/// <summary>
/// Adds a local name to this name resolver.</summary>
/// <param name="name">
/// Specifies the identifier.</param>
/// <param name="resolveToExpression">
/// The expression to which the specified identifier should resolve.</param>
public void AddLocalName(string name, Expression resolveToExpression)
{
if (_localNames.ContainsKey(name))
{
throw new InvalidOperationException("The variable “{0}” cannot be redeclared because it is already used (perhaps in a parent scope) to denote something else.".Fmt(name));
}
_localNames[name] = new ResolveContextExpression(resolveToExpression);
}
/// <summary>
/// Adds a local name to this name resolver.</summary>
/// <param name="name">
/// Specifies the identifier.</param>
/// <param name="resolveToExpression">
/// The expression to which the specified identifier should resolve.</param>
public void AddLocalName(string name, Expression resolveToExpression)
{
if (_localNames.ContainsKey(name))
throw new InvalidOperationException("The variable “{0}” cannot be redeclared because it is already used (perhaps in a parent scope) to denote something else.".Fmt(name));
_localNames[name] = new ResolveContextExpression(resolveToExpression);
}
private bool infer()
{
// First of all, make sure that all the lambda expressions have the right number of parameters,
// and that we don’t have lambdas where there is no delegate or expression-tree type
for (int i = 0; i < _arguments.Length; i++)
{
var lambda = _arguments[i] as ResolveContextLambda;
if (lambda == null)
{
continue;
}
var dlgParam = ParserUtil.GetDelegateParameterTypes(_parameters[i].ParameterType);
if (dlgParam == null || dlgParam.Count() != lambda.Lambda.Parameters.Count)
{
return(false);
}
}
// §7.5.2.1 The first phase
for (int p = 0; p < _arguments.Length; p++)
{
// If Ei is an anonymous function, an explicit parameter type inference (§7.5.2.7) is made from Ei to Ti.
// This applies only if the anonymous function is explicitly-typed, in which case it will already have been resolved to an expression tree
var expr = _arguments[p] as ResolveContextExpression;
if (expr != null && expr.Expression is LambdaExpression)
{
if (!explicitParameterTypeInference((LambdaExpression)expr.Expression, _parameters[p].ParameterType))
{
return(false);
}
}
else if (_arguments[p] is ResolveContextLambda)
{
// Ignore implicitly-typed lambdas for now
}
// Otherwise, if Ei has a type U and xi is a value parameter then a lower-bound inference is made from U to Ti.
else if (_parameters[p].Mode == ArgumentMode.In)
{
if (!lowerBoundInference(_arguments[p].ExpressionType, _parameters[p].ParameterType))
{
return(false);
}
}
else
{
if (!exactInference(_arguments[p].ExpressionType, _parameters[p].ParameterType))
{
return(false);
}
}
}
// §7.5.2.2 The second phase
while (true)
{
// If no unfixed type parameters exist then type inference succeeds.
if (_fixed.All(b => b))
{
// Change all the implicitly-typed lambda expressions to explicit ones
for (int p = 0; p < _parameters.Length; p++)
{
var lambda = _arguments[p] as ResolveContextLambda;
if (lambda == null)
{
continue;
}
var dlgParameterTypes = ParserUtil.GetDelegateParameterTypes(_parameters[p].ParameterType);
var linqExpr = lambda.Lambda.ToLinqExpression(_resolver, dlgParameterTypes.Select(dlgp => substituteFixed(dlgp)).ToArray(), false);
_arguments[p] = new ResolveContextExpression(linqExpr, wasAnonymousFunction: true);
}
return(true);
}
// If there exists one or more arguments Ei with corresponding parameter type Ti such that the output type of Ei with type Ti
// contains at least one unfixed type parameter Xj, and none of the input types of Ei with type Ti contains any unfixed type
// parameter Xj, then an output type inference is made from all such Ei to Ti.
// (Plain English: infer the return types of all the lambda expressions where all the input types to the lambda are fixed.)
// (While we’re at it, we will also collection information about which parameter types are still dependent on each other.)
var isDependent = new bool[_genericParameters.Length];
for (int p = 0; p < _parameters.Length; p++)
{
// Is it a lambda?
var arg = _arguments[p] as ResolveContextLambda;
if (arg != null)
{
var dlgParameterTypes = ParserUtil.GetDelegateParameterTypes(_parameters[p].ParameterType);
if (dlgParameterTypes == null)
{
throw new InvalidOperationException("Cannot apply lambda expression argument “{0}” to a parameter that is not of a delegate or expression-tree type.".Fmt(arg.Lambda.ToString()));
}
var dlgReturnType = ParserUtil.GetDelegateReturnType(_parameters[p].ParameterType);
var occurInReturnType = getContainedIn(dlgReturnType).ToArray();
// Any unfixed parameters ⇒ not interested
if (dlgParameterTypes.SelectMany(t => getContainedIn(t)).Any(i => !_fixed[i]))
{
// An unfixed type parameter occurs in the delegate parameter types, so the
// type parameters that occur in the delegate return type depend on it
foreach (var inRet in occurInReturnType)
{
isDependent[inRet] = true;
}
continue;
}
// Generate the lambda expression so it becomes explicitly typed and determine its return type
var linqExpr = arg.Lambda.ToLinqExpression(_resolver, dlgParameterTypes.Select(dlgp => substituteFixed(dlgp)).ToArray(), false);
var argReturnType = ((LambdaExpression)linqExpr).ReturnType;
_arguments[p] = new ResolveContextExpression(linqExpr, wasAnonymousFunction: true);
if (!lowerBoundInference(argReturnType, dlgReturnType))
{
return(false);
}
}
else
{
// Is it a method group?
var mg = _arguments[p] as ResolveContextMethodGroup;
if (mg != null)
{
throw new NotImplementedException();
}
}
}
// Whether or not the previous step actually made an inference, we must now fix at least one type parameter, as follows:
// If there exists one or more type parameters Xi such that Xi is unfixed, and Xi has a non-empty set of bounds, and Xi
// does not depend on any Xj then each such Xi is fixed. If any fixing operation fails then type inference fails.
bool any = false;
for (int i = 0; i < _genericParameters.Length; i++)
{
if (!_fixed[i] && _bounds[i] != null && !isDependent[i])
{
if (!fix(i))
{
return(false);
}
any = true;
}
}
if (!any)
{
// Otherwise, if there exists one or more type parameters Xi such that Xi is unfixed, and Xi has a non-empty set of bounds,
// and there is at least one type parameter Xj that depends on Xi then each such Xi is fixed. If any fixing operation fails
// then type inference fails.
for (int i = 0; i < _genericParameters.Length; i++)
{
if (!_fixed[i] && _bounds[i] != null)
{
if (!fix(i))
{
return(false);
}
}
any = true;
}
}
if (!any)
{
// Otherwise, we are unable to make progress and there are unfixed parameters. Type inference fails.
return(false);
}
}
}
