t.Fatal(err)
			}
			lines, err := PlusBuildLines(x)
			if err != nil {
				if tt.err == nil {
					t.Errorf("PlusBuildLines(%q): unexpected error: %v", tt.in, err)
				} else if tt.err != err {
					t.Errorf("PlusBuildLines(%q): error %v, want %v", tt.in, err, tt.err)
				}
				return
			}
			if tt.err != nil {
				t.Errorf("PlusBuildLines(%q) = %v, want error %v", tt.in, lines, tt.err)
				return

	}
	return true
}

var errComplex = errors.New("expression too complex for // +build lines")

// PlusBuildLines returns a sequence of “// +build” lines that evaluate to the build expression x.
// If the expression is too complex to convert directly to “// +build” lines, PlusBuildLines returns an error.
func PlusBuildLines(x Expr) ([]string, error) {

		block = append(block, "//go:build "...)
		block = append(block, x.String()...)
		block = append(block, tabwriter.Escape, '\n')
		if len(p.plusBuild) > 0 {
			lines, err := constraint.PlusBuildLines(x)
			if err != nil {
				lines = []string{"// +build error: " + err.Error()}
			}
			for _, line := range lines {
				block = append(block, tabwriter.Escape)
				block = append(block, line...)

		return
	}

	// Have both //go:build and // +build,
	// with no errors found (crossCheck still true).
	// Check they match.
	var want constraint.Expr
	lines, err := constraint.PlusBuildLines(check.goBuild)
	if err != nil {
		check.pass.Reportf(check.goBuildPos, "%v", err)
		return
	}
	for _, line := range lines {
		y, err := constraint.Parse(line)
		if err != nil {

		{"IsPlusBuild", Func, 16},
		{"NotExpr", Type, 16},
		{"NotExpr.X", Field, 16},
		{"OrExpr", Type, 16},
		{"OrExpr.X", Field, 16},
		{"OrExpr.Y", Field, 16},
		{"Parse", Func, 16},
		{"PlusBuildLines", Func, 16},
		{"SyntaxError", Type, 16},
		{"SyntaxError.Err", Field, 16},
		{"SyntaxError.Offset", Field, 16},
		{"TagExpr", Type, 16},
		{"TagExpr.Tag", Field, 16},
	},
	"go/constant": {

pkg go/build/constraint, func IsGoBuild(string) bool
pkg go/build/constraint, func IsPlusBuild(string) bool
pkg go/build/constraint, func Parse(string) (Expr, error)
pkg go/build/constraint, func PlusBuildLines(Expr) ([]string, error)
pkg go/build/constraint, method (*AndExpr) Eval(func(string) bool) bool
pkg go/build/constraint, method (*AndExpr) String() string
pkg go/build/constraint, method (*NotExpr) Eval(func(string) bool) bool