50 lines
1.1 KiB
JavaScript
50 lines
1.1 KiB
JavaScript
type CovArrayVerbose<X,Y:X> = Array<Y>;
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var b: CovArrayVerbose<number,*> = [];
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var y: CovArrayVerbose<mixed,*> = b;
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y[0] = ""; // error
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class NVerbose<E,I:E> {
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x: CovArrayVerbose<E,I>;
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foo(): CovArrayVerbose<mixed,I> { return this.x; }
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}
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var nv: NVerbose<number,*> = new NVerbose;
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nv.x = [0];
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(nv.x[0]: string); // error
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(nv.foo()[0]: string); // error
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/* TODO: use existentials for non-verbose covariance?
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type CovArray<X> = Array<*:X>;
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var c: CovArray<number> = [0];
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var z: CovArray<string> = c; // error
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var d: CovArray<number> = [];
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var w: CovArray<mixed> = d;
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w[0] = ""; // error
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type P<X> = CovArray<X>;
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var p: P<mixed> = [];
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(p[0]: number); // not an error!
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p[0] = ""; // error
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class M {
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x: CovArray<number>;
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foo(): CovArray<mixed> { return this.x; }
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bar(x: string) { this.foo()[0] = x; } // error
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}
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class N<E> {
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x: CovArray<E>;
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foo(): CovArray<mixed> { return this.x; }
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bar(e: string) { this.foo()[0] = e; } // error
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qux(e: E) { this.foo()[0] = e; }
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}
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var n: N<number> = new N;
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n.x = [0];
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(n.x[0]: string); // error
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(n.foo()[0]: string); // not an error!
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*/
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