Function getSimplifiedIndexedAccessType

test/fixtures/snapshot/typescript.js:62306–62353

(type, writing)

        // the type itself if no transformation is possible. The writing flag indicates that the type is
        // the target of an assignment.
        function getSimplifiedIndexedAccessType(type, writing) {
            var cache = writing ? "simplifiedForWriting" : "simplifiedForReading";
            if (type[cache]) {
                return type[cache] === circularConstraintType ? type : type[cache];
            }
            type[cache] = circularConstraintType;
            // We recursively simplify the object type as it may in turn be an indexed access type. For example, with
            // '{ [P in T]: { [Q in U]: number } }[T][U]' we want to first simplify the inner indexed access type.
            var objectType = getSimplifiedType(type.objectType, writing);
            var indexType = getSimplifiedType(type.indexType, writing);
            // T[A | B] -> T[A] | T[B] (reading)
            // T[A | B] -> T[A] & T[B] (writing)
            var distributedOverIndex = distributeObjectOverIndexType(objectType, indexType, writing);
            if (distributedOverIndex) {
                return type[cache] = distributedOverIndex;
            }
            // Only do the inner distributions if the index can no longer be instantiated to cause index distribution again
            if (!(indexType.flags & 465829888 /* TypeFlags.Instantiable */)) {
                // (T | U)[K] -> T[K] | U[K] (reading)
                // (T | U)[K] -> T[K] & U[K] (writing)
                // (T & U)[K] -> T[K] & U[K]
                var distributedOverObject = distributeIndexOverObjectType(objectType, indexType, writing);
                if (distributedOverObject) {
                    return type[cache] = distributedOverObject;
                }
            }
            // So ultimately (reading):
            // ((A & B) | C)[K1 | K2] -> ((A & B) | C)[K1] | ((A & B) | C)[K2] -> (A & B)[K1] | C[K1] | (A & B)[K2] | C[K2] -> (A[K1] & B[K1]) | C[K1] | (A[K2] & B[K2]) | C[K2]
            // A generic tuple type indexed by a number exists only when the index type doesn't select a
            // fixed element. We simplify to either the combined type of all elements (when the index type
            // the actual number type) or to the combined type of all non-fixed elements.
            if (isGenericTupleType(objectType) && indexType.flags & 296 /* TypeFlags.NumberLike */) {
                var elementType = getElementTypeOfSliceOfTupleType(objectType, indexType.flags & 8 /* TypeFlags.Number */ ? 0 : objectType.target.fixedLength, /*endSkipCount*/ 0, writing);
                if (elementType) {
                    return type[cache] = elementType;
                }
            }
            // If the object type is a mapped type { [P in K]: E }, where K is generic, or { [P in K as N]: E }, where
            // K is generic and N is assignable to P, instantiate E using a mapper that substitutes the index type for P.
            // For example, for an index access { [P in K]: Box<T[P]> }[X], we construct the type Box<T[X]>.
            if (isGenericMappedType(objectType)) {
                var nameType = getNameTypeFromMappedType(objectType);
                if (!nameType || isTypeAssignableTo(nameType, getTypeParameterFromMappedType(objectType))) {
                    return type[cache] = mapType(substituteIndexedMappedType(objectType, type.indexType), function (t) { return getSimplifiedType(t, writing); });
                }
            }
            return type[cache] = type;
        }
        function getSimplifiedConditionalType(type, writing) {
            var checkType = type.checkType;
            var extendsType = type.extendsType;