Don't assume that an expression cannot be associated with a function declaration

libsolidity/codegen/ir/IRGeneratorForStatements.cpp

@@ -675,8 +675,6 @@ void IRGeneratorForStatements::endVisit(FunctionCall const& _functionCall)
 
 			solAssert(functionDef->isImplemented(), "");
 		}
-		else
-			solAssert(!functionType->hasDeclaration(), "");
 
 		solAssert(!functionType->takesArbitraryParameters(), "");
 

test/libsolidity/semanticTests/functionCall/call_internal_function_via_expression.sol

@@ -0,0 +1,24 @@
+contract C {
+    function foo() internal returns (uint) {
+        return 42;
+    }
+
+    function get_ptr(function() internal returns (uint) ptr) internal returns(function() internal returns (uint)) {
+        return ptr;
+    }
+
+    function associated() public returns (uint) {
+        // This expression directly references function definition
+        return (foo)();
+    }
+
+    function unassociated() public returns (uint) {
+        // This expression is not associated with a specific function definition
+        return (get_ptr(foo))();
+    }
+}
+// ====
+// compileViaYul: also
+// ----
+// associated() -> 42
+// unassociated() -> 42