foreach loops now use "var" if the element type is a tuple and can be inferred from the collection type.

Additionally, the tuple element names inferred from the collection type are now used when translating the foreach body.

ICSharpCode.Decompiler.Tests/TestCases/Pretty/TupleTests.cs

@@ -109,9 +109,9 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 			Console.WriteLine(valueTuple.GetType().FullName);
 		}
 
-		public void Foreach(IEnumerable<(int Index, string Data)> input)
+		public void Foreach(IEnumerable<(int, string)> input)
 		{
-			foreach ((int, string) item3 in input) {
+			foreach (var item3 in input) {
 				int item = item3.Item1;
 				string item2 = item3.Item2;
 				Console.WriteLine($"{item}: {item2}");
@@ -120,9 +120,9 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 
 		public void ForeachNamedElements(IEnumerable<(int Index, string Data)> input)
 		{
-			foreach ((int, string) item3 in input) {
-				int item = item3.Item1;
-				string item2 = item3.Item2;
+			foreach (var item3 in input) {
+				int item = item3.Index;
+				string item2 = item3.Data;
 				Console.WriteLine($"{item}: {item2}");
 			}
 		}

ICSharpCode.Decompiler.Tests/TestCases/Pretty/TupleTests.opt.roslyn.il

@@ -492,9 +492,6 @@
   .method public hidebysig instance void 
           Foreach(class [mscorlib]System.Collections.Generic.IEnumerable`1<valuetype [mscorlib]System.ValueTuple`2<int32,string>> input) cil managed
   {
-    .param [1]
-    .custom instance void [mscorlib]System.Runtime.CompilerServices.TupleElementNamesAttribute::.ctor(string[]) = ( 01 00 02 00 00 00 05 49 6E 64 65 78 04 44 61 74   // .......Index.Dat
-                                                                                                                    61 00 00 )                                        // a..
     // Code size       71 (0x47)
     .maxstack  3
     .locals init (class [mscorlib]System.Collections.Generic.IEnumerator`1<valuetype [mscorlib]System.ValueTuple`2<int32,string>> V_0,

ICSharpCode.Decompiler.Tests/TestCases/Pretty/TupleTests.roslyn.il

@@ -517,9 +517,6 @@
   .method public hidebysig instance void 
           Foreach(class [mscorlib]System.Collections.Generic.IEnumerable`1<valuetype [mscorlib]System.ValueTuple`2<int32,string>> input) cil managed
   {
-    .param [1]
-    .custom instance void [mscorlib]System.Runtime.CompilerServices.TupleElementNamesAttribute::.ctor(string[]) = ( 01 00 02 00 00 00 05 49 6E 64 65 78 04 44 61 74   // .......Index.Dat
-                                                                                                                    61 00 00 )                                        // a..
     // Code size       79 (0x4f)
     .maxstack  3
     .locals init (class [mscorlib]System.Collections.Generic.IEnumerator`1<valuetype [mscorlib]System.ValueTuple`2<int32,string>> V_0,

