Index: include/clang/Basic/Diagnostic.td
===================================================================
--- include/clang/Basic/Diagnostic.td
+++ include/clang/Basic/Diagnostic.td
@@ -39,6 +39,15 @@
 def SFINAE_Report              : SFINAEResponse;
 def SFINAE_AccessControl       : SFINAEResponse;
 
+// Textual substitutions which may be performed on the text of diagnostics
+class TextSubstitution<string Text> {
+  string Substitution = Text;
+  // FIXME: These are only here to allow substitutions to be declared with
+  // diagnostics
+  string Component = "";
+  string CategoryName = "";
+}
+
 // Diagnostic Categories.  These can be applied to groups or individual
 // diagnostics to specify a category.
 class DiagCategory<string Name> {
Index: include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- include/clang/Basic/DiagnosticSemaKinds.td
+++ include/clang/Basic/DiagnosticSemaKinds.td
@@ -3613,8 +3613,7 @@
 def note_ovl_candidate_non_deduced_mismatch_qualified : Note<
     "candidate template ignored: could not match %q0 against %q1">;
 
-// Note that we don't treat templates differently for this diagnostic.
-def note_ovl_candidate_arity : Note<"candidate "
+def select_ovl_candidate_kind : TextSubstitution<
     "%select{function|function|constructor|function|function|constructor|"
     "constructor (the implicit default constructor)|"
     "constructor (the implicit copy constructor)|"
@@ -3622,32 +3621,31 @@
     "function (the implicit copy assignment operator)|"
     "function (the implicit move assignment operator)|"
     "inherited constructor|"
-    "inherited constructor}0 %select{|template }1"
-    "not viable: requires%select{ at least| at most|}2 %3 argument%s3, but %4 "
-    "%plural{1:was|:were}4 provided">;
-
-def note_ovl_candidate_arity_one : Note<"candidate "
-    "%select{function|function|constructor|function|function|constructor|"
+    "inherited constructor}">;
+def select_ovl_template_kind : TextSubstitution<
+    "%select{function|function|constructor|"
+    "function |function |constructor |"
     "constructor (the implicit default constructor)|"
     "constructor (the implicit copy constructor)|"
     "constructor (the implicit move constructor)|"
     "function (the implicit copy assignment operator)|"
     "function (the implicit move assignment operator)|"
     "inherited constructor|"
-    "inherited constructor}0 %select{|template }1not viable: "
+    "inherited constructor }">;
+
+// Note that we don't treat templates differently for this diagnostic.
+def note_ovl_candidate_arity : Note<"candidate "
+    "%sub{select_ovl_candidate_kind}0 %select{|template }1"
+    "not viable: requires%select{ at least| at most|}2 %3 argument%s3, but %4 "
+    "%plural{1:was|:were}4 provided">;
+
+def note_ovl_candidate_arity_one : Note<"candidate "
+    "%sub{select_ovl_candidate_kind}0 %select{|template }1not viable: "
     "%select{requires at least|allows at most single|requires single}2 "
     "argument %3, but %plural{0:no|:%4}4 arguments were provided">;
 
 def note_ovl_candidate_deleted : Note<
-    "candidate %select{function|function|constructor|"
-    "function |function |constructor |"
-    "constructor (the implicit default constructor)|"
-    "constructor (the implicit copy constructor)|"
-    "constructor (the implicit move constructor)|"
-    "function (the implicit copy assignment operator)|"
-    "function (the implicit move assignment operator)|"
-    "inherited constructor|"
-    "inherited constructor }0%1 has been "
+    "candidate %sub{select_ovl_template_kind}0%1 has been "
     "%select{explicitly made unavailable|explicitly deleted|"
     "implicitly deleted}2">;
 
