Function narrowTypeByTruthiness

test/fixtures/snapshot/typescript.js:70841–70854

(type, expr, assumeTrue)

                return narrowTypeByDiscriminant(type, access, function (t) { return narrowTypeBySwitchOnDiscriminant(t, switchStatement, clauseStart, clauseEnd); });
            }
            function narrowTypeByTruthiness(type, expr, assumeTrue) {
                if (isMatchingReference(reference, expr)) {
                    return type.flags & 2 /* TypeFlags.Unknown */ && assumeTrue ? nonNullUnknownType :
                        getTypeWithFacts(type, assumeTrue ? 4194304 /* TypeFacts.Truthy */ : 8388608 /* TypeFacts.Falsy */);
                }
                if (strictNullChecks && assumeTrue && optionalChainContainsReference(expr, reference)) {
                    type = getTypeWithFacts(type, 2097152 /* TypeFacts.NEUndefinedOrNull */);
                }
                var access = getDiscriminantPropertyAccess(expr, type);
                if (access) {
                    return narrowTypeByDiscriminant(type, access, function (t) { return getTypeWithFacts(t, assumeTrue ? 4194304 /* TypeFacts.Truthy */ : 8388608 /* TypeFacts.Falsy */); });
                }
                return type;
            }
            function isTypePresencePossible(type, propName, assumeTrue) {
                var prop = getPropertyOfType(type, propName);
                if (prop) {