check index access for fixed length tuple

src/compiler/checker.ts

@@ -18293,6 +18293,13 @@ namespace ts {
                 error(indexExpression, Diagnostics.A_const_enum_member_can_only_be_accessed_using_a_string_literal);
                 return errorType;
             }
+            if (isTupleType(objectType) && !objectType.target.hasRestElement && isNumericLiteral(indexExpression)) {
+                const index = +indexExpression.text;
+                const maximumIndex = length(objectType.target.typeParameters);
+                if (index >= maximumIndex) {
+                    error(indexExpression, Diagnostics.Index_0_is_out_of_bounds_in_tuple_of_length_1, index, maximumIndex);
+                }
+            }
 
             return checkIndexedAccessIndexType(getIndexedAccessType(objectType, indexType, node), node);
         }

src/compiler/diagnosticMessages.json

@@ -2437,6 +2437,10 @@
         "category": "Error",
         "code": 2732
     },
+    "Index '{0}' is out-of-bounds in tuple of length {1}.": {
+        "category": "Error",
+        "code": 2733
+    },
 
     "Import declaration '{0}' is using private name '{1}'.": {
         "category": "Error",

tests/baselines/reference/bestCommonTypeOfTuple.errors.txt

@@ -0,0 +1,40 @@
+tests/cases/conformance/types/typeRelationships/bestCommonType/bestCommonTypeOfTuple.ts(22,13): error TS2733: Index '2' is out-of-bounds in tuple of length 2.
+tests/cases/conformance/types/typeRelationships/bestCommonType/bestCommonTypeOfTuple.ts(23,13): error TS2733: Index '2' is out-of-bounds in tuple of length 2.
+tests/cases/conformance/types/typeRelationships/bestCommonType/bestCommonTypeOfTuple.ts(24,13): error TS2733: Index '2' is out-of-bounds in tuple of length 2.
+tests/cases/conformance/types/typeRelationships/bestCommonType/bestCommonTypeOfTuple.ts(25,13): error TS2733: Index '3' is out-of-bounds in tuple of length 3.
+
+
+==== tests/cases/conformance/types/typeRelationships/bestCommonType/bestCommonTypeOfTuple.ts (4 errors) ====
+    function f1(x: number): string { return "foo"; }
+
+    function f2(x: number): number { return 10; }
+
+    function f3(x: number): boolean { return true; }
+
+    enum E1 { one }
+
+    enum E2 { two }
+
+
+    var t1: [(x: number) => string, (x: number) => number];
+    var t2: [E1, E2];
+    var t3: [number, any];
+    var t4: [E1, E2, number];
+
+    // no error
+    t1 = [f1, f2];
+    t2 = [E1.one, E2.two];
+    t3 = [5, undefined];
+    t4 = [E1.one, E2.two, 20];
+    var e1 = t1[2];  // {}
+                ~
+!!! error TS2733: Index '2' is out-of-bounds in tuple of length 2.
+    var e2 = t2[2];  // {}
+                ~
+!!! error TS2733: Index '2' is out-of-bounds in tuple of length 2.
+    var e3 = t3[2];  // any
+                ~
+!!! error TS2733: Index '2' is out-of-bounds in tuple of length 2.
+    var e4 = t4[3];  // number
+                ~
+!!! error TS2733: Index '3' is out-of-bounds in tuple of length 3.

