Function inferFromIndexTypes

test/fixtures/snapshot/typescript.js:69062–69095

(source, target)

                applyToReturnTypes(source, target, inferFromTypes);
            }
            function inferFromIndexTypes(source, target) {
                // Inferences across mapped type index signatures are pretty much the same a inferences to homomorphic variables
                var priority = (ts.getObjectFlags(source) & ts.getObjectFlags(target) & 32 /* ObjectFlags.Mapped */) ? 8 /* InferencePriority.HomomorphicMappedType */ : 0;
                var indexInfos = getIndexInfosOfType(target);
                if (isObjectTypeWithInferableIndex(source)) {
                    for (var _i = 0, indexInfos_6 = indexInfos; _i < indexInfos_6.length; _i++) {
                        var targetInfo = indexInfos_6[_i];
                        var propTypes = [];
                        for (var _a = 0, _b = getPropertiesOfType(source); _a < _b.length; _a++) {
                            var prop = _b[_a];
                            if (isApplicableIndexType(getLiteralTypeFromProperty(prop, 8576 /* TypeFlags.StringOrNumberLiteralOrUnique */), targetInfo.keyType)) {
                                var propType = getTypeOfSymbol(prop);
                                propTypes.push(prop.flags & 16777216 /* SymbolFlags.Optional */ ? removeMissingOrUndefinedType(propType) : propType);
                            }
                        }
                        for (var _c = 0, _d = getIndexInfosOfType(source); _c < _d.length; _c++) {
                            var info = _d[_c];
                            if (isApplicableIndexType(info.keyType, targetInfo.keyType)) {
                                propTypes.push(info.type);
                            }
                        }
                        if (propTypes.length) {
                            inferWithPriority(getUnionType(propTypes), targetInfo.type, priority);
                        }
                    }
                }
                for (var _e = 0, indexInfos_7 = indexInfos; _e < indexInfos_7.length; _e++) {
                    var targetInfo = indexInfos_7[_e];
                    var sourceInfo = getApplicableIndexInfo(source, targetInfo.keyType);
                    if (sourceInfo) {
                        inferWithPriority(sourceInfo.type, targetInfo.type, priority);
                    }
                }
            }
        }
        function isTypeOrBaseIdenticalTo(s, t) {
            return exactOptionalPropertyTypes && t === missingType ? s === t :