PREFIX_EXPRESSION -> tree.unsupported(node, UnsupportedLanguageFeature.PrefixExpression)
            OPERATION_REFERENCE -> tree.unsupported(node, UnsupportedLanguageFeature.UnsupportedOperator)
            PARENTHESIZED -> parenthesized(tree, node)
            LAMBDA_EXPRESSION -> tree.unsupported(node, UnsupportedLanguageFeature.FunctionDeclaration)
            THIS_EXPRESSION -> Element(This(tree.sourceData(node)))

// be incomplete.
type Info struct {
	// Types maps expressions to their types, and for constant
	// expressions, also their values. Invalid expressions are
	// omitted.
	//
	// For (possibly parenthesized) identifiers denoting built-in
	// functions, the recorded signatures are call-site specific:
	// if the call result is not a constant, the recorded type is
	// an argument-specific signature. Otherwise, the recorded type

// be incomplete.
type Info struct {
	// Types maps expressions to their types, and for constant
	// expressions, also their values. Invalid expressions are
	// omitted.
	//
	// For (possibly parenthesized) identifiers denoting built-in
	// functions, the recorded signatures are call-site specific:
	// if the call result is not a constant, the recorded type is
	// an argument-specific signature. Otherwise, the recorded type

	go ( /* ERROR "expression in go must not be parenthesized" */ gos())
	go gos()
	var c chan int
	go close(c)
	go len /* ERROR "go discards result" */ (c)
}

func defers() {
	defer 1; /* ERROR "must be function call" */
	defer int /* ERROR "defer requires function call, not conversion" */ (0)
	defer ( /* ERROR "expression in defer must not be parenthesized" */ defers())
	defer defers()
	var c chan int

	}
	if m := check.Types; m != nil {
		m[x] = TypeAndValue{mode, typ, val}
	}
}

func (check *Checker) recordBuiltinType(f ast.Expr, sig *Signature) {
	// f must be a (possibly parenthesized, possibly qualified)
	// identifier denoting a built-in (including unsafe's non-constant
	// functions Add and Slice): record the signature for f and possible
	// children.
	for {

			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)
	// identifier denoting a built-in (including unsafe's non-constant
	// functions Add and Slice): record the signature for f and possible
	// children.
	for {

}

// An LParen represents the beginning of a parenthesized line block.
// It is a place to store suffix comments.
type LParen struct {
	Comments
	Pos Position
}

func (x *LParen) Span() (start, end Position) {
	return x.Pos, x.Pos.add(")")
}

// An RParen represents the end of a parenthesized line block.
// It is a place to store whole-line (before) comments.

		return check.instantiatedType(e.X, syntax.UnpackListExpr(e.Index), def)

	case *syntax.ParenExpr:
		// Generic types must be instantiated before they can be used in any form.
		// Consequently, generic types cannot be parenthesized.
		return check.definedType(e.X, def)

	case *syntax.ArrayType:
		typ := new(Array)
		setDefType(def, typ)
		if e.Len != nil {
			typ.len = check.arrayLength(e.Len)
		} else {
			// [...]array

		return check.instantiatedType(ix, def)

	case *ast.ParenExpr:
		// Generic types must be instantiated before they can be used in any form.
		// Consequently, generic types cannot be parenthesized.
		return check.definedType(e.X, def)

	case *ast.ArrayType:
		if e.Len == nil {
			typ := new(Slice)
			setDefType(def, typ)
			typ.elem = check.varType(e.Elt)
			return typ
		}

	_, err = parser.ParseFile(fset, "", got, 0)
	if err != nil {
		t.Errorf("%v\norig: %q\ngot : %q", err, src, got)
	}
}

// If a declaration has multiple specifications, a parenthesized
// declaration must be printed even if Lparen is token.NoPos.
func TestParenthesizedDecl(t *testing.T) {
	// a package with multiple specs in a single declaration
	const src = "package p; var ( a float64; b int )"