tests/baselines/reference/bestCommonTypeOfTuple2.errors.txt

@@ -0,0 +1,40 @@
+tests/cases/conformance/types/typeRelationships/bestCommonType/bestCommonTypeOfTuple2.ts(17,14): error TS2733: Index '4' is out-of-bounds in tuple of length 2.
+tests/cases/conformance/types/typeRelationships/bestCommonType/bestCommonTypeOfTuple2.ts(18,14): error TS2733: Index '4' is out-of-bounds in tuple of length 2.
+tests/cases/conformance/types/typeRelationships/bestCommonType/bestCommonTypeOfTuple2.ts(19,14): error TS2733: Index '4' is out-of-bounds in tuple of length 2.
+tests/cases/conformance/types/typeRelationships/bestCommonType/bestCommonTypeOfTuple2.ts(20,14): error TS2733: Index '2' is out-of-bounds in tuple of length 2.
+tests/cases/conformance/types/typeRelationships/bestCommonType/bestCommonTypeOfTuple2.ts(21,14): error TS2733: Index '2' is out-of-bounds in tuple of length 2.
+
+
+==== tests/cases/conformance/types/typeRelationships/bestCommonType/bestCommonTypeOfTuple2.ts (5 errors) ====
+    interface base { }
+    interface base1 { i }
+    class C implements base { c }
+    class D implements base { d }
+    class E implements base { e }
+    class F extends C { f }
+
+    class C1 implements base1 { i = "foo"; c }
+    class D1 extends C1 { i = "bar"; d }
+
+    var t1: [C, base];
+    var t2: [C, D];
+    var t3: [C1, D1];
+    var t4: [base1, C1];
+    var t5: [C1, F]
+
+    var e11 = t1[4]; // base
+                 ~
+!!! error TS2733: Index '4' is out-of-bounds in tuple of length 2.
+    var e21 = t2[4]; // {}
+                 ~
+!!! error TS2733: Index '4' is out-of-bounds in tuple of length 2.
+    var e31 = t3[4]; // C1
+                 ~
+!!! error TS2733: Index '4' is out-of-bounds in tuple of length 2.
+    var e41 = t4[2]; // base1
+                 ~
+!!! error TS2733: Index '2' is out-of-bounds in tuple of length 2.
+    var e51 = t5[2]; // {}
+                 ~
+!!! error TS2733: Index '2' is out-of-bounds in tuple of length 2.
+

tests/baselines/reference/castingTuple.errors.txt

@@ -6,6 +6,7 @@ tests/cases/conformance/types/tuple/castingTuple.ts(14,15): error TS2352: Conver
 tests/cases/conformance/types/tuple/castingTuple.ts(15,14): error TS2352: Conversion of type '[number, string]' to type '[number, string, boolean]' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
 tests/cases/conformance/types/tuple/castingTuple.ts(18,21): error TS2352: Conversion of type '[C, D]' to type '[C, D, A]' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
   Property '2' is missing in type '[C, D]'.
+tests/cases/conformance/types/tuple/castingTuple.ts(20,33): error TS2733: Index '5' is out-of-bounds in tuple of length 3.
 tests/cases/conformance/types/tuple/castingTuple.ts(30,10): error TS2352: Conversion of type '[number, string]' to type '[number, number]' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
   Type 'string' is not comparable to type 'number'.
 tests/cases/conformance/types/tuple/castingTuple.ts(31,10): error TS2352: Conversion of type '[C, D]' to type '[A, I]' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
@@ -15,7 +16,7 @@ tests/cases/conformance/types/tuple/castingTuple.ts(32,5): error TS2403: Subsequ
 tests/cases/conformance/types/tuple/castingTuple.ts(33,1): error TS2304: Cannot find name 't4'.
 
 
-==== tests/cases/conformance/types/tuple/castingTuple.ts (8 errors) ====
+==== tests/cases/conformance/types/tuple/castingTuple.ts (9 errors) ====
     interface I { }
     class A { a = 10; }
     class C implements I { c };
@@ -48,6 +49,8 @@ tests/cases/conformance/types/tuple/castingTuple.ts(33,1): error TS2304: Cannot
 !!! error TS2352:   Property '2' is missing in type '[C, D]'.
     var eleFromCDA1 = classCDATuple[2]; // A
     var eleFromCDA2 = classCDATuple[5]; // C | D | A
+                                    ~
+!!! error TS2733: Index '5' is out-of-bounds in tuple of length 3.
     var t10: [E1, E2] = [E1.one, E2.one];
     var t11 = <[number, number]>t10;
     var array1 = <{}[]>emptyObjTuple;

tests/baselines/reference/emptyTuplesTypeAssertion01.errors.txt

@@ -0,0 +1,8 @@
+tests/cases/conformance/types/tuple/emptyTuples/emptyTuplesTypeAssertion01.ts(2,11): error TS2733: Index '0' is out-of-bounds in tuple of length 0.
+
+
+==== tests/cases/conformance/types/tuple/emptyTuples/emptyTuplesTypeAssertion01.ts (1 errors) ====
+    let x = <[]>[];
+    let y = x[0];
+              ~
+!!! error TS2733: Index '0' is out-of-bounds in tuple of length 0.

