bool IPatternVisitor <bool> .Visit(UnionPattern expr)
{
// if this union case has never been matched, add it
bool covered = false;
if (!mCoveredValues.ContainsKey(expr.Name))
{
var matchedCase = ((Union)mMatchType).Cases.First(unionCase => unionCase.Name == expr.Name);
mCoveredValues[expr.Name] = new Coverage(matchedCase.ValueType.Bound);
}
else
{
// union case already present, so we may be covered
covered = true;
}
// if we have a value for the case, recurse in to cover it
if (expr.Value != null)
{
covered = mCoveredValues[expr.Name].CoverPattern(expr.Value);
}
// if we have all cases, and all of their values are covered, we're covered
if ((mCoveredValues.Count == ((Union)mMatchType).Cases.Count) &&
mCoveredValues.Values.All(cover => cover.FullyCovered))
{
FullyCovered = true;
}
return(covered);
}
IUnboundExpr IPatternVisitor <IUnboundExpr> .Visit(UnionPattern expr)
{
var unionDecl = (Union)mDecl;
var unionCase = unionDecl.Cases.First(thisCase => thisCase.Name == expr.Name);
// create an expression to match the union case
var matchExpr = mC.Call(unionCase.Name + "?", mValue);
// match the value
if (expr.Value != null)
{
// create an expression to pull out the union value
var unionValue = mC.Call(unionCase.Name + "Value", mValue);
// match it
var matchValue = Match(mContext, unionCase.ValueType.Bound, expr.Value,
unionValue, mVariables);
if (matchValue != null)
{
// combine with the previous check
matchExpr = mC.Op(matchExpr, "&", matchValue);
}
}
return(matchExpr);
}
bool IPatternVisitor <bool> .Visit(UnionPattern expr)
{
var union = mType as Union;
// it must be a union
if (union == null)
{
throw new CompileException(expr.Position,
String.Format("A union case pattern cannot be used to match against a value of type {0}.", mType));
}
// and it must be a valid case
var unionCase = union.Cases.FirstOrDefault(it => it.Name == expr.Name);
if (unionCase == null)
{
throw new CompileException(expr.Position,
String.Format("Union type {0} does not have a case named {1}.", union.Name, expr.Name));
}
// and the value must match
if (unionCase.ValueType.Bound == Decl.Unit)
{
if (expr.Value != null)
{
throw new CompileException(expr.Position,
String.Format("Union case {0} does not expect a value.", unionCase.Name));
}
}
else
{
if (expr.Value == null)
{
throw new CompileException(expr.Position,
String.Format("Union case {0} expects a value.", unionCase.Name));
}
expr.Value.Accept(new ShapeChecker(unionCase.ValueType.Bound, mUsedVariables));
}
return(true);
}
