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Use generator trampolines during instantiation #32611

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Use generator trampolines during instantiation #32611

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83eeab6
Trampolines for all instantiation
weswigham Jul 2, 2019
4798de0
Integrate a version of indexed access setup into the instantiation tr…
weswigham Jul 30, 2019
bfc608e
Add test capturing much higher work limit
weswigham Jul 30, 2019
8377927
Move collectGeneratorReturn into core
weswigham Jul 30, 2019
1ef46f6
Simplify the .types baseline for new test hugely by naming inner type
weswigham Jul 30, 2019
0978036
No using array spread in hot codepath :(
weswigham Jul 30, 2019
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284 changes: 236 additions & 48 deletions src/compiler/checker.ts
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20 changes: 20 additions & 0 deletions src/compiler/core.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -572,6 +572,26 @@ namespace ts {
};
}

export function* mapByIterator<T, U, TOut, TIn>(iter: IterableIterator<T>, mapFn: (x: T, idx: number) => Generator<TOut, U, TIn>): Generator<TOut, U[] | undefined, TIn> {
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Suggested change
export function* mapByIterator<T, U, TOut, TIn>(iter: IterableIterator<T>, mapFn: (x: T, idx: number) => Generator<TOut, U, TIn>): Generator<TOut, U[] | undefined, TIn> {
export function* mapIterator<T, U, TOut, TIn>(iter: IterableIterator<T>, mapFn: (x: T, idx: number) => Generator<TOut, U, TIn>): Generator<TOut, U[] | undefined, TIn> {

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    export function mapIterator<T, U>(iter: Iterator<T>, mapFn: (x: T) => U): Iterator<U> {
        return {
            next() {
                const iterRes = iter.next();
                return iterRes.done ? iterRes as { done: true, value: never } : { value: mapFn(iterRes.value), done: false };
            }
        };
    }

already exists, except that applies a mapping function to an iterator, rather than applying a mapping generator to an iterator~

let i = 0;
let result: U[] | undefined;
for (const e of iter) {
(result || (result = [])).push(yield* mapFn(e, i));
i++;
}
return result;
}


export function collectGeneratorReturn<TYield, TStep, TReturn>(gen: Generator<TYield, TReturn, TStep>, feedforward: (yielded: TYield) => TStep): TReturn {
let result;
for (result = gen.next(); !result.done;) {
result = gen.next(feedforward(result.value as TYield));
}
return (result as IteratorReturnResult<TReturn>).value;
}


// Maps from T to T and avoids allocation if all elements map to themselves
export function sameMap<T>(array: T[], f: (x: T, i: number) => T): T[];
export function sameMap<T>(array: ReadonlyArray<T>, f: (x: T, i: number) => T): ReadonlyArray<T>;
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1 change: 1 addition & 0 deletions src/tsconfig-base.json
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Expand Up @@ -22,6 +22,7 @@

"alwaysStrict": true,
"preserveConstEnums": true,
"downlevelIteration": true,
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@weswigham weswigham Jul 29, 2019 •
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#32221 tracks what we'd need to do to target native generators (mostly fixing TDZ bugs to do with real runtime const/let), which is pretty appealing at this point, since all versions of node we support use them, and they consume roughly 1/3rd of the memory of the downlevel form.

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@rbuckton rbuckton Jul 30, 2019 •
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"downlevelIteration" will seriously degrade the performance of all of our for..of statements in the compiler. Using native generators would also be a problem for VSCode/Monaco as they still have web hosting scenarios they need to support where native generators are not available.

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Oh yeah, I know - that's why I did testing with native generators (and other es6 features). Native generators are fine for most people, though, and we can always just ship a secondary bundle with downleveled generators for older webhosts.

"newLine": "lf",

"types": []
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41 changes: 41 additions & 0 deletions tests/baselines/reference/instantiationHandledLargeVolumeOfSimpleWork.js
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