PY-86019 [python]: show error when class pattern uses non-class type

GitOrigin-RevId: 1e0d0926155459d3112bf921967a822073f327f8

python/python-psi-impl/resources/messages/PyPsiBundle.properties

@@ -1373,6 +1373,7 @@ INSP.patterns.pattern.can.be.simplified=Pattern can be simplified
 INSP.patterns.class.does.not.support.pattern.matching.with.positional.arguments=Class {0} does not support pattern matching with positional arguments
 INSP.patterns.too.many.positional.patterns.expected=Too many positional patterns, expected {0}
 INSP.patterns.attribute.already.specified.as.positional.pattern.at.position=Attribute ''{0}'' is already specified as positional pattern at position {1}
+INSP.patterns.not.a.class=Class pattern requires a class, but ''{0}'' can be ''{1}''
 QFIX.simplify.as.pattern=Simplify 'as' pattern
 QFIX.NAME.remove.element=Remove element
 QFIX.remove.pattern=Remove pattern

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

@@ -15,10 +15,7 @@ import com.jetbrains.python.psi.*
 import com.jetbrains.python.psi.impl.PyBuiltinCache
 import com.jetbrains.python.psi.impl.PyClassPatternImpl
 import com.jetbrains.python.psi.impl.PyPsiUtils
-import com.jetbrains.python.psi.types.PyClassType
-import com.jetbrains.python.psi.types.PyTupleType
-import com.jetbrains.python.psi.types.PyTypeChecker
-import com.jetbrains.python.psi.types.TypeEvalContext
+import com.jetbrains.python.psi.types.*
 
 class PyPatternInspection : PyInspection() {
   override fun buildVisitor(holder: ProblemsHolder, isOnTheFly: Boolean, session: LocalInspectionToolSession): PsiElementVisitor {
@@ -49,7 +46,20 @@ private class PyPatternInspectionVisitor(holder: ProblemsHolder, context: TypeEv
 
 
   override fun visitPyClassPattern(node: PyClassPattern) {
-    val classType = myTypeEvalContext.getType(node.classNameReference) as? PyClassType ?: return
+    val type = myTypeEvalContext.getType(node.classNameReference)
+    val types = PyTypeUtil.toStream(type).toList()
+    if (types.isNotEmpty() && types.none { PyTypeChecker.isUnknown(it, myTypeEvalContext) }) {
+      val invalidTypes = types.filter { it !is PyClassType || !it.isDefinition }
+      if (invalidTypes.isNotEmpty()) {
+        val invalidTypesUnion = PyUnionType.union(invalidTypes)
+        val invalidTypeName = PythonDocumentationProvider.getTypeName(invalidTypesUnion, myTypeEvalContext)
+        holder.problem(node.classNameReference,
+                       PyPsiBundle.message("INSP.patterns.not.a.class", node.classNameReference.text, invalidTypeName)).register()
+        return
+      }
+    }
+
+    val classType = type as? PyClassType ?: return
     val pyClass = classType.pyClass
     if (pyClass.name in PyClassPattern.SPECIAL_BUILTINS) return
 

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

@@ -323,6 +323,70 @@ def f(c):
     """);
   }
 
+  // PY-86019
+  public void testFunctionPattern() {
+    doTestByText("""
+                   def f():
+                       pass
+                   
+                   match 1:
+                       case <warning descr="Class pattern requires a class, but 'f' can be '() -> None'">f</warning>():
+                           pass
+                   """);
+  }
+
+  // PY-86019
+  public void testInstancePattern() {
+    doTestByText("""
+                   x = 1
+                   match 1:
+                       case <warning descr="Class pattern requires a class, but 'x' can be 'int'">x</warning>():
+                           pass
+                   """);
+  }
+
+  // PY-86019
+  public void testUnionOfClassesPattern() {
+    doTestByText("""
+                   class A: pass
+                   class B: pass
+                   
+                   def g(cond):
+                       if cond:
+                           c = A
+                       else:
+                           c = B
+                       match 1:
+                           case c():
+                               pass
+                   """);
+  }
+
+  // PY-86019
+  public void testUnionOfClassAndFunctionPattern() {
+    doTestByText("""
+                   class A: pass
+                   def f(): pass
+                   
+                   def g(cond):
+                       c = A if cond else f
+                       match 1:
+                           case <warning descr="Class pattern requires a class, but 'c' can be '() -> None'">c</warning>():
+                               pass
+                   """);
+  }
+
+  // PY-86019
+  public void testAnyPattern() {
+    doTestByText("""
+                   from typing import Any
+                   def g(c: Any):
+                       match 1:
+                           case c():
+                               pass
+                   """);
+  }
+
   @NotNull
   @Override
   protected Class<? extends PyInspection> getInspectionClass() {