func (f exprFlags) IsNil() bool           { return f&16 != 0 }
func (f exprFlags) Addressable() bool     { return f&32 != 0 }
func (f exprFlags) Assignable() bool      { return f&64 != 0 }
func (f exprFlags) HasOk() bool           { return f&128 != 0 }
func (f exprFlags) IsRuntimeHelper() bool { return f&256 != 0 } // a runtime function called from transformed syntax

func (f *exprFlags) SetIsVoid()          { *f |= 1 }

func (tv TypeAndValue) Assignable() bool {
	return tv.mode == variable || tv.mode == mapindex
}

// HasOk reports whether the corresponding expression may be
// used on the rhs of a comma-ok assignment.
func (tv TypeAndValue) HasOk() bool {
	return tv.mode == commaok || tv.mode == mapindex
}

// Instance reports the type arguments and instantiated type for type and

func (tv TypeAndValue) Assignable() bool {
	return tv.mode == variable || tv.mode == mapindex
}

// HasOk reports whether the corresponding expression may be
// used on the rhs of a comma-ok assignment.
func (tv TypeAndValue) HasOk() bool {
	return tv.mode == commaok || tv.mode == mapindex
}

// Instance reports the type arguments and instantiated type for type and

		{`package s0; var (m map[int]int; _ = m[0])`, `m[0]`, `value, assignable, hasOk`},
		{`package s1; var (m map[int]int; _, _ = m[0])`, `m[0]`, `value, assignable, hasOk`},

		// hasOk expressions
		{`package k0; var (ch chan int; _ = <-ch)`, `<-ch`, `value, hasOk`},
		{`package k1; var (ch chan int; _, _ = <-ch)`, `<-ch`, `value, hasOk`},

		// missing entries
		// - package names are collected in the Uses map

		{`package s0; var (m map[int]int; _ = m[0])`, `m[0]`, `value, assignable, hasOk`},
		{`package s1; var (m map[int]int; _, _ = m[0])`, `m[0]`, `value, assignable, hasOk`},

		// hasOk expressions
		{`package k0; var (ch chan int; _ = <-ch)`, `<-ch`, `value, hasOk`},
		{`package k1; var (ch chan int; _, _ = <-ch)`, `<-ch`, `value, hasOk`},

		// missing entries
		// - package names are collected in the Uses map

			stv.SetIsValue()
		}
		if tv.IsNil() {
			stv.SetIsNil()
		}
		if tv.Addressable() {
			stv.SetAddressable()
		}
		if tv.Assignable() {
			stv.SetAssignable()
		}
		if tv.HasOk() {
			stv.SetHasOk()
		}
		x.SetTypeInfo(stv)
	}
}

func (check *Checker) recordBuiltinType(f syntax.Expr, sig *Signature) {
	// f must be a (possibly parenthesized, possibly qualified)

pkg go/types, method (Error) Error() string
pkg go/types, method (TypeAndValue) Addressable() bool
pkg go/types, method (TypeAndValue) Assignable() bool
pkg go/types, method (TypeAndValue) HasOk() bool
pkg go/types, method (TypeAndValue) IsBuiltin() bool
pkg go/types, method (TypeAndValue) IsNil() bool
pkg go/types, method (TypeAndValue) IsType() bool
pkg go/types, method (TypeAndValue) IsValue() bool

		{"(Checker).PkgNameOf", Method, 22},
		{"(Checker).TypeOf", Method, 5},
		{"(Error).Error", Method, 5},
		{"(TypeAndValue).Addressable", Method, 5},
		{"(TypeAndValue).Assignable", Method, 5},
		{"(TypeAndValue).HasOk", Method, 5},
		{"(TypeAndValue).IsBuiltin", Method, 5},
		{"(TypeAndValue).IsNil", Method, 5},
		{"(TypeAndValue).IsType", Method, 5},
		{"(TypeAndValue).IsValue", Method, 5},
		{"(TypeAndValue).IsVoid", Method, 5},