ICSharpCode.Decompiler/CSharp/Resolver/CSharpResolver.cs

@@ -1678,7 +1678,122 @@ namespace ICSharpCode.Decompiler.CSharp.Resolver
 			return memberLookup.Lookup(this.CurrentObjectInitializer, identifier, EmptyList<IType>.Instance, false);
 		}
 		#endregion
-		
+
+		#region ResolveForeach
+		public ForEachResolveResult ResolveForeach(ResolveResult expression)
+		{
+			var memberLookup = CreateMemberLookup();
+
+			IType collectionType, enumeratorType, elementType;
+			ResolveResult getEnumeratorInvocation;
+			ResolveResult currentRR = null;
+			// C# 4.0 spec: §8.8.4 The foreach statement
+			if (expression.Type.Kind == TypeKind.Array || expression.Type.Kind == TypeKind.Dynamic) {
+				collectionType = compilation.FindType(KnownTypeCode.IEnumerable);
+				enumeratorType = compilation.FindType(KnownTypeCode.IEnumerator);
+				if (expression.Type.Kind == TypeKind.Array) {
+					elementType = ((ArrayType)expression.Type).ElementType;
+				} else {
+					elementType = SpecialType.Dynamic;
+				}
+				getEnumeratorInvocation = ResolveCast(collectionType, expression);
+				getEnumeratorInvocation = ResolveMemberAccess(getEnumeratorInvocation, "GetEnumerator", EmptyList<IType>.Instance, NameLookupMode.InvocationTarget);
+				getEnumeratorInvocation = ResolveInvocation(getEnumeratorInvocation, new ResolveResult[0]);
+			} else {
+				var getEnumeratorMethodGroup = memberLookup.Lookup(expression, "GetEnumerator", EmptyList<IType>.Instance, true) as MethodGroupResolveResult;
+				if (getEnumeratorMethodGroup != null) {
+					var or = getEnumeratorMethodGroup.PerformOverloadResolution(
+						compilation, new ResolveResult[0],
+						allowExtensionMethods: false, allowExpandingParams: false, allowOptionalParameters: false);
+					if (or.FoundApplicableCandidate && !or.IsAmbiguous && !or.BestCandidate.IsStatic && or.BestCandidate.Accessibility == Accessibility.Public) {
+						collectionType = expression.Type;
+						getEnumeratorInvocation = or.CreateResolveResult(expression);
+						enumeratorType = getEnumeratorInvocation.Type;
+						currentRR = memberLookup.Lookup(new ResolveResult(enumeratorType), "Current", EmptyList<IType>.Instance, false);
+						elementType = currentRR.Type;
+					} else {
+						CheckForEnumerableInterface(expression, out collectionType, out enumeratorType, out elementType, out getEnumeratorInvocation);
+					}
+				} else {
+					CheckForEnumerableInterface(expression, out collectionType, out enumeratorType, out elementType, out getEnumeratorInvocation);
+				}
+			}
+			IMethod moveNextMethod = null;
+			var moveNextMethodGroup = memberLookup.Lookup(new ResolveResult(enumeratorType), "MoveNext", EmptyList<IType>.Instance, false) as MethodGroupResolveResult;
+			if (moveNextMethodGroup != null) {
+				var or = moveNextMethodGroup.PerformOverloadResolution(
+					compilation, new ResolveResult[0],
+					allowExtensionMethods: false, allowExpandingParams: false, allowOptionalParameters: false);
+				moveNextMethod = or.GetBestCandidateWithSubstitutedTypeArguments() as IMethod;
+			}
+
+			if (currentRR == null)
+				currentRR = memberLookup.Lookup(new ResolveResult(enumeratorType), "Current", EmptyList<IType>.Instance, false);
+			IProperty currentProperty = null;
+			if (currentRR is MemberResolveResult)
+				currentProperty = ((MemberResolveResult)currentRR).Member as IProperty;
+
+			var voidType = compilation.FindType(KnownTypeCode.Void);
+			return new ForEachResolveResult(getEnumeratorInvocation, collectionType, enumeratorType, elementType,
+											currentProperty, moveNextMethod, voidType);
+		}
+
+		void CheckForEnumerableInterface(ResolveResult expression, out IType collectionType, out IType enumeratorType, out IType elementType, out ResolveResult getEnumeratorInvocation)
+		{
+			bool? isGeneric;
+			elementType = GetElementTypeFromIEnumerable(expression.Type, compilation, false, out isGeneric);
+			if (isGeneric == true) {
+				ITypeDefinition enumerableOfT = compilation.FindType(KnownTypeCode.IEnumerableOfT).GetDefinition();
+				if (enumerableOfT != null)
+					collectionType = new ParameterizedType(enumerableOfT, new[] { elementType });
+				else
+					collectionType = SpecialType.UnknownType;
+
+				ITypeDefinition enumeratorOfT = compilation.FindType(KnownTypeCode.IEnumeratorOfT).GetDefinition();
+				if (enumeratorOfT != null)
+					enumeratorType = new ParameterizedType(enumeratorOfT, new[] { elementType });
+				else
+					enumeratorType = SpecialType.UnknownType;
+			} else if (isGeneric == false) {
+				collectionType = compilation.FindType(KnownTypeCode.IEnumerable);
+				enumeratorType = compilation.FindType(KnownTypeCode.IEnumerator);
+			} else {
+				collectionType = SpecialType.UnknownType;
+				enumeratorType = SpecialType.UnknownType;
+			}
+			getEnumeratorInvocation = ResolveCast(collectionType, expression);
+			getEnumeratorInvocation = ResolveMemberAccess(getEnumeratorInvocation, "GetEnumerator", EmptyList<IType>.Instance, NameLookupMode.InvocationTarget);
+			getEnumeratorInvocation = ResolveInvocation(getEnumeratorInvocation, new ResolveResult[0]);
+		}
+
+		static IType GetElementTypeFromIEnumerable(IType collectionType, ICompilation compilation, bool allowIEnumerator, out bool? isGeneric)
+		{
+			bool foundNonGenericIEnumerable = false;
+			foreach (IType baseType in collectionType.GetAllBaseTypes()) {
+				ITypeDefinition baseTypeDef = baseType.GetDefinition();
+				if (baseTypeDef != null) {
+					KnownTypeCode typeCode = baseTypeDef.KnownTypeCode;
+					if (typeCode == KnownTypeCode.IEnumerableOfT || (allowIEnumerator && typeCode == KnownTypeCode.IEnumeratorOfT)) {
+						ParameterizedType pt = baseType as ParameterizedType;
+						if (pt != null) {
+							isGeneric = true;
+							return pt.GetTypeArgument(0);
+						}
+					}
+					if (typeCode == KnownTypeCode.IEnumerable || (allowIEnumerator && typeCode == KnownTypeCode.IEnumerator))
+						foundNonGenericIEnumerable = true;
+				}
+			}
+			// System.Collections.IEnumerable found in type hierarchy -> Object is element type.
+			if (foundNonGenericIEnumerable) {
+				isGeneric = false;
+				return compilation.FindType(KnownTypeCode.Object);
+			}
+			isGeneric = null;
+			return SpecialType.UnknownType;
+		}
+		#endregion
+
 		#region GetExtensionMethods
 		/// <summary>
 		/// Gets all extension methods that are available in the current context.

