fix(31909): show suggestions for second type argument of generic (#36024)

Author: a-tarasyuk

src/services/completions.ts

@@ -2077,7 +2077,7 @@ namespace ts.Completions {
             switch (contextToken.kind) {
                 case SyntaxKind.CommaToken:
                     return containingNodeKind === SyntaxKind.VariableDeclaration ||
-                        containingNodeKind === SyntaxKind.VariableDeclarationList ||
+                        isVariableDeclarationListButNotTypeArgument(contextToken) ||
                         containingNodeKind === SyntaxKind.VariableStatement ||
                         containingNodeKind === SyntaxKind.EnumDeclaration ||                        // enum a { foo, |
                         isFunctionLikeButNotConstructor(containingNodeKind) ||
@@ -2209,6 +2209,11 @@ namespace ts.Completions {
             return false;
         }
 
+        function isVariableDeclarationListButNotTypeArgument(node: Node): boolean {
+            return node.parent.kind === SyntaxKind.VariableDeclarationList
+                && !isPossiblyTypeArgumentPosition(node, sourceFile, typeChecker);
+        }
+
         /**
          * Filters out completion suggestions for named imports or exports.
          *

tests/cases/fourslash/completionsAtGenericTypeArguments.ts

@@ -0,0 +1,12 @@
+/// <reference path='fourslash.ts' />
+
+////class Foo<T1, T2> {}
+////const foo = new Foo</*1*/, /*2*/,
+////
+////function foo<T1, T2>() {}
+////const f = foo</*3*/, /*4*/,
+
+verify.completions({ marker: "1", exact: completion.globalTypesPlus(['Foo']) });
+verify.completions({ marker: "2", exact: completion.globalTypesPlus(['Foo']) });
+verify.completions({ marker: "3", exact: completion.globalTypesPlus(['Foo']) });
+verify.completions({ marker: "4", exact: completion.globalTypesPlus(['Foo']) });