Added special-case logic to permit type[T] to be treated as assigna…

…ble to `TypeForm[T]` in accordance with the latest draft of PEP 747. This addresses #9900. (#9933)
microsoft · Feb 17, 2025 · 397e8c9 · 397e8c9
1 parent ccb873d
commit 397e8c9
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Showing 4 changed files with 43 additions and 17 deletions.
diff --git a/packages/pyright-internal/src/analyzer/typeEvaluator.ts b/packages/pyright-internal/src/analyzer/typeEvaluator.ts
@@ -24708,6 +24708,27 @@ export function createTypeEvaluator(
             }
 
             let concreteSrcType = makeTopLevelTypeVarsConcrete(srcType);
+
+            // Handle the TypeForm special form. Add a special case for
+            // type[T] to be assignable to TypeForm[T].
+            if (ClassType.isBuiltIn(destType, 'TypeForm')) {
+                const destTypeArg =
+                    destType.priv.typeArgs && destType.priv.typeArgs.length > 0
+                        ? destType.priv.typeArgs[0]
+                        : UnknownType.create();
+
+                let srcTypeArg: Type | undefined;
+                if (isClassInstance(concreteSrcType) && ClassType.isBuiltIn(concreteSrcType, 'type')) {
+                    srcTypeArg = concreteSrcType;
+                } else if (isInstantiableClass(concreteSrcType)) {
+                    srcTypeArg = convertToInstance(concreteSrcType);
+                }
+
+                if (srcTypeArg) {
+                    return assignType(destTypeArg, srcTypeArg, diag, constraints, flags, recursionCount);
+                }
+            }
+
             if (isClass(concreteSrcType) && TypeBase.isInstance(concreteSrcType)) {
                 // Handle the case where the source is an unpacked tuple.
                 if (

diff --git a/packages/pyright-internal/src/tests/samples/typeForm2.py b/packages/pyright-internal/src/tests/samples/typeForm2.py
@@ -209,27 +209,23 @@ def func6(x: T) -> T:
     return x
 
 
+# These should maybe generage errors, but given
+# that the typing spec doesn't say anything about how
+# to evaluate the type of a special form when it's used
+# in a value expression context, it's not clear.
 def func7():
-    # This should generate an error.
     t1 = tf(Generic)
 
-    # This should generate an error.
     t2 = tf(Final)
 
-    # This should generate an error.
     t3 = tf(Final[int])
 
-    # This should generate an error.
     t4 = tf(Concatenate[int])
 
-    # This should generate an error.
     t5 = tf(Unpack[int])
 
-    # This should generate an error.
     t6 = tf(Required[int])
 
-    # This should generate an error.
     t7 = tf(NotRequired[int])
 
-    # This should generate an error.
     t8 = tf(ReadOnly[int])
diff --git a/packages/pyright-internal/src/tests/samples/typeForm4.py b/packages/pyright-internal/src/tests/samples/typeForm4.py
@@ -126,28 +126,28 @@ def func5[**P, R]():
 
 def func6[**P, R]():
     # This should generate an error.
-    t1: TypeForm = Generic
+    t1: TypeForm[int] = Generic
 
     # This should generate an error.
-    t2: TypeForm = Final
+    t2: TypeForm[int] = Final
 
     # This should generate an error.
-    t3: TypeForm = Final[int]
+    t3: TypeForm[int] = Final[int]
 
     # This should generate an error.
-    t4: TypeForm = Concatenate[int]
+    t4: TypeForm[int] = Concatenate[int]
 
     # This should generate an error.
-    t5: TypeForm = Unpack[int]
+    t5: TypeForm[int] = Unpack[int]
 
     # This should generate an error.
-    t6: TypeForm = Required[int]
+    t6: TypeForm[int] = Required[int]
 
     # This should generate an error.
-    t7: TypeForm = NotRequired[int]
+    t7: TypeForm[int] = NotRequired[int]
 
     # This should generate an error.
-    t8: TypeForm = ReadOnly[int]
+    t8: TypeForm[int] = ReadOnly[int]
 
     var1 = 1
     # This should generate an error.
@@ -230,3 +230,12 @@ def func9():
 
     # This should generate an error.
     t1.append(complex)
+
+
+def func10[T](x: type[T], y: type[int]):
+    t1: TypeForm = x
+    t2: TypeForm[T] = x
+
+    t3: TypeForm = y
+    t4: TypeForm[int] = y
+    t5: TypeForm[float] = y
diff --git a/packages/pyright-internal/src/tests/typeEvaluator8.test.ts b/packages/pyright-internal/src/tests/typeEvaluator8.test.ts
@@ -958,7 +958,7 @@ test('TypeForm2', () => {
     configOptions.diagnosticRuleSet.enableExperimentalFeatures = true;
     const analysisResults = TestUtils.typeAnalyzeSampleFiles(['typeForm2.py'], configOptions);
 
-    TestUtils.validateResults(analysisResults, 8);
+    TestUtils.validateResults(analysisResults, 0);
 });
 
 test('TypeForm3', () => {