fix(36023): fix crash in document highlight service (#36233)

src/services/documentHighlights.ts

@@ -66,8 +66,12 @@ namespace ts {
                 case SyntaxKind.SwitchKeyword:
                     return useParent(node.parent, isSwitchStatement, getSwitchCaseDefaultOccurrences);
                 case SyntaxKind.CaseKeyword:
-                case SyntaxKind.DefaultKeyword:
-                    return useParent(node.parent.parent.parent, isSwitchStatement, getSwitchCaseDefaultOccurrences);
+                case SyntaxKind.DefaultKeyword: {
+                    if (isDefaultClause(node.parent) || isCaseClause(node.parent)) {
+                        return useParent(node.parent.parent.parent, isSwitchStatement, getSwitchCaseDefaultOccurrences);
+                    }
+                    return undefined;
+                }
                 case SyntaxKind.BreakKeyword:
                 case SyntaxKind.ContinueKeyword:
                     return useParent(node.parent, isBreakOrContinueStatement, getBreakOrContinueStatementOccurrences);

tests/cases/fourslash/documentHighlightDefaultInKeyword.ts

@@ -0,0 +1,8 @@
+/// <reference path='fourslash.ts'/>
+
+////[|case|]
+////[|default|]
+
+const [defaultKeywordRange, caseKeywordRange] = test.ranges();
+verify.noDocumentHighlights(defaultKeywordRange);
+verify.noDocumentHighlights(caseKeywordRange);

tests/cases/fourslash/documentHighlightDefaultInSwitch.ts

@@ -0,0 +1,13 @@
+/// <reference path='fourslash.ts'/>
+
+////const foo = 'foo';
+////[|switch|] (foo) {
+////   [|case|] 'foo':
+////       [|break|];
+////   [|default|]:
+////       [|break|];
+////}
+
+const [r0, r1, r2, r3, r4] = test.ranges();
+verify.documentHighlightsOf(r1, [r0, r1, r2, r3, r4]);
+verify.documentHighlightsOf(r4, [r0, r1, r2, r3, r4]);