feat(47983): Negative tuple index access should not be allowed (#49901)

* feat(47983): disallow negative integers for indexing tuple

* change error message

* add additional tests

Author: a-tarasyuk

src/compiler/checker.ts

@@ -15584,22 +15584,29 @@ namespace ts {
                         getFlowTypeOfReference(accessExpression, propType) :
                         propType;
                 }
-                if (everyType(objectType, isTupleType) && isNumericLiteralName(propName) && +propName >= 0) {
+                if (everyType(objectType, isTupleType) && isNumericLiteralName(propName)) {
+                    const index = +propName;
                     if (accessNode && everyType(objectType, t => !(t as TupleTypeReference).target.hasRestElement) && !(accessFlags & AccessFlags.NoTupleBoundsCheck)) {
                         const indexNode = getIndexNodeForAccessExpression(accessNode);
                         if (isTupleType(objectType)) {
+                            if (index < 0) {
+                                error(indexNode, Diagnostics.A_tuple_type_cannot_be_indexed_with_a_negative_value);
+                                return undefinedType;
+                            }
                             error(indexNode, Diagnostics.Tuple_type_0_of_length_1_has_no_element_at_index_2,
                                 typeToString(objectType), getTypeReferenceArity(objectType), unescapeLeadingUnderscores(propName));
                         }
                         else {
                             error(indexNode, Diagnostics.Property_0_does_not_exist_on_type_1, unescapeLeadingUnderscores(propName), typeToString(objectType));
                         }
                     }
-                    errorIfWritingToReadonlyIndex(getIndexInfoOfType(objectType, numberType));
-                    return mapType(objectType, t => {
-                        const restType = getRestTypeOfTupleType(t as TupleTypeReference) || undefinedType;
-                        return accessFlags & AccessFlags.IncludeUndefined ? getUnionType([restType, undefinedType]) : restType;
-                    });
+                    if (index >= 0) {
+                        errorIfWritingToReadonlyIndex(getIndexInfoOfType(objectType, numberType));
+                        return mapType(objectType, t => {
+                            const restType = getRestTypeOfTupleType(t as TupleTypeReference) || undefinedType;
+                            return accessFlags & AccessFlags.IncludeUndefined ? getUnionType([restType, undefinedType]) : restType;
+                        });
+                    }
                 }
             }
             if (!(indexType.flags & TypeFlags.Nullable) && isTypeAssignableToKind(indexType, TypeFlags.StringLike | TypeFlags.NumberLike | TypeFlags.ESSymbolLike)) {

src/compiler/diagnosticMessages.json

@@ -2360,6 +2360,10 @@
         "category": "Error",
         "code": 2513
     },
+    "A tuple type cannot be indexed with a negative value.": {
+        "category": "Error",
+        "code": 2514
+    },
     "Non-abstract class '{0}' does not implement inherited abstract member '{1}' from class '{2}'.": {
         "category": "Error",
         "code": 2515

tests/baselines/reference/indexerWithTuple.errors.txt

@@ -1,14 +1,16 @@
 tests/cases/conformance/types/tuple/indexerWithTuple.ts(11,25): error TS2493: Tuple type '[string, number]' of length '2' has no element at index '2'.
 tests/cases/conformance/types/tuple/indexerWithTuple.ts(17,27): error TS2493: Tuple type '[number, [string, number]]' of length '2' has no element at index '2'.
-tests/cases/conformance/types/tuple/indexerWithTuple.ts(20,30): error TS2493: Tuple type '[number, string | number]' of length '2' has no element at index '2'.
-tests/cases/conformance/types/tuple/indexerWithTuple.ts(28,30): error TS2493: Tuple type '[boolean, string | number]' of length '2' has no element at index '2'.
+tests/cases/conformance/types/tuple/indexerWithTuple.ts(18,25): error TS2514: A tuple type cannot be indexed with a negative value.
+tests/cases/conformance/types/tuple/indexerWithTuple.ts(22,30): error TS2493: Tuple type '[number, string | number]' of length '2' has no element at index '2'.
+tests/cases/conformance/types/tuple/indexerWithTuple.ts(30,30): error TS2493: Tuple type '[boolean, string | number]' of length '2' has no element at index '2'.
+tests/cases/conformance/types/tuple/indexerWithTuple.ts(38,28): error TS2514: A tuple type cannot be indexed with a negative value.
 
