Remove the "assign" keyword from assignment syntax

4 files changed, 21 insertions, 20 deletions

diff --git a/GRAMMAR.txt b/GRAMMAR.txt
index 4882ff8..bd7b4d4 100644
--- a/GRAMMAR.txt
+++ b/GRAMMAR.txt
@@ -17,7 +17,7 @@ declaration -> constant | mutable
 constant -> "const" IDENTIFIER "=" expression
 mutable -> "mut" IDENTIFIER "=" expression
 
-assignment -> "assign" IDENTIFIER "=" expression
+assignment -> IDENTIFIER "=" expression
 
 expression -> equality
 equality -> comparison ( ( "==" | "!=" ) comparison )*
diff --git a/lex.go b/lex.go
index 961291a..7450888 100644
--- a/lex.go
+++ b/lex.go
@@ -300,8 +300,6 @@ func addKeywordOrIdentifier(name string, line int) token {
 		return token{kind: constKeyword, line: line}
 	case "mut":
 		return token{kind: mut, line: line}
-	case "assign":
-		return token{kind: assign, line: line}
 	default:
 		return token{kind: identifier, value: name, line: line}
 	}
diff --git a/parse.go b/parse.go
index a9c7b9d..7b4469e 100644
--- a/parse.go
+++ b/parse.go
@@ -24,7 +24,11 @@ func (t *tokens) consumeToken() (token, bool) {
 }
 
 func (t *tokens) unreadToken() {
-	t.index--
+	t.unreadTokens(1)
+}
+
+func (t *tokens) unreadTokens(n int) {
+	t.index -= n
 }
 
 func (t *tokens) current() token {
@@ -396,32 +400,34 @@ func parseMutStmt(toks *tokens) (*mutStmt, error) {
 }
 
 func parseAssignStmt(toks *tokens) (*assignStmt, error) {
-	ok, err := toks.match(assign)
-	if err != nil {
-		return nil, err
-	}
-	if !ok {
-		toks.unreadToken()
-		return nil, nil
-	}
-
-	line := toks.current().line
-
 	nameTok, ok := toks.consumeToken()
 	if !ok {
 		return nil, unexpectedEOF
 	}
+	if nameTok.kind != identifier {
+		toks.unreadToken()
+		return nil, nil
+	}
 
-	if err := toks.mustMatch(equals); err != nil {
+	ok, err := toks.match(equals)
+	if err != nil {
 		return nil, err
 	}
+	if !ok {
+		toks.unreadTokens(2)
+		return nil, nil
+	}
 
 	expr, err := parseExpression(toks)
 	if err != nil {
 		return nil, err
 	}
 
-	return &assignStmt{name: nameTok.value, value: expr, ln: line}, nil
+	return &assignStmt{
+		name:  nameTok.value,
+		value: expr,
+		ln:    nameTok.line,
+	}, nil
 }
 
 func parseExpression(toks *tokens) (exprExpr, error) {
diff --git a/token.go b/token.go
index 14d23a1..20d4727 100644
--- a/token.go
+++ b/token.go
@@ -104,8 +104,6 @@ func (k tokenKind) String() string {
 		return "const"
 	case mut:
 		return "mut"
-	case assign:
-		return "assign"
 	}
 
 	return "invalid token"
@@ -161,7 +159,6 @@ const (
 	ret
 	constKeyword
 	mut
-	assign
 )
 
 type token struct {