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Only parameterless arrow functions have early stage inference from return type

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This commit is contained in:
Anders Hejlsberg
2020-01-27 11:12:55 -08:00
parent 20e8eba143
commit b09afb913e
1 changed files with 3 additions and 3 deletions
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src/compiler/checker.ts
+3 -3
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@@ -7136,7 +7136,7 @@ namespace ts {
}
}
// Use contextual parameter type if one is available
const type = declaration.symbol.escapedName === InternalSymbolName.This ? getContextualThisParameterType(func) : getContextuallyTypedParameterType(declaration, /*forCache*/ true);
const type = declaration.symbol.escapedName === InternalSymbolName.This ? getContextualThisParameterType(func) : getContextuallyTypedParameterType(declaration, /*forCache*/ false);
if (type) {
return addOptionality(type, isOptional);
}
@@ -26430,14 +26430,14 @@ namespace ts {
}
}
function checkFunctionExpressionOrObjectLiteralMethod(node: FunctionExpression | MethodDeclaration, checkMode?: CheckMode): Type {
function checkFunctionExpressionOrObjectLiteralMethod(node: FunctionExpression | ArrowFunction | MethodDeclaration, checkMode?: CheckMode): Type {
Debug.assert(node.kind !== SyntaxKind.MethodDeclaration || isObjectLiteralMethod(node));
checkNodeDeferred(node);
// The identityMapper object is used to indicate that function expressions are wildcards
if (checkMode && checkMode & CheckMode.SkipContextSensitive && isContextSensitive(node)) {
// Skip parameters, return signature with return type that retains noncontextual parts so inferences can still be drawn in an early stage
if (!getEffectiveReturnTypeNode(node) && hasContextSensitiveReturnExpression(node)) {
if (!getEffectiveReturnTypeNode(node) && node.kind === SyntaxKind.ArrowFunction && node.parameters.length === 0) {
// Return plain anyFunctionType if there is no possibility we'll make inferences from the return type
const contextualSignature = getContextualSignature(node);
if (contextualSignature && couldContainTypeVariables(getReturnTypeOfSignature(contextualSignature))) {