bool IBoundExprVisitor <bool> .Visit(BoundIfExpr expr)
{
// evaluate the condition
expr.Condition.Accept(this);
mJumpTable.JumpIfFalse("else");
// thenBody
expr.ThenBody.Accept(this);
if (expr.ElseBody == null)
{
// jump past it
mJumpTable.PatchJump("else");
}
else
{
// jump to end
mJumpTable.Jump("end");
// elseBody
mJumpTable.PatchJump("else");
expr.ElseBody.Accept(this);
// end
mJumpTable.PatchJump("end");
}
return(true);
}
IBoundExpr IUnboundExprVisitor<IBoundExpr>.Visit(IfExpr expr)
{
var bound = new BoundIfExpr(
expr.Condition.Accept(this),
expr.ThenBody.Accept(this),
(expr.ElseBody == null) ? null : expr.ElseBody.Accept(this));
if (bound.Condition.Type != Decl.Bool)
{
throw new CompileException(expr.Position, String.Format(
"Condition of if/then/else is returning type {0} but should be Bool.",
bound.Condition.Type));
}
if (bound.ElseBody != null)
{
// has an else, so make sure both arms match
if (!DeclComparer.TypesMatch(bound.ThenBody.Type, bound.ElseBody.Type))
{
throw new CompileException(expr.Position, String.Format(
"Branches of if/then/else do not return the same type. Then arm returns {0} while else arm returns {1}.",
bound.ThenBody.Type, bound.ElseBody.Type));
}
}
else
{
// no else, so make the then body doesn't return a value
if ((bound.ThenBody.Type != Decl.Unit) && (bound.ThenBody.Type != Decl.EarlyReturn))
{
throw new CompileException(expr.Position, String.Format(
"Body of if/then is returning type {0} but must be Unit (or a return) if there is no else branch.",
bound.ThenBody.Type));
}
}
return bound;
}
