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JSX uses mixed signatures and union sigs use subtype on partial match#28141

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weswigham merged 2 commits intomicrosoft:masterfrom
weswigham:jsx-union-kludge
Oct 26, 2018
Merged

JSX uses mixed signatures and union sigs use subtype on partial match#28141
weswigham merged 2 commits intomicrosoft:masterfrom
weswigham:jsx-union-kludge

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Fixes #27948 in the general case where the union elements are like ComponentType - very similar signatures in each union member.

if (refKind === JsxReferenceKind.Function) {
const sfcReturnConstraint = getJsxStatelessElementTypeAt(openingLikeElement);
if (sfcReturnConstraint) {
checkTypeRelatedTo(elemInstanceType, sfcReturnConstraint, assignableRelation, openingLikeElement, Diagnostics.JSX_element_type_0_is_not_a_constructor_function_for_JSX_elements);
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@Jessidhia Jessidhia Oct 26, 2018

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(note) as of React 16, components are also allowed to return number / string / boolean (in other words, anything other than undefined, symbol or a non-Element, non-Array object), but at least TS@latest will reject SFC which include those return types. It does validate with classes, just not functions.

If fixed this probably goes in another PR though.

@weswigham weswigham merged commit 972c403 into microsoft:master Oct 26, 2018
@weswigham weswigham deleted the jsx-union-kludge branch October 26, 2018 23:02
@microsoft microsoft locked as resolved and limited conversation to collaborators Oct 21, 2025
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3 participants