2010-05-25 Jb Evain <jbevain@novell.com>

[mcs.git] / mcs / pending.cs

//
// pending.cs: Pending method implementation
//
// Authors:
//   Miguel de Icaza (miguel@gnu.org)
//   Marek Safar (marek.safar@gmail.com)
//
// Dual licensed under the terms of the MIT X11 or GNU GPL
//
// Copyright 2001, 2002 Ximian, Inc (http://www.ximian.com)
// Copyright 2003-2008 Novell, Inc.
//

using System;
using System.Collections.Generic;
using System.Reflection;
using System.Reflection.Emit;
using System.Linq;

namespace Mono.CSharp {

        struct TypeAndMethods {
                public TypeSpec          type;
                public IList<MethodSpec> methods;

                // 
                // Whether it is optional, this is used to allow the explicit/implicit
                // implementation when a base class already implements an interface. 
                //
                // For example:
                //
                // class X : IA { }  class Y : X, IA { IA.Explicit (); }
                //
                public bool          optional;
                                
                //
                // This flag on the method says `We found a match, but
                // because it was private, we could not use the match
                //
                public MethodData [] found;

                // If a method is defined here, then we always need to
                // create a proxy for it.  This is used when implementing
                // an interface's indexer with a different IndexerName.
                public MethodSpec [] need_proxy;
        }

        public class PendingImplementation
        {
                /// <summary>
                ///   The container for this PendingImplementation
                /// </summary>
                TypeContainer container;
                
                /// <summary>
                ///   This is the array of TypeAndMethods that describes the pending implementations
                ///   (both interfaces and abstract methods in base class)
                /// </summary>
                TypeAndMethods [] pending_implementations;

                PendingImplementation (TypeContainer container, MissingInterfacesInfo[] missing_ifaces, IList<MethodSpec> abstract_methods, int total)
                {
                        var type_builder = container.Definition;
                        
                        this.container = container;
                        pending_implementations = new TypeAndMethods [total];

                        int i = 0;
                        if (abstract_methods != null) {
                                int count = abstract_methods.Count;
                                pending_implementations [i].methods = new MethodSpec [count];
                                pending_implementations [i].need_proxy = new MethodSpec [count];

                                pending_implementations [i].methods = abstract_methods;
                                pending_implementations [i].found = new MethodData [count];
                                pending_implementations [i].type = type_builder;
                                ++i;
                        }

                        foreach (MissingInterfacesInfo missing in missing_ifaces) {
                                var iface = missing.Type;
                                var mi = MemberCache.GetInterfaceMembers (iface);

                                int count = mi.Count;
                                pending_implementations [i].type = iface;
                                pending_implementations [i].optional = missing.Optional;
                                pending_implementations [i].methods = mi;
                                pending_implementations [i].found = new MethodData [count];
                                pending_implementations [i].need_proxy = new MethodSpec [count];
                                i++;
                        }
                }

                struct MissingInterfacesInfo {
                        public TypeSpec Type;
                        public bool Optional;

                        public MissingInterfacesInfo (TypeSpec t)
                        {
                                Type = t;
                                Optional = false;
                        }
                }

                static MissingInterfacesInfo [] EmptyMissingInterfacesInfo = new MissingInterfacesInfo [0];
                
                static MissingInterfacesInfo [] GetMissingInterfaces (TypeContainer container)
                {
                        //
                        // Notice that Interfaces will only return the interfaces that the Type
                        // is supposed to implement, not all the interfaces that the type implements.
                        //
                        var impl = container.Definition.Interfaces;

                        if (impl == null || impl.Count == 0)
                                return EmptyMissingInterfacesInfo;

                        MissingInterfacesInfo[] ret = new MissingInterfacesInfo[impl.Count];

                        for (int i = 0; i < impl.Count; i++)
                                ret [i] = new MissingInterfacesInfo (impl [i]);

                        // we really should not get here because Object doesnt implement any
                        // interfaces. But it could implement something internal, so we have
                        // to handle that case.
                        if (container.BaseType == null)
                                return ret;
                        
