // Can the flag be implied by another flag?
   bit CanBeImplied = !not(!empty(flag.ImpliedBy));
 
   // C++ code that will be assigned to the keypath when the flag is present.
-  code ValueAsCode = !cond(flag.Value : "true", true: "false");
+  code ValueAsCode = !if(flag.Value, "true", "false");
 }
 
 // TableGen record for a single marshalled flag.
@@ -404,11 +404,19 @@
   defvar flag2 = FlagDefExpanded<ApplySuffix<flag2_base, suffix>.Result, prefix,
                                  NAME, spelling_base>;
 
-  // TODO: Assert that the flags have different polarity.
-  // TODO: Assert that the flags have different value.
-  // TODO: Assert that only one of the flags can be implied.
+  // The flags must have different polarity, different values, and only
+  // one can be implied.
+  assert !xor(flag1.Polarity, flag2.Polarity),
+         "the flags must have different polarity: flag1: " #
+             flag1.Polarity # ", flag2: " # flag2.Polarity;
+  assert !ne(flag1.Value, flag2.Value),
+         "the flags must have different values: flag1: " #
+             flag1.Value # ", flag2: " # flag2.Value;
+  assert !not(!and(flag1.CanBeImplied, flag2.CanBeImplied)),
+         "only one of the flags can be implied: flag1: " #
+             flag1.CanBeImplied # ", flag2: " # flag2.CanBeImplied;
 
-  defvar implied = !cond(flag1.CanBeImplied: flag1, true: flag2);
+  defvar implied = !if(flag1.CanBeImplied, flag1, flag2);
 
   def flag1.RecordName : MarshalledFlagRec<flag1, flag2, implied, kpm, default>;
   def flag2.RecordName : MarshalledFlagRec<flag2, flag1, implied, kpm, default>;
@@ -1077,7 +1085,8 @@
 def fasynchronous_unwind_tables : Flag<["-"], "fasynchronous-unwind-tables">, Group<f_Group>;
 
 defm double_square_bracket_attributes : BoolFOption<"double-square-bracket-attributes",
-  LangOpts<"DoubleSquareBracketAttributes">, Default<!strconcat(cpp11.KeyPath, "||", c2x.KeyPath)>,
+  LangOpts<"DoubleSquareBracketAttributes">,
+  Default<!strconcat(cpp11.KeyPath, "||", c2x.KeyPath)>,
   PosFlag<SetTrue, [], "Enable">, NegFlag<SetFalse, [], "Disable">,
   BothFlags<[NoXarchOption, CC1Option], " '[[]]' attributes in all C and C++ language modes">>;
 
@@ -1896,8 +1905,9 @@
                     "LangOptions::LaxVectorConversionKind::Integer",
                     "LangOptions::LaxVectorConversionKind::All"]>,
   MarshallingInfoEnum<LangOpts<"LaxVectorConversions">,
-                      !strconcat(open_cl.KeyPath, " ? LangOptions::LaxVectorConversionKind::None"
-                                                  " : LangOptions::LaxVectorConversionKind::All")>;
+                      open_cl.KeyPath #
+                          " ? LangOptions::LaxVectorConversionKind::None" #
+                          " : LangOptions::LaxVectorConversionKind::All">;
 def flax_vector_conversions : Flag<["-"], "flax-vector-conversions">, Group<f_Group>,
   Alias<flax_vector_conversions_EQ>, AliasArgs<["integer"]>;
 def flimited_precision_EQ : Joined<["-"], "flimited-precision=">, Group<f_Group>;