 
-==== tests/cases/conformance/types/tuple/indexerWithTuple.ts (4 errors) ====
-    var strNumTuple: [string, number] = ["foo", 10]; 
+==== tests/cases/conformance/types/tuple/indexerWithTuple.ts (6 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"]; 
+    var unionTuple1: [number, string| number] = [10, "foo"];
+    var unionTuple2: [boolean, string| number] = [true, "foo"];
 
     // no error
     var idx0 = 0;
@@ -26,6 +28,10 @@ tests/cases/conformance/types/tuple/indexerWithTuple.ts(28,30): error TS2493: Tu
     var ele17 = numTupleTuple[2]; // number | [string, number]
                               ~
 !!! error TS2493: Tuple type '[number, [string, number]]' of length '2' has no element at index '2'.
+    var ele19 = strNumTuple[-1]   // undefined
+                            ~~
+!!! error TS2514: A tuple type cannot be indexed with a negative value.
+    
     var eleUnion10 = unionTuple1[0]; // number
     var eleUnion11 = unionTuple1[1]; // string | number
     var eleUnion12 = unionTuple1[2]; // string | number
@@ -44,4 +50,11 @@ tests/cases/conformance/types/tuple/indexerWithTuple.ts(28,30): error TS2493: Tu
     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
+    var eleUnion26 = unionTuple2["1"]; // string | number
+    
+    type t1 = [string, number][0];  // string
+    type t2 = [string, number][1];  // number
+    type t3 = [string, number][-1]; // undefined
+                               ~~
+!!! error TS2514: A tuple type cannot be indexed with a negative value.
+    

tests/baselines/reference/indexerWithTuple.js

@@ -1,8 +1,8 @@
 //// [indexerWithTuple.ts]
-var strNumTuple: [string, number] = ["foo", 10]; 
+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"]; 
+var unionTuple1: [number, string| number] = [10, "foo"];
+var unionTuple2: [boolean, string| number] = [true, "foo"];
 
 // no error
 var idx0 = 0;
@@ -16,6 +16,8 @@ var ele15 = strNumTuple["0"]; // string
 var ele16 = strNumTuple["1"]; // number
 var strNumTuple1 = numTupleTuple[1];  //[string, number];
 var ele17 = numTupleTuple[2]; // number | [string, number]
+var ele19 = strNumTuple[-1]   // undefined
+
 var eleUnion10 = unionTuple1[0]; // number
 var eleUnion11 = unionTuple1[1]; // string | number
 var eleUnion12 = unionTuple1[2]; // string | number
@@ -30,7 +32,12 @@ var eleUnion22 = unionTuple2[2]; // string | number | boolean
 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
+var eleUnion26 = unionTuple2["1"]; // string | number
+
+type t1 = [string, number][0];  // string
+type t2 = [string, number][1];  // number
+type t3 = [string, number][-1]; // undefined
+
 
 //// [indexerWithTuple.js]
 var strNumTuple = ["foo", 10];
@@ -49,6 +56,7 @@ var ele15 = strNumTuple["0"]; // string
 var ele16 = strNumTuple["1"]; // number
 var strNumTuple1 = numTupleTuple[1]; //[string, number];
 var ele17 = numTupleTuple[2]; // number | [string, number]
+var ele19 = strNumTuple[-1]; // undefined
 var eleUnion10 = unionTuple1[0]; // number
 var eleUnion11 = unionTuple1[1]; // string | number
 var eleUnion12 = unionTuple1[2]; // string | number

tests/baselines/reference/indexerWithTuple.symbols

@@ -1,14 +1,14 @@
 === tests/cases/conformance/types/tuple/indexerWithTuple.ts ===
-var strNumTuple: [string, number] = ["foo", 10]; 
+var strNumTuple: [string, number] = ["foo", 10];
 >strNumTuple : Symbol(strNumTuple, Decl(indexerWithTuple.ts, 0, 3))
 
 var numTupleTuple: [number, [string, number]] = [10, ["bar", 20]];
 >numTupleTuple : Symbol(numTupleTuple, Decl(indexerWithTuple.ts, 1, 3))
 
