fix(statementsem): correctly resolve opDispatch in WithStatement

compiler/src/dmd/statementsem.d

@@ -3183,19 +3183,19 @@ Statement statementSemanticVisit(Statement s, Scope* sc)
         else
         {
             Type texp = ws.exp.type;
-            Type t = texp.toBasetype();
+            if (!texp)
+            {
+                error(ws.loc, "Expression has no type.");
+                return setError();
+            }
 
-            Expression olde = ws.exp;
-            if (t.ty == Tpointer)
+            Type t = texp.toBasetype();
+            if (!t)
             {
-                ws.exp = new PtrExp(ws.loc, ws.exp);
-                ws.exp = ws.exp.expressionSemantic(sc);
-                texp = ws.exp.type;
-                t = texp.toBasetype();
+                error(ws.loc, "Unable to resolve base type.");
+                return setError();
             }
 
-            assert(t);
-            t = t.toBasetype();
             if (t.isClassHandle())
             {
                 _init = new ExpInitializer(ws.loc, ws.exp);
@@ -3234,8 +3234,7 @@ Statement statementSemanticVisit(Statement s, Scope* sc)
                 ws.wthis.storage_class |= STC.temp;
                 ws.wthis.dsymbolSemantic(sc);
                 sym = new WithScopeSymbol(ws);
-                // Need to set the scope to make use of resolveAliasThis
-                sym.setScope(sc);
+                sym.setScope(sc); // Enable resolveAliasThis
                 sym.parent = sc.scopesym;
                 sym.endlinnum = ws.endloc.linnum;
             }
@@ -3248,7 +3247,7 @@ Statement statementSemanticVisit(Statement s, Scope* sc)
             }
             else
             {
-                error(ws.loc, "`with` expression types must be enums or aggregates or pointers to them, not `%s`", olde.type.toChars());
+                error(ws.loc, "`with` expression types must be enums, structs, or classes, not `%s`", t.toChars());
                 return setError();
             }
         }

compiler/test/fail_compilation/test20274.d

@@ -0,0 +1,38 @@
+/*
+TEST_OUTPUT:
+---
+fail_compilation/test20274.d(28): Error: function expected before `()`, not `(*__withSym).opDispatch()` of type `void`
+fail_compilation/test20274.d(35): Error: undefined identifier `foo`
+---
+*/
+
+// https://issues.dlang.org/show_bug.cgi?id=20274
+
+struct A {
+	void opDispatch(string name, A...)(A a) {
+	}
+}
+
+struct B {
+	void opDispatch(string name, T)(T a) {
+	}
+}
+
+void main()
+{
+	A a;
+	a.foo(2); // ok
+
+	with (a)
+	{
+		foo(2); // fails
+	}
+
+	B b;
+	b.foo(3); // ok
+
+	with(b) {
+		foo(3); // fails
+	}
+
+}