Fix Issue 21927 - ICE (illegal instruction) with static foreach over …

…empty member template

src/dmd/dinterpret.d

@@ -71,6 +71,10 @@ public Expression ctfeInterpret(Expression e)
         case TOK.super_:
         case TOK.type:
         case TOK.typeid_:
+        case TOK.template_:              // non-eponymous template/instance
+        case TOK.scope_:                 // ditto
+        case TOK.dotTemplateDeclaration: // ditto, e.e1 doesn't matter here
+        case TOK.dot:                    // ditto
              if (e.type.ty == Terror)
                 return ErrorExp.get();
             goto case TOK.error;

test/compilable/interpret5.d

@@ -0,0 +1,30 @@
+// https://issues.dlang.org/show_bug.cgi?id=21927
+/*
+TEST_OUTPUT:
+---
+T1(Args...)
+T1!()
+T2(Args2...)
+T2!()
+this.T2(Args2...)
+this.T2!()
+---
+*/
+template T1(Args...) {}
+
+pragma(msg, T1);    // TOK.template_
+pragma(msg, T1!()); // TOK.scope_
+
+struct S
+{
+    template T2(Args2...) {}
+
+    pragma(msg, S.T2);    // TOK.template_
+    pragma(msg, S.T2!()); // TOK.scope_
+
+    void fun()
+    {
+        pragma(msg, this.T2);    // TOK.dotTemplateDeclaration
+        pragma(msg, this.T2!()); // TOK.dot
+    }
+}

test/fail_compilation/test21927.d

@@ -0,0 +1,22 @@
+// https://issues.dlang.org/show_bug.cgi?id=21927
+/*
+TEST_OUTPUT:
+---
+fail_compilation/test21927.d(19): Error: invalid `foreach` aggregate `this.T2(Args2...)`
+fail_compilation/test21927.d(19): Error: invalid `foreach` aggregate `this.T2(Args2...)`
+fail_compilation/test21927.d(20): Error: invalid `foreach` aggregate `this.T2!()`
+fail_compilation/test21927.d(20): Error: invalid `foreach` aggregate `this.T2!()`
+---
+*/
+
+struct S
+{
+    template T2(Args2...) {}
+
+    void fun()
+    {
+        // original test case
+        static foreach (p; this.T2) {} // ICE
+        static foreach (p; this.T2!()) {} // ICE
+    }
+}