Add regression test for inlay hints crash on reparsed nodes (#2460)

[Copilot]

Regression test for the panic when computing inlay hints on a JS file using module.exports = function() {...}, which produces reparsed AST nodes. The fix (checking node.Flags&ast.NodeFlagsReparsed != 0 in inlay_hints.go) was applied in #2593; this test ensures it doesn't regress.

Changes

• internal/fourslash/tests/inlayHintsReparsedNodeCrash_test.go — fourslash test exercising inlay hints on a CommonJS module.exports function with return type and parameter hints enabled
• testdata/baselines/reference/fourslash/inlayHints/inlayHintsReparsedNodeCrash.baseline — expected baseline: : number return type hint on the anonymous function

// @allowJs: true
// @checkJs: true
module.exports = function () {
  return 1;
};
// inlay hint → `: number` return type

Original prompt

Add a regression test for the inlay hints crash reported in #2460, using the minimal reproduction from #2460 (comment).

The fix was applied in PR #2593, which added a check for node.Flags&ast.NodeFlagsReparsed != 0 in the visit method of internal/ls/inlay_hints.go. This test should verify that the fix works and would fail/panic without it.

What to do

Create a new test file at internal/fourslash/tests/inlayHintsReparsedNodeCrash_test.go with the following content:

package fourslash_test

import (
	"testing"

	"github.com/microsoft/typescript-go/internal/fourslash"
	"github.com/microsoft/typescript-go/internal/ls/lsutil"
	"github.com/microsoft/typescript-go/internal/testutil"
)

func TestInlayHintsReparsedNodeCrash(t *testing.T) {
	t.Parallel()

	defer testutil.RecoverAndFail(t, "Panic on fourslash test")
	const content = `
// @allowJs: true
// @checkJs: true

// @Filename: /a.js
module.exports = function () {
  return 1;
};
`

	f, done := fourslash.NewFourslash(t, nil /*capabilities*/, content)
	defer done()
	f.VerifyBaselineInlayHints(t, nil /*span*/, &lsutil.UserPreferences{InlayHints: lsutil.InlayHintsPreferences{
		IncludeInlayFunctionLikeReturnTypeHints: true,
		IncludeInlayFunctionParameterTypeHints:  true,
	}})
}

This follows the same patterns as other manually-written inlay hints tests in internal/fourslash/tests/ such as inlayHintsTupleTypeCrash_test.go and inlayHintsUsing_test.go.

Also generate/update the corresponding baseline file. Run the test to make sure it passes. The test exercises inlay hints on a JavaScript file using module.exports = function() { ... } which involves reparsed nodes. Without the fix from PR #2593, this would panic.

Verification

Confirm the test passes with the current code (which includes the fix from #2593). The key fix is in internal/ls/inlay_hints.go at line 63:

func (s *inlayHintState) visit(node *ast.Node) bool {
	if node == nil || node.End()-node.Pos() == 0 || node.Flags&ast.NodeFlagsReparsed != 0 {
		return false
	}

Without the node.Flags&ast.NodeFlagsReparsed != 0 check, the test would crash/panic when processing inlay hints on the reparsed nodes from the CommonJS module.exports pattern.

This pull request was created from Copilot chat.

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