Function narrowTypeByOptionalChainContainment

test/fixtures/snapshot/typescript.js:70971–70988

(type, operator, value, assumeTrue)

                return getNarrowedType(type, targetType, assumeTrue, isTypeDerivedFrom);
            }
            function narrowTypeByOptionalChainContainment(type, operator, value, assumeTrue) {
                // We are in a branch of obj?.foo === value (or any one of the other equality operators). We narrow obj as follows:
                // When operator is === and type of value excludes undefined, null and undefined is removed from type of obj in true branch.
                // When operator is !== and type of value excludes undefined, null and undefined is removed from type of obj in false branch.
                // When operator is == and type of value excludes null and undefined, null and undefined is removed from type of obj in true branch.
                // When operator is != and type of value excludes null and undefined, null and undefined is removed from type of obj in false branch.
                // When operator is === and type of value is undefined, null and undefined is removed from type of obj in false branch.
                // When operator is !== and type of value is undefined, null and undefined is removed from type of obj in true branch.
                // When operator is == and type of value is null or undefined, null and undefined is removed from type of obj in false branch.
                // When operator is != and type of value is null or undefined, null and undefined is removed from type of obj in true branch.
                var equalsOperator = operator === 34 /* SyntaxKind.EqualsEqualsToken */ || operator === 36 /* SyntaxKind.EqualsEqualsEqualsToken */;
                var nullableFlags = operator === 34 /* SyntaxKind.EqualsEqualsToken */ || operator === 35 /* SyntaxKind.ExclamationEqualsToken */ ? 98304 /* TypeFlags.Nullable */ : 32768 /* TypeFlags.Undefined */;
                var valueType = getTypeOfExpression(value);
                // Note that we include any and unknown in the exclusion test because their domain includes null and undefined.
                var removeNullable = equalsOperator !== assumeTrue && everyType(valueType, function (t) { return !!(t.flags & nullableFlags); }) ||
                    equalsOperator === assumeTrue && everyType(valueType, function (t) { return !(t.flags & (3 /* TypeFlags.AnyOrUnknown */ | nullableFlags)); });
                return removeNullable ? getTypeWithFacts(type, 2097152 /* TypeFacts.NEUndefinedOrNull */) : type;
            }
            function narrowTypeByEquality(type, operator, value, assumeTrue) {
                if (type.flags & 1 /* TypeFlags.Any */) {
                    return type;