mirror of
https://github.com/microsoft/pyright.git
synced 2024-10-26 19:01:08 +03:00
Added smarter handling of empty lists ([]
) and dicts ({}
). Previously, these were inferred to have types list[Unknown]
and dict[Unknown, Unknown]
, respectively. They are now provided with a known type if the variable is assigned a known list or dict type along another code path.
This commit is contained in:
parent
ca2e35d217
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e5714b3365
@ -107,6 +107,20 @@ var5 = (3,) # Type is assumed to be Tuple[int]
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var6: Tuple[float, ...] = (3,) # Type of RHS is now Tuple[float, ...]
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```
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### Empty List and Dictionary Type Inference
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It is common to initialize a local variable or instance variable to an empty list (`[]`) or empty dictionary (`{}`) on one code path but initialize it to a non-empty list or dictionary on other code paths. In such cases, Pyright will infer the type based on the non-empty list or dictionary and suppress errors about a “partially unknown type”.
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```python
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if some_condition:
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my_list = []
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else:
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my_list = ["a", "b"]
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reveal_type(my_list) # list[str]
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```
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### Return Type Inference
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As with variable assignments, function return types can be inferred from the `return` statements found within that function. The returned type is assumed to be the union of all types returned from all `return` statements. If a `return` statement is not followed by an expression, it is assumed to return `None`. Likewise, if the function does not end in a `return` statement, and the end of the function is reachable, an implicit `return None` is assumed.
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@ -221,7 +235,7 @@ def func1(a: int):
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When inferring the type of a list expression (in the absence of bidirectional inference hints), Pyright uses the following heuristics:
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1. If the list is empty (`[]`), assume `List[Unknown]`.
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1. If the list is empty (`[]`), assume `List[Unknown]` (unless a known list type is assigned to the same variable along another code path).
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2. If the list contains at least one element and all elements are the same type T, infer the type `List[T]`.
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3. If the list contains multiple elements that are of different types, the behavior depends on the `strictListInference` configuration setting. By default this setting is off.
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@ -1153,14 +1153,21 @@ export function createTypeEvaluator(
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node.leftExpression,
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typeResult.type,
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/* isTypeIncomplete */ false,
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node.rightExpression
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node.rightExpression,
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/* ignoreEmptyContainers */ true
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);
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break;
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}
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case ParseNodeType.AssignmentExpression: {
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typeResult = getTypeOfExpression(node.rightExpression);
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assignTypeToExpression(node.name, typeResult.type, /* isTypeIncomplete */ false, node.rightExpression);
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assignTypeToExpression(
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node.name,
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typeResult.type,
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/* isTypeIncomplete */ false,
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node.rightExpression,
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/* ignoreEmptyContainers */ true
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);
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break;
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}
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@ -2979,7 +2986,8 @@ export function createTypeEvaluator(
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DiagnosticRule.reportUnknownMemberType,
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node.memberName,
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srcType,
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node
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node,
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/* ignoreEmptyContainers */ true
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);
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}
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}
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@ -3076,7 +3084,7 @@ export function createTypeEvaluator(
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}
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}
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assignTypeToExpression(expr, targetType, isTypeIncomplete, srcExpr);
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assignTypeToExpression(expr, targetType, isTypeIncomplete, srcExpr, /* ignoreEmptyContainers */ true);
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});
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writeTypeCache(target, type, isTypeIncomplete);
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@ -3194,6 +3202,7 @@ export function createTypeEvaluator(
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type: Type,
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isTypeIncomplete: boolean,
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srcExpr: ExpressionNode,
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ignoreEmptyContainers = false,
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expectedTypeDiagAddendum?: DiagnosticAddendum
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) {
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// Is the source expression a TypeVar() call?
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@ -3235,7 +3244,8 @@ export function createTypeEvaluator(
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DiagnosticRule.reportUnknownVariableType,
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target,
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type,
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target
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target,
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ignoreEmptyContainers
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);
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}
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@ -3304,6 +3314,7 @@ export function createTypeEvaluator(
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type,
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/* isIncomplete */ false,
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srcExpr,
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ignoreEmptyContainers,
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expectedTypeDiagAddendum
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);
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break;
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@ -3321,7 +3332,13 @@ export function createTypeEvaluator(
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const iteratedType = getTypeFromIterator(type, /* isAsync */ false, srcExpr) || UnknownType.create();
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target.entries.forEach((entry) => {
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assignTypeToExpression(entry, iteratedType, /* isIncomplete */ false, srcExpr);
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assignTypeToExpression(
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entry,
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iteratedType,
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/* isIncomplete */ false,
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srcExpr,
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ignoreEmptyContainers
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);
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});
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break;
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}
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@ -4385,7 +4402,8 @@ export function createTypeEvaluator(
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DiagnosticRule.reportUnknownMemberType,
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node.memberName,
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type,
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node
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node,
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/* ignoreEmptyContainers */ false
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);
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}
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}
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@ -9761,6 +9779,8 @@ export function createTypeEvaluator(
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let keyTypes: Type[] = [];
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let valueTypes: Type[] = [];
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let isEmptyContainer = false;
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// Infer the key and value types if possible.
