Function inferFromTypes

test/fixtures/snapshot/typescript.js:68468–68676

(source, target)

            var expandingFlags = 0 /* ExpandingFlags.None */;
            inferFromTypes(originalSource, originalTarget);
            function inferFromTypes(source, target) {
                if (!couldContainTypeVariables(target)) {
                    return;
                }
                if (source === wildcardType) {
                    // We are inferring from an 'any' type. We want to infer this type for every type parameter
                    // referenced in the target type, so we record it as the propagation type and infer from the
                    // target to itself. Then, as we find candidates we substitute the propagation type.
                    var savePropagationType = propagationType;
                    propagationType = source;
                    inferFromTypes(target, target);
                    propagationType = savePropagationType;
                    return;
                }
                if (source.aliasSymbol && source.aliasTypeArguments && source.aliasSymbol === target.aliasSymbol) {
                    // Source and target are types originating in the same generic type alias declaration.
                    // Simply infer from source type arguments to target type arguments.
                    inferFromTypeArguments(source.aliasTypeArguments, target.aliasTypeArguments, getAliasVariances(source.aliasSymbol));
                    return;
                }
                if (source === target && source.flags & 3145728 /* TypeFlags.UnionOrIntersection */) {
                    // When source and target are the same union or intersection type, just relate each constituent
                    // type to itself.
                    for (var _i = 0, _a = source.types; _i < _a.length; _i++) {
                        var t = _a[_i];
                        inferFromTypes(t, t);
                    }
                    return;
                }
                if (target.flags & 1048576 /* TypeFlags.Union */) {
                    // First, infer between identically matching source and target constituents and remove the
                    // matching types.
                    var _b = inferFromMatchingTypes(source.flags & 1048576 /* TypeFlags.Union */ ? source.types : [source], target.types, isTypeOrBaseIdenticalTo), tempSources = _b[0], tempTargets = _b[1];
                    // Next, infer between closely matching source and target constituents and remove
                    // the matching types. Types closely match when they are instantiations of the same
                    // object type or instantiations of the same type alias.
                    var _c = inferFromMatchingTypes(tempSources, tempTargets, isTypeCloselyMatchedBy), sources = _c[0], targets = _c[1];
                    if (targets.length === 0) {
                        return;
                    }
                    target = getUnionType(targets);
                    if (sources.length === 0) {
                        // All source constituents have been matched and there is nothing further to infer from.
                        // However, simply making no inferences is undesirable because it could ultimately mean
                        // inferring a type parameter constraint. Instead, make a lower priority inference from
                        // the full source to whatever remains in the target. For example, when inferring from
                        // string to 'string | T', make a lower priority inference of string for T.
                        inferWithPriority(source, target, 1 /* InferencePriority.NakedTypeVariable */);
                        return;
                    }
                    source = getUnionType(sources);
                }
                else if (target.flags & 2097152 /* TypeFlags.Intersection */ && ts.some(target.types, function (t) { return !!getInferenceInfoForType(t) || (isGenericMappedType(t) && !!getInferenceInfoForType(getHomomorphicTypeVariable(t) || neverType)); })) {
                    // We reduce intersection types only when they contain naked type parameters. For example, when
                    // inferring from 'string[] & { extra: any }' to 'string[] & T' we want to remove string[] and
                    // infer { extra: any } for T. But when inferring to 'string[] & Iterable<T>' we want to keep the
                    // string[] on the source side and infer string for T.
                    // Likewise, we consider a homomorphic mapped type constrainted to the target type parameter as similar to a "naked type variable"