Function getConditionalType

test/fixtures/snapshot/typescript.js:62531–62689

(root, mapper, aliasSymbol, aliasTypeArguments)

            return isTypicalNondistributiveConditional(root) && isTupleType(type) ? getTypeArguments(type)[0] : type;
        }
        function getConditionalType(root, mapper, aliasSymbol, aliasTypeArguments) {
            var result;
            var extraTypes;
            var tailCount = 0;
            var _loop_18 = function () {
                if (tailCount === 1000) {
                    error(currentNode, ts.Diagnostics.Type_instantiation_is_excessively_deep_and_possibly_infinite);
                    result = errorType;
                    return "break";
                }
                var isUnwrapped = isTypicalNondistributiveConditional(root);
                var checkType = instantiateType(unwrapNondistributiveConditionalTuple(root, getActualTypeVariable(root.checkType)), mapper);
                var checkTypeInstantiable = isGenericType(checkType);
                var extendsType = instantiateType(unwrapNondistributiveConditionalTuple(root, root.extendsType), mapper);
                if (checkType === wildcardType || extendsType === wildcardType) {
                    return { value: wildcardType };
                }
                var combinedMapper = void 0;
                if (root.inferTypeParameters) {
                    // When we're looking at making an inference for an infer type, when we get its constraint, it'll automagically be
                    // instantiated with the context, so it doesn't need the mapper for the inference contex - however the constraint
                    // may refer to another _root_, _uncloned_ `infer` type parameter [1], or to something mapped by `mapper` [2].
                    // [1] Eg, if we have `Foo<T, U extends T>` and `Foo<number, infer B>` - `B` is constrained to `T`, which, in turn, has been instantiated
                    // as `number`
                    // Conversely, if we have `Foo<infer A, infer B>`, `B` is still constrained to `T` and `T` is instantiated as `A`
                    // [2] Eg, if we have `Foo<T, U extends T>` and `Foo<Q, infer B>` where `Q` is mapped by `mapper` into `number` - `B` is constrained to `T`
                    // which is in turn instantiated as `Q`, which is in turn instantiated as `number`.
                    // So we need to:
                    //    * Clone the type parameters so their constraints can be instantiated in the context of `mapper` (otherwise theyd only get inference context information)
                    //    * Set the clones to both map the conditional's enclosing `mapper` and the original params
                    //    * instantiate the extends type with the clones
                    //    * incorporate all of the component mappers into the combined mapper for the true and false members
                    // This means we have three mappers that need applying:
                    //    * The original `mapper` used to create this conditional
                    //    * The mapper that maps the old root type parameter to the clone (`freshMapper`)
                    //    * The mapper that maps the clone to its inference result (`context.mapper`)
                    var freshParams = ts.sameMap(root.inferTypeParameters, maybeCloneTypeParameter);
                    var freshMapper = freshParams !== root.inferTypeParameters ? createTypeMapper(root.inferTypeParameters, freshParams) : undefined;
                    var context = createInferenceContext(freshParams, /*signature*/ undefined, 0 /* InferenceFlags.None */);
                    if (freshMapper) {
                        var freshCombinedMapper = combineTypeMappers(mapper, freshMapper);
                        for (var _i = 0, freshParams_1 = freshParams; _i < freshParams_1.length; _i++) {
                            var p = freshParams_1[_i];
                            if (root.inferTypeParameters.indexOf(p) === -1) {
                                p.mapper = freshCombinedMapper;
                            }
                        }
                    }
                    // We skip inference of the possible `infer` types unles the `extendsType` _is_ an infer type
                    // if it was, it's trivial to say that extendsType = checkType, however such a pattern is used to
                    // "reset" the type being build up during constraint calculation and avoid making an apparently "infinite" constraint
                    // so in those cases we refain from performing inference and retain the uninfered type parameter
                    if (!checkTypeInstantiable || !ts.some(root.inferTypeParameters, function (t) { return t === extendsType; })) {
                        // We don't want inferences from constraints as they may cause us to eagerly resolve the
                        // conditional type instead of deferring resolution. Also, we always want strict function
                        // types rules (i.e. proper contravariance) for inferences.
                        inferTypes(context.inferences, checkType, instantiateType(extendsType, freshMapper), 512 /* InferencePriority.NoConstraints */ | 1024 /* InferencePriority.AlwaysStrict */);
                    }