Optimize relationship checks for arrays and tuples

Author: ahejlsberg

src/compiler/checker.ts

@@ -11829,6 +11829,9 @@ namespace ts {
                             errorInfo = saveErrorInfo;
                         }
                     }
+                    else if (isTupleType(source) && (isArrayType(target) || isReadonlyArrayType(target)) || isArrayType(source) && isReadonlyArrayType(target)) {
+                        return isRelatedTo(getIndexTypeOfType(source, IndexKind.Number) || anyType, getIndexTypeOfType(target, IndexKind.Number) || anyType, reportErrors);
+                    }
                     // Even if relationship doesn't hold for unions, intersections, or generic type references,
                     // it may hold in a structural comparison.
                     // In a check of the form X = A & B, we will have previously checked if A relates to X or B relates