public void visit(AssignCommand that)
{
// determine the type of the right-hand-side (RHS) by visiting it
that.Expression.visit(this);
// check that the symbol exists - by trying to look it up
Declaration declaration = _symbols.Lookup(that.Name);
if (declaration == null)
{
throw new CheckerError(that.Position, "Variable '" + that.Name + "' not declared in assignment statement");
}
// check that the symbol is indeed a variable
switch (declaration.Kind)
{
case SymbolKind.Constant:
throw new CheckerError(that.Position, "Cannot assign to a constant");
case SymbolKind.Function:
throw new CheckerError(that.Position, "Cannot assign to a function");
case SymbolKind.Parameter:
throw new CheckerError(that.Position, "Cannot call parameter");
case SymbolKind.Variable:
break;
default:
throw new CheckerError(that.Position, "Unknown symbol kind: " + declaration.Kind.ToString());
}
// check that the types of the left-hand-side is equal to the type of the right-hand-side
TypeKind firstType = declaration.Type.Kind;
TypeKind otherType = that.Expression.Type.Kind;
if (firstType != otherType)
{
throw new CheckerError(that.Position, "Type mismatch in assignment");
}
}
