fix: false-positive downcast warnings

Fixes false-positive downcast warnings on integrally promoted expressions. This is achieved by checking
each element's type in the expression individually and comparing it to the resulting type rather than checking
the expression's type as a whole.

TODO: literals that are out of range of the target type (i.e. x + 300 when assigning to USINT)

src/validation/statement.rs

@@ -2,8 +2,8 @@ use std::{collections::HashSet, mem::discriminant};
 
 use plc_ast::{
     ast::{
-        flatten_expression_list, AstNode, AstStatement, DirectAccess, DirectAccessType, JumpStatement,
-        Operator, ReferenceAccess,
+        flatten_expression_list, AstNode, AstStatement, BinaryExpression, DirectAccess, DirectAccessType,
+        JumpStatement, Operator, ReferenceAccess,
     },
     control_statements::{AstControlStatement, ConditionalBlock},
     literals::{Array, AstLiteral, StringValue},
@@ -815,9 +815,9 @@ fn validate_assignment<T: AnnotationMap>(
                     location.clone(),
                 ));
             }
-        } else if right.is_literal() {
-            // TODO: See https://github.com/PLC-lang/rusty/issues/857
-            // validate_assignment_type_sizes(validator, left_type, right_type, location, context)
+        } else {
+            // todo: literals
+            validate_assignment_type_sizes(validator, left_type, right, context)
         }
     }
 }
@@ -1272,21 +1272,56 @@ fn validate_type_nature<T: AnnotationMap>(
     }
 }
 
-fn _validate_assignment_type_sizes<T: AnnotationMap>(
+fn validate_assignment_type_sizes<T: AnnotationMap>(
     validator: &mut Validator,
     left: &DataType,
-    right: &DataType,
-    location: &SourceLocation,
+    right: &AstNode,
     context: &ValidationContext<T>,
 ) {
+    use std::collections::HashMap;
+    // todo: check literal sizes in expressions
+    let mut types_in_expr: HashMap<Option<&DataType>, SourceLocation> = HashMap::new();
+    fn helper<'b, T: AnnotationMap>(
+        node: &AstNode,
+        set: &mut HashMap<Option<&'b DataType>, SourceLocation>,
+        context: &'b ValidationContext<T>,
+    ) {
+        match node.get_stmt_peeled() {
+            AstStatement::BinaryExpression(BinaryExpression { operator, left, right, .. }) => {
+                if operator.is_bool_type() {
+                    return;
+                };
+                helper(left, set, context);
+                helper(right, set, context);
+            }
+            AstStatement::Literal(_) => (),
+            _ => {
+                if context.annotations.get_generic_nature(node).is_some() {
+                    return;
+                }
+                set.insert(context.annotations.get_type(node, context.index), node.get_location());
+            }
+        };
+    }
+
+    helper(right, &mut types_in_expr, context);
+
+    let mut dts = types_in_expr.keys().filter_map(|it| *it);
+    let Some(mut biggest) = dts.next() else { return };
+    for dt in dts {
+        biggest = typesystem::get_bigger_type(biggest, dt, context.index);
+    }
+
+    let location = types_in_expr.get(&Some(biggest)).unwrap();
+
     if left.get_type_information().get_size(context.index)
-        < right.get_type_information().get_size(context.index)
+        < biggest.get_type_information().get_size(context.index)
     {
         validator.push_diagnostic(
             Diagnostic::info(format!(
-                "Potential loss of information due to assigning '{}' to variable of type '{}'.",
-                left.get_name(),
-                right.get_name()
+                "Implicit downcast from '{}' to '{}'.",
+                biggest.get_name(),
+                left.get_name()
             ))
             .with_error_code("E067")
             .with_location(location.clone()),

src/validation/tests/assignment_validation_tests.rs

@@ -962,3 +962,37 @@ fn string_type_alias_assignment_can_be_validated() {
 
     assert_snapshot!(diagnostics);
 }
+
+#[test]
+fn integral_promotion_in_expression_does_not_cause_downcast_warning() {
+    let diagnostics = parse_and_validate_buffered(
+        "
+        FUNCTION main : INT
+        VAR
+            a, b, c : SINT;
+        END_VAR
+
+            a := a + b + c + 100;
+        END_FUNCTION
+        ",
+    );
+
+    assert!(diagnostics.is_empty())
+}
+
+#[test]
+fn downcast_will_report_biggest_type_in_expression() {
+    let diagnostics = parse_and_validate_buffered(
+        "
+        FUNCTION main : INT
+        VAR
+            a, b, c : SINT;
+            d : DINT;
+        END_VAR
+            a := a + b + c + d;
+        END_FUNCTION
+        ",
+    );
+
+    assert_snapshot!(diagnostics)
+}

src/validation/tests/builtin_validation_tests.rs

@@ -19,8 +19,7 @@ fn arithmetic_builtins_allow_mixing_of_fp_and_int_params() {
         END_FUNCTION
        ",
     );
-
-    assert!(diagnostics.is_empty());
+    assert_snapshot!(diagnostics);
 }
 
