Improve decompiler behavior is System.ValueTuple exists in multiple referenced assemblies.

This can happen if an application is compiled for .NET 4.6.2 and references
System.ValueTuple.dll; but ILSpy loads the latest mscorlib (e.g. .NET 4.7)
which also contains struct System.ValueTuple.

ICSharpCode.Decompiler/CSharp/CallBuilder.cs

@@ -164,7 +164,8 @@ namespace ICSharpCode.Decompiler.CSharp
 				}
 				return tuple.WithRR(new TupleResolveResult(
 					expressionBuilder.compilation,
-					elementRRs.ToImmutableArray()
+					elementRRs.ToImmutableArray(),
+					valueTupleAssembly: inst.Method.DeclaringType.GetDefinition()?.ParentModule
 				)).WithILInstruction(inst);
 			}
 			return Build(inst.OpCode, inst.Method, inst.Arguments, constrainedTo: inst.ConstrainedTo)

ICSharpCode.Decompiler/CSharp/Syntax/TypeSystemAstBuilder.cs

@@ -384,9 +384,9 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 		bool TypeMatches(IType type, ITypeDefinition typeDef, IReadOnlyList<IType> typeArguments)
 		{
 			if (typeDef.TypeParameterCount == 0) {
-				return typeDef.Equals(type);
+				return TypeDefMatches(typeDef, type);
 			} else {
-				if (!typeDef.Equals(type.GetDefinition()))
+				if (!TypeDefMatches(typeDef, type.GetDefinition()))
 					return false;
 				ParameterizedType pt = type as ParameterizedType;
 				if (pt == null) {
@@ -401,6 +401,18 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 			}
 		}
 
+		bool TypeDefMatches(ITypeDefinition typeDef, IType type)
+		{
+			if (type.Name != typeDef.Name || type.Namespace != typeDef.Namespace || type.TypeParameterCount != typeDef.TypeParameterCount)
+				return false;
+			bool defIsNested = typeDef.DeclaringTypeDefinition != null;
+			bool typeIsNested = type.DeclaringType != null;
+			if (defIsNested && typeIsNested)
+				return TypeDefMatches(typeDef.DeclaringTypeDefinition, type.DeclaringType);
+			else
+				return defIsNested == typeIsNested;
+		}
+
 		/// <summary>
 		/// Adds type arguments to the result type.
 		/// </summary>

ICSharpCode.Decompiler/CSharp/TranslatedExpression.cs

@@ -224,7 +224,10 @@ namespace ICSharpCode.Decompiler.CSharp
 					newElementRRs.Add(newElementExpr.ResolveResult);
 				}
 				return newTupleExpr.WithILInstruction(this.ILInstructions)
-					.WithRR(new TupleResolveResult(expressionBuilder.compilation, newElementRRs.ToImmutableArray()));
+					.WithRR(new TupleResolveResult(
+						expressionBuilder.compilation, newElementRRs.ToImmutableArray(), 
+						valueTupleAssembly: targetTupleType.GetDefinition()?.ParentModule
+					));
 			}
 			var compilation = expressionBuilder.compilation;
 			var conversions = Resolver.CSharpConversions.Get(compilation);

ICSharpCode.Decompiler/Semantics/TupleResolveResult.cs

@@ -35,8 +35,9 @@ namespace ICSharpCode.Decompiler.Semantics
 
 		public TupleResolveResult(ICompilation compilation,
 			ImmutableArray<ResolveResult> elements,
-			ImmutableArray<string> elementNames = default(ImmutableArray<string>))
+			ImmutableArray<string> elementNames = default(ImmutableArray<string>),
-		: base(GetTupleType(compilation, elements, elementNames))
+			IModule valueTupleAssembly = null)
+		: base(GetTupleType(compilation, elements, elementNames, valueTupleAssembly))
 		{
 			this.Elements = elements;
 		}
@@ -46,12 +47,12 @@ namespace ICSharpCode.Decompiler.Semantics
 			return Elements;
 		}
 
-		static IType GetTupleType(ICompilation compilation, ImmutableArray<ResolveResult> elements, ImmutableArray<string> elementNames)
+		static IType GetTupleType(ICompilation compilation, ImmutableArray<ResolveResult> elements, ImmutableArray<string> elementNames, IModule valueTupleAssembly)
 		{
 			if (elements.Any(e => e.Type.Kind == TypeKind.None || e.Type.Kind == TypeKind.Null))
 				return SpecialType.NoType;
 			else
-				return new TupleType(compilation, elements.Select(e => e.Type).ToImmutableArray(), elementNames);
+				return new TupleType(compilation, elements.Select(e => e.Type).ToImmutableArray(), elementNames, valueTupleAssembly);
 		}
 	}
 }

ICSharpCode.Decompiler/TypeSystem/TupleType.cs

@@ -84,7 +84,7 @@ namespace ICSharpCode.Decompiler.TypeSystem
 
 		private static IType FindValueTupleType(ICompilation compilation, IModule valueTupleAssembly, int tpc)
 		{
-			FullTypeName typeName = new TopLevelTypeName("System", "ValueTuple", tpc);
+			var typeName = new TopLevelTypeName("System", "ValueTuple", tpc);
 			if (valueTupleAssembly != null) {
 				var typeDef = valueTupleAssembly.GetTypeDefinition(typeName);
 				if (typeDef != null)