fix (parser): don't panic if assign of define untyped value (#10)

* fix (parser): don't panic if assign of define untyped value

In case of defining or assigning to untyped value, the type has
to be taken from the source value instead of the target value.

The vm test coverage has also been slightly improved.

* fix and simplify Token.Name()

* improve parser errors

1 files changed, 94 insertions, 10 deletions

diff --git a/vm/vm_test.go b/vm/vm_test.go
index 8fa8e71..43333ad 100644
--- a/vm/vm_test.go
+++ b/vm/vm_test.go
@@ -3,6 +3,7 @@ package vm
 import (
 	"fmt"
 	"log"
+	"reflect"
 	"testing"
 )
 
@@ -61,7 +62,90 @@ var tests = []struct {
 		{0, Exit},
 	},
 	start: 0, end: 1, mem: "[3]",
-}, { // #01 -- Calling a function defined outside the VM.
+}, { // #01 -- A simple subtraction.
+	code: [][]int64{
+		{0, Push, 2},
+		{0, Push, 3},
+		{0, Sub},
+		{0, Exit},
+	},
+	start: 0, end: 1, mem: "[1]",
+}, { // #02 -- A simple multiplication.
+	code: [][]int64{
+		{0, Push, 3},
+		{0, Push, 2},
+		{0, Mul},
+		{0, Exit},
+	},
+	start: 0, end: 1, mem: "[6]",
+}, { // #03 -- lower.
+	code: [][]int64{
+		{0, Push, 3},
+		{0, Push, 2},
+		{0, Lower},
+		{0, Exit},
+	},
+	start: 0, end: 1, mem: "[true]",
+}, { // #04 -- greater.
+	code: [][]int64{
+		{0, Push, 2},
+		{0, Push, 3},
+		{0, Greater},
+		{0, Exit},
+	},
+	start: 0, end: 1, mem: "[true]",
+}, { // #05 -- equal.
+	code: [][]int64{
+		{0, Push, 2},
+		{0, Push, 3},
+		{0, Equal},
+		{0, Exit},
+	},
+	start: 0, end: 1, mem: "[false]",
+}, { // #06 -- equalSet.
+	code: [][]int64{
+		{0, Push, 2},
+		{0, Push, 3},
+		{0, EqualSet},
+		{0, Exit},
+	},
+	start: 0, end: 2, mem: "[2 false]",
+}, { // #07 -- equalSet.
+	code: [][]int64{
+		{0, Push, 3},
+		{0, Push, 3},
+		{0, EqualSet},
+		{0, Exit},
+	},
+	start: 0, end: 1, mem: "[true]",
+}, { // #08 not.
+	code: [][]int64{
+		{0, Push, 3},
+		{0, Push, 3},
+		{0, Equal},
+		{0, Not},
+		{0, Exit},
+	},
+	start: 0, end: 1, mem: "[false]",
+}, { // #09 pop.
+	code: [][]int64{
+		{0, Push, 3},
+		{0, Push, 2},
+		{0, Pop, 1},
+		{0, Exit},
+	},
+	start: 0, end: 1, mem: "[3]",
+}, { // #10 -- Assign a variable.
+	sym: []Value{{Type: TypeOf(0), Data: reflect.ValueOf(0)}},
+	code: [][]int64{
+		{0, Grow, 1},
+		{0, New, 2, 0},
+		{0, Push, 2},
+		{0, Assign, 1},
+		{0, Exit},
+	},
+	start: 1, end: 2, mem: "[2]",
+}, { // #11 -- Calling a function defined outside the VM.
 	sym: []Value{ValueOf(fmt.Println), ValueOf("Hello")},
 	code: [][]int64{
 		{0, Dup, 0},
@@ -69,7 +153,7 @@ var tests = []struct {
 		{0, Exit},
 	},
 	start: 1, end: 3, mem: "[6 <nil>]",
-}, { // #02 -- Defining and calling a function in VM.
+}, { // #12 -- Defining and calling a function in VM.
 	code: [][]int64{
 		{0, Jump, 3},      // 0
 		{0, Push, 3},      // 1
@@ -79,7 +163,7 @@ var tests = []struct {
 		{0, Exit},         // 5
 	},
 	start: 0, end: 1, mem: "[3]",
-}, { // #03 -- Defining and calling a function in VM.
+}, { // #13 -- Defining and calling a function in VM.
 	code: [][]int64{
 		{0, Jump, 3},      // 0
 		{0, Push, 3},      // 1
@@ -90,7 +174,7 @@ var tests = []struct {
 		{0, Exit},         // 6
 	},
 	start: 0, end: 1, mem: "[3]",
-}, { // #04 -- Defining and calling a function in VM.
+}, { // #14 -- Defining and calling a function in VM.
 	code: [][]int64{
 		{0, Jump, 5},      // 0
 		{0, Push, 3},      // 1
@@ -103,20 +187,20 @@ var tests = []struct {
 		{0, Exit},         // 8
 	},
 	start: 0, end: 1, mem: "[3]",
-}, { // #05 -- Fibonacci numbers, hand written. Showcase recursivity.
+}, { // #15 -- Fibonacci numbers, hand written. Showcase recursivity.
 	code: [][]int64{
 		{0, Jump, 19},     // 0
 		{0, Push, 2},      // 2  [2]
 		{0, Fdup, -2},     // 1  [2 i]
 		{0, Lower},        // 3  [true/false]
 		{0, JumpTrue, 13}, // 4  [], goto 17
-		{0, Push, 2},      // 6  [i 2]
-		{0, Fdup, -2},     // 5  [i]
+		{0, Push, 2},      // 5  [i 2]
+		{0, Fdup, -2},     // 6  [i]
 		{0, Sub},          // 7  [(i-2)]
 		{0, Push, 1},      // 8
 		{0, Call},         // 9  [fib(i-2)]
-		{0, Push, 1},      // 11 [(i-2) i 1]
-		{0, Fdup, -2},     // 10 [fib(i-2) i]
+		{0, Push, 1},      // 10 [(i-2) i 1]
+		{0, Fdup, -2},     // 11 [fib(i-2) i]
 		{0, Sub},          // 12 [(i-2) (i-1)]
 		{0, Push, 1},      // 13
 		{0, Call},         // 14 [fib(i-2) fib(i-1)]
@@ -130,7 +214,7 @@ var tests = []struct {
 		{0, Exit},         // 22
 	},
 	start: 0, end: 1, mem: "[8]",
-}, { // #06 -- Fibonacci with some immediate instructions.
+}, { // #16 -- Fibonacci with some immediate instructions.
 	code: [][]int64{
 		{0, Jump, 14},     // 0
 		{0, Fdup, -2},     // 1  [i]