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getKeyAndValueTypesFromDictionary(
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node,
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@ -9794,9 +9814,23 @@ export function createTypeEvaluator(
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}
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} else {
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valueType = expectedType ? AnyType.create() : UnknownType.create();
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isEmptyContainer = true;
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}
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const type = getBuiltInObject(node, 'dict', [keyType, valueType]);
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const dictClass = getBuiltInType(node, 'dict');
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const type = isClass(dictClass)
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? ObjectType.create(
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ClassType.cloneForSpecialization(
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dictClass,
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[keyType, valueType],
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/* isTypeArgumentExplicit */ true,
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/* skipAbstractClassTest */ false,
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/* TupleTypeArguments */ undefined,
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isEmptyContainer
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)
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)
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: UnknownType.create();
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return { type, node };
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}
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@ -10012,6 +10046,8 @@ export function createTypeEvaluator(
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// Attempts to infer the type of a list statement with no "expected type".
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function getTypeFromListInferred(node: ListNode, expectedType: Type | undefined): TypeResult {
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let isEmptyContainer = false;
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// If we received an expected entry type that of "object",
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// allow Any rather than generating an "Unknown".
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let expectedEntryType: Type | undefined;
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@ -10050,9 +10086,24 @@ export function createTypeEvaluator(
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// Is the list homogeneous? If so, use stricter rules. Otherwise relax the rules.
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inferredEntryType = areTypesSame(entryTypes) ? entryTypes[0] : inferredEntryType;
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}
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} else {
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isEmptyContainer = true;
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}
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const type = getBuiltInObject(node, 'list', [inferredEntryType]);
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const listClass = getBuiltInType(node, 'list');
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const type = isClass(listClass)
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? ObjectType.create(
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ClassType.cloneForSpecialization(
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listClass,
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[inferredEntryType],
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/* isTypeArgumentExplicit */ true,
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/* skipAbstractClassTest */ false,
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/* TupleTypeArguments */ undefined,
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isEmptyContainer
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)
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)
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: UnknownType.create();
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return { type, node };
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}
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@ -10258,7 +10309,8 @@ export function createTypeEvaluator(
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rule: string,
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target: NameNode,
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type: Type,
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errorNode: ExpressionNode
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errorNode: ExpressionNode,
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ignoreEmptyContainers: boolean
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) {
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// Don't bother if the feature is disabled.
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if (diagLevel === 'none') {
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@ -10275,6 +10327,10 @@ export function createTypeEvaluator(
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if (isUnknown(simplifiedType)) {
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addDiagnostic(diagLevel, rule, Localizer.Diagnostic.typeUnknown().format({ name: nameValue }), errorNode);
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} else if (isPartlyUnknown(simplifiedType)) {
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// If ignoreEmptyContainers is true, don't report the problem for
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// empty containers(lists or dictionaries). We'll report the problem
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// only if the assigned value is used later.
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if (!ignoreEmptyContainers || !isObject(type) || !type.classType.isEmptyContainer) {
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const diagAddendum = new DiagnosticAddendum();
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diagAddendum.addMessage(
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Localizer.DiagnosticAddendum.typeOfSymbol().format({
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@ -10290,6 +10346,7 @@ export function createTypeEvaluator(
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);
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}
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}
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}
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// Returns the type of one entry returned by the list comprehension,
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// as opposed to the entire list.
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@ -11366,7 +11423,8 @@ export function createTypeEvaluator(
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rightHandType,
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isIncomplete,
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node.rightExpression,
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expectedTypeDiagAddendum
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/* ignoreEmptyContainers */ true,
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expectedTypeDiagAddendum,
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);
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writeTypeCache(node, rightHandType, isIncomplete);
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@ -13283,7 +13341,12 @@ export function createTypeEvaluator(
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});
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if (node.name) {
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assignTypeToExpression(node.name, targetType, /* isIncomplete */ false, node.name);
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assignTypeToExpression(
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node.name,
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targetType,
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/* isIncomplete */ false,
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node.name
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);
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}
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writeTypeCache(node, targetType, /* isIncomplete */ false);
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@ -13406,7 +13469,12 @@ export function createTypeEvaluator(
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});
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if (node.target) {
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assignTypeToExpression(node.target, scopedType, !!exprTypeResult.isIncomplete, node.target);
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assignTypeToExpression(
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node.target,
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scopedType,
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!!exprTypeResult.isIncomplete,
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node.target
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);
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}
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writeTypeCache(node, scopedType, !!exprTypeResult.isIncomplete);
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@ -354,6 +354,12 @@ export interface ClassType extends TypeBase {
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// some or all of the type parameters.
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typeArguments?: Type[];
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// If a generic container class (like a list or dict) is known
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// to contain no elements, its type arguments may be "Unknown".
