Function getNarrowableTypeForReference

test/fixtures/snapshot/typescript.js:71515–71527

(type, reference, checkMode)

            return contextualType && !isGenericType(contextualType);
        }
        function getNarrowableTypeForReference(type, reference, checkMode) {
            // When the type of a reference is or contains an instantiable type with a union type constraint, and
            // when the reference is in a constraint position (where it is known we'll obtain the apparent type) or
            // has a contextual type containing no top-level instantiables (meaning constraints will determine
            // assignability), we substitute constraints for all instantiables in the type of the reference to give
            // control flow analysis an opportunity to narrow it further. For example, for a reference of a type
            // parameter type 'T extends string | undefined' with a contextual type 'string', we substitute
            // 'string | undefined' to give control flow analysis the opportunity to narrow to type 'string'.
            var substituteConstraints = !(checkMode && checkMode & 2 /* CheckMode.Inferential */) &&
                someType(type, isGenericTypeWithUnionConstraint) &&
                (isConstraintPosition(type, reference) || hasContextualTypeWithNoGenericTypes(reference, checkMode));
            return substituteConstraints ? mapType(type, function (t) { return t.flags & 465829888 /* TypeFlags.Instantiable */ ? getBaseConstraintOrType(t) : t; }) : type;
        }
        function isExportOrExportExpression(location) {
            return !!ts.findAncestor(location, function (n) {
                var parent = n.parent;