ICSharpCode.Decompiler/CSharp/StatementBuilder.cs

@@ -454,6 +454,7 @@ namespace ICSharpCode.Decompiler.CSharp
 			// For example: foreach (ClassA item in nonGenericEnumerable)
 			var type = singleGetter.Method.ReturnType;
 			ILInstruction instToReplace = singleGetter;
+			bool useVar = false;
 			switch (instToReplace.Parent) {
 				case CastClass cc:
 					type = cc.Type;
@@ -463,7 +464,18 @@ namespace ICSharpCode.Decompiler.CSharp
 					type = ua.Type;
 					instToReplace = ua;
 					break;
+				default:
+					if (TupleType.IsTupleCompatible(type, out _)) {
+						// foreach with get_Current returning a tuple type, let's check which type "var" would infer:
+						var foreachRR = exprBuilder.resolver.ResolveForeach(collectionExpr.GetResolveResult());
+						if (EqualErasedType(type, foreachRR.ElementType)) {
+							type = foreachRR.ElementType;
+							useVar = true;
+						}
+					}
+					break;
 			}
+
 			// Handle the required foreach-variable transformation:
 			switch (transformation) {
 				case RequiredGetCurrentTransformation.UseExistingVariable:
@@ -507,9 +519,12 @@ namespace ICSharpCode.Decompiler.CSharp
 			Debug.Assert(firstStatement is ExpressionStatement);
 			firstStatement.Remove();
 
+			if (settings.AnonymousTypes && type.ContainsAnonymousType())
+				useVar = true;
+
 			// Construct the foreach loop.
 			var foreachStmt = new ForeachStatement {
-				VariableType = settings.AnonymousTypes && foreachVariable.Type.ContainsAnonymousType() ? new SimpleType("var") : exprBuilder.ConvertType(foreachVariable.Type),
+				VariableType = useVar ? new SimpleType("var") : exprBuilder.ConvertType(foreachVariable.Type),
 				VariableName = foreachVariable.Name,
 				InExpression = collectionExpr.Detach(),
 				EmbeddedStatement = foreachBody
@@ -529,6 +544,13 @@ namespace ICSharpCode.Decompiler.CSharp
 			return foreachStmt;
 		}
 
+		static bool EqualErasedType(IType a, IType b)
+		{
+			a = a.AcceptVisitor(NormalizeTypeVisitor.TypeErasure);
+			b = b.AcceptVisitor(NormalizeTypeVisitor.TypeErasure);
+			return a.Equals(b);
+		}
+
 		private bool IsDynamicCastToIEnumerable(Expression expr, out Expression dynamicExpr)
 		{
 			if (!(expr is CastExpression cast)) {

ICSharpCode.Decompiler/Semantics/ForEachResolveResult.cs

@@ -48,11 +48,6 @@ namespace ICSharpCode.Decompiler.Semantics
 		/// </summary>
 		public readonly IType ElementType;
 		
-		/// <summary>
-		/// Gets the element variable.
-		/// </summary>
-		public readonly IVariable ElementVariable;
-		
 		/// <summary>
 		/// Gets the Current property on the IEnumerator.
 		/// Returns null if the property is not found.
@@ -65,7 +60,7 @@ namespace ICSharpCode.Decompiler.Semantics
 		/// </summary>
 		public readonly IMethod MoveNextMethod;
 		
-		public ForEachResolveResult(ResolveResult getEnumeratorCall, IType collectionType, IType enumeratorType, IType elementType, IVariable elementVariable, IProperty currentProperty, IMethod moveNextMethod, IType voidType)
+		public ForEachResolveResult(ResