fix Issue 20520 - Runtime segfault when taking typeid of a class instanciated within an enum

compiler/src/dmd/e2ir.d

@@ -799,6 +799,18 @@ elem* toElem(Expression e, IRState *irs)
         }
         if (Expression ex = isExpression(e.obj))
         {
+            if (auto ev = ex.isVarExp())
+            {
+                if (auto em = ev.var.isEnumMember())
+                    ex = em.value;
+            }
+            if (auto ecr = ex.isClassReferenceExp())
+            {
+                Type t = ecr.type;
+                elem* result = getTypeInfo(ecr, t, irs);
+                return el_bin(OPadd, result.Ety, result, el_long(TYsize_t, t.vtinfo.offset));
+            }
+
             auto tc = ex.type.toBasetype().isTypeClass();
             assert(tc);
             // generate **classptr to get the classinfo

compiler/src/dmd/printast.d

@@ -14,6 +14,7 @@ module dmd.printast;
 import core.stdc.stdio;
 
 import dmd.expression;
+import dmd.ctfeexpr;
 import dmd.tokens;
 import dmd.visitor;
 import dmd.hdrgen;
@@ -210,6 +211,14 @@ extern (C++) final class PrintASTVisitor : Visitor
         printf(".init: %s\n", e.initializer ? e.initializer.toChars() : "");
     }
 
+    override void visit(ClassReferenceExp e)
+    {
+        visit(cast(Expression)e);
+        printIndent(indent + 2);
+        printf(".value: %s\n", e.value ? e.value.toChars() : "");
+        printAST(e.value, indent + 2);
+    }
+
     static void printIndent(int indent)
     {
         foreach (i; 0 .. indent)

compiler/test/runnable/test20520.d

@@ -0,0 +1,13 @@
+// https://issues.dlang.org/show_bug.cgi?id=20520
+
+class C {}
+
+enum Foo {
+    Bar = new C()
+}
+
+void main()
+{
+    //pragma(msg, typeid(Foo.Bar)); // Works fine: typeid(C())
+    auto t = typeid(Foo.Bar);     // Segfault here
+}