@@ -3657,15 +3655,7 @@
 // to complete the type, which doesn't involve changes to the call line
 // anyway.  If people complain, we can change it.
 def note_ovl_candidate_bad_conv_incomplete : Note<"candidate "
-    "%select{function|function|constructor|"
-    "function |function |constructor |"
-    "constructor (the implicit default constructor)|"
-    "constructor (the implicit copy constructor)|"
-    "constructor (the implicit move constructor)|"
-    "function (the implicit copy assignment operator)|"
-    "function (the implicit move assignment operator)|"
-    "inherited constructor|"
-    "inherited constructor }0%1 "
+    "%sub{select_ovl_template_kind}0%1 "
     "not viable: cannot convert argument of incomplete type "
     "%diff{$ to $|to parameter type}2,3 for "
     "%select{%ordinal5 argument|object argument}4"
@@ -3674,37 +3664,13 @@
     "; remove *|"
     "; remove &}6">;
 def note_ovl_candidate_bad_list_argument : Note<"candidate "
-    "%select{function|function|constructor|"
-    "function |function |constructor |"
-    "constructor (the implicit default constructor)|"
-    "constructor (the implicit copy constructor)|"
-    "constructor (the implicit move constructor)|"
-    "function (the implicit copy assignment operator)|"
-    "function (the implicit move assignment operator)|"
-    "inherited constructor|"
-    "inherited constructor }0%1 "
+    "%sub{select_ovl_template_kind}0%1 "
     "not viable: cannot convert initializer list argument to %3">;
 def note_ovl_candidate_bad_overload : Note<"candidate "
-    "%select{function|function|constructor|"
-    "function |function |constructor |"
-    "constructor (the implicit default constructor)|"
-    "constructor (the implicit copy constructor)|"
-    "constructor (the implicit move constructor)|"
-    "function (the implicit copy assignment operator)|"
-    "function (the implicit move assignment operator)|"
-    "inherited constructor|"
-    "inherited constructor }0%1"
+    "%sub{select_ovl_template_kind}0%1"
     " not viable: no overload of %3 matching %2 for %ordinal4 argument">;
 def note_ovl_candidate_bad_conv : Note<"candidate "
-    "%select{function|function|constructor|"
-    "function |function |constructor |"
-    "constructor (the implicit default constructor)|"
-    "constructor (the implicit copy constructor)|"
-    "constructor (the implicit move constructor)|"
-    "function (the implicit copy assignment operator)|"
-    "function (the implicit move assignment operator)|"
-    "inherited constructor|"
-    "inherited constructor }0%1"
+    "%sub{select_ovl_template_kind}0%1"
     " not viable: no known conversion "
     "%diff{from $ to $|from argument type to parameter type}2,3 for "
     "%select{%ordinal5 argument|object argument}4"
@@ -3713,64 +3679,24 @@
     "; remove *|"
     "; remove &}6">;
 def note_ovl_candidate_bad_arc_conv : Note<"candidate "
-    "%select{function|function|constructor|"
-    "function |function |constructor |"
-    "constructor (the implicit default constructor)|"
-    "constructor (the implicit copy constructor)|"
-    "constructor (the implicit move constructor)|"
-    "function (the implicit copy assignment operator)|"
-    "function (the implicit move assignment operator)|"
-    "inherited constructor|"
-    "inherited constructor }0%1"
+    "%sub{select_ovl_template_kind}0%1"
     " not viable: cannot implicitly convert argument "
     "%diff{of type $ to $|type to parameter type}2,3 for "
     "%select{%ordinal5 argument|object argument}4 under ARC">;
 def note_ovl_candidate_bad_lvalue : Note<"candidate "
-    "%select{function|function|constructor|"
-    "function |function |constructor |"
-    "constructor (the implicit default constructor)|"
-    "constructor (the implicit copy constructor)|"
-    "constructor (the implicit move constructor)|"
-    "function (the implicit copy assignment operator)|"
-    "function (the implicit move assignment operator)|"
-    "inherited constructor|"
-    "inherited constructor }0%1"
+    "%sub{select_ovl_template_kind}0%1"
     " not viable: expects an l-value for "
     "%select{%ordinal3 argument|object argument}2">;
 def note_ovl_candidate_bad_addrspace : Note<"candidate "
-    "%select{function|function|constructor|"
-    "function |function |constructor |"
-    "constructor (the implicit default constructor)|"
-    "constructor (the implicit copy constructor)|"
-    "constructor (the implicit move constructor)|"
-    "function (the implicit copy assignment operator)|"
-    "function (the implicit move assignment operator)|"
-    "inherited constructor|"
-    "inherited constructor }0%1 not viable: "
+    "%sub{select_ovl_template_kind}0%1 not viable: "
     "%select{%ordinal6|'this'}5 argument (%2) is in "
     "address space %3, but parameter must be in address space %4">;
 def note_ovl_candidate_bad_gc : Note<"candidate "
-    "%select{function|function|constructor|"
-    "function |function |constructor |"
-    "constructor (the implicit default constructor)|"
-    "constructor (the implicit copy constructor)|"
-    "constructor (the implicit move constructor)|"
-    "function (the implicit copy assignment operator)|"
-    "function (the implicit move assignment operator)|"
-    "inherited constructor|"
-    "inherited constructor }0%1 not viable: "
+    "%sub{select_ovl_template_kind}0%1 not viable: "
     "%select{%ordinal6|'this'}5 argument (%2) has %select{no|__weak|__strong}3 "
     "ownership, but parameter has %select{no|__weak|__strong}4 ownership">;
 def note_ovl_candidate_bad_ownership : Note<"candidate "
-    "%select{function|function|constructor|"
-    "function |function |constructor |"
-    "constructor (the implicit default constructor)|"
-    "constructor (the implicit copy constructor)|"
-    "constructor (the implicit move constructor)|"
-    "function (the implicit copy assignment operator)|"
-    "function (the implicit move assignment operator)|"
-    "inherited constructor|"
-    "inherited constructor }0%1 not viable: "
+    "%sub{select_ovl_template_kind}0%1 not viable: "
     "%select{%ordinal6|'this'}5 argument (%2) has "
     "%select{no|__unsafe_unretained|__strong|__weak|__autoreleasing}3 ownership,"
     " but parameter has %select{no|__unsafe_unretained|__strong|__weak|"
@@ -3783,54 +3709,22 @@
     "%select{const|restrict|const or restrict|volatile|const or volatile|"
     "volatile or restrict|const, volatile, or restrict}3">;
 def note_ovl_candidate_bad_cvr : Note<"candidate "
-    "%select{function|function|constructor|"
-    "function |function |constructor |"
-    "constructor (the implicit default constructor)|"
-    "constructor (the implicit copy constructor)|"
-    "constructor (the implicit move constructor)|"
-    "function (the implicit copy assignment operator)|"
-    "function (the implicit move assignment operator)|"
-    "inherited constructor|"
-    "inherited constructor }0%1 not viable: "
+    "%sub{select_ovl_template_kind}0%1 not viable: "
     "%ordinal4 argument (%2) would lose "
     "%select{const|restrict|const and restrict|volatile|const and volatile|"
     "volatile and restrict|const, volatile, and restrict}3 qualifier"
     "%select{||s||s|s|s}3">;
 def note_ovl_candidate_bad_unaligned : Note<"candidate "
-    "%select{function|function|constructor|"
-    "function |function |constructor |"
-    "constructor (the implicit default constructor)|"
-    "constructor (the implicit copy constructor)|"
-    "constructor (the implicit move constructor)|"
-    "function (the implicit copy assignment operator)|"
-    "function (the implicit move assignment operator)|"
-    "inherited constructor|"
-    "inherited constructor }0%1 not viable: "
+    "%sub{select_ovl_template_kind}0%1 not viable: "
     "%ordinal4 argument (%2) would lose __unaligned qualifier">;
 def note_ovl_candidate_bad_base_to_derived_conv : Note<"candidate "
-    "%select{function|function|constructor|"
-    "function |function |constructor |"
-    "constructor (the implicit default constructor)|"
-    "constructor (the implicit copy constructor)|"
-    "constructor (the implicit move constructor)|"
-    "function (the implicit copy assignment operator)|"
-    "function (the implicit move assignment operator)|"
-    "inherited constructor|"
-    "inherited constructor }0%1 not viable: "
+    "%sub{select_ovl_template_kind}0%1 not viable: "
     "cannot %select{convert from|convert from|bind}2 "
     "%select{base class pointer|superclass|base class object of type}2 %3 to "
     "%select{derived class pointer|subclass|derived class reference}2 %4 for "
     "%ordinal5 argument">;
 def note_ovl_candidate_bad_target : Note<
-    "candidate %select{function|function|constructor|"
-    "function|function|constructor|"
-    "constructor (the implicit default constructor)|"
-    "constructor (the implicit copy constructor)|"
-    "constructor (the implicit move constructor)|"
-    "function (the implicit copy assignment operator)|"
-    "function (the implicit move assignment operator)|"
-    "inherited constructor|"
-    "inherited constructor}0 not viable: "
+    "candidate %sub{select_ovl_candidate_kind}0 not viable: "
     "call to "
     "%select{__device__|__global__|__host__|__host__ __device__|invalid}1 function from"
     " %select{__device__|__global__|__host__|__host__ __device__|invalid}2 function">;
@@ -7749,6 +7643,10 @@
   "explicit conversion functions are incompatible with C++98">,
   InGroup<CXX98Compat>, DefaultIgnore;
 