-var unionTuple1: [number, string| number] = [10, "foo"]; 
+var unionTuple1: [number, string| number] = [10, "foo"];
 >unionTuple1 : Symbol(unionTuple1, Decl(indexerWithTuple.ts, 2, 3))
 
-var unionTuple2: [boolean, string| number] = [true, "foo"]; 
+var unionTuple2: [boolean, string| number] = [true, "foo"];
 >unionTuple2 : Symbol(unionTuple2, Decl(indexerWithTuple.ts, 3, 3))
 
 // no error
@@ -61,71 +61,84 @@ var ele17 = numTupleTuple[2]; // number | [string, number]
 >ele17 : Symbol(ele17, Decl(indexerWithTuple.ts, 16, 3))
 >numTupleTuple : Symbol(numTupleTuple, Decl(indexerWithTuple.ts, 1, 3))
 
+var ele19 = strNumTuple[-1]   // undefined
+>ele19 : Symbol(ele19, Decl(indexerWithTuple.ts, 17, 3))
+>strNumTuple : Symbol(strNumTuple, Decl(indexerWithTuple.ts, 0, 3))
+
 var eleUnion10 = unionTuple1[0]; // number
->eleUnion10 : Symbol(eleUnion10, Decl(indexerWithTuple.ts, 17, 3))
+>eleUnion10 : Symbol(eleUnion10, Decl(indexerWithTuple.ts, 19, 3))
 >unionTuple1 : Symbol(unionTuple1, Decl(indexerWithTuple.ts, 2, 3))
 >0 : Symbol(0)
 
 var eleUnion11 = unionTuple1[1]; // string | number
->eleUnion11 : Symbol(eleUnion11, Decl(indexerWithTuple.ts, 18, 3))
+>eleUnion11 : Symbol(eleUnion11, Decl(indexerWithTuple.ts, 20, 3))
 >unionTuple1 : Symbol(unionTuple1, Decl(indexerWithTuple.ts, 2, 3))
 >1 : Symbol(1)
 
 var eleUnion12 = unionTuple1[2]; // string | number
->eleUnion12 : Symbol(eleUnion12, Decl(indexerWithTuple.ts, 19, 3))
+>eleUnion12 : Symbol(eleUnion12, Decl(indexerWithTuple.ts, 21, 3))
 >unionTuple1 : Symbol(unionTuple1, Decl(indexerWithTuple.ts, 2, 3))
 
 var eleUnion13 = unionTuple1[idx0]; // string | number
->eleUnion13 : Symbol(eleUnion13, Decl(indexerWithTuple.ts, 20, 3))
+>eleUnion13 : Symbol(eleUnion13, Decl(indexerWithTuple.ts, 22, 3))
 >unionTuple1 : Symbol(unionTuple1, Decl(indexerWithTuple.ts, 2, 3))
 >idx0 : Symbol(idx0, Decl(indexerWithTuple.ts, 6, 3))
 
 var eleUnion14 = unionTuple1[idx1]; // string | number
->eleUnion14 : Symbol(eleUnion14, Decl(indexerWithTuple.ts, 21, 3))
+>eleUnion14 : Symbol(eleUnion14, Decl(indexerWithTuple.ts, 23, 3))
 >unionTuple1 : Symbol(unionTuple1, Decl(indexerWithTuple.ts, 2, 3))
 >idx1 : Symbol(idx1, Decl(indexerWithTuple.ts, 7, 3))
 