tests/baselines/reference/emptyTuplesTypeAssertion02.errors.txt

@@ -0,0 +1,8 @@
+tests/cases/conformance/types/tuple/emptyTuples/emptyTuplesTypeAssertion02.ts(2,11): error TS2733: Index '0' is out-of-bounds in tuple of length 0.
+
+
+==== tests/cases/conformance/types/tuple/emptyTuples/emptyTuplesTypeAssertion02.ts (1 errors) ====
+    let x = [] as [];
+    let y = x[0];
+              ~
+!!! error TS2733: Index '0' is out-of-bounds in tuple of length 0.

tests/baselines/reference/genericCallWithTupleType.errors.txt

@@ -1,8 +1,11 @@
 tests/cases/conformance/types/typeRelationships/typeInference/genericCallWithTupleType.ts(12,1): error TS2322: Type '[string, number, boolean, boolean]' is not assignable to type '[string, number]'.
   Types of property 'length' are incompatible.
     Type '4' is not assignable to type '2'.
+tests/cases/conformance/types/typeRelationships/typeInference/genericCallWithTupleType.ts(13,20): error TS2733: Index '2' is out-of-bounds in tuple of length 2.
 tests/cases/conformance/types/typeRelationships/typeInference/genericCallWithTupleType.ts(14,1): error TS2322: Type '{ a: string; }' is not assignable to type 'string | number'.
   Type '{ a: string; }' is not assignable to type 'number'.
+tests/cases/conformance/types/typeRelationships/typeInference/genericCallWithTupleType.ts(14,11): error TS2733: Index '3' is out-of-bounds in tuple of length 2.
+tests/cases/conformance/types/typeRelationships/typeInference/genericCallWithTupleType.ts(15,20): error TS2733: Index '3' is out-of-bounds in tuple of length 2.
 tests/cases/conformance/types/typeRelationships/typeInference/genericCallWithTupleType.ts(22,14): error TS2322: Type 'number' is not assignable to type 'string'.
 tests/cases/conformance/types/typeRelationships/typeInference/genericCallWithTupleType.ts(22,17): error TS2322: Type 'string' is not assignable to type 'number'.
 tests/cases/conformance/types/typeRelationships/typeInference/genericCallWithTupleType.ts(23,14): error TS2322: Type '{}' is not assignable to type 'string'.
@@ -11,7 +14,7 @@ tests/cases/conformance/types/typeRelationships/typeInference/genericCallWithTup
   Property '1' is missing in type '[{}]'.
 
 
-==== tests/cases/conformance/types/typeRelationships/typeInference/genericCallWithTupleType.ts (7 errors) ====
+==== tests/cases/conformance/types/typeRelationships/typeInference/genericCallWithTupleType.ts (10 errors) ====
     interface I<T, U> {
         tuple1: [T, U];
     } 
@@ -29,11 +32,17 @@ tests/cases/conformance/types/typeRelationships/typeInference/genericCallWithTup
 !!! error TS2322:   Types of property 'length' are incompatible.
 !!! error TS2322:     Type '4' is not assignable to type '2'.
     var e3 = i1.tuple1[2];  // {}
+                       ~
+!!! error TS2733: Index '2' is out-of-bounds in tuple of length 2.
     i1.tuple1[3] = { a: "string" };
     ~~~~~~~~~~~~
 !!! error TS2322: Type '{ a: string; }' is not assignable to type 'string | number'.
 !!! error TS2322:   Type '{ a: string; }' is not assignable to type 'number'.
+              ~
+!!! error TS2733: Index '3' is out-of-bounds in tuple of length 2.
     var e4 = i1.tuple1[3];  // {}
+                       ~
+!!! error TS2733: Index '3' is out-of-bounds in tuple of length 2.
     i2.tuple1 = ["foo", 5];
     i2.tuple1 = ["foo", "bar"];
     i2.tuple1 = [5, "bar"];