                        var base_impls = container.BaseType.Interfaces;
                        if (base_impls != null) {
                                foreach (TypeSpec t in base_impls) {
                                        for (int i = 0; i < ret.Length; i++) {
                                                if (t == ret[i].Type) {
                                                        ret[i].Optional = true;
                                                        break;
                                                }
                                        }
                                }
                        }

                        return ret;
                }
                
                //
                // Factory method: if there are pending implementation methods, we return a PendingImplementation
                // object, otherwise we return null.
                //
                // Register method implementations are either abstract methods
                // flagged as such on the base class or interface methods
                //
                static public PendingImplementation GetPendingImplementations (TypeContainer container)
                {
                        TypeSpec b = container.BaseType;

                        var missing_interfaces = GetMissingInterfaces (container);

                        //
                        // If we are implementing an abstract class, and we are not
                        // ourselves abstract, and there are abstract methods (C# allows
                        // abstract classes that have no abstract methods), then allocate
                        // one slot.
                        //
                        // We also pre-compute the methods.
                        //
                        bool implementing_abstract = ((b != null) && b.IsAbstract && (container.ModFlags & Modifiers.ABSTRACT) == 0);
                        IList<MethodSpec> abstract_methods = null;

                        if (implementing_abstract){
                                abstract_methods = MemberCache.GetNotImplementedAbstractMethods (b);
                                
                                if (abstract_methods == null)
                                        implementing_abstract = false;
                        }
                        
                        int total = missing_interfaces.Length +  (implementing_abstract ? 1 : 0);
                        if (total == 0)
                                return null;

                        return new PendingImplementation (container, missing_interfaces, abstract_methods, total);
                }

                public enum Operation {
                        //
                        // If you change this, review the whole InterfaceMethod routine as there
                        // are a couple of assumptions on these three states
                        //
                        Lookup, ClearOne, ClearAll
                }

                /// <summary>
                ///   Whether the specified method is an interface method implementation
                /// </summary>
                public MethodSpec IsInterfaceMethod (MemberName name, TypeSpec ifaceType, MethodData method)
                {
                        return InterfaceMethod (name, ifaceType, method, Operation.Lookup);
                }

                public void ImplementMethod (MemberName name, TypeSpec ifaceType, MethodData method, bool clear_one) 
                {
                        InterfaceMethod (name, ifaceType, method, clear_one ? Operation.ClearOne : Operation.ClearAll);
                }

                /// <remarks>
                ///   If a method in Type `t' (or null to look in all interfaces
                ///   and the base abstract class) with name `Name', return type `ret_type' and
                ///   arguments `args' implements an interface, this method will
                ///   return the MethodInfo that this method implements.
                ///
                ///   If `name' is null, we operate solely on the method's signature.  This is for
                ///   instance used when implementing indexers.
                ///
                ///   The `Operation op' controls whether to lookup, clear the pending bit, or clear
                ///   all the methods with the given signature.
                ///
                ///   The `MethodInfo need_proxy' is used when we're implementing an interface's
                ///   indexer in a class.  If the new indexer's IndexerName does not match the one
                ///   that was used in the interface, then we always need to create a proxy for it.
                ///
                /// </remarks>
                public MethodSpec InterfaceMethod (MemberName name, TypeSpec iType, MethodData method, Operation op)
                {
                        if (pending_implementations == null)
                                return null;

                        TypeSpec ret_type = method.method.ReturnType;
                        ParametersCompiled args = method.method.ParameterInfo;
                        bool is_indexer = method.method is Indexer.SetIndexerMethod || method.method is Indexer.GetIndexerMethod;

                        foreach (TypeAndMethods tm in pending_implementations){
                                if (!(iType == null || tm.type == iType))
                                        continue;

                                int method_count = tm.methods.Count;
                                MethodSpec m;
                                for (int i = 0; i < method_count; i++){
                                        m = tm.methods [i];

                                        if (m == null)
                                                continue;

                                        if (is_indexer) {
                                                if (!m.IsAccessor || m.Parameters.IsEmpty)
                                                        continue;
                                        } else {
                                                if (name.Name != m.Name)
                                                        continue;

