Change 'keyof T' to always be string-like#12425
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ahejlsberg merged 7 commits intomasterfrom Nov 21, 2016
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Now that keyof T only returns string or string subtypes (microsoft#12425), there’s no need to do keyof T & string.
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Nov 28, 2016
Removes number from all the keyof types, and adds a test that numeric indexes are ignored.
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Update keyof tests to reflect #12425
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This PR revises
keyof Tto always be a subtype ofstringvs. a subtype ofstring | number. This more accurately reflects how properties work in JavaScript and allows us to usekeyof Tas the inferred type of afor...invariable when the object is of a type parameter type.This change means that numeric index signatures are ignored by the
keyof Toperator and that it is never possible to use numbers as values for akeyof T.Fixes #12314.