+def select_special_member : TextSubstitution<
+  "%select{default constructor|copy constructor|move constructor|"
+  "copy assignment operator|move assignment operator|destructor}">;
+
 // C++11 defaulted functions
 def err_defaulted_special_member_params : Error<
   "an explicitly-defaulted %select{|copy |move }0constructor cannot "
@@ -7763,9 +7661,8 @@
   "an explicitly-defaulted %select{copy|move}0 assignment operator may not "
   "have 'const'%select{, 'constexpr'|}1 or 'volatile' qualifiers">;
 def err_defaulted_special_member_volatile_param : Error<
-  "the parameter for an explicitly-defaulted %select{<<ERROR>>|"
-  "copy constructor|move constructor|copy assignment operator|"
-  "move assignment operator|<<ERROR>>}0 may not be volatile">;
+  "the parameter for an explicitly-defaulted %sub{select_special_member}0 "
+  "may not be volatile">;
 def err_defaulted_special_member_move_const_param : Error<
   "the parameter for an explicitly-defaulted move "
   "%select{constructor|assignment operator}0 may not be const">;
@@ -7777,17 +7674,13 @@
   "the parameter for an explicitly-defaulted copy assignment operator must be an "
   "lvalue reference type">;
 def err_incorrect_defaulted_exception_spec : Error<
-  "exception specification of explicitly defaulted %select{default constructor|"
-  "copy constructor|move constructor|copy assignment operator|move assignment "
-  "operator|destructor}0 does not match the "
-  "calculated one">;
+  "exception specification of explicitly defaulted %sub{select_special_member}0 "
+  "does not match the calculated one">;
 def err_incorrect_defaulted_constexpr : Error<
-  "defaulted definition of %select{default constructor|copy constructor|"
-  "move constructor|copy assignment operator|move assignment operator}0 "
+  "defaulted definition of %sub{select_special_member}0 "
   "is not constexpr">;
 def err_out_of_line_default_deletes : Error<
-  "defaulting this %select{default constructor|copy constructor|move "
-  "constructor|copy assignment operator|move assignment operator|destructor}0 "
+  "defaulting this %sub{select_special_member}0 "
   "would delete it after its first declaration">;
 def warn_vbase_moved_multiple_times : Warning<
   "defaulted move assignment operator of %0 will move assign virtual base "
Index: utils/TableGen/ClangDiagnosticsEmitter.cpp
===================================================================
--- utils/TableGen/ClangDiagnosticsEmitter.cpp
+++ utils/TableGen/ClangDiagnosticsEmitter.cpp
@@ -14,12 +14,13 @@
 #include "llvm/ADT/DenseSet.h"
 #include "llvm/ADT/Optional.h"
 #include "llvm/ADT/PointerUnion.h"
+#include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringMap.h"
-#include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/Twine.h"
+#include "llvm/Support/Regex.h"
 #include "llvm/TableGen/Error.h"
 #include "llvm/TableGen/Record.h"
 #include "llvm/TableGen/StringToOffsetTable.h"
@@ -455,6 +456,39 @@
   return ClsName == "CLASS_REMARK";
 }
 
