In getModifierOccurrences, support additional container kinds (microsoft#18947)

Author: Andy

src/services/documentHighlights.ts

@@ -302,12 +302,15 @@ namespace ts.DocumentHighlights {
         switch (container.kind) {
             case SyntaxKind.ModuleBlock:
             case SyntaxKind.SourceFile:
+            case SyntaxKind.Block:
+            case SyntaxKind.CaseClause:
+            case SyntaxKind.DefaultClause:
                 // Container is either a class declaration or the declaration is a classDeclaration
                 if (modifierFlag & ModifierFlags.Abstract) {
                     nodes = [...(<ClassDeclaration>declaration).members, declaration];
                 }
                 else {
-                    nodes = (<Block>container).statements;
+                    nodes = (<ModuleBlock | SourceFile | Block | CaseClause | DefaultClause>container).statements;
                 }
                 break;
             case SyntaxKind.Constructor:

tests/cases/fourslash/getOccurrencesAbstract03.ts

@@ -0,0 +1,21 @@
+/// <reference path='fourslash.ts' />
+
+// Tests that we don't crash when encountering an abstract class in these scopes:
+
+////function f() {
+////    [|abstract|] class A {
+////        [|abstract|] m(): void;
+////    }
+////    abstract class B {}
+////}
+////switch (0) {
+////    case 0:
+////        [|abstract|] class A { [|abstract|] m(): void; }
+////    default:
+////        [|abstract|] class B { [|abstract|] m(): void; }
+////}
+
+const [r0, r1, r2, r3, r4, r5] = test.ranges();
+verify.rangesAreDocumentHighlights([r0, r1]);
+verify.rangesAreDocumentHighlights([r2, r3]);
+verify.rangesAreDocumentHighlights([r4, r5]);