PY-86310 Code Insight: Fix false-positive "Type alias is not generic or already specialized"

Correctly resolve type aliases to their declarations

GitOrigin-RevId: 1bf29bf68e8c79dc3e403b7addf9e62ead8cd7d3

python/python-psi-impl/src/com/jetbrains/python/codeInsight/typing/PyTypingTypeProvider.java

@@ -2291,18 +2291,23 @@ public final class PyTypingTypeProvider extends PyTypeProviderWithCustomContext<
    * It can be done either with a variable annotation or a type comment.
    */
   public static boolean isExplicitTypeAlias(@NotNull PyAssignmentStatement assignment, @NotNull TypeEvalContext context) {
-    PyExpression annotationValue = getAnnotationValue(assignment, context);
+    PyTargetExpression target = as(ArrayUtil.getFirstElement(assignment.getTargets()), PyTargetExpression.class);
+    if (target == null) {
+      return false;
+    }
+    return isExplicitTypeAlias(target, context);
+  }
+
+  public static boolean isExplicitTypeAlias(@NotNull PyTargetExpression targetExpression, @NotNull TypeEvalContext context) {
+    PyExpression annotationValue = getAnnotationValue(targetExpression, context);
     if (annotationValue instanceof PyReferenceExpression) {
       return resolvesToQualifiedNames(annotationValue, context, TYPE_ALIAS, TYPE_ALIAS_EXT);
     }
-    PyTargetExpression target = as(ArrayUtil.getFirstElement(assignment.getTargets()), PyTargetExpression.class);
-    if (target != null) {
-      String typeCommentAnnotation = target.getTypeCommentAnnotation();
-      if (typeCommentAnnotation != null) {
-        PyExpression commentValue = toExpression(typeCommentAnnotation, assignment);
-        if (commentValue instanceof PyReferenceExpression) {
-          return resolvesToQualifiedNames(commentValue, context, TYPE_ALIAS, TYPE_ALIAS_EXT);
-        }
+    String typeCommentAnnotation = targetExpression.getTypeCommentAnnotation();
+    if (typeCommentAnnotation != null) {
+      PyExpression commentValue = toExpression(typeCommentAnnotation, targetExpression);
+      if (commentValue instanceof PyReferenceExpression) {
+        return resolvesToQualifiedNames(commentValue, context, TYPE_ALIAS, TYPE_ALIAS_EXT);
       }
     }
     return false;

python/python-psi-impl/src/com/jetbrains/python/inspections/PyTypeHintsInspection.kt

@@ -1096,8 +1096,14 @@ class PyTypeHintsInspection : PyInspection() {
     }
 
     private fun checkGenericTypeParameterization(node: PySubscriptionExpression) {
-      val declaration = node.operand.reference
-        ?.let { PyResolveUtil.resolveDeclaration(it, resolveContext) }
+      val operandRefExpression = node.operand as? PyReferenceExpression ?: return
+      val declaration = multiFollowAssignmentsChain(operandRefExpression) {
+        return@multiFollowAssignmentsChain when {
+          PyTypingTypeProvider.isExplicitTypeAlias(it, myTypeEvalContext) -> false
+          PyTypingAliasStubType.getAssignedValueStubLike(it) is PyReferenceExpression -> followNotTypingOpaque(it)
+          else -> false
+        }
+      }.firstOrNull()
 
       when (declaration) {
         is PyTargetExpression -> checkTypeAliasParameterization(node, declaration)
@@ -1134,11 +1140,9 @@ class PyTypeHintsInspection : PyInspection() {
 
     private fun checkTypeAliasParameterization(node: PySubscriptionExpression, declaration: PyTargetExpression) {
       val assignedValue = PyTypingAliasStubType.getAssignedValueStubLike(declaration) ?: return
-      if (PyTypingTypeProvider.resolveToQualifiedNames(assignedValue, myTypeEvalContext)
-          .any { PyTypingTypeProvider.OPAQUE_NAMES.contains(it) }) return
       val assignedValueType = Ref.deref(PyTypingTypeProvider.getType(assignedValue, myTypeEvalContext)) ?: return
 
-      val isExplicitTypeAlias = declaration.annotationValue != null
+      val isExplicitTypeAlias = PyTypingTypeProvider.isExplicitTypeAlias(declaration, myTypeEvalContext)
       val generics = collectTypeParametersFromTypeAlias(assignedValue, assignedValueType, isExplicitTypeAlias)
       if (generics.isEmpty) {
         registerProblem(node.indexExpression, PyPsiBundle.message("INSP.type.hints.generic.type.alias.is.not.generic.or.already.parameterized"), ProblemHighlightType.WARNING)

python/testSrc/com/jetbrains/python/inspections/PyTypeHintsInspectionTest.java

@@ -3243,6 +3243,15 @@ public class PyTypeHintsInspectionTest extends PyInspectionTestCase {
                    """);
   }
 
+  // PY-86310
+  public void testTargetExpressionWithReassignmentNotProcessedAsImplicitTypeAlias() {
+    doTestByText("""
+                   b = []
+                   a = b
+                   _ = a[0] # No error expected
+                   """);
+  }
+
   @NotNull
   @Override
   protected Class<? extends PyInspection> getInspectionClass() {