+static void substituteDiagText(Record *Diag, StringMap<Record *> SubsMap) {
+  llvm::Regex RE("%sub{[^}]*}");
+  std::string Error;
+  ((void)Error);
+  assert(RE.isValid(Error) && RE.getNumMatches() == 0);
+
+  RecordVal *RV = Diag->getValue("Text");
+  std::string Text = RV->getValue()->getAsString();
+
+  unsigned Count = 0;
+  SmallVector<StringRef, 1> Matches;
+  while (RE.match(Text, &Matches)) {
+    ++Count;
+    assert(Matches.size() == 1);
+    StringRef M = Matches[0];
+    std::pair<unsigned, unsigned> Range(M.data() - Text.data(), M.size());
+
+    assert(Text.size() > Range.first + Range.second);
+    StringRef Found(Text);
+
+    Found = Found.substr(Range.first, Range.second);
+    StringRef FoundName = Found.substr(5, Found.size() - 6);
+    Record *S = SubsMap.lookup(FoundName);
+    if (!S) {
+      PrintFatalError(Diag->getLoc(), "Diag " + Diag->getName() +
+                                          " has no substitution for: " + Found);
+    }
+    Text.replace(Range.first, Range.second,
+                 S->getValueAsString("Substitution"));
+  }
+  RV->setValue(StringInit::get(Text));
+}
+
 /// ClangDiagsDefsEmitter - The top-level class emits .def files containing
 /// declarations of Clang diagnostics.
 namespace clang {
@@ -470,8 +504,14 @@
     OS << "#endif\n\n";
   }
 
