//let-statement ::= 'let' <var-name> ('[' <expression> ']')? '=' <expression> ';'
private void ParseLetStatement()
{
Match(new Token(TokenType.Keyword, "let"));
Token varName = NextToken();
if (GetClosestSymbol(varName.Value) == null)
{
ThrowCompilationException("Undefined variable '" + varName.Value + "'");
}
if (!_methodSymTable.HasSymbol(varName.Value))
{
Symbol variable = _classSymTable.GetSymbol(varName.Value);
if (variable.Kind == SymbolKind.Field &&
_currentSub.Kind != SubroutineKind.Constructor &&
_currentSub.Kind != SubroutineKind.Method)
{
ThrowCompilationException("Instance fields may be used only from a method or a constructor");
}
}
bool withArrayIndex = false;
if (LookAheadToken.Value == "[")
{
VerifyArrayAccessAllowed(varName);
withArrayIndex = true;
Match(new Token(TokenType.Symbol, "["));
ParseExpression();
Match(new Token(TokenType.Symbol, "]"));
}
Match(new Token(TokenType.Symbol, "="));
ParseExpression();
_codeGenerator.Assignment(varName, withArrayIndex);
Match(new Token(TokenType.Symbol, ";"));
//TODO: Type checking, but this is really hard . . . (we need
//to propagate the type of the LHS expression so that we can
//verify that it's the same as the RHS, and if RHS is an array
//access then we have no way of knowing what should come from the
//array, unless we start tracking all array types and not just
//use 'Array' for all arrays)
}
