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Extended support for narrowing of index expressions to include those with negative subscripts, such as a[-1]
. This is supported for all supported type guard patterns.
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@ -186,7 +186,7 @@ In addition to assignment-based type narrowing, Pyright supports the following t
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* `bool(x)` (where x is any expression that is statically verifiable to be truthy or falsy in all cases).
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* `x` (where x is any expression that is statically verifiable to be truthy or falsy in all cases)
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Expressions supported for type guards include simple names, member access chains (e.g. `a.b.c.d`), the unary `not` operator, the binary `and` and `or` operators, subscripts that are constant numbers (e.g. `a[2]`), and call expressions. Other operators (such as arithmetic operators or other subscripts) are not supported.
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Expressions supported for type guards include simple names, member access chains (e.g. `a.b.c.d`), the unary `not` operator, the binary `and` and `or` operators, subscripts that are integer literals (e.g. `a[2]` or `a[-1]`), and call expressions. Other operators (such as arithmetic operators or other subscripts) are not supported.
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Some type guards are able to narrow in both the positive and negative cases. Positive cases are used in `if` statements, and negative cases are used in `else` statements. (Positive and negative cases are flipped if the type guard expression is preceded by a `not` operator.) In some cases, the type can be narrowed only in the positive or negative case but not both. Consider the following examples:
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@ -29,6 +29,7 @@ import {
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StringNode,
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SuiteNode,
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} from '../parser/parseNodes';
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import { OperatorType } from '../parser/tokenizerTypes';
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export enum FlowFlags {
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Unreachable = 1 << 0, // Unreachable code
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@ -188,12 +189,18 @@ export function isCodeFlowSupportedForReference(reference: ExpressionNode): bool
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const subscriptNode = reference.items[0].valueExpression;
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const isIntegerIndex =
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subscriptNode.nodeType === ParseNodeType.Number && !subscriptNode.isImaginary && subscriptNode.isInteger;
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const isNegativeIntegerIndex =
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subscriptNode.nodeType === ParseNodeType.UnaryOperation &&
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subscriptNode.operator === OperatorType.Subtract &&
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subscriptNode.expression.nodeType === ParseNodeType.Number &&
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!subscriptNode.expression.isImaginary &&
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subscriptNode.expression.isInteger;
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const isStringIndex =
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subscriptNode.nodeType === ParseNodeType.StringList &&
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subscriptNode.strings.length === 1 &&
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subscriptNode.strings[0].nodeType === ParseNodeType.String;
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if (!isIntegerIndex && !isStringIndex) {
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if (!isIntegerIndex && !isNegativeIntegerIndex && !isStringIndex) {
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return false;
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}
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@ -213,12 +220,19 @@ export function createKeyForReference(reference: CodeFlowReferenceExpressionNode
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} else if (reference.nodeType === ParseNodeType.Index) {
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const leftKey = createKeyForReference(reference.baseExpression as CodeFlowReferenceExpressionNode);
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assert(reference.items.length === 1);
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if (reference.items[0].valueExpression.nodeType === ParseNodeType.Number) {
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key = `${leftKey}[${(reference.items[0].valueExpression as NumberNode).value.toString()}]`;
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} else if (reference.items[0].valueExpression.nodeType === ParseNodeType.StringList) {
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const valExpr = reference.items[0].valueExpression;
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const expr = reference.items[0].valueExpression;
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if (expr.nodeType === ParseNodeType.Number) {
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key = `${leftKey}[${(expr as NumberNode).value.toString()}]`;
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} else if (expr.nodeType === ParseNodeType.StringList) {
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const valExpr = expr;
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assert(valExpr.strings.length === 1 && valExpr.strings[0].nodeType === ParseNodeType.String);
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key = `${leftKey}["${(valExpr.strings[0] as StringNode).value}"]`;
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} else if (
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expr.nodeType === ParseNodeType.UnaryOperation &&
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expr.operator === OperatorType.Subtract &&
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expr.expression.nodeType === ParseNodeType.Number
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) {
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key = `${leftKey}[-${(expr.expression as NumberNode).value.toString()}]`;
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} else {
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fail('createKeyForReference received unexpected index type');
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}
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@ -978,8 +978,8 @@ export function isMatchingExpression(reference: ExpressionNode, expression: Expr
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return false;
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}
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if (reference.items[0].valueExpression.nodeType === ParseNodeType.Number) {
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const referenceNumberNode = reference.items[0].valueExpression;
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const expr = reference.items[0].valueExpression;
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if (expr.nodeType === ParseNodeType.Number) {
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const subscriptNode = expression.items[0].valueExpression;
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if (
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subscriptNode.nodeType !== ParseNodeType.Number ||
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@ -989,11 +989,30 @@ export function isMatchingExpression(reference: ExpressionNode, expression: Expr
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return false;
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}
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return referenceNumberNode.value === subscriptNode.value;
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return expr.value === subscriptNode.value;
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}
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if (reference.items[0].valueExpression.nodeType === ParseNodeType.StringList) {
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const referenceStringListNode = reference.items[0].valueExpression;
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if (
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expr.nodeType === ParseNodeType.UnaryOperation &&
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expr.operator === OperatorType.Subtract &&
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expr.expression.nodeType === ParseNodeType.Number
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) {
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const subscriptNode = expression.items[0].valueExpression;
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if (
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subscriptNode.nodeType !== ParseNodeType.UnaryOperation ||
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subscriptNode.operator !== OperatorType.Subtract ||
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subscriptNode.expression.nodeType !== ParseNodeType.Number ||
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subscriptNode.expression.isImaginary ||
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!subscriptNode.expression.isInteger
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) {
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return false;
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}
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return expr.expression.value === subscriptNode.expression.value;
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}
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if (expr.nodeType === ParseNodeType.StringList) {
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const referenceStringListNode = expr;
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const subscriptNode = expression.items[0].valueExpression;
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if (
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referenceStringListNode.strings.length === 1 &&
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@ -36,12 +36,18 @@ def func1(v1: List[Optional[complex]]):
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foo.val = []
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reveal_type(foo.val[0][2], expected_text="str | None")
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if v1[-1]:
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reveal_type(v1[-1], expected_text="complex")
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def func2(v1: List[Union[Dict[str, str], List[str]]]):
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if isinstance(v1[0], dict):
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reveal_type(v1[0], expected_text="Dict[str, str]")
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reveal_type(v1[1], expected_text="Dict[str, str] | List[str]")
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if isinstance(v1[-1], list):
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reveal_type(v1[-1], expected_text="List[str]")
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def func3():
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v1: Dict[str, int] = {}
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