// reports whether the call is valid, with *x holding the result;
// but x.expr is not set. If the call is invalid, the result is
// false, and *x is undefined.
func (check *Checker) builtin(x *operand, call *syntax.CallExpr, id builtinId) (_ bool) {
	argList := call.ArgList

	// append is the only built-in that permits the use of ... for the last argument
	bin := predeclaredFuncs[id]
	if hasDots(call) && id != _Append {

			goto Error
		}
		T := check.varType(e.Type)
		if !isValid(T) {
			goto Error
		}
		check.typeAssertion(e, x, T, false)
		x.mode = commaok
		x.typ = T

	case *ast.CallExpr:
		return check.callExpr(x, e)

	case *ast.StarExpr:
		check.exprOrType(x, e.X, false)
		switch x.mode {
		case invalid:
			goto Error
		case typexpr:
			check.validVarType(e.X, x.typ)

		// x.(type) expressions are handled explicitly in type switches
		check.error(e, InvalidSyntaxTree, "use of .(type) outside type switch")
		check.use(e.X)
		goto Error

	case *syntax.CallExpr:
		return check.callExpr(x, e)

	case *syntax.ListExpr:
		// catch-all for unexpected expression lists
		check.error(e, InvalidSyntaxTree, "unexpected list of expressions")
		goto Error

			}
		case Or:
			if name, lhs := extractName(x.X, force || isTypeElem(x.Y)); name != nil && lhs != nil {
				// x = name lhs|x.Y
				op := *x
				op.X = lhs
				return name, &op
			}
		}
	case *CallExpr:
		if name, _ := x.Fun.(*Name); name != nil {
			if len(x.ArgList) == 1 && !x.HasDots && (force || isTypeElem(x.ArgList[0])) {
				// x = name "(" x.ArgList[0] ")"
				return name, x.ArgList[0]
			}
		}
	}

	fn.Nname.Defn = fn
	pkg.Funcs = append(pkg.Funcs, fn)

	return fn
}

// IsFuncPCIntrinsic returns whether n is a direct call of internal/abi.FuncPCABIxxx functions.
func IsFuncPCIntrinsic(n *CallExpr) bool {
	if n.Op() != OCALLFUNC || n.Fun.Op() != ONAME {
		return false
	}
	fn := n.Fun.(*Name).Sym()
	return (fn.Name == "FuncPCABI0" || fn.Name == "FuncPCABIInternal") &&
		fn.Pkg.Path == "internal/abi"
}

// ParenExpr, is correctly formatted with parens.
// Test case for issue #63362.
func TestChanType(t *testing.T) {
	expr := &ast.UnaryExpr{
		Op: token.ARROW,
		X: &ast.CallExpr{
			Fun: &ast.ChanType{
				Dir:   ast.RECV,
				Value: &ast.Ident{Name: "int"},
			},
			Args: []ast.Expr{&ast.Ident{Name: "nil"}},
		},
	}
	var buf bytes.Buffer

	}
	conf.Check("p", []*syntax.File{f}, info) // ignore result
	for e, tv := range info.Types {
		if _, ok := e.(*syntax.CallExpr); ok {
			if tv.Type != Typ[Int16] {
				t.Errorf("CallExpr has type %v, want int16", tv.Type)
			}
			return
		}
	}
	t.Errorf("CallExpr has no type")
}

// TestCompositeLitTypes verifies that Info.Types registers the correct

	inTParamList  bool                   // set if inside a type parameter list
	sig           *Signature             // function signature if inside a function; nil otherwise
	isPanic       map[*ast.CallExpr]bool // set of panic call expressions (used for termination check)
	hasLabel      bool                   // set if a function makes use of labels (only ~1% of functions); unused outside functions

	}
	conf.Check("p", fset, []*ast.File{f}, info) // ignore result
	for e, tv := range info.Types {
		if _, ok := e.(*ast.CallExpr); ok {
			if tv.Type != Typ[Int16] {
				t.Errorf("CallExpr has type %v, want int16", tv.Type)
			}
			return
		}
	}
	t.Errorf("CallExpr has no type")
}

// TestCompositeLitTypes verifies that Info.Types registers the correct

	inTParamList  bool                      // set if inside a type parameter list
	sig           *Signature                // function signature if inside a function; nil otherwise
	isPanic       map[*syntax.CallExpr]bool // set of panic call expressions (used for termination check)
	hasLabel      bool                      // set if a function makes use of labels (only ~1% of functions); unused outside functions