IBoundExpr IUnboundExprVisitor<IBoundExpr>.Visit(AssignExpr expr)
{
var value = expr.Value.Accept(this);
if (expr.Target is TupleExpr) throw new NotSupportedException("Assignment to a tuple must be simplified before binding.");
// handle a name target: foo <- 3
var nameTarget = expr.Target as NameExpr;
if (nameTarget != null)
{
// see if it's a local
if (Scope.Contains(nameTarget.Name))
{
if (!Scope.IsMutable(nameTarget.Name)) throw new CompileException(expr.Position, "Cannot assign to immutable local.");
// direct assign to local
return new StoreExpr(new LocalsExpr(), Scope[nameTarget.Name], value);
}
// look for an assignment function
return TranslateAssignment(nameTarget.Position, nameTarget.Name, nameTarget.TypeArgs, new UnitExpr(Position.None), value);
}
// handle a function apply target: Foo 1 <- 3 ==> Foo<- (1, 3)
var callTarget = expr.Target as CallExpr;
if (callTarget != null)
{
var callArg = callTarget.Arg.Accept(this);
// see if it's a direct function call
var funcName = callTarget.Target as NameExpr;
if ((funcName != null) && !mContext.Compiler.IsLocal(mFunction, Scope, funcName.Name))
{
// translate the call
return TranslateAssignment(callTarget.Position, funcName.Name, funcName.TypeArgs, callArg, value);
}
// not calling a function, so try to desugar to a __Call<-
var desugaredCallTarget = callTarget.Target.Accept(this);
var desugaredCallArg = new BoundTupleExpr(new IBoundExpr[] { desugaredCallTarget, callArg, value });
var call = mContext.ResolveFunction(mFunction, expr.Target.Position,
"__Call<-", new IUnboundDecl[0], desugaredCallArg);
if (call != null) return call;
throw new CompileException(expr.Position, "Couldn't figure out what you're trying to do on the left side of an assignment.");
}
// if we got here, it's not a valid assignment expression
throw new CompileException(expr.Position, "Cannot assign to " + expr.Target);
}
public override IUnboundExpr Transform(AssignExpr expr)
{
// replaces:
//
// a, b <- Foo
//
// with:
//
// def __temp1 <- Foo
// a <- _temp1.0
// b <- _temp1.1
TupleExpr tuple = expr.Target as TupleExpr;
// ignore other assignments
if (tuple == null)
{
return(expr);
}
var exprs = new List <IUnboundExpr>();
var temp = mNameGenerator.Generate();
// evaluate the right-hand side once
exprs.Add(new DefineExpr(expr.Target.Position, temp, expr.Value, false));
// split out the fields
int index = 0;
foreach (var field in tuple.Fields)
{
exprs.Add(new AssignExpr(expr.Position, field, new CallExpr(new IntExpr(index), new NameExpr(expr.Position, temp))));
index++;
}
return(new BlockExpr(false, exprs));
}
public virtual IUnboundExpr Transform(AssignExpr expr)
{
return(expr);
}
IUnboundExpr IUnboundExprVisitor <IUnboundExpr> .Visit(AssignExpr expr)
{
return(Call("AssignExpr", Tuple(expr.Target.Accept(this), expr.Value.Accept(this))));
}