add support for rest types elements in the middle of a tuple

javascript/extractor/lib/typescript/src/type_table.ts

@@ -632,7 +632,14 @@ export class TypeTable {
           ? tupleType.minLength
           : this.typeChecker.getTypeArguments(tupleReference).length;
       let hasRestElement = tupleType.hasRestElement ? 't' : 'f';
-      let prefix = `tuple;${minLength};${hasRestElement}`;
+      let restIndex = -1;
+      for (let i = 0; i < tupleType.elementFlags.length; i++) {
+        if (tupleType.elementFlags[i] & ts.ElementFlags.Rest) {
+          restIndex = i;
+          break;
+        }
+      }
+      let prefix = `tuple;${minLength};${restIndex}`;
       return this.makeTypeStringVectorFromTypeReferenceArguments(prefix, type);
     }
     if (objectFlags & ts.ObjectFlags.Anonymous) {

javascript/extractor/src/com/semmle/ts/extractor/TypeExtractor.java

@@ -118,10 +118,11 @@ public class TypeExtractor {
         }
       case tupleKind:
         {
-          // The first two parts denote minimum length and presence of rest element.
+          // The first two parts denote minimum length and index of rest element (or -1 if no rest element).
           trapWriter.addTuple("tuple_type_min_length", lbl, Integer.parseInt(parts[1]));
-          if (parts[2].equals("t")) {
-            trapWriter.addTuple("tuple_type_rest", lbl);
+          int restIndex = Integer.parseInt(parts[2]);
+          if (restIndex != -1) {
+            trapWriter.addTuple("tuple_type_rest_index", lbl, restIndex);
           }
           firstChild += 2;
           break;

javascript/ql/src/semmle/javascript/TypeScript.qll

@@ -2149,18 +2149,23 @@ class TupleType extends ArrayType, @tuple_type {
   int getMinimumLength() { tuple_type_min_length(this, result) }
 
   /**
-   * Holds if this tuple type ends with a rest element, such as `[number, ...string[]]`.
+   * Gets the index of the rest element.
+   * E.g. for a type `[number, ...string[]]` the result is 1,
+   * or for a type `[...number[], string]` the result is 0.
    */
-  predicate hasRestElement() { tuple_type_rest(this) }
+  int getRestElementIndex() { tuple_type_rest_index(this, result) }
+
+  /**
+   * Holds if this tuple type has a rest element, such as `[number, ...string[]]` or `[...number[], string]`.
+   */
+  predicate hasRestElement() { exists(getRestElementIndex()) }
 
   /**
    * Gets the type of the rest element, if there is one.
    *
    * For example, the rest element of `[number, ...string[]]` is `string`.
    */
-  Type getRestElementType() {
-    hasRestElement() and result = getElementType(getNumElementType() - 1)
-  }
+  Type getRestElementType() { result = getElementType(getRestElementIndex()) }
 }
 
 /**

javascript/ql/src/semmlecode.javascript.dbscheme

@@ -799,8 +799,9 @@ tuple_type_min_length(
   int minLength: int ref
 );
 
-tuple_type_rest(
-  unique int typ: @type ref
+tuple_type_rest_index(
+  unique int typ: @type ref,
+  int index: int ref
 );
 
 // comments

javascript/ql/test/library-tests/TypeScript/Types/middle-rest.ts

@@ -0,0 +1,3 @@
+let foo: [boolean, ...string[], number];
+
+foo = [true, "hello", 123];

