[lldb] [clang] [clang-tools-extra] [c++20] P1907R1: Support for generalized non-type template arguments of scalar type. (PR #78041)

[via cfe-commits]

================
@@ -8129,29 +8067,133 @@ Sema::BuildExpressionFromIntegralTemplateArgument(const TemplateArgument &Arg,
     else
       Kind = CharacterLiteralKind::Ascii;
 
-    E = new (Context) CharacterLiteral(Arg.getAsIntegral().getZExtValue(),
-                                       Kind, T, Loc);
+    E = new (S.Context) CharacterLiteral(Int.getZExtValue(), Kind, T, Loc);
   } else if (T->isBooleanType()) {
-    E = CXXBoolLiteralExpr::Create(Context, Arg.getAsIntegral().getBoolValue(),
-                                   T, Loc);
-  } else if (T->isNullPtrType()) {
-    E = new (Context) CXXNullPtrLiteralExpr(Context.NullPtrTy, Loc);
+    E = CXXBoolLiteralExpr::Create(S.Context, Int.getBoolValue(), T, Loc);
   } else {
-    E = IntegerLiteral::Create(Context, Arg.getAsIntegral(), T, Loc);
+    E = IntegerLiteral::Create(S.Context, Int, T, Loc);
   }
 
   if (OrigT->isEnumeralType()) {
     // FIXME: This is a hack. We need a better way to handle substituted
     // non-type template parameters.
-    E = CStyleCastExpr::Create(Context, OrigT, VK_PRValue, CK_IntegralCast, E,
-                               nullptr, CurFPFeatureOverrides(),
-                               Context.getTrivialTypeSourceInfo(OrigT, Loc),
+    E = CStyleCastExpr::Create(S.Context, OrigT, VK_PRValue, CK_IntegralCast, E,
+                               nullptr, S.CurFPFeatureOverrides(),
+                               S.Context.getTrivialTypeSourceInfo(OrigT, Loc),
                                Loc, Loc);
   }
 
   return E;
 }
 
+static Expr *BuildExpressionFromNonTypeTemplateArgumentValue(
+    Sema &S, QualType T, const APValue &Val, SourceLocation Loc) {
+  auto MakeInitList = [&](ArrayRef<Expr *> Elts) -> Expr * {
+    auto *ILE = new (S.Context) InitListExpr(S.Context, Loc, Elts, Loc);
+    ILE->setType(T);
+    return ILE;
+  };
+
+  switch (Val.getKind()) {
+  case APValue::AddrLabelDiff:
+    // This cannot occur in a template argument at all.
+  case APValue::Array:
+  case APValue::Struct:
+  case APValue::Union:
+    // These can only occur within a template parameter object, which is
+    // represented as a TemplateArgument::Declaration.
+    llvm_unreachable("unexpected template argument value");
+
+  case APValue::Int:
+    return BuildExpressionFromIntegralTemplateArgumentValue(S, T, Val.getInt(),
+                                                            Loc);
+
+  case APValue::Float:
+    return FloatingLiteral::Create(S.Context, Val.getFloat(), /*IsExact=*/true,
+                                   T, Loc);
+
+  case APValue::FixedPoint:
+    return FixedPointLiteral::CreateFromRawInt(
+        S.Context, Val.getFixedPoint().getValue(), T, Loc,
+        Val.getFixedPoint().getScale());
+
+  case APValue::ComplexInt: {
+    QualType ElemT = T->castAs<ComplexType>()->getElementType();
+    return MakeInitList({BuildExpressionFromIntegralTemplateArgumentValue(
+                             S, ElemT, Val.getComplexIntReal(), Loc),
+                         BuildExpressionFromIntegralTemplateArgumentValue(
+                             S, ElemT, Val.getComplexIntImag(), Loc)});
+  }
+
+  case APValue::ComplexFloat: {
+    QualType ElemT = T->castAs<ComplexType>()->getElementType();
+    return MakeInitList(
+        {FloatingLiteral::Create(S.Context, Val.getComplexFloatReal(), true,
+                                 ElemT, Loc),
+         FloatingLiteral::Create(S.Context, Val.getComplexFloatImag(), true,
+                                 ElemT, Loc)});
+  }
+
+  case APValue::Vector: {
+    QualType ElemT = T->castAs<VectorType>()->getElementType();
+    llvm::SmallVector<Expr *, 8> Elts;
+    for (unsigned I = 0, N = Val.getVectorLength(); I != N; ++I)
+      Elts.push_back(BuildExpressionFromNonTypeTemplateArgumentValue(
+          S, ElemT, Val.getVectorElt(I), Loc));
+    return MakeInitList(Elts);
+  }
+
+  case APValue::None:
+  case APValue::Indeterminate:
+    llvm_unreachable("Unexpected APValue kind.");
+  case APValue::LValue:
+  case APValue::MemberPointer:
+    // There isn't necessarily a valid equivalent source-level syntax for
+    // these; in particular, a naive lowering might violate access control.
+    // So for now we lower to a ConstantExpr holding the value, wrapped around
+    // an OpaqueValueExpr.
+    // FIXME: We should have a better representation for this.
+    ExprValueKind VK = VK_PRValue;
+    if (T->isReferenceType()) {
+      T = T->getPointeeType();
+      VK = VK_LValue;
+    }
+    auto *OVE = new (S.Context) OpaqueValueExpr(Loc, T, VK);
----------------
cor3ntin wrote:

Here we create an OpaqueValueExpr without a source expression and the static analyser assume `cast<OpaqueValueExpr>(E)->getSourceExpr()` is not null in `ignoreTransparentExprs` 

@steakhal 


https://github.com/llvm/llvm-project/pull/78041