Suggest completions within tuple type arguments

Author: mkantor

src/services/completions.ts

@@ -5794,6 +5794,8 @@ export function getConstraintOfTypeArgumentProperty(node: Node, checker: TypeChe
         case SyntaxKind.TypeLiteral:
         case SyntaxKind.UnionType:
             return t;
+        case SyntaxKind.OpenBracketToken:
+            return checker.getElementTypeOfArrayType(t);
     }
 }
 

tests/cases/fourslash/completionListInTypeLiteralInTypeParameter21.ts

@@ -0,0 +1,18 @@
+/// <reference path="fourslash.ts" />
+
+////class Foo<T extends ('one' | 2)[]> {}
+////function foo<T extends ('one' | 2)[]>() {}
+////
+////type A = Foo<[/*0*/]>;
+////new Foo<[/*1*/]>();
+////foo<[/*2*/]>();
+////foo<[/*3*/]>;
+////Foo<[/*4*/]>;
+
+verify.completions(
+    { marker: "0", includes: ['"one"', '2'], isNewIdentifierLocation: true },
+    { marker: "1", includes: ['"one"', '2'], isNewIdentifierLocation: true },
+    { marker: "2", includes: ['"one"', '2'], isNewIdentifierLocation: true },
+    { marker: "3", includes: ['"one"', '2'], isNewIdentifierLocation: true },
+    { marker: "4", includes: ['"one"', '2'], isNewIdentifierLocation: true }
+);