 #[test]

src/validation/tests/snapshots/rusty__validation__tests__assignment_validation_tests__array_assignment_validation.snap

@@ -56,6 +56,30 @@ error: Array assignments must be surrounded with `[]`
 39 │     v_arr_int_3 := (1, 2, 3, 4, 5, 6); // INVALID -> missing
    │                     ^^^^^^^^^^^^^^^^ Array assignments must be surrounded with `[]`
 
+note: Implicit downcast from 'DINT' to 'INT'.
+   ┌─ <internal>:40:23
+   │
+40 │     v_arr_int_3[0] := v_dint; // valid
+   │                       ^^^^^^ Implicit downcast from 'DINT' to 'INT'.
+
+note: Implicit downcast from 'DINT' to 'INT'.
+   ┌─ <internal>:41:23
+   │
+41 │     v_arr_int_3[0] := DINT#10; // valid
+   │                       ^^^^^^^ Implicit downcast from 'DINT' to 'INT'.
+
+note: Implicit downcast from 'REAL' to 'INT'.
+   ┌─ <internal>:42:23
+   │
+42 │     v_arr_int_3[0] := v_real; // valid
+   │                       ^^^^^^ Implicit downcast from 'REAL' to 'INT'.
+
+note: Implicit downcast from 'REAL' to 'INT'.
+   ┌─ <internal>:43:23
+   │
+43 │     v_arr_int_3[0] := REAL#2.0; // valid
+   │                       ^^^^^^^^ Implicit downcast from 'REAL' to 'INT'.
+
 error: Invalid assignment: cannot assign 'STRING' to 'INT'
    ┌─ <internal>:44:5
    │
@@ -103,5 +127,3 @@ error: Invalid assignment: cannot assign 'ARRAY[0..3] OF INT' to 'DINT'
    │
 52 │     v_dint := v_arr_int_3; // INVALID
    │     ^^^^^^^^^^^^^^^^^^^^^ Invalid assignment: cannot assign 'ARRAY[0..3] OF INT' to 'DINT'
-
-

src/validation/tests/snapshots/rusty__validation__tests__assignment_validation_tests__bit_assignment_validation.snap

@@ -2,6 +2,60 @@
 source: src/validation/tests/assignment_validation_tests.rs
 expression: diagnostics
 ---
+note: Implicit downcast from 'LREAL' to 'BYTE'.
+   ┌─ <internal>:29:15
+   │
+29 │     v_byte := v_lreal; // valid
+   │               ^^^^^^^ Implicit downcast from 'LREAL' to 'BYTE'.
+
+note: Implicit downcast from 'REAL' to 'BYTE'.
+   ┌─ <internal>:30:15
+   │
+30 │     v_byte := REAL#2.0; // valid
+   │               ^^^^^^^^ Implicit downcast from 'REAL' to 'BYTE'.
+
+note: Implicit downcast from 'UDINT' to 'BYTE'.
+   ┌─ <internal>:31:15
+   │
+31 │     v_byte := v_udint; // valid
+   │               ^^^^^^^ Implicit downcast from 'UDINT' to 'BYTE'.
+
+note: Implicit downcast from 'UDINT' to 'BYTE'.
+   ┌─ <internal>:32:15
+   │
+32 │     v_byte := UDINT#10; // valid
+   │               ^^^^^^^^ Implicit downcast from 'UDINT' to 'BYTE'.
+
+note: Implicit downcast from 'DINT' to 'BYTE'.
+   ┌─ <internal>:33:15
+   │
+33 │     v_byte := v_dint; // valid
+   │               ^^^^^^ Implicit downcast from 'DINT' to 'BYTE'.
+
+note: Implicit downcast from 'DINT' to 'BYTE'.
+   ┌─ <internal>:34:15
+   │
+34 │     v_byte := DINT#20; // valid
+   │               ^^^^^^^ Implicit downcast from 'DINT' to 'BYTE'.
+
+note: Implicit downcast from 'TIME' to 'BYTE'.
+   ┌─ <internal>:35:15
+   │
+35 │     v_byte := v_time; // valid
+   │               ^^^^^^ Implicit downcast from 'TIME' to 'BYTE'.
+
+note: Implicit downcast from 'WORD' to 'BYTE'.
+   ┌─ <internal>:37:15
+   │
+37 │     v_byte := v_word; // valid
+   │               ^^^^^^ Implicit downcast from 'WORD' to 'BYTE'.
+
+note: Implicit downcast from 'WORD' to 'BYTE'.
+   ┌─ <internal>:38:15
+   │
+38 │     v_byte := WORD#16#ffff; // valid
+   │               ^^^^^^^^^^^^ Implicit downcast from 'WORD' to 'BYTE'.
+
 error: Invalid assignment: cannot assign 'STRING' to 'BYTE'
    ┌─ <internal>:39:5
    │
@@ -32,16 +86,32 @@ error: Invalid assignment: cannot assign 'CHAR' to 'BYTE'
 43 │     v_byte := CHAR#'c'; // INVALID
    │     ^^^^^^^^^^^^^^^^^^ Invalid assignment: cannot assign 'CHAR' to 'BYTE'
 
