cg: Propagate unsupported type to lower visitors.

Author: xlauko

include/vast/CodeGen/CodeGenTypeVisitor.hpp

@@ -248,9 +248,7 @@ namespace vast::cg {
                 return VisitTypeOfType(t, quals);
             }
 
-            ty.dump();
-            VAST_UNREACHABLE("unsupported qualified type");
-            return Type{};
+            return {};
         }
 
         auto VisitElaboratedType(const clang::ElaboratedType *ty, qualifiers quals) -> mlir_type {
@@ -274,7 +272,6 @@ namespace vast::cg {
                 }
             }
 
-
             auto *mctx = &mcontext();
             if (ty->getReturnType()->isVoidType()) {
                 return mlir::FunctionType::get(mctx, args, {});
@@ -481,12 +478,18 @@ namespace vast::cg {
         }
 
         auto Visit(const clang_type *ty) -> mlir_type {
-            return StoreDataLayout(ty, Base::Visit(ty));
+            if (auto gen = Base::Visit(ty)) {
+                return StoreDataLayout(ty, gen);
+            }
+            return {};
         }
 
         auto Visit(clang::QualType ty) -> mlir_type {
-            auto [underlying, quals] = ty.split();
-            return StoreDataLayout(underlying, Base::Visit(ty));
+            if (auto gen = Base::Visit(ty)) {
+                auto [underlying, quals] = ty.split();
+                return StoreDataLayout(underlying, gen);
+            }
+            return {};
         }
     };