Parse dereferences and subscripts

parser/expression.go

@@ -22,8 +22,8 @@ import "git.tebibyte.media/sashakoshka/fspl/entity"
 //   |           |        | 'break'  =Break
 //   |           |        | 'return' =Return
 //   |           | 
-//   |           | +Dot +Expression =Dereference *
-//   |           |                  | +Expression =Subscript *
+//   |           | +Dot +Expression =Dereference
+//   |           |                  | +Expression =Subscript
 //   |           | +Symbol X
 //   |                     | '\'      =Slice     *
 //   |                     | '#'      =Length    *
@@ -134,7 +134,7 @@ func (this *Parser) parseExpressionRootLBracket () (entity.Expression, error) {
 	if err != nil { return nil, err }
 	switch this.kind() {
 	case lexer.Ident:  return this.parseExpressionRootLBracketIdent(pos)
-	case lexer.Dot:    // TODO return this.parseExpressionRootLBracketDot(pos)
+	case lexer.Dot:    return this.parseDereferenceOrSubscriptCore(pos)
 	case lexer.Symbol: return this.parseExpressionRootLBracketSymbol(pos)
 	}
 	panic(this.bug())
@@ -158,7 +158,7 @@ func (this *Parser) parseReturnOrBreakCore (pos errors.Position) (entity.Express
 	name := this.value()
 	
 	err = this.expectNextDesc (
-		"Expression or end of " + name,
+		"expression or end of " + name,
 		appendCopy(startTokensExpression, lexer.RBracket)...)
 	if err != nil { return nil, err }
 	var value entity.Expression
@@ -188,6 +188,47 @@ func (this *Parser) parseReturnOrBreakCore (pos errors.Position) (entity.Express
 	panic(this.bug())
 }
 
+func (this *Parser) parseDereferenceOrSubscriptCore (pos errors.Position) (entity.Expression, error) {
+	err := this.expect(lexer.Dot)
+	if err != nil { return nil, err }
+
+	this.next()
+	argument, err := this.parseExpression()
+	if err != nil { return nil, err }
+
+	err = this.expectDesc (
+		"element offset expression or end of dereference",
+		appendCopy(startTokensExpression, lexer.RBracket)...)
+	if err != nil { return nil, err }
+	
+	if this.token.Is(lexer.RBracket) {
+		// RBracket: dereference
+		pos = pos.Union(this.pos())
+		this.next()
+
+		return &entity.Dereference {
+			Position: pos,
+			Pointer:  argument,
+		}, nil
+	} else {
+		// startTokensExpression...: subscript
+		offset, err := this.parseExpression()
+		if err != nil { return nil, err }
+		
+		err = this.expect(lexer.RBracket)
+		if err != nil { return nil, err }
+		pos = pos.Union(this.pos())
+		this.next()
+
+		return &entity.Subscript {
+			Position: pos,
+			Slice:    argument,
+			Offset:   offset,
+		}, nil
+	}
+}
+
+
 func (this *Parser) parseCallCore (pos errors.Position) (*entity.Call, error) {
 	err := this.expect(lexer.Ident)
 	if err != nil { return nil, err }