tests/baselines/reference/indexerWithTuple.errors.txt

@@ -0,0 +1,47 @@
+tests/cases/conformance/types/tuple/indexerWithTuple.ts(11,25): error TS2733: Index '2' is out-of-bounds in tuple of length 2.
+tests/cases/conformance/types/tuple/indexerWithTuple.ts(17,27): error TS2733: Index '2' is out-of-bounds in tuple of length 2.
+tests/cases/conformance/types/tuple/indexerWithTuple.ts(20,30): error TS2733: Index '2' is out-of-bounds in tuple of length 2.
+tests/cases/conformance/types/tuple/indexerWithTuple.ts(28,30): error TS2733: Index '2' is out-of-bounds in tuple of length 2.
+
+
+==== tests/cases/conformance/types/tuple/indexerWithTuple.ts (4 errors) ====
+    var strNumTuple: [string, number] = ["foo", 10]; 
+    var numTupleTuple: [number, [string, number]] = [10, ["bar", 20]];
+    var unionTuple1: [number, string| number] = [10, "foo"]; 
+    var unionTuple2: [boolean, string| number] = [true, "foo"]; 
+
+    // no error
+    var idx0 = 0;
+    var idx1 = 1;
+    var ele10 = strNumTuple[0]; // string
+    var ele11 = strNumTuple[1]; // number
+    var ele12 = strNumTuple[2]; // string | number
+                            ~
+!!! error TS2733: Index '2' is out-of-bounds in tuple of length 2.
+    var ele13 = strNumTuple[idx0]; // string | number
+    var ele14 = strNumTuple[idx1]; // string | number
+    var ele15 = strNumTuple["0"]; // string
+    var ele16 = strNumTuple["1"]; // number
+    var strNumTuple1 = numTupleTuple[1];  //[string, number];
+    var ele17 = numTupleTuple[2]; // number | [string, number]
+                              ~
+!!! error TS2733: Index '2' is out-of-bounds in tuple of length 2.
+    var eleUnion10 = unionTuple1[0]; // number
+    var eleUnion11 = unionTuple1[1]; // string | number
+    var eleUnion12 = unionTuple1[2]; // string | number
+                                 ~
+!!! error TS2733: Index '2' is out-of-bounds in tuple of length 2.
+    var eleUnion13 = unionTuple1[idx0]; // string | number
+    var eleUnion14 = unionTuple1[idx1]; // string | number
+    var eleUnion15 = unionTuple1["0"]; // number
+    var eleUnion16 = unionTuple1["1"]; // string | number
+
+    var eleUnion20 = unionTuple2[0]; // boolean
+    var eleUnion21 = unionTuple2[1]; // string | number
+    var eleUnion22 = unionTuple2[2]; // string | number | boolean
+                                 ~
+!!! error TS2733: Index '2' is out-of-bounds in tuple of length 2.
+    var eleUnion23 = unionTuple2[idx0]; // string | number | boolean
+    var eleUnion24 = unionTuple2[idx1]; // string | number | boolean
+    var eleUnion25 = unionTuple2["0"]; // boolean
+    var eleUnion26 = unionTuple2["1"]; // string | number