-  const std::vector<Record*> &Diags =
-    Records.getAllDerivedDefinitions("Diagnostic");
+  std::vector<Record *> Substitutions =
+      Records.getAllDerivedDefinitions("TextSubstitution");
+  StringMap<Record *> SubsMap;
+  for (auto *R : Substitutions)
+    SubsMap.try_emplace(R->getName(), R);
+
+  std::vector<Record *> Diags = Records.getAllDerivedDefinitions("Diagnostic");
+  llvm::for_each(Diags, [&](Record *R) { substituteDiagText(R, SubsMap); });
 
   std::vector<Record*> DiagGroups
     = Records.getAllDerivedDefinitions("DiagGroup");
@@ -953,6 +993,9 @@
     StringRef Modifier = Text.slice(0, ModLength);
     Text = Text.slice(ModLength, StringRef::npos);
 
+    assert(Modifier != "sub" &&
+           "substitutions should have already taken place!");
+
     // FIXME: Handle %ordinal here.
     if (Modifier == "select" || Modifier == "plural") {
       DiagText::SelectPiece Select;
@@ -1208,9 +1251,16 @@
   }
 
   OS << Documentation->getValueAsString("Intro") << "\n";
+  std::vector<Record *> Substitutions =
+      Records.getAllDerivedDefinitions("TextSubstitution");
+  StringMap<Record *> SubsMap;
+  for (Record *R : Substitutions)
+    SubsMap.try_emplace(R->getName(), R);
 
   std::vector<Record*> Diags =
       Records.getAllDerivedDefinitions("Diagnostic");
+  llvm::for_each(Diags, [&](Record *R) { substituteDiagText(R, SubsMap); });
+
   std::vector<Record*> DiagGroups =
       Records.getAllDerivedDefinitions("DiagGroup");
   llvm::sort(DiagGroups.begin(), DiagGroups.end(), diagGroupBeforeByName);
@@ -1300,6 +1350,7 @@
         Severity[0] = tolower(Severity[0]);
         if (Severity == "ignored")
           Severity = IsRemarkGroup ? "remark" : "warning";
+
         writeDiagnosticText(Severity, D->getValueAsString("Text"), OS);
       }
     }