Fix crash in import statement completions (#2805)

Author: Andarist

internal/fourslash/tests/completionsAtTopLevelImportAssignmentNoCrash1_test.go

@@ -0,0 +1,35 @@
+package fourslash_test
+
+import (
+	"testing"
+
+	"github.com/microsoft/typescript-go/internal/fourslash"
+	"github.com/microsoft/typescript-go/internal/testutil"
+)
+
+func TestCompletionsAtTopLevelImportAssignmentNoCrash1(t *testing.T) {
+	t.Parallel()
+	defer testutil.RecoverAndFail(t, "Panic on fourslash test")
+
+	const content = `// @filename: /a.ts
+import x =/*1*/
+class Foo {}
+// @filename: /b.ts
+import x = /*2*/
+class Foo {}
+// @filename: /c.ts
+import x =/*3*/
+`
+	f, done := fourslash.NewFourslash(t, nil /*capabilities*/, content)
+	defer done()
+
+	f.VerifyCompletions(t, []string{"1", "2", "3"}, &fourslash.CompletionsExpectedList{
+		IsIncomplete: false,
+		ItemDefaults: &fourslash.CompletionsExpectedItemDefaults{
+			CommitCharacters: &[]string{},
+		},
+		Items: &fourslash.CompletionsExpectedItems{
+			Includes: []fourslash.CompletionsExpectedItem{}, // no crash check
+		},
+	})
+}

internal/ls/completions.go

@@ -670,7 +670,7 @@ func (l *LanguageService) getCompletionData(
 	symbolToSortTextMap := map[ast.SymbolId]SortText{}
 	var seenPropertySymbols collections.Set[ast.SymbolId]
 	isTypeOnlyLocation := insideJSDocTagTypeExpression || insideJsDocImportTag ||
-		importStatementCompletion != nil && ast.IsTypeOnlyImportOrExportDeclaration(location.Parent) ||
+		importStatementCompletion != nil && location.Parent != nil && ast.IsTypeOnlyImportOrExportDeclaration(location.Parent) ||
 		!isContextTokenValueLocation(contextToken) &&
 			(isPossiblyTypeArgumentPosition(contextToken, file, typeChecker) ||
 				ast.IsPartOfTypeNode(location) ||