tests/baselines/reference/tupleLengthCheck.errors.txt

@@ -0,0 +1,21 @@
+tests/cases/conformance/types/tuple/tupleLengthCheck.ts(5,14): error TS2733: Index '2' is out-of-bounds in tuple of length 2.
+tests/cases/conformance/types/tuple/tupleLengthCheck.ts(6,14): error TS2733: Index '1000' is out-of-bounds in tuple of length 2.
+
+
+==== tests/cases/conformance/types/tuple/tupleLengthCheck.ts (2 errors) ====
+    declare const a: [number, string]
+    declare const rest: [number, string, ...boolean[]]
+
+    const a1 = a[1]
+    const a2 = a[2]
+                 ~
+!!! error TS2733: Index '2' is out-of-bounds in tuple of length 2.
+    const a3 = a[1000]
+                 ~~~~
+!!! error TS2733: Index '1000' is out-of-bounds in tuple of length 2.
+
+    const a4 = rest[1]
+    const a5 = rest[2]
+    const a6 = rest[3]
+    const a7 = rest[1000]
+

tests/baselines/reference/tupleLengthCheck.js

@@ -0,0 +1,22 @@
+//// [tupleLengthCheck.ts]
+declare const a: [number, string]
+declare const rest: [number, string, ...boolean[]]
+
+const a1 = a[1]
+const a2 = a[2]
+const a3 = a[1000]
+
+const a4 = rest[1]
+const a5 = rest[2]
+const a6 = rest[3]
+const a7 = rest[1000]
+
+
+//// [tupleLengthCheck.js]
+var a1 = a[1];
+var a2 = a[2];
+var a3 = a[1000];
+var a4 = rest[1];
+var a5 = rest[2];
+var a6 = rest[3];
+var a7 = rest[1000];

tests/baselines/reference/tupleLengthCheck.symbols

@@ -0,0 +1,37 @@
+=== tests/cases/conformance/types/tuple/tupleLengthCheck.ts ===
+declare const a: [number, string]
+>a : Symbol(a, Decl(tupleLengthCheck.ts, 0, 13))
+
+declare const rest: [number, string, ...boolean[]]
+>rest : Symbol(rest, Decl(tupleLengthCheck.ts, 1, 13))
+
+const a1 = a[1]
+>a1 : Symbol(a1, Decl(tupleLengthCheck.ts, 3, 5))
+>a : Symbol(a, Decl(tupleLengthCheck.ts, 0, 13))
+>1 : Symbol(1)
+
+const a2 = a[2]
+>a2 : Symbol(a2, Decl(tupleLengthCheck.ts, 4, 5))
+>a : Symbol(a, Decl(tupleLengthCheck.ts, 0, 13))
+
+const a3 = a[1000]
+>a3 : Symbol(a3, Decl(tupleLengthCheck.ts, 5, 5))
+>a : Symbol(a, Decl(tupleLengthCheck.ts, 0, 13))
+
+const a4 = rest[1]
+>a4 : Symbol(a4, Decl(tupleLengthCheck.ts, 7, 5))
+>rest : Symbol(rest, Decl(tupleLengthCheck.ts, 1, 13))
+>1 : Symbol(1)
+
+const a5 = rest[2]
+>a5 : Symbol(a5, Decl(tupleLengthCheck.ts, 8, 5))
+>rest : Symbol(rest, Decl(tupleLengthCheck.ts, 1, 13))
+
+const a6 = rest[3]
+>a6 : Symbol(a6, Decl(tupleLengthCheck.ts, 9, 5))
+>rest : Symbol(rest, Decl(tupleLengthCheck.ts, 1, 13))
+
+const a7 = rest[1000]
+>a7 : Symbol(a7, Decl(tupleLengthCheck.ts, 10, 5))
+>rest : Symbol(rest, Decl(tupleLengthCheck.ts, 1, 13))
+

tests/baselines/reference/tupleLengthCheck.types

@@ -0,0 +1,49 @@
+=== tests/cases/conformance/types/tuple/tupleLengthCheck.ts ===
+declare const a: [number, string]
+>a : [number, string]
+
+declare const rest: [number, string, ...boolean[]]
+>rest : [number, string, ...boolean[]]
+
+const a1 = a[1]
+>a1 : string
+>a[1] : string
+>a : [number, string]
+>1 : 1
+
+const a2 = a[2]
+>a2 : string | number
+>a[2] : string | number
+>a : [number, string]
+>2 : 2
+
+const a3 = a[1000]
+>a3 : string | number
+>a[1000] : string | number
+>a : [number, string]
+>1000 : 1000
+
+const a4 = rest[1]
+>a4 : string
+>rest[1] : string
+>rest : [number, string, ...boolean[]]
+>1 : 1
+
+const a5 = rest[2]
+>a5 : boolean
+>rest[2] : boolean
+>rest : [number, string, ...boolean[]]
+>2 : 2
+
+const a6 = rest[3]
+>a6 : boolean
+>rest[3] : boolean
+>rest : [number, string, ...boolean[]]
+>3 : 3
+
+const a7 = rest[1000]
+>a7 : boolean
+>rest[1000] : boolean
+>rest : [number, string, ...boolean[]]
+>1000 : 1000
+