                                                if (m.Arity != name.Arity)
                                                        continue;
                                        }

                                        if (!TypeSpecComparer.Override.IsEqual (m.Parameters, args))
                                                continue;

                                        if (!TypeSpecComparer.Override.IsEqual (m.ReturnType, ret_type)) {
                                                tm.found[i] = method;
                                                continue;
                                        }

                                        //
                                        // `need_proxy' is not null when we're implementing an
                                        // interface indexer and this is Clear(One/All) operation.
                                        //
                                        // If `name' is null, then we do a match solely based on the
                                        // signature and not on the name (this is done in the Lookup
                                        // for an interface indexer).
                                        //
                                        if (op != Operation.Lookup) {
                                                // If `t != null', then this is an explicitly interface
                                                // implementation and we can always clear the method.
                                                // `need_proxy' is not null if we're implementing an
                                                // interface indexer.  In this case, we need to create
                                                // a proxy if the implementation's IndexerName doesn't
                                                // match the IndexerName in the interface.
                                                if (m.DeclaringType.IsInterface && iType == null && name.Name != m.Name) {      // TODO: This is very expensive comparison
                                                        tm.need_proxy[i] = method.method.Spec;
                                                } else {
                                                        tm.methods[i] = null;
                                                }
                                        } else {
                                                tm.found [i] = method;
                                        }

                                        //
                                        // Lookups and ClearOne return
                                        //
                                        if (op != Operation.ClearAll)
                                                return m;
                                }

                                // If a specific type was requested, we can stop now.
                                if (tm.type == iType)
                                        return null;
                        }
                        return null;
                }

                /// <summary>
                ///   C# allows this kind of scenarios:
                ///   interface I { void M (); }
                ///   class X { public void M (); }
                ///   class Y : X, I { }
                ///
                ///   For that case, we create an explicit implementation function
                ///   I.M in Y.
                /// </summary>
                void DefineProxy (TypeSpec iface, MethodSpec base_method, MethodSpec iface_method)
                {
                        // TODO: Handle nested iface names
                        string proxy_name;
                        var ns = iface.MemberDefinition.Namespace;
                        if (string.IsNullOrEmpty (ns))
                                proxy_name = iface.MemberDefinition.Name + "." + iface_method.Name;
                        else
                                proxy_name = ns + "." + iface.MemberDefinition.Name + "." + iface_method.Name;

                        var param = iface_method.Parameters;

                        MethodBuilder proxy = container.TypeBuilder.DefineMethod (
                                proxy_name,
                                MethodAttributes.HideBySig |
                                MethodAttributes.NewSlot |
                                MethodAttributes.CheckAccessOnOverride |
                                MethodAttributes.Virtual,
                                CallingConventions.Standard | CallingConventions.HasThis,
                                base_method.ReturnType.GetMetaInfo (), param.GetMetaInfo ());

                        if (iface_method.IsGeneric) {
                                var gnames = iface_method.GenericDefinition.TypeParameters.Select (l => l.Name).ToArray ();
                                proxy.DefineGenericParameters (gnames);
                        }

                        for (int i = 0; i < param.Count; i++) {
                                string name = param.FixedParameters [i].Name;
                                ParameterAttributes attr = ParametersCompiled.GetParameterAttribute (param.FixedParameters [i].ModFlags);
                                proxy.DefineParameter (i + 1, attr, name);
                        }

                        int top = param.Count;
                        var ec = new EmitContext (null, proxy.GetILGenerator (), null);

                        for (int i = 0; i <= top; i++)
                                ParameterReference.EmitLdArg (ec, i);

                        ec.Emit (OpCodes.Call, base_method);
                        ec.Emit (OpCodes.Ret);

                        container.TypeBuilder.DefineMethodOverride (proxy, (MethodInfo) iface_method.GetMetaInfo ());
                }
                