javascript/ql/test/library-tests/TypeScript/Types/tests.expected

@@ -15,6 +15,13 @@ getExprType
 | boolean-type.ts:15:5:15:12 | boolean6 | boolean |
 | dummy.ts:2:12:2:12 | x | number |
 | dummy.ts:2:16:2:16 | 5 | 5 |
+| middle-rest.ts:1:5:1:7 | foo | [boolean, ...string[], number] |
+| middle-rest.ts:3:1:3:3 | foo | [boolean, ...string[], number] |
+| middle-rest.ts:3:1:3:26 | foo = [ ... ", 123] | [true, string, number] |
+| middle-rest.ts:3:7:3:26 | [true, "hello", 123] | [boolean, ...string[], number] |
+| middle-rest.ts:3:8:3:11 | true | true |
+| middle-rest.ts:3:14:3:20 | "hello" | "hello" |
+| middle-rest.ts:3:23:3:25 | 123 | 123 |
 | tst.ts:1:13:1:17 | dummy | typeof library-tests/TypeScript/Types/dummy.ts |
 | tst.ts:1:24:1:32 | "./dummy" | any |
 | tst.ts:3:5:3:10 | numVar | number |
@@ -185,6 +192,12 @@ getTypeExprType
 | boolean-type.ts:15:15:15:19 | false | false |
 | boolean-type.ts:15:15:15:29 | false \| boolean | boolean |
 | boolean-type.ts:15:23:15:29 | boolean | boolean |
+| middle-rest.ts:1:10:1:39 | [boolea ... number] | [boolean, ...string[], number] |
+| middle-rest.ts:1:11:1:17 | boolean | boolean |
+| middle-rest.ts:1:20:1:30 | ...string[] | string |
+| middle-rest.ts:1:23:1:28 | string | string |
+| middle-rest.ts:1:23:1:30 | string[] | string[] |
+| middle-rest.ts:1:33:1:38 | number | number |
 | tst.ts:3:13:3:18 | number | number |
 | tst.ts:9:13:9:18 | string | string |
 | tst.ts:14:20:14:25 | string | string |
@@ -311,6 +324,18 @@ referenceDefinition
 | ValueOrArray<number> | type_alias.ts:5:1:5:50 | type Va ... ay<T>>; |
 | VirtualNode | type_alias.ts:19:1:21:57 | type Vi ... ode[]]; |
 tupleTypes
+| middle-rest.ts:1:5:1:7 | foo | [boolean, ...string[], number] | 0 | boolean | 2 | string |
+| middle-rest.ts:1:5:1:7 | foo | [boolean, ...string[], number] | 1 | string | 2 | string |
+| middle-rest.ts:1:5:1:7 | foo | [boolean, ...string[], number] | 2 | number | 2 | string |
+| middle-rest.ts:3:1:3:3 | foo | [boolean, ...string[], number] | 0 | boolean | 2 | string |
+| middle-rest.ts:3:1:3:3 | foo | [boolean, ...string[], number] | 1 | string | 2 | string |
+| middle-rest.ts:3:1:3:3 | foo | [boolean, ...string[], number] | 2 | number | 2 | string |
+| middle-rest.ts:3:1:3:26 | foo = [ ... ", 123] | [true, string, number] | 0 | true | 3 | no-rest |
+| middle-rest.ts:3:1:3:26 | foo = [ ... ", 123] | [true, string, number] | 1 | string | 3 | no-rest |
+| middle-rest.ts:3:1:3:26 | foo = [ ... ", 123] | [true, string, number] | 2 | number | 3 | no-rest |
+| middle-rest.ts:3:7:3:26 | [true, "hello", 123] | [boolean, ...string[], number] | 0 | boolean | 2 | string |
+| middle-rest.ts:3:7:3:26 | [true, "hello", 123] | [boolean, ...string[], number] | 1 | string | 2 | string |
+| middle-rest.ts:3:7:3:26 | [true, "hello", 123] | [boolean, ...string[], number] | 2 | number | 2 | string |
 | tst.ts:34:5:34:9 | tuple | [number, string] | 0 | number | 2 | no-rest |
 | tst.ts:34:5:34:9 | tuple | [number, string] | 1 | string | 2 | no-rest |
 | tst.ts:36:5:36:28 | tupleWi ... Element | [number, string, number?] | 0 | number | 2 | no-rest |

javascript/upgrades/930898a4fe07cb48de46800904922ca118b31e50/tuple_type_rest_index.ql

@@ -0,0 +1,9 @@
+class TupleType extends @tuple_type {
+  predicate hasChild(int i) { type_child(_, this, i) }
+
+  string toString() { result = "" }
+}
+
+from TupleType tuple, int index
+where index = max(int i | tuple.hasChild(i))
+select tuple, index

javascript/upgrades/930898a4fe07cb48de46800904922ca118b31e50/upgrade.properties

@@ -0,0 +1,4 @@
+description: add support for TypeScript 4.2
+compatibility: full
+tuple_type_rest_index.rel: run tuple_type_rest_index.qlo
+tuple_type_rest.rel: delete