<pre>
const (
	c1 = imag(2i)                    // imag(2i) = 2.0 is a constant
	c2 = len([10]float64{2})         // [10]float64{2} contains no function calls
	c3 = len([10]float64{c1})        // [10]float64{c1} contains no function calls
	c4 = len([10]float64{imag(2i)})  // imag(2i) is a constant and no function call is issued
	c5 = len([10]float64{imag(z)})   // invalid: imag(z) is a (non-constant) function call
)
var z complex128
</pre>

pkg go/constant, func Float32Val(Value) (float32, bool)
pkg go/constant, func Float64Val(Value) (float64, bool)
pkg go/constant, func Imag(Value) Value
pkg go/constant, func Int64Val(Value) (int64, bool)
pkg go/constant, func MakeBool(bool) Value
pkg go/constant, func MakeFloat64(float64) Value
pkg go/constant, func MakeFromBytes([]uint8) Value
pkg go/constant, func MakeFromLiteral(string, token.Token, uint) Value

Example

As a simple example, consider a package that uses cgo to call C.sin.
The following code will be generated by cgo:

	// compiled by gc

	//go:cgo_ldflag "-lm"

	type _Ctype_double float64

	//go:cgo_import_static _cgo_gcc_Cfunc_sin
	//go:linkname __cgo_gcc_Cfunc_sin _cgo_gcc_Cfunc_sin
	var __cgo_gcc_Cfunc_sin byte
	var _cgo_gcc_Cfunc_sin = unsafe.Pointer(&__cgo_gcc_Cfunc_sin)

pkg syscall (windows-amd64), type SysProcAttr struct, ThreadAttributes *SecurityAttributes
pkg testing, func Init()
pkg testing, method (*B) ReportMetric(float64, string)
pkg testing, type BenchmarkResult struct, Extra map[string]float64
pkg text/template, method (ExecError) Unwrap() error
pkg time, method (Duration) Microseconds() int64
pkg time, method (Duration) Milliseconds() int64

pkg math, func Jn(int, float64) float64
pkg math, func Ldexp(float64, int) float64
pkg math, func Lgamma(float64) (float64, int)
pkg math, func Log(float64) float64
pkg math, func Log10(float64) float64
pkg math, func Log1p(float64) float64
pkg math, func Log2(float64) float64
pkg math, func Logb(float64) float64
pkg math, func Max(float64, float64) float64
pkg math, func Min(float64, float64) float64

	c.uint8 = c.Ident("uint8")
	c.uint16 = c.Ident("uint16")
	c.uint32 = c.Ident("uint32")
	c.uint64 = c.Ident("uint64")
	c.uintptr = c.Ident("uintptr")
	c.float32 = c.Ident("float32")
	c.float64 = c.Ident("float64")
	c.complex64 = c.Ident("complex64")
	c.complex128 = c.Ident("complex128")
	c.void = c.Ident("void")
	c.string = c.Ident("string")
	c.goVoid = c.Ident("_Ctype_void")

pkg encoding/json, type UnmarshalTypeError struct, Field string
pkg encoding/json, type UnmarshalTypeError struct, Struct string
pkg expvar, func Handler() http.Handler
pkg expvar, method (*Float) Value() float64
pkg expvar, method (Func) Value() interface{}
pkg expvar, method (*Int) Value() int64
pkg expvar, method (*String) Value() string
pkg go/doc, func IsPredeclared(string) bool
pkg go/types, func Default(Type) Type

pkg hash/maphash, type Hash struct
pkg hash/maphash, type Seed struct
pkg log, const Lmsgprefix = 64
pkg log, const Lmsgprefix ideal-int
pkg math, func FMA(float64, float64, float64) float64
pkg math/bits, func Rem(uint, uint, uint) uint
pkg math/bits, func Rem32(uint32, uint32, uint32) uint32
pkg math/bits, func Rem64(uint64, uint64, uint64) uint64

pkg runtime/metrics, const KindUint64 = 1
pkg runtime/metrics, const KindUint64 ValueKind
pkg runtime/metrics, func All() []Description
pkg runtime/metrics, func Read([]Sample)
pkg runtime/metrics, method (Value) Float64() float64
pkg runtime/metrics, method (Value) Float64Histogram() *Float64Histogram
pkg runtime/metrics, method (Value) Kind() ValueKind
pkg runtime/metrics, method (Value) Uint64() uint64

<pre>
const (
	c1 = imag(2i)                    // imag(2i) = 2.0 is a constant
	c2 = len([10]float64{2})         // [10]float64{2} contains no function calls
	c3 = len([10]float64{c1})        // [10]float64{c1} contains no function calls
	c4 = len([10]float64{imag(2i)})  // imag(2i) is a constant and no function call is issued
	c5 = len([10]float64{imag(z)})   // invalid: imag(z) is a (non-constant) function call
)
var z complex128
</pre>