+note: Implicit downcast from 'TIME_OF_DAY' to 'BYTE'.
+   ┌─ <internal>:44:15
+   │
+44 │     v_byte := v_tod; // valid
+   │               ^^^^^ Implicit downcast from 'TIME_OF_DAY' to 'BYTE'.
+
+note: Implicit downcast from 'INT' to 'BYTE'.
+   ┌─ <internal>:46:15
+   │
+46 │     v_byte := v_ptr_int^; // valid
+   │               ^^^^^^^^^^ Implicit downcast from 'INT' to 'BYTE'.
+
 error: Invalid assignment: cannot assign 'STRING' to 'BYTE'
    ┌─ <internal>:47:5
    │
 47 │     v_byte := v_ptr_string^; // INVALID
    │     ^^^^^^^^^^^^^^^^^^^^^^^ Invalid assignment: cannot assign 'STRING' to 'BYTE'
 
+note: Implicit downcast from 'INT' to 'BYTE'.
+   ┌─ <internal>:48:15
+   │
+48 │     v_byte := v_arr_int_3[0]; // valid
+   │               ^^^^^^^^^^^^^^ Implicit downcast from 'INT' to 'BYTE'.
+
 error: Invalid assignment: cannot assign 'STRING' to 'BYTE'
    ┌─ <internal>:49:5
    │
 49 │     v_byte := v_arr_string_3[0]; // INVALID
    │     ^^^^^^^^^^^^^^^^^^^^^^^^^^^ Invalid assignment: cannot assign 'STRING' to 'BYTE'
-
-

src/validation/tests/snapshots/rusty__validation__tests__assignment_validation_tests__downcast_will_report_biggest_type_in_expression.snap

@@ -0,0 +1,9 @@
+---
+source: src/validation/tests/assignment_validation_tests.rs
+expression: diagnostics
+---
+note: Implicit downcast from 'DINT' to 'SINT'.
+  ┌─ <internal>:7:30
+  │
+7 │             a := a + b + c + d;
+  │                              ^ Implicit downcast from 'DINT' to 'SINT'.

src/validation/tests/snapshots/rusty__validation__tests__assignment_validation_tests__implicit_action_downcasts_are_validated.snap

@@ -2,10 +2,20 @@
 source: src/validation/tests/assignment_validation_tests.rs
 expression: "&diagnostics"
 ---
+note: Implicit downcast from 'LINT' to 'DINT'.
+   ┌─ <internal>:26:20
+   │
+26 │             fb.foo(var1, var2, var3);
+   │                    ^^^^ Implicit downcast from 'LINT' to 'DINT'.
+
+note: Implicit downcast from 'LWORD' to 'DWORD'.
+   ┌─ <internal>:26:26
+   │
+26 │             fb.foo(var1, var2, var3);
+   │                          ^^^^ Implicit downcast from 'LWORD' to 'DWORD'.
+
 error: Invalid assignment: cannot assign 'STRING' to 'BYTE'
    ┌─ <internal>:26:32
    │
 26 │             fb.foo(var1, var2, var3);
    │                                ^^^^ Invalid assignment: cannot assign 'STRING' to 'BYTE'
-
-

src/validation/tests/snapshots/rusty__validation__tests__assignment_validation_tests__int_assignment_validation.snap

