Fix #4779 - C++ classes need TypeInfo

Author: rikkimax

gen/typinf.cpp

@@ -506,8 +506,19 @@ class DeclareOrDefineVisitor : public Visitor {
     auto cd = decl->tinfo->isTypeClass()->sym;
     DtoResolveClass(cd);
 
+    auto irclass = getIrAggr(cd, true);
     IrGlobal *irg = getIrGlobal(decl, true);
-    irg->value = getIrAggr(cd)->getClassInfoSymbol();
+    
+    auto ti = irclass->getClassInfoSymbol();
+    irg->value = ti;
+    
+    // check if the definition can be elided
+    if (irclass->suppressTypeInfo()) {
+        return;
+    }
+    
+    irclass->getClassInfoSymbol(true);
+    ti->setLinkage(TYPEINFO_LINKAGE_TYPE);
   }
 
   // Build all other TypeInfos.

ir/irclass.cpp

@@ -175,6 +175,7 @@ LLGlobalVariable *IrClass::getInterfaceArraySymbol() {
   classInterfacesArray =
       declareGlobal(cd->loc, gIR->module, array_type, irMangle,
                     /*isConstant=*/true, false, false);
+  classInterfacesArray->setLinkage(TYPEINFO_LINKAGE_TYPE);
 
   return classInterfacesArray;
 }

tests/linking/inputs/typeinfo_on_demand2.d

@@ -0,0 +1,4 @@
+module inputs.typeinfo_on_demand2;
+
+extern(C++) class MyClass {
+}

tests/linking/typeinfo_on_demand.d

@@ -0,0 +1,13 @@
+// Tests that TypeInfo is generated per CU to enable on demand usage
+
+// RUN: %ldc -of%t_lib%obj -betterC -c %S/inputs/typeinfo_on_demand2.d
+// RUN: %ldc -I%S %s
+
+import inputs.typeinfo_on_demand2;
+
+void main() {
+  MyChildClass mcc = new MyChildClass;
+}
+
+extern(C++) class MyChildClass : MyClass {
+}