feat(language): validate assignment expressions

2 files changed, 93 insertions, 0 deletions

diff --git a/subprojects/language/src/main/java/tools/refinery/language/validation/ProblemValidator.java b/subprojects/language/src/main/java/tools/refinery/language/validation/ProblemValidator.java
index 560f612a..7f45bc20 100644
--- a/subprojects/language/src/main/java/tools/refinery/language/validation/ProblemValidator.java
+++ b/subprojects/language/src/main/java/tools/refinery/language/validation/ProblemValidator.java
@@ -63,6 +63,8 @@ public class ProblemValidator extends AbstractProblemValidator {
 
         public static final String UNSUPPORTED_ASSERTION_ISSUE = ISSUE_PREFIX + "UNSUPPORTED_ASSERTION";
 
+        public static final String INVALID_ASSIGNMENT_ISSUE = ISSUE_PREFIX + "INVALID_ASSIGNMENT";
+
         @Inject
         private ReferenceCounter referenceCounter;
 
@@ -493,4 +495,34 @@ public class ProblemValidator extends AbstractProblemValidator {
                         }
                 }
         }
+
+        @Check
+        private void checkAssignmentExpr(AssignmentExpr assignmentExpr) {
+                var left = assignmentExpr.getLeft();
+                if (left == null) {
+                        // Syntactically invalid, so we already emit an error.
+                        return;
+                }
+                if (!(left instanceof VariableOrNodeExpr variableOrNodeExpr)) {
+                        var message = "Left side of an assignment must be variable.";
+                        acceptError(message, assignmentExpr, ProblemPackage.Literals.BINARY_EXPR__LEFT,
+                                        0, INVALID_ASSIGNMENT_ISSUE);
+                        return;
+                }
+                var target = variableOrNodeExpr.getVariableOrNode();
+                if (target == null) {
+                        // Syntactically invalid, so we already emit an error.
+                        return;
+                }
+                if (target instanceof Parameter) {
+                        var message = "Parameters cannot be assigned.";
+                        acceptError(message, variableOrNodeExpr, ProblemPackage.Literals.VARIABLE_OR_NODE_EXPR__VARIABLE_OR_NODE,
+                                        0, INVALID_ASSIGNMENT_ISSUE);
+                }
+                if (target instanceof Node) {
+                        var message = "Nodes cannot be assigned.";
+                        acceptError(message, variableOrNodeExpr, ProblemPackage.Literals.VARIABLE_OR_NODE_EXPR__VARIABLE_OR_NODE,
+                                        0, INVALID_ASSIGNMENT_ISSUE);
+                }
+        }
 }
diff --git a/subprojects/language/src/test/java/tools/refinery/language/tests/validation/AssignmentValidationTest.java b/subprojects/language/src/test/java/tools/refinery/language/tests/validation/AssignmentValidationTest.java
new file mode 100644
index 00000000..a9e0e311
--- /dev/null
+++ b/subprojects/language/src/test/java/tools/refinery/language/tests/validation/AssignmentValidationTest.java
@@ -0,0 +1,61 @@
+/*
+ * SPDX-FileCopyrightText: 2024 The Refinery Authors <https://refinery.tools/>
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+package tools.refinery.language.tests.validation;
+
+
+import com.google.inject.Inject;
+import org.eclipse.xtext.testing.InjectWith;
+import org.eclipse.xtext.testing.extensions.InjectionExtension;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
+import tools.refinery.language.model.tests.utils.ProblemParseHelper;
+import tools.refinery.language.tests.ProblemInjectorProvider;
+import tools.refinery.language.validation.ProblemValidator;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.*;
+
+@ExtendWith(InjectionExtension.class)
+@InjectWith(ProblemInjectorProvider.class)
+class AssignmentValidationTest {
+        @Inject
+        private ProblemParseHelper parseHelper;
+
+        @ParameterizedTest
+        @ValueSource(strings = {"""
+                        pred foo(node a) <-> 5 is 5.
+                        """, """
+                        pred foo(node a) <-> b + 2 is 5.
+                        """, """
+                        pred foo(node a) <-> a is 5.
+                        """, """
+                        node(n).
+                        pred foo(node a) <-> n is 5.
+                        """, """
+                        enum E { A, B }
+                        pred foo(node a) <-> B is 5.
+                        """})
+        void invalidAssignmentTest(String text) {
+                var problem = parseHelper.parse(text);
+                var issues = problem.validate();
+                assertThat(issues, hasItem(hasProperty("issueCode", is(
+                                ProblemValidator.INVALID_ASSIGNMENT_ISSUE
+                ))));
+        }
+
+        @Test
+        void validAssignmentTest() {
+                var problem = parseHelper.parse("""
+                                pred foo(node a) <-> b is 5.
+                                """);
+                var issues = problem.validate();
+                assertThat(issues, not(hasItem(hasProperty("issueCode", is(
+                                ProblemValidator.INVALID_ASSIGNMENT_ISSUE
+                )))));
+        }
+}