 var eleUnion15 = unionTuple1["0"]; // number
->eleUnion15 : Symbol(eleUnion15, Decl(indexerWithTuple.ts, 22, 3))
+>eleUnion15 : Symbol(eleUnion15, Decl(indexerWithTuple.ts, 24, 3))
 >unionTuple1 : Symbol(unionTuple1, Decl(indexerWithTuple.ts, 2, 3))
 >"0" : Symbol(0)
 
 var eleUnion16 = unionTuple1["1"]; // string | number
->eleUnion16 : Symbol(eleUnion16, Decl(indexerWithTuple.ts, 23, 3))
+>eleUnion16 : Symbol(eleUnion16, Decl(indexerWithTuple.ts, 25, 3))
 >unionTuple1 : Symbol(unionTuple1, Decl(indexerWithTuple.ts, 2, 3))
 >"1" : Symbol(1)
 
 var eleUnion20 = unionTuple2[0]; // boolean
->eleUnion20 : Symbol(eleUnion20, Decl(indexerWithTuple.ts, 25, 3))
+>eleUnion20 : Symbol(eleUnion20, Decl(indexerWithTuple.ts, 27, 3))
 >unionTuple2 : Symbol(unionTuple2, Decl(indexerWithTuple.ts, 3, 3))
 >0 : Symbol(0)
 
 var eleUnion21 = unionTuple2[1]; // string | number
->eleUnion21 : Symbol(eleUnion21, Decl(indexerWithTuple.ts, 26, 3))
+>eleUnion21 : Symbol(eleUnion21, Decl(indexerWithTuple.ts, 28, 3))
 >unionTuple2 : Symbol(unionTuple2, Decl(indexerWithTuple.ts, 3, 3))
 >1 : Symbol(1)
 
 var eleUnion22 = unionTuple2[2]; // string | number | boolean
->eleUnion22 : Symbol(eleUnion22, Decl(indexerWithTuple.ts, 27, 3))
+>eleUnion22 : Symbol(eleUnion22, Decl(indexerWithTuple.ts, 29, 3))
 >unionTuple2 : Symbol(unionTuple2, Decl(indexerWithTuple.ts, 3, 3))
 
 var eleUnion23 = unionTuple2[idx0]; // string | number | boolean
->eleUnion23 : Symbol(eleUnion23, Decl(indexerWithTuple.ts, 28, 3))
+>eleUnion23 : Symbol(eleUnion23, Decl(indexerWithTuple.ts, 30, 3))
 >unionTuple2 : Symbol(unionTuple2, Decl(indexerWithTuple.ts, 3, 3))
 >idx0 : Symbol(idx0, Decl(indexerWithTuple.ts, 6, 3))
 
 var eleUnion24 = unionTuple2[idx1]; // string | number | boolean
->eleUnion24 : Symbol(eleUnion24, Decl(indexerWithTuple.ts, 29, 3))
+>eleUnion24 : Symbol(eleUnion24, Decl(indexerWithTuple.ts, 31, 3))
 >unionTuple2 : Symbol(unionTuple2, Decl(indexerWithTuple.ts, 3, 3))
 >idx1 : Symbol(idx1, Decl(indexerWithTuple.ts, 7, 3))
 
 var eleUnion25 = unionTuple2["0"]; // boolean
->eleUnion25 : Symbol(eleUnion25, Decl(indexerWithTuple.ts, 30, 3))
+>eleUnion25 : Symbol(eleUnion25, Decl(indexerWithTuple.ts, 32, 3))
 >unionTuple2 : Symbol(unionTuple2, Decl(indexerWithTuple.ts, 3, 3))
 >"0" : Symbol(0)
 
 var eleUnion26 = unionTuple2["1"]; // string | number
->eleUnion26 : Symbol(eleUnion26, Decl(indexerWithTuple.ts, 31, 3))
+>eleUnion26 : Symbol(eleUnion26, Decl(indexerWithTuple.ts, 33, 3))
 >unionTuple2 : Symbol(unionTuple2, Decl(indexerWithTuple.ts, 3, 3))
 >"1" : Symbol(1)
 
