Fixed a class member completion crash after JSDoc comment with degenerate JSDoc tag in it

internal/astnav/tokens.go

@@ -579,7 +579,11 @@ func findRightmostValidToken(endPos int, sourceFile *ast.SourceFile, containingN
 		if rightmostValidNode != nil {
 			endPos = rightmostValidNode.End()
 		}
-		return find(rightmostValidNode, endPos)
+		result := find(rightmostValidNode, endPos)
+		if result == nil && n != containingNode {
+			return n
+		}
+		return result
 	}
 
 	return find(containingNode, endPos)

internal/fourslash/tests/completionsAtTopLevelImportAssignmentNoCrash1_test.go

@@ -28,8 +28,6 @@ import x =/*3*/
 		ItemDefaults: &fourslash.CompletionsExpectedItemDefaults{
 			CommitCharacters: &[]string{},
 		},
-		Items: &fourslash.CompletionsExpectedItems{
-			Includes: []fourslash.CompletionsExpectedItem{}, // no crash check
-		},
+		Items: &fourslash.CompletionsExpectedItems{},
 	})
 }

internal/fourslash/tests/manual/completionClassMemberAfterJSDocWithInvalidJSDocTagInTheComment1_test.go

@@ -0,0 +1,38 @@
+package fourslash_test
+
+import (
+	"testing"
+
+	"github.com/microsoft/typescript-go/internal/fourslash"
+	. "github.com/microsoft/typescript-go/internal/fourslash/tests/util"
+	"github.com/microsoft/typescript-go/internal/testutil"
+)
+
+func TestCompletionClassMemberAfterJSDocWithInvalidJSDocTagInTheComment1(t *testing.T) {
+	t.Parallel()
+	defer testutil.RecoverAndFail(t, "Panic on fourslash test")
+	const content = `export class NeedsPrefix {
+  private _prefixes: {
+    add: Record<string, any>;
+    browsers: {selected: string[]};
+  };
+
+  constructor(browsers: string[]) {
+  }
+
+  /** Checks whether an @-rule needs to be prefixed. */
+  /**/atRule(identifier: string): boolean {
+    return true;
+  }
+}`
+	f, done := fourslash.NewFourslash(t, nil /*capabilities*/, content)
+	defer done()
+	f.VerifyCompletions(t, "", &fourslash.CompletionsExpectedList{
+		IsIncomplete: false,
+		ItemDefaults: &fourslash.CompletionsExpectedItemDefaults{
+			CommitCharacters: &[]string{},
+			EditRange:        Ignored,
+		},
+		Items: &fourslash.CompletionsExpectedItems{},
+	})
+}