                /// <summary>
                ///   This function tells whether one of our base classes implements
                ///   the given method (which turns out, it is valid to have an interface
                ///   implementation in a base
                /// </summary>
                bool BaseImplements (TypeSpec iface_type, MethodSpec mi, out MethodSpec base_method)
                {
                        var base_type = container.BaseType;
                        base_method = (MethodSpec) MemberCache.FindMember (base_type, new MemberFilter (mi), BindingRestriction.None);

                        if (base_method == null || (base_method.Modifiers & Modifiers.PUBLIC) == 0)
                                return false;

                        if (base_method.DeclaringType.IsInterface)
                                return false;

                        // Why was it here ????
                        //if (TypeManager.ImplementsInterface (base_type, iface_type)) {
                        //      return true;
                        //}

                        if (!base_method.IsAbstract && !base_method.IsVirtual)
                                // FIXME: We can avoid creating a proxy if base_method can be marked 'final virtual' instead.
                                //        However, it's too late now, the MethodBuilder has already been created (see bug 377519)
                                DefineProxy (iface_type, base_method, mi);

                        return true;
                }

                /// <summary>
                ///   Verifies that any pending abstract methods or interface methods
                ///   were implemented.
                /// </summary>
                public bool VerifyPendingMethods (Report Report)
                {
                        int top = pending_implementations.Length;
                        bool errors = false;
                        int i;
                        
                        for (i = 0; i < top; i++){
                                TypeSpec type = pending_implementations [i].type;

                                bool base_implements_type = type.IsInterface &&
                                        container.BaseType != null &&
                                        container.BaseType.ImplementsInterface (type);

                                for (int j = 0; j < pending_implementations [i].methods.Count; ++j) {
                                        var mi = pending_implementations[i].methods[j];
                                        if (mi == null)
                                                continue;

                                        if (type.IsInterface){
                                                var need_proxy =
                                                        pending_implementations [i].need_proxy [j];

                                                if (need_proxy != null) {
                                                        DefineProxy (type, need_proxy, mi);
                                                        continue;
                                                }

                                                if (pending_implementations [i].optional)
                                                        continue;

                                                MethodSpec candidate = null;
                                                if (base_implements_type || BaseImplements (type, mi, out candidate))
                                                        continue;

                                                if (candidate == null) {
                                                        MethodData md = pending_implementations [i].found [j];
                                                        if (md != null)
                                                                candidate = md.method.Spec;
                                                }

                                                Report.SymbolRelatedToPreviousError (mi);
                                                if (candidate != null) {
                                                        Report.SymbolRelatedToPreviousError (candidate);
                                                        if (candidate.IsStatic) {
                                                                Report.Error (736, container.Location,
                                                                        "`{0}' does not implement interface member `{1}' and the best implementing candidate `{2}' is static",
                                                                        container.GetSignatureForError (), mi.GetSignatureForError (), TypeManager.CSharpSignature (candidate));
                                                        } else if ((candidate.Modifiers & Modifiers.PUBLIC) == 0) {
                                                                Report.Error (737, container.Location,
                                                                        "`{0}' does not implement interface member `{1}' and the best implementing candidate `{2}' in not public",
                                                                        container.GetSignatureForError (), mi.GetSignatureForError (), candidate.GetSignatureForError ());
                                                        } else {
                                                                Report.Error (738, container.Location,
                                                                        "`{0}' does not implement interface member `{1}' and the best implementing candidate `{2}' return type `{3}' does not match interface member return type `{4}'",
                                                                        container.GetSignatureForError (), mi.GetSignatureForError (), TypeManager.CSharpSignature (candidate),
                                                                        TypeManager.CSharpName (candidate.ReturnType), TypeManager.CSharpName (mi.ReturnType));
                                                        }
                                                } else {
                                                        Report.Error (535, container.Location, "`{0}' does not implement interface member `{1}'",
                                                                container.GetSignatureForError (), mi.GetSignatureForError ());
                                                }
                                        } else {
                                                Report.SymbolRelatedToPreviousError (mi);
                                                Report.Error (534, container.Location, "`{0}' does not implement inherited abstract member `{1}'",
                                                        container.GetSignatureForError (), mi.GetSignatureForError ());
                                        }
                                        errors = true;
                                }
                        }
                        return errors;
                }
        }
}