cl: support const & iota

[visualfc]

fix #682
fix #684

• support constant declarations
• predeclared identifier iota
• fix golang const float64 typecast

Go+ code

const Pi float64 = 3.14159265358979323846
const zero = 0.0         // untyped floating-point constant
const (
	size int64 = 1024
	eof        = -1  // untyped integer constant
)
const va, vb, vc = 3, 4, "foo"  // a = 3, b = 4, c = "foo", untyped integer and string constants
const fu, fv float32 = 0, 3    // u = 0.0, v = 3.0

const (
	c0 = iota  // c0 == 0
	c1 = iota  // c1 == 1
	c2 = iota  // c2 == 2
)

const (
	a = 1 << iota  // a == 1  (iota == 0)
	b = 1 << iota  // b == 2  (iota == 1)
	c = 3          // c == 3  (iota == 2, unused)
	d = 1 << iota  // d == 8  (iota == 3)
)

const (
	u         = iota * 42  // u == 0     (untyped integer constant)
	v float64 = iota * 42  // v == 42.0  (float64 constant)
	w         = iota * 42  // w == 84    (untyped integer constant)
)

const x = iota  // x == 0
const y = iota  // y == 0

const (
	bit0, mask0 = 1 << iota, 1<<iota - 1  // bit0 == 1, mask0 == 0  (iota == 0)
	bit1, mask1                           // bit1 == 2, mask1 == 1  (iota == 1)
	_, _                                  //                        (iota == 2, unused)
	bit3, mask3                           // bit3 == 8, mask3 == 7  (iota == 3)
)

println(Pi)
println(zero,size,eof)
println(va,vb,vc)
println(fu,fv)

println(c0,c1,c2)
println(a,b,c,d)
println(x,y)
println(u,v,w)
println(bit0,mask0,bit1,mask1,bit3,mask3)

generate Golang code

package main

import fmt "fmt"

func main() { 
//line ./main.gop:40
	fmt.Println(float64(3.141592653589793))
//line ./main.gop:41
	fmt.Println(float64(0), int64(1024), -1)
//line ./main.gop:42
	fmt.Println(3, 4, "foo")
//line ./main.gop:43
	fmt.Println(float32(0), float32(3))
//line ./main.gop:45
	fmt.Println(0, 1, 2)
//line ./main.gop:46
	fmt.Println(1, 2, 3, 8)
//line ./main.gop:47
	fmt.Println(0, 0)
//line ./main.gop:48
	fmt.Println(0, float64(42), 84)
//line ./main.gop:49
	fmt.Println(1, 0, 2, 1, 8, 7)
}

[codecov-io]

Codecov Report

Merging #683 (52aa5b9) into master (6b6993f) will increase coverage by 0.06%.
The diff coverage is 95.45%.

@@            Coverage Diff             @@
##           master     #683      +/-   ##
==========================================
+ Coverage   90.06%   90.12%   +0.06%     
==========================================
  Files          42       42              
  Lines        9298     9339      +41     
==========================================
+ Hits         8374     8417      +43     
+ Misses        655      654       -1     
+ Partials      269      268       -1     

Impacted Files	Coverage Δ
cl/compile.go	86.04% <94.11%> (+3.43%)	⬆️
cl/expr.go	89.55% <100.00%> (+0.09%)	⬆️
exec/golang/expr.go	94.11% <100.00%> (+0.52%)	⬆️

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