public static FindResult Deconstruction(DeconstructInstruction deconstruction)
{
return(new FindResult(FindResultType.Deconstruction, deconstruction, null));
}
bool TransformDeconstruction(Block block, int pos)
{
int startPos = pos;
Action <DeconstructInstruction> delayedActions = null;
if (MatchDeconstruction(block.Instructions[pos], out IMethod deconstructMethod,
out ILInstruction rootTestedOperand))
{
pos++;
}
if (!MatchConversions(block, ref pos, out var conversions, out var conversionStLocs, ref delayedActions))
{
return(false);
}
if (!MatchAssignments(block, ref pos, conversions, conversionStLocs, ref delayedActions))
{
return(false);
}
// first tuple element may not be discarded,
// otherwise we would run this transform on a suffix of the actual pattern.
if (deconstructionResults[0] == null)
{
return(false);
}
context.Step("Deconstruction", block.Instructions[startPos]);
DeconstructInstruction replacement = new DeconstructInstruction();
IType deconstructedType;
if (deconstructMethod == null)
{
deconstructedType = this.tupleType;
rootTestedOperand = new LdLoc(this.tupleVariable);
}
else
{
if (deconstructMethod.IsStatic)
{
deconstructedType = deconstructMethod.Parameters[0].Type;
}
else
{
deconstructedType = deconstructMethod.DeclaringType;
}
}
var rootTempVariable = context.Function.RegisterVariable(VariableKind.PatternLocal, deconstructedType);
replacement.Pattern = new MatchInstruction(rootTempVariable, deconstructMethod, rootTestedOperand)
{
IsDeconstructCall = deconstructMethod != null,
IsDeconstructTuple = this.tupleType != null
};
int index = 0;
foreach (ILVariable v in deconstructionResults)
{
var result = v;
if (result == null)
{
var freshVar = new ILVariable(VariableKind.PatternLocal, this.tupleType.ElementTypes[index])
{
Name = "E_" + index
};
context.Function.Variables.Add(freshVar);
result = freshVar;
}
else
{
result.Kind = VariableKind.PatternLocal;
}
replacement.Pattern.SubPatterns.Add(
new MatchInstruction(
result,
new DeconstructResultInstruction(index, result.StackType, new LdLoc(rootTempVariable))
)
);
index++;
}
replacement.Conversions = new Block(BlockKind.DeconstructionConversions);
foreach (var convInst in conversionStLocs)
{
replacement.Conversions.Instructions.Add(convInst);
}
replacement.Assignments = new Block(BlockKind.DeconstructionAssignments);
delayedActions?.Invoke(replacement);
block.Instructions[startPos] = replacement;
block.Instructions.RemoveRange(startPos + 1, pos - startPos - 1);
return(true);
}