add error code

compiler/plc_diagnostics/src/diagnostics/diagnostics_registry.rs

@@ -210,6 +210,7 @@ lazy_static! {
         E106,   Warning,    include_str!("./error_codes/E106.md"),  // VAR_EXTERNAL have no effect
         E107,   Error,      include_str!("./error_codes/E107.md"),  // Missing configuration for template variable
         E108,   Error,      include_str!("./error_codes/E108.md"),  // Template variable is configured multiple times
+        E109,   Error,      include_str!("./error_codes/E109.md"),  // Stateful pointer variable initialized with temporary value
     );
 }
 

compiler/plc_diagnostics/src/diagnostics/error_codes/E109.md

@@ -0,0 +1,16 @@
+# Stateful member variable initialized with temporary reference
+
+Stack-local variables do not yet exist at the time of initialization. Additionally, pointing to a temporary variable will lead to a dangling pointer
+as soon as it goes out of scope - potential use after free.
+
+Erroneous code example:
+```
+FUNCTION_BLOCK foo
+    VAR
+        a : REF_TO BOOL := REF(b);
+    END_VAR
+    VAR_TEMP
+        b : BOOL;
+    END_VAR
+END_FUNCTION_BLOCK
+```

src/validation/tests/variable_validation_tests.rs

@@ -1288,24 +1288,23 @@ fn assigning_a_temp_reference_to_stateful_var_is_error() {
         "#,
     );
 
-    assert_snapshot!(diagnostics, @r#"
-    error[E001]: Cannot assign address of temporary variable to a member-variable
+    assert_snapshot!(diagnostics, @r###"
+    error[E109]: Cannot assign address of temporary variable to a member-variable
       ┌─ <internal>:4:40
       │
     4 │                 s1: REF_TO DINT := REF(t1);     // error
       │                                        ^^ Cannot assign address of temporary variable to a member-variable
 
-    error[E001]: Cannot assign address of temporary variable to a member-variable
+    error[E109]: Cannot assign address of temporary variable to a member-variable
       ┌─ <internal>:5:23
       │
     5 │                 s2 AT t1 : DINT;                // error
       │                       ^^ Cannot assign address of temporary variable to a member-variable
 
-    error[E001]: Cannot assign address of temporary variable to a member-variable
+    error[E109]: Cannot assign address of temporary variable to a member-variable
       ┌─ <internal>:6:45
       │
     6 │                 s3 : REFERENCE TO DINT REF= t1; // error
       │                                             ^^ Cannot assign address of temporary variable to a member-variable
-
-    "#)
+    "###)
 }

src/validation/variable.rs

@@ -398,7 +398,8 @@ fn report_temporary_address_in_pointer_initializer<T: AnnotationMap>(
 
     validator.diagnostics.push(
         Diagnostic::new("Cannot assign address of temporary variable to a member-variable")
-            .with_location(location),
+            .with_location(location)
+            .with_error_code("E109"),
     );
 }