type actionDesc struct {
	pos    poser
	format string
	args   []interface{}
}

// A Checker maintains the state of the type checker.
// It must be created with NewChecker.
type Checker struct {
	// package information
	// (initialized by NewChecker, valid for the life-time of checker)
	conf *Config
	ctxt *Context // context for de-duplicating instances
	pkg  *Package
	*Info

	if err != nil {
		return err
	}

	check := newChecker(pass, filename, nil)
	check.nonGoFile(token.Pos(tf.Base()), string(content))
	return nil
}

type checker struct {
	pass     *analysis.Pass
	filename string
	file     *ast.File // nil for non-Go file
	inHeader bool      // in file header (before or adjoining package declaration)
}

func newChecker(pass *analysis.Pass, filename string, file *ast.File) *checker {

type actionDesc struct {
	pos    positioner
	format string
	args   []any
}

// A Checker maintains the state of the type checker.
// It must be created with [NewChecker].
type Checker struct {
	// package information
	// (initialized by NewChecker, valid for the life-time of checker)
	conf *Config
	ctxt *Context // context for de-duplicating instances
	fset *token.FileSet
	pkg  *Package
	*Info

			}
			// s == nil || s == pkg.scope
			if s == nil {
				return fmt.Errorf("no position %s found in package %s", fset.Position(pos), pkg.name)
			}
		}
	}

	// initialize checker
	check := NewChecker(nil, fset, pkg, info)
	check.scope = scope
	check.pos = pos
	defer check.handleBailout(&err)

	// evaluate node
	var x operand
	check.rawExpr(nil, &x, expr, nil, true) // allow generic expressions

	*Tree[T]
}

func (Node[Q]) M(Q) {}

type Inst = *Tree[int]
`

	fset := token.NewFileSet()
	f := mustParse(fset, src)
	pkg := NewPackage("p", f.Name.Name)
	if err := NewChecker(nil, fset, pkg, nil).Files([]*ast.File{f}); err != nil {
		t.Fatal(err)
	}

	firstFieldType := func(n *Named) *Named {
		return n.Underlying().(*Struct).Field(0).Type().(*Pointer).Elem().(*Named)
	}

type Node[T any] struct {
	*Tree[T]
}

func (Node[Q]) M(Q) {}

type Inst = *Tree[int]
`

	f := mustParse(src)
	pkg := NewPackage("p", f.PkgName.Value)
	if err := NewChecker(nil, pkg, nil).Files([]*syntax.File{f}); err != nil {
		t.Fatal(err)
	}

	firstFieldType := func(n *Named) *Named {
		return n.Underlying().(*Struct).Field(0).Type().(*Pointer).Elem().(*Named)
	}

// Package types2 declares the data types and implements
// the algorithms for type-checking of Go packages. Use
// Config.Check to invoke the type checker for a package.
// Alternatively, create a new type checker with NewChecker
// and invoke it incrementally by calling Checker.Files.
//
// Type-checking consists of several interdependent phases:
//
// Name resolution maps each identifier (syntax.Name) in the program to the

// Package types declares the data types and implements
// the algorithms for type-checking of Go packages. Use
// [Config.Check] to invoke the type checker for a package.
// Alternatively, create a new type checker with [NewChecker]
// and invoke it incrementally by calling [Checker.Files].
//
// Type-checking consists of several interdependent phases:
//
// Name resolution maps each identifier ([ast.Ident]) in the program

type Instance = *Tree[int]
`

	fset := token.NewFileSet()
	f, err := parser.ParseFile(fset, "foo.go", src, 0)
	if err != nil {
		panic(err)
	}
	pkg := NewPackage("pkg", f.Name.Name)
	if err := NewChecker(nil, fset, pkg, nil).Files([]*ast.File{f}); err != nil {
		panic(err)
	}

	T := pkg.Scope().Lookup("Instance").Type()
	_ = NewMethodSet(T) // verify that NewMethodSet terminates
}

	var conf Config
	info := &Info{Defs: make(map[*syntax.Name]Object)}
	check := NewChecker(&conf, NewPackage("", "p"), info)
	if err := check.Files([]*syntax.File{f1, f2}); err != nil {
		t.Fatal(err)
	}
	want := printInfo(info)

	// type-check incrementally
	info = &Info{Defs: make(map[*syntax.Name]Object)}
	check = NewChecker(&conf, NewPackage("", "p"), info)
	if err := check.Files([]*syntax.File{f1}); err != nil {