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, 17 insertions, 8 deletions

diff --git a/parser/parse.go b/parser/parse.go
index add1600..537b68e 100644
--- a/parser/parse.go
+++ b/parser/parse.go
@@ -29,6 +29,15 @@ type Parser struct {
 	clonum        int // closure instance number
 }
 
+// Parser errors.
+var (
+	ErrBody     = errors.New("missign body")
+	ErrBreak    = errors.New("invalid break statement")
+	ErrContinue = errors.New("invalid continue statement")
+	ErrFor      = errors.New("invalid for statement")
+	ErrGoto     = errors.New("invalid goto statement")
+)
+
 // Scan performs lexical analysis on s and returns Tokens or an error.
 func (p *Parser) Scan(s string, endSemi bool) (Tokens, error) {
 	return p.Scanner.Scan(s, endSemi)
@@ -36,11 +45,11 @@ func (p *Parser) Scan(s string, endSemi bool) (Tokens, error) {
 
 // Parse performs syntax analysis on s and return Tokens or an error.
 func (p *Parser) Parse(src string) (out Tokens, err error) {
-	log.Printf("Parse src: %#v\n", src)
 	in, err := p.Scan(src, true)
 	if err != nil {
 		return out, err
 	}
+	log.Printf("Parse src: %#v\n", src)
 	return p.parseStmts(in)
 }
 
@@ -122,12 +131,12 @@ func (p *Parser) parseBreak(in Tokens) (out Tokens, err error) {
 		label = p.breakLabel
 	case 2:
 		if in[1].Tok != lang.Ident {
-			return nil, fmt.Errorf("invalid break statement")
+			return nil, ErrBreak
 		}
 		// TODO: check validity of user provided label
 		label = in[1].Str
 	default:
-		return nil, fmt.Errorf("invalid break statement")
+		return nil, ErrBreak
 	}
 	out = Tokens{{Tok: lang.Goto, Str: label}}
 	return out, err
@@ -140,12 +149,12 @@ func (p *Parser) parseContinue(in Tokens) (out Tokens, err error) {
 		label = p.continueLabel
 	case 2:
 		if in[1].Tok != lang.Ident {
-			return nil, fmt.Errorf("invalid continue statement")
+			return nil, ErrContinue
 		}
 		// TODO: check validity of user provided label
 		label = in[1].Str
 	default:
-		return nil, fmt.Errorf("invalid continue statement")
+		return nil, ErrContinue
 	}
 	out = Tokens{{Tok: lang.Goto, Str: label}}
 	return out, err
@@ -153,7 +162,7 @@ func (p *Parser) parseContinue(in Tokens) (out Tokens, err error) {
 
 func (p *Parser) parseGoto(in Tokens) (out Tokens, err error) {
 	if len(in) != 2 || in[1].Tok != lang.Ident {
-		return nil, fmt.Errorf("invalid goto statement")
+		return nil, ErrGoto
 	}
 	// TODO: check validity of user provided label
 	return Tokens{{Tok: lang.Goto, Str: p.funcScope + "/" + in[1].Str}}, nil
@@ -171,7 +180,7 @@ func (p *Parser) parseFor(in Tokens) (out Tokens, err error) {
 	case 3:
 		init, cond, post = pre[0], pre[1], pre[2]
 	default:
-		return nil, fmt.Errorf("invalild for statement")
+		return nil, ErrFor
 	}
 	breakLabel, continueLabel := p.breakLabel, p.continueLabel
 	p.pushScope("for" + fc)
@@ -247,7 +256,7 @@ func (p *Parser) parseFunc(in Tokens) (out Tokens, err error) {
 
 	bi := in.Index(lang.BraceBlock)
 	if bi < 0 {
-		return out, fmt.Errorf("no function body")
+		return out, ErrBody
 	}
 	typ, err := p.parseTypeExpr(in[:bi])
 	if err != nil {