@@ -2,6 +2,30 @@
 source: src/validation/tests/assignment_validation_tests.rs
 expression: diagnostics
 ---
+note: Implicit downcast from 'LREAL' to 'UDINT'.
+   ┌─ <internal>:31:16
+   │
+31 │     v_udint := v_lreal; // valid
+   │                ^^^^^^^ Implicit downcast from 'LREAL' to 'UDINT'.
+
+note: Implicit downcast from 'ULINT' to 'UDINT'.
+   ┌─ <internal>:33:16
+   │
+33 │     v_udint := v_ulint; // valid
+   │                ^^^^^^^ Implicit downcast from 'ULINT' to 'UDINT'.
+
+note: Implicit downcast from 'ULINT' to 'UDINT'.
+   ┌─ <internal>:34:16
+   │
+34 │     v_udint := ULINT#10; // valid
+   │                ^^^^^^^^ Implicit downcast from 'ULINT' to 'UDINT'.
+
+note: Implicit downcast from 'TIME' to 'UDINT'.
+   ┌─ <internal>:37:16
+   │
+37 │     v_udint := v_time; // valid
+   │                ^^^^^^ Implicit downcast from 'TIME' to 'UDINT'.
+
 error: Invalid assignment: cannot assign 'STRING' to 'UDINT'
    ┌─ <internal>:41:5
    │
@@ -32,6 +56,12 @@ error: Invalid assignment: cannot assign 'CHAR' to 'UDINT'
 45 │     v_udint := CHAR#'c'; // INVALID
    │     ^^^^^^^^^^^^^^^^^^^ Invalid assignment: cannot assign 'CHAR' to 'UDINT'
 
+note: Implicit downcast from 'TIME_OF_DAY' to 'UDINT'.
+   ┌─ <internal>:46:16
+   │
+46 │     v_udint := v_tod; // valid
+   │                ^^^^^ Implicit downcast from 'TIME_OF_DAY' to 'UDINT'.
+
 error: Invalid assignment: cannot assign 'STRING' to 'UDINT'
    ┌─ <internal>:49:5
    │
@@ -44,6 +74,30 @@ error: Invalid assignment: cannot assign 'STRING' to 'UDINT'
 51 │     v_udint := v_arr_string_3[0]; // INVALID
    │     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Invalid assignment: cannot assign 'STRING' to 'UDINT'
 
+note: Implicit downcast from 'LREAL' to 'DINT'.
+   ┌─ <internal>:54:15
+   │
+54 │     v_dint := v_lreal; // valid
+   │               ^^^^^^^ Implicit downcast from 'LREAL' to 'DINT'.
+
+note: Implicit downcast from 'LINT' to 'DINT'.
+   ┌─ <internal>:58:15
+   │
+58 │     v_dint := v_lint; // valid
+   │               ^^^^^^ Implicit downcast from 'LINT' to 'DINT'.
+
+note: Implicit downcast from 'LINT' to 'DINT'.
+   ┌─ <internal>:59:15
+   │
+59 │     v_dint := LINT#20; // valid
+   │               ^^^^^^^ Implicit downcast from 'LINT' to 'DINT'.
+
+note: Implicit downcast from 'TIME' to 'DINT'.
+   ┌─ <internal>:60:15
+   │
+60 │     v_dint := v_time; // valid
+   │               ^^^^^^ Implicit downcast from 'TIME' to 'DINT'.
+
 error: Invalid assignment: cannot assign 'STRING' to 'DINT'
    ┌─ <internal>:64:5
    │
@@ -74,6 +128,12 @@ error: Invalid assignment: cannot assign 'CHAR' to 'DINT'
 68 │     v_dint := CHAR#'c'; // INVALID
    │     ^^^^^^^^^^^^^^^^^^ Invalid assignment: cannot assign 'CHAR' to 'DINT'
 
+note: Implicit downcast from 'TIME_OF_DAY' to 'DINT'.
+   ┌─ <internal>:69:15
+   │
+69 │     v_dint := v_tod; // valid
+   │               ^^^^^ Implicit downcast from 'TIME_OF_DAY' to 'DINT'.
+
 error: Invalid assignment: cannot assign 'STRING' to 'DINT'
    ┌─ <internal>:72:5
    │
@@ -85,5 +145,3 @@ error: Invalid assignment: cannot assign 'STRING' to 'DINT'
    │
 74 │     v_dint := v_arr_string_3[0]; // INVALID
    │     ^^^^^^^^^^^^^^^^^^^^^^^^^^^ Invalid assignment: cannot assign 'STRING' to 'DINT'
-
-