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// This value allows us to elide the Unknown when it's safe to
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// do so.
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isEmptyContainer?: boolean;
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// For tuples, the class definition calls for a single type parameter but
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// the spec allows the programmer to provide variadic type arguments.
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// To make these compatible, we need to derive a single typeArgument value
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@ -425,7 +431,8 @@ export namespace ClassType {
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typeArguments: Type[] | undefined,
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isTypeArgumentExplicit: boolean,
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skipAbstractClassTest = false,
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tupleTypeArguments?: Type[]
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tupleTypeArguments?: Type[],
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isEmptyContainer?: boolean
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): ClassType {
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const newClassType = { ...classType };
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@ -440,6 +447,10 @@ export namespace ClassType {
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? tupleTypeArguments.map((t) => (isNever(t) ? UnknownType.create() : t))
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: undefined;
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if (isEmptyContainer !== undefined) {
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newClassType.isEmptyContainer = isEmptyContainer;
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}
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return newClassType;
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}
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@ -2059,7 +2070,7 @@ export function combineConstrainedTypes(subtypes: ConstrainedSubtype[], maxSubty
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}
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}
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// Sort all of the literal types to the end.
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// Sort all of the literal and empty types to the end.
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expandedTypes = expandedTypes.sort((constrainedType1, constrainedType2) => {
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const type1 = constrainedType1.type;
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const type2 = constrainedType2.type;
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@ -2074,6 +2085,13 @@ export function combineConstrainedTypes(subtypes: ConstrainedSubtype[], maxSubty
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) {
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return -1;
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}
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if (isObject(type1) && type1.classType.isEmptyContainer) {
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return 1;
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} else if (isObject(type2) && type2.classType.isEmptyContainer) {
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return -1;
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}
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return 0;
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});
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@ -2199,6 +2217,14 @@ function _addTypeIfUnique(unionType: UnionType, typeToAdd: UnionableType, constr
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}
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}
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}
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// If the typeToAdd is an empty container and there's already
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// non-empty container of the same type, don't add the empty container.
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if (isObject(typeToAdd) && typeToAdd.classType.isEmptyContainer) {
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if (isObject(type) && ClassType.isSameGenericClass(type.classType, typeToAdd.classType)) {
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return;
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}
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}
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}
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UnionType.addType(unionType, typeToAdd, constraintsToAdd);
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@ -0,0 +1,87 @@
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# This sample tests type inference for empty lists and dictionaries.
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# pyright: reportUnknownVariableType=true, reportUnknownArgumentType=true
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from typing import List, Literal
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def func1(a: bool):
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val1 = []
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if a:
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val1 = [2, 3]
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t_val1: Literal["list[int]"] = reveal_type(val1)
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if a:
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val2 = []
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else:
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val2 = []
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t_val2: Literal["list[Unknown]"] = reveal_type(val2)
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# This should generate an error because val2 is partially unknown.
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val2 += [3]
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val3 = val2
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# This should generate an error because val3 is partially unknown.
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print(val3)
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t_val3_1: Literal["list[Unknown]"] = reveal_type(val3)
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if a:
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val3 = [3.4]
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print(val3)
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t_val3_2: Literal["list[float]"] = reveal_type(val3)
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def func2(a: bool):
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val1 = {}
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if a:
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val1 = {"a": 2}
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t_val1: Literal["dict[str, int]"] = reveal_type(val1)
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if a:
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val2 = {}
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else:
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val2 = {}
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t_val2: Literal["dict[Unknown, Unknown]"] = reveal_type(val2)
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# This should generate an error because val2 is partially unknown.
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val2.pop()
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val3 = val2
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# This should generate an error because val3 is partially unknown.
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print(val3)
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t_val3_1: Literal["dict[Unknown, Unknown]"] = reveal_type(val3)
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if a:
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val3 = {"b": 3.4}
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print(val3)
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t_val3_2: Literal["dict[str, float]"] = reveal_type(val3)
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class A:
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def method1(self):
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self.val1 = []
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self.val2 = {}
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self.val3 = []
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def method2(self):
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self.val1 = [3.4]
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self.val2 = {"a": 1}
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def method3(self):
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t_val1: Literal["list[float]"] = reveal_type(self.val1)
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t_val2: Literal["dict[str, int]"] = reveal_type(self.val2)
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t_val3: Literal["list[Unknown]"] = reveal_type(self.val3)
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def method4(self) -> List[int]:
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# This should generate an error because of a type mismatch.
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return self.val1
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@ -1428,3 +1428,8 @@ test('Comparison1', () => {
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const analysisResults = TestUtils.typeAnalyzeSampleFiles(['comparison1.py']);
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TestUtils.validateResults(analysisResults, 3);
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});
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test('EmptyContainers1', () => {
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const analysisResults = TestUtils.typeAnalyzeSampleFiles(['emptyContainers1.py']);
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TestUtils.validateResults(analysisResults, 5);
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});
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