func (m *Match) AddError(err error) {
	m.Errs = append(m.Errs, &MatchError{Match: m, Err: err})
}

// IsLiteral reports whether the pattern is free of wildcards and meta-patterns.
//
// A literal pattern must match at most one package.
func (m *Match) IsLiteral() bool {
	return !strings.Contains(m.pattern, "...") && !m.IsMeta()
}

	if tok, is_keyword := keywords[ident]; is_keyword {
		return tok
	}
	return IDENT
}

// Predicates

// IsLiteral returns true for tokens corresponding to identifiers
// and basic type literals; it returns false otherwise.
func (tok Token) IsLiteral() bool { return literal_beg < tok && tok < literal_end }

// IsOperator returns true for tokens corresponding to operators and

			// don't use the position of auto-inserted (invisible) semicolons
			if lit != ";" {
				break
			}
			fallthrough
		default:
			prev = pos
			var l int // token length
			if tok.IsLiteral() {
				l = len(lit)
			} else {
				l = len(tok.String())
			}
			here = prev + token.Pos(l)
		}
	}
}

// compareErrors compares the map of expected error messages with the list

	match := search.NewMatch(pattern)
	if m == (module.Version{}) {
		matchPackages(ctx, match, tags, includeStd, nil)
	}

	LoadModFile(ctx) // Sets Target, needed by fetch and matchPackages.

	if !match.IsLiteral() {
		matchPackages(ctx, match, tags, omitStd, []module.Version{m})
		return match
	}

	root, isLocal, err := fetch(ctx, m)
	if err != nil {
		match.Errs = []error{err}
		return match
	}

		// Literal method needs to scan the pattern.
		re := MustCompile(tc.pattern)
		str, complete := re.LiteralPrefix()
		if complete != tc.isLiteral {
			t.Errorf("LiteralPrefix(`%s`) = %t; want %t", tc.pattern, complete, tc.isLiteral)
		}
		if str != tc.literal {
			t.Errorf("LiteralPrefix(`%s`) = `%s`; want `%s`", tc.pattern, str, tc.literal)
		}
	}
}

type subexpIndex struct {

	"strings"
	"testing"
)

var fset = token.NewFileSet()

const /* class */ (
	special = iota
	literal
	operator
	keyword
)

func tokenclass(tok token.Token) int {
	switch {
	case tok.IsLiteral():
		return literal
	case tok.IsOperator():
		return operator
	case tok.IsKeyword():
		return keyword
	}
	return special
}

type elt struct {
	tok   token.Token
	lit   string
	class int
}

		for _, pkg := range m.Pkgs {
			if pkg == "" {
				panic(fmt.Sprintf("ImportPaths returned empty package for pattern %s", m.Pattern()))
			}
			mode := cmdlinePkg
			if m.IsLiteral() {
				// Note: do not set = m.IsLiteral unconditionally
				// because maybe we'll see p matching both
				// a literal and also a non-literal pattern.
				mode |= cmdlinePkgLiteral
			}

	// very first token (!p.pos.IsValid()) is not initialized
	// (it is token.ILLEGAL), so don't print it.
	if p.trace && p.pos.IsValid() {
		s := p.tok.String()
		switch {
		case p.tok.IsLiteral():
			p.printTrace(s, p.lit)
		case p.tok.IsOperator(), p.tok.IsKeyword():
			p.printTrace("\"" + s + "\"")
		default:
			p.printTrace(s)
		}
	}

	for {
		p.pos, p.tok, p.lit = p.scanner.Scan()

	// very first token (!p.pos.IsValid()) is not initialized
	// (it is token.ILLEGAL), so don't print it.
	if p.trace && p.pos.IsValid() {
		s := p.tok.String()
		switch {
		case p.tok.IsLiteral():
			p.printTrace(s, p.lit)
		case p.tok.IsOperator(), p.tok.IsKeyword():
			p.printTrace("\"" + s + "\"")
		default:
			p.printTrace(s)
		}
	}

	p.pos, p.tok, p.lit = p.scanner.Scan()
}

				// the loader iterations.
				m.Pkgs = m.Pkgs[:0]
				for _, dir := range m.Dirs {
					pkg, err := resolveLocalPackage(ctx, dir, rs)
					if err != nil {
						if !m.IsLiteral() && (err == errPkgIsBuiltin || err == errPkgIsGorootSrc) {
							continue // Don't include "builtin" or GOROOT/src in wildcard patterns.
						}

						// If we're outside of a module, ensure that the failure mode