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Cache inference for recursive mapped types #20622

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Cache inference for recursive mapped types #20622

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fd3a185
Cache recursive mapped type inferences
sandersn Dec 11, 2017
bea1f81
Test:XMLHttpRequest inference to PartialDeep<T>
sandersn Dec 11, 2017
1db8f32
Infer homomorphic mapped types to primitives
sandersn Dec 11, 2017
e2932fb
Inference: Turn visited marker into a cache
sandersn Dec 11, 2017
808abb6
Update baselines
sandersn Dec 11, 2017
e664a6e
Inference:back to two caches+fix cache lookup
sandersn Dec 11, 2017
6e00b0e
Merge branch 'master' into cache-inference-for-resursive-mapped-types
sandersn Dec 11, 2017
786fc33
Undo gratuitous changes
sandersn Dec 13, 2017
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18 changes: 8 additions & 10 deletions src/compiler/checker.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -11217,7 +11217,7 @@ namespace ts {
* property is computed by inferring from the source property type to X for the type
* variable T[P] (i.e. we treat the type T[P] as the type variable we're inferring for).
*/
function inferTypeForHomomorphicMappedType(source: Type, target: MappedType, mappedTypeStack: string[]): Type {
function inferTypeForHomomorphicMappedType(source: Type, target: MappedType, visited: Map<true>): Type {
const properties = getPropertiesOfType(source);
let indexInfo = getIndexInfoOfType(source, IndexKind.String);
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Is this tested anywhere in a more obvious way? e.g.

// @declaration: true

type MyReadonly<T> = { readonly [K in keyof T]: T[K] };

export declare function foo<T>(x: MyReadonly<T>): T;

export let x = foo(100);

if (properties.length === 0 && !indexInfo) {
Expand Down Expand Up @@ -11250,7 +11250,7 @@ namespace ts {

function inferTargetType(sourceType: Type): Type {
inference.candidates = undefined;
inferTypes(inferences, sourceType, templateType, 0, mappedTypeStack);
inferTypes(inferences, sourceType, templateType, 0, visited);
return inference.candidates ? getUnionType(inference.candidates, /*subtypeReduction*/ true) : emptyObjectType;
}
}
Expand All @@ -11268,9 +11268,8 @@ namespace ts {
return undefined;
}

function inferTypes(inferences: InferenceInfo[], originalSource: Type, originalTarget: Type, priority: InferencePriority = 0, mappedTypeStack?: string[]) {
function inferTypes(inferences: InferenceInfo[], originalSource: Type, originalTarget: Type, priority: InferencePriority = 0, visited?: Map<true>) {
let symbolStack: Symbol[];
let visited: Map<boolean>;
inferFromTypes(originalSource, originalTarget);

function inferFromTypes(source: Type, target: Type) {
Expand Down Expand Up @@ -11424,7 +11423,7 @@ namespace ts {
if (visited && visited.get(key)) {
return;
}
(visited || (visited = createMap<boolean>())).set(key, true);
(visited || (visited = createMap<true>())).set(key, true);
// If we are already processing another target type with the same associated symbol (such as
// an instantiation of the same generic type), we do not explore this target as it would yield
// no further inferences. We exclude the static side of classes from this check since it shares
Expand Down Expand Up @@ -11485,13 +11484,12 @@ namespace ts {
// such that direct inferences to T get priority over inferences to Partial<T>, for example.
const inference = getInferenceInfoForType((<IndexType>constraintType).type);
if (inference && !inference.isFixed) {
const key = (source.symbol ? getSymbolId(source.symbol) + "," : "") + getSymbolId(target.symbol);
if (contains(mappedTypeStack, key)) {
const key = (source.symbol ? getSymbolId(source.symbol) + "s" : "") + getSymbolId(target.symbol);
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Normally we distinguish different types of cache keys with a leading character, rather than a different separator, see getLiteralType for prior art. Plus, I think something like T123,12 vs S11,14 is going to make more sense in the debugger than 123,12 vs 11s14.

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Sure. Done.

if (visited && visited.has(key)) {
return;
}
(mappedTypeStack || (mappedTypeStack = [])).push(key);
const inferredType = inferTypeForHomomorphicMappedType(source, <MappedType>target, mappedTypeStack);
mappedTypeStack.pop();
(visited || (visited = createMap<true>())).set(key, true);
const inferredType = inferTypeForHomomorphicMappedType(source, <MappedType>target, visited);
if (inferredType) {
const savePriority = priority;
priority |= InferencePriority.MappedType;
Expand Down
5 changes: 5 additions & 0 deletions tests/baselines/reference/mappedTypeRecursiveInference.js
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Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,12 @@ declare let a: A;
type Deep<T> = { [K in keyof T]: Deep<T[K]> }
declare function foo<T>(deep: Deep<T>): T;
const out = foo(a);

let xhr: XMLHttpRequest;
const out2 = foo(xhr);


//// [mappedTypeRecursiveInference.js]
var out = foo(a);
var xhr;
var out2 = foo(xhr);
9 changes: 9 additions & 0 deletions tests/baselines/reference/mappedTypeRecursiveInference.symbols
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Expand Up @@ -30,3 +30,12 @@ const out = foo(a);
>foo : Symbol(foo, Decl(mappedTypeRecursiveInference.ts, 2, 45))
>a : Symbol(a, Decl(mappedTypeRecursiveInference.ts, 1, 11))

let xhr: XMLHttpRequest;
>xhr : Symbol(xhr, Decl(mappedTypeRecursiveInference.ts, 6, 3))
>XMLHttpRequest : Symbol(XMLHttpRequest, Decl(lib.dom.d.ts, --, --), Decl(lib.dom.d.ts, --, --))

const out2 = foo(xhr);
>out2 : Symbol(out2, Decl(mappedTypeRecursiveInference.ts, 7, 5))
>foo : Symbol(foo, Decl(mappedTypeRecursiveInference.ts, 2, 45))
>xhr : Symbol(xhr, Decl(mappedTypeRecursiveInference.ts, 6, 3))

10 changes: 10 additions & 0 deletions tests/baselines/reference/mappedTypeRecursiveInference.types
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4 changes: 4 additions & 0 deletions tests/cases/compiler/mappedTypeRecursiveInference.ts
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Original file line number Diff line number Diff line change
@@ -1,5 +1,9 @@
// @lib: es6, dom
interface A { a: A }
declare let a: A;
type Deep<T> = { [K in keyof T]: Deep<T[K]> }
declare function foo<T>(deep: Deep<T>): T;
const out = foo(a);

let xhr: XMLHttpRequest;
const out2 = foo(xhr);