revert hack/tests. Next commit will clean up error messages

Author: Aidan

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -4877,8 +4877,7 @@ def note_ovl_candidate_explicit_arg_mismatch_detail : Note<
     "|: expected a type, but got value '%1'"
     "|: expected constant of type %3 but got type %1"
     "|: could not convert '%1' from %2 to %3"
-    "| for %ordinal4 template parameter"
-    "|: expr is not a valid const expr in the expected context}0">;
+    "| for %ordinal4 template parameter}0">;
 
 def note_ovl_candidate_unsatisfied_constraints : Note<
     "candidate template ignored: constraints not satisfied%0">;

clang/lib/AST/ExprConstant.cpp

@@ -16814,17 +16814,8 @@ bool Expr::EvaluateAsConstantExpr(EvalResult &Result, const ASTContext &Ctx,
       (!EvaluateDestruction(Ctx, Base, Result.Val, T, getBeginLoc(), Result,
                             true) ||
        Result.HasSideEffects)) {
-
-    // FIXME: err_constexpr_var_requires_const_destruction?
-    PartialDiagnostic PD(diag::err_constexpr_var_requires_const_destruction,
-                         const_cast<ASTContext &>(Ctx).getDiagAllocator());
-    std::string ExprStr;
-    llvm::raw_string_ostream OS(ExprStr);
-    this->printPretty(OS, nullptr, PrintingPolicy(Ctx.getLangOpts()));
-    PD << ExprStr;
-    SourceLocation Loc = this->getBeginLoc();
-    Result.Diag->insert(Result.Diag->begin(), PartialDiagnosticAt(Loc, PD));
-
+    // FIXME: Prefix a note to indicate that the problem is lack of constant
+    // destruction.
     return false;
   }
 

clang/lib/Sema/SemaOverload.cpp

@@ -11730,15 +11730,15 @@ static void DiagnoseBadDeduction(Sema &S, NamedDecl *Found, Decl *Templated,
         if (SecondArg.isNull())
           return {2, NTTPD->getIndex(), NTTPD->getType()};
         else {
-          // FIXME: this is a hack, we should do this in SemaTempalteDeduction
-          // or even ExprConstant. Perhaps an InvalidExplicitArguments error
-          // is not what we want
+          // FIXME: This is a hack. We should emit a better message
+          // for ill-formed const exprs in >=C++20.
           QualType qt = NTTPD->getType();
-          if (qt.getCanonicalType() !=
-              SecondArg.getAsType().getCanonicalType()) {
-            return {3, NTTPD->getIndex(), NTTPD->getType()};
+          if (qt.getCanonicalType() ==
+                  SecondArg.getAsType().getCanonicalType() &&
+              __cplusplus <= 201703) {
+            return {4, NTTPD->getIndex(), NTTPD->getType()};
           } else {
-            return {5, NTTPD->getIndex(), NTTPD->getType()};
+            return {3, NTTPD->getIndex(), NTTPD->getType()};
           }
         }
       }

clang/lib/Sema/SemaTemplateDeduction.cpp

@@ -3573,9 +3573,6 @@ TemplateDeductionResult Sema::SubstituteExplicitTemplateArguments(
                                 /*UpdateArgsWithConversions=*/false) ||
       Trap.hasErrorOccurred()) {
 
-    // FIXME: decide if ill formed const expr or regular
-    // InvalidExplicitArguments?
-
     unsigned Index = SugaredBuilder.size();
     if (Index >= TemplateParams->size())
       return TemplateDeductionResult::SubstitutionFailure;

clang/test/AST/ByteCode/cxx20.cpp

@@ -751,7 +751,7 @@ namespace FailingDestructor {
     }
   };
   template<D d> // both-note{{template parameter is declared here}}
-  void f() {} // both-note{{candidate template ignored: invalid explicitly-specified argument: expr is not a valid const expr in the expected context}}
+  void f() {} // both-note{{andidate template ignored: invalid explicitly-specified argument for 1st template parameter}}
 
   void g() {
     f<D{0, false}>(); // both-error {{no matching function}}

clang/test/CXX/drs/cwg3xx.cpp

@@ -982,7 +982,7 @@ namespace cwg354 { // cwg354: 3.1 c++11
   int b1 = both<(int*)0>();
   // cxx98-error@-1 {{no matching function for call to 'both'}}
   // cxx98-note@#cwg354-both-int-ptr {{template parameter is declared here}}
-  // cxx98-note@#cwg354-both-int-ptr {{candidate template ignored: invalid explicitly-specified argument: could not convert '(int *)0' from 'int *' to 'int'}}
+  // cxx98-note@#cwg354-both-int-ptr {{candidate template ignored: invalid explicitly-specified argument for 1st template parameter}}
   // cxx98-note@#cwg354-both-int {{template parameter is declared here}}
   // cxx98-note@#cwg354-both-int {{candidate template ignored: invalid explicitly-specified argument: could not convert '(int *)0' from 'int *' to 'int'}}
 

clang/test/CXX/temp/temp.param/p8-cxx20.cpp

@@ -40,7 +40,7 @@ namespace ConstDestruction {
   };
 
   template<D d> // expected-note 2{{template parameter is declared here}}
-  void f() {} // expected-note 2{{candidate template ignored: invalid explicitly-specified argument: expr is not a valid const expr in the expected context}}
+  void f() {} // expected-note 2{{candidate template ignored: invalid explicitly-specified argument for 1st template parameter}}
 
   void g() {
     f<D{0, true}>();

clang/test/SemaCXX/constexpr-function-recovery-crash.cpp

@@ -60,7 +60,7 @@ constexpr void test8() {
   throw "bad";
 }
 
-template<int x> constexpr int f(int y) { //expected-note {{template parameter is declared here}} // expected-note {{candidate template ignored: invalid explicitly-specified argument: expr is not a valid const expr in the expected context}}
+template<int x> constexpr int f(int y) { //expected-note {{template parameter is declared here}} // expected-note {{candidate template ignored: invalid explicitly-specified argument for 1st template parameter}}
   return x * y;
 }
 constexpr int test9(int x) {