fix(47783): show globals completion in case keyword outside of switch statement (microsoft#47786)

Author: a-tarasyuk

src/services/completions.ts

@@ -1680,7 +1680,8 @@ namespace ts.Completions {
             case SyntaxKind.NewKeyword:
                 return checker.getContextualType(parent as Expression);
             case SyntaxKind.CaseKeyword:
-                return getSwitchedType(cast(parent, isCaseClause), checker);
+                const caseClause = tryCast(parent, isCaseClause);
+                return caseClause ? getSwitchedType(caseClause, checker) : undefined;
             case SyntaxKind.OpenBraceToken:
                 return isJsxExpression(parent) && !isJsxElement(parent.parent) && !isJsxFragment(parent.parent) ? checker.getContextualTypeForJsxAttribute(parent.parent) : undefined;
             default:

tests/cases/fourslash/completionAtCaseClause.ts

@@ -0,0 +1,6 @@
+/// <reference path="fourslash.ts" />
+
+////case /**/
+
+verify.completions({ marker: "", exact: completion.globals });
+