feat: Validate if statements

src/validation/statement.rs

@@ -1,6 +1,6 @@
 use std::{collections::HashSet, mem::discriminant};
 
-use plc_ast::control_statements::ForLoopStatement;
+use plc_ast::control_statements::{ForLoopStatement, IfStatement};
 use plc_ast::{
     ast::{
         flatten_expression_list, AstNode, AstStatement, DirectAccess, DirectAccessType, JumpStatement,
@@ -287,13 +287,34 @@ fn validate_for_loop<T: AnnotationMap>(
     //       by a VAR_INPUT {ref} function call.
 }
 
+fn validate_if_statement<T: AnnotationMap>(
+    validator: &mut Validator,
+    context: &ValidationContext<T>,
+    statement: &IfStatement,
+) {
+    for block in &statement.blocks {
+        let kind = context.annotations.get_type_or_void(&block.condition, context.index);
+
+        if !kind.get_type_information().is_bool() {
+            let slice = get_datatype_name_or_slice(validator.context, kind);
+            let message = format!("Expected a boolean, got `{slice}`");
+            validator.push_diagnostic(
+                Diagnostic::error(message)
+                    .with_location(block.condition.get_location())
+                    .with_error_code("E093"),
+            )
+        }
+    }
+}
+
 fn validate_control_statement<T: AnnotationMap>(
     validator: &mut Validator,
     control_statement: &AstControlStatement,
     context: &ValidationContext<T>,
 ) {
     match control_statement {
         AstControlStatement::If(stmt) => {
+            validate_if_statement(validator, context, stmt);
             stmt.blocks.iter().for_each(|b| {
                 visit_statement(validator, b.condition.as_ref(), context);
                 b.body.iter().for_each(|s| visit_statement(validator, s, context));

src/validation/tests/statement_validation_tests.rs

@@ -1402,7 +1402,7 @@ fn for_loop_conditions_are_numerical() {
 
         FOR i := 100000 TO x BY y DO
         END_FOR
-            
+
         END_PROGRAM
         ",
     );
@@ -1436,7 +1436,7 @@ fn for_loop_conditions_are_real_and_trigger_error() {
 
         FOR i := 10.0 TO x BY y DO
         END_FOR
-            
+
         END_PROGRAM
         ",
     );
@@ -1468,3 +1468,57 @@ fn for_loop_conditions_are_real_and_trigger_error() {
 
     "###);
 }
+
+#[test]
+fn if_statement_triggers_error_if_condition_is_not_boolean() {
+    let diagnostic = parse_and_validate_buffered(
+        "
+        FUNCTION main
+            VAR
+                x : BOOL;
+                y : DINT;
+                z : STRING;
+            END_VAR
+
+            IF      x THEN
+            ELSIF   y THEN
+            ELSIF   z THEN
+            ELSIF   0 THEN
+            ELSIF   1 THEN
+
+            // These should be Ok
+            ELSIF   (0 < 1)         THEN
+            ELSIF   (y < 0)         THEN
+            ELSIF   ((1 = 2) = 3)   THEN
+            END_IF
+        END_FUNCTION
+        ",
+    );
+
+    assert_snapshot!(diagnostic, @r###"
+    error: Expected a boolean, got `DINT`
+       ┌─ <internal>:10:21
+       │
+    10 │             ELSIF   y THEN
+       │                     ^ Expected a boolean, got `DINT`
+
+    error: Expected a boolean, got `STRING`
+       ┌─ <internal>:11:21
+       │
+    11 │             ELSIF   z THEN
+       │                     ^ Expected a boolean, got `STRING`
+
+    error: Expected a boolean, got `DINT`
+       ┌─ <internal>:12:21
+       │
+    12 │             ELSIF   0 THEN
+       │                     ^ Expected a boolean, got `DINT`
+
+    error: Expected a boolean, got `DINT`
+       ┌─ <internal>:13:21
+       │
+    13 │             ELSIF   1 THEN
+       │                     ^ Expected a boolean, got `DINT`
+
+    "###);
+}