Check for keyof constraint type instead of syntactic check #24098
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I'm not sure I like this. It's really odd that |
weswigham
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@ahejlsberg So I've generalized it to just being a type variable constrained to any of string or number or symbol (rather than exactly one of them)... and there's no diff to any tests, |
ahejlsberg
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May 20, 2018
| return isTypeParameterWithKeyofConstraint(contextualType) && maybeTypeOfKind(candidateType, TypeFlags.StringLiteral | TypeFlags.NumberLiteral | TypeFlags.UniqueESSymbol) || | ||
| constraint.flags & TypeFlags.String && maybeTypeOfKind(candidateType, TypeFlags.StringLiteral) || | ||
| constraint.flags & TypeFlags.Number && maybeTypeOfKind(candidateType, TypeFlags.NumberLiteral) || | ||
| constraint.flags & TypeFlags.Boolean && maybeTypeOfKind(candidateType, TypeFlags.BooleanLiteral) || |
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The line that checks for TypeFlags.Boolean isn't necessary. The logic already covers unions of literal types, and TypeFlags.Boolean is just a convenience flag we set on the built-in true | false union.
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May 23, 2018
…#24098) * Check for keyof constraint type instead of syntactic check * Readopt older candidateType check, even though it shouldnt really matter * OK. Just use maybetypeOfKind * Remove redundant boolean check
mhegazy
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May 23, 2018
Check for keyof constraint type instead of syntactic check (#24098)
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Fixes #24080
Downside:
T extends string | symbol | numberwill now produce literals. (technically a break)Upside:
T extends string | symbol | numberwill now produce literals. (probably desirably, given any one of those on their own would produce literals)