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Description
Bug Report
🔎 Search Terms
"Expression produces a union type that is too complex to represent"
(found #33130 which seems unrelated as it has been fixed)
🕗 Version & Regression Information
- Present from 4.1.5 to 5.0.2 in playground.
⏯ Playground Link
💻 Code
function computed<N extends keyof Longhands>(
property: Longhands[N][1],
specified: Longhands[N][0]
) {
// error happens on this line
property.compute(specified);
}
interface Property<T> {
compute: (value: T) => T;
}
type Wrapper<T> = [T, Property<T>];
interface Longhands {
"font-family": Wrapper<Family>;
"font-size": Wrapper<Size>;
"font-stretch": Wrapper<Stretch>;
"font-variant-caps": Wrapper<Caps>;
"font-variant-east-asian": Wrapper<EastAsian>;
"font-variant-ligatures": Wrapper<Ligatures>;
"font-variant-numeric": Wrapper<Numeric>;
"font-variant-position": Wrapper<Position>;
"font-weight": Wrapper<Weight>;
}
class Keyword<K extends string> {
keyword: K;
constructor(keyword: K) {
this.keyword = keyword;
}
}
type Family = Keyword<"serif">;
type Size = Keyword<"length">;
type Stretch =
| Keyword<"percentage">
| Keyword<"ultra-condensed">
| Keyword<"extra-condensed">
| Keyword<"condensed">
| Keyword<"semi-condensed">
| Keyword<"normal">
| Keyword<"semi-expanded">
| Keyword<"expanded">
| Keyword<"extra-expanded">
| Keyword<"ultra-expanded">;
type Caps = Keyword<"normal">;
type EastAsian =
| Keyword<"normal">
| Keyword<"jis78">
| Keyword<"jis83">
| Keyword<"jis90">
| Keyword<"jis04">
| Keyword<"simplified">
| Keyword<"traditional">
| Keyword<"proportional-width">
| Keyword<"full-width">
| Keyword<"ruby">;
type Ligatures =
| Keyword<"none">
| Keyword<"normal">
| Keyword<"common-ligatures">
| Keyword<"no-common-ligatures">
| Keyword<"discretionary-ligatures">
| Keyword<"no-discretionary-ligatures">
| Keyword<"historical-ligatures">
| Keyword<"no-historical-ligatures">
| Keyword<"contextual">
| Keyword<"no-contextual">;
type Numeric =
| Keyword<"normal">
| Keyword<"lining-nums">
| Keyword<"oldstyle-nums">
| Keyword<"proportional-nums">
| Keyword<"tabular-nums">
| Keyword<"diagonal-fractions">
| Keyword<"stacked-fractions">
| Keyword<"ordinal">
| Keyword<"slashed-zero">;
type Position = Keyword<"normal"> | Keyword<"sub"> | Keyword<"super">;
type Weight =
| Keyword<"number">
| Keyword<"normal">
| Keyword<"bold">
| Keyword<"bolder">
| Keyword<"lighter">;Note: interestingly, I detected the error in the much more complex real code of Alfa where it only triggers in TS 4.9.3, but not in 4.8.4 🤔 I am not sure which simplification happens in my real code to keep the union smaller…
🙁 Actual behavior
The code produces the error:
Expression produces a union type that is too complex to represent
🙂 Expected behavior
The union should be around 50 items big, far below the limit.