SONARPY-2181 Ensure UnionType can never contain LazyType (#2043)

Author: guillaume-dequenne

python-frontend/src/main/java/org/sonar/python/types/v2/UnionType.java

@@ -74,6 +74,7 @@ public TypeSource typeSource() {
 
   @Beta
   public static PythonType or(Collection<PythonType> candidates) {
+    ensureCandidatesAreNotLazyTypes(candidates);
     if (candidates.isEmpty()) {
       return PythonType.UNKNOWN;
     }
@@ -102,6 +103,7 @@ public static PythonType or(@Nullable PythonType type1, @Nullable PythonType typ
     if (types.size() == 1) {
       return types.iterator().next();
     }
+    ensureCandidatesAreNotLazyTypes(types);
     return new UnionType(types);
   }
 
@@ -112,4 +114,10 @@ private static void addTypes(PythonType type, Set<PythonType> types) {
       types.add(type);
     }
   }
+
+  private static void ensureCandidatesAreNotLazyTypes(Collection<PythonType> types) {
+    if (types.stream().anyMatch(LazyType.class::isInstance)) {
+      throw new IllegalArgumentException("UnionType cannot contain Lazy types");
+    }
+  }
 }

python-frontend/src/test/java/org/sonar/python/types/v2/UnionTypeTest.java

@@ -24,11 +24,14 @@
 import java.util.Set;
 import org.assertj.core.api.InstanceOfAssertFactories;
 import org.junit.jupiter.api.Test;
+import org.mockito.Mockito;
 import org.sonar.plugins.python.api.tree.ExpressionStatement;
 import org.sonar.plugins.python.api.tree.FileInput;
 import org.sonar.python.semantic.v2.FunctionTypeBuilder;
+import org.sonar.python.semantic.v2.LazyTypesContext;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
 import static org.sonar.python.types.v2.TypesTestUtils.BOOL_TYPE;
 import static org.sonar.python.types.v2.TypesTestUtils.INT_TYPE;
 import static org.sonar.python.types.v2.TypesTestUtils.STR_TYPE;
@@ -148,4 +151,12 @@ void unionTypeCandidatesResolution() {
       .hasSize(2)
       .contains(candidate1, candidate2);
   }
+
+  @Test
+  void noLazyTypeInUnionType() {
+    PythonType lazyType = new LazyType("foo", Mockito.mock(LazyTypesContext.class));
+    assertThatThrownBy(() -> UnionType.or(INT_TYPE, lazyType))
+      .isInstanceOf(IllegalArgumentException.class)
+      .hasMessage("UnionType cannot contain Lazy types");
+  }
 }