if r < utf8.RuneSelf {
				const allowed = "!#$%&()+,-.=@^_{}~ "
				if '0' <= r && r <= '9' ||
					'a' <= r && r <= 'z' ||
					'A' <= r && r <= 'Z' {
					return r
				}
				if strings.ContainsRune(allowed, r) {
					return r
				}
			} else if unicode.IsLetter(r) || unicode.IsNumber(r) {
				return r
			}
			return -1
		}
		pattern := strings.Map(mapper, c.Name())

	// Should match Go spec, compilers, and ../../go/parser/parser.go:/isValidImport.
	const illegalChars = `!"#$%&'()*,:;<=>?[\]^{|}` + "`\uFFFD"
	if !unicode.IsGraphic(r) || unicode.IsSpace(r) || strings.ContainsRune(illegalChars, r) {
		return '_'
	}
	return r
}

// Mode flags for loadImport and download (in get.go).
const (
	// ResolveImport means that loadImport should do import path expansion.

		{"(*Reader).WriteTo", Method, 1},
		{"Buffer", Type, 0},
		{"Clone", Func, 20},
		{"Compare", Func, 0},
		{"Contains", Func, 0},
		{"ContainsAny", Func, 7},
		{"ContainsFunc", Func, 21},
		{"ContainsRune", Func, 7},
		{"Count", Func, 0},
		{"Cut", Func, 18},
		{"CutPrefix", Func, 20},
		{"CutSuffix", Func, 20},
		{"Equal", Func, 0},
		{"EqualFold", Func, 0},
		{"ErrTooLarge", Var, 0},