+type t1 = [string, number][0];  // string
+>t1 : Symbol(t1, Decl(indexerWithTuple.ts, 33, 34))
+
+type t2 = [string, number][1];  // number
+>t2 : Symbol(t2, Decl(indexerWithTuple.ts, 35, 30))
+
+type t3 = [string, number][-1]; // undefined
+>t3 : Symbol(t3, Decl(indexerWithTuple.ts, 36, 30))
+

tests/baselines/reference/indexerWithTuple.types

@@ -1,5 +1,5 @@
 === tests/cases/conformance/types/tuple/indexerWithTuple.ts ===
-var strNumTuple: [string, number] = ["foo", 10]; 
+var strNumTuple: [string, number] = ["foo", 10];
 >strNumTuple : [string, number]
 >["foo", 10] : [string, number]
 >"foo" : "foo"
@@ -13,13 +13,13 @@ var numTupleTuple: [number, [string, number]] = [10, ["bar", 20]];
 >"bar" : "bar"
 >20 : 20
 
-var unionTuple1: [number, string| number] = [10, "foo"]; 
+var unionTuple1: [number, string| number] = [10, "foo"];
 >unionTuple1 : [number, string | number]
 >[10, "foo"] : [number, string]
 >10 : 10
 >"foo" : "foo"
 
-var unionTuple2: [boolean, string| number] = [true, "foo"]; 
+var unionTuple2: [boolean, string| number] = [true, "foo"];
 >unionTuple2 : [boolean, string | number]
 >[true, "foo"] : [true, string]
 >true : true
@@ -88,6 +88,13 @@ var ele17 = numTupleTuple[2]; // number | [string, number]
 >numTupleTuple : [number, [string, number]]
 >2 : 2
 
+var ele19 = strNumTuple[-1]   // undefined
+>ele19 : undefined
+>strNumTuple[-1] : undefined
+>strNumTuple : [string, number]
+>-1 : -1
+>1 : 1
+
 var eleUnion10 = unionTuple1[0]; // number
 >eleUnion10 : number
 >unionTuple1[0] : number
@@ -172,3 +179,14 @@ var eleUnion26 = unionTuple2["1"]; // string | number
 >unionTuple2 : [boolean, string | number]
 >"1" : "1"
 
+type t1 = [string, number][0];  // string
+>t1 : string
+
+type t2 = [string, number][1];  // number
+>t2 : number
+
+type t3 = [string, number][-1]; // undefined
+>t3 : undefined
+>-1 : -1
+>1 : 1
+

tests/cases/conformance/types/tuple/indexerWithTuple.ts

@@ -1,7 +1,7 @@
-var strNumTuple: [string, number] = ["foo", 10]; 
+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"]; 
+var unionTuple1: [number, string| number] = [10, "foo"];
+var unionTuple2: [boolean, string| number] = [true, "foo"];
 
 // no error
 var idx0 = 0;
@@ -15,6 +15,8 @@ var ele15 = strNumTuple["0"]; // string
 var ele16 = strNumTuple["1"]; // number
 var strNumTuple1 = numTupleTuple[1];  //[string, number];
 var ele17 = numTupleTuple[2]; // number | [string, number]
+var ele19 = strNumTuple[-1]   // undefined
+
 var eleUnion10 = unionTuple1[0]; // number
 var eleUnion11 = unionTuple1[1]; // string | number
 var eleUnion12 = unionTuple1[2]; // string | number
@@ -29,4 +31,8 @@ var eleUnion22 = unionTuple2[2]; // string | number | boolean
 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
+var eleUnion26 = unionTuple2["1"]; // string | number
+
+type t1 = [string, number][0];  // string
+type t2 = [string, number][1];  // number
+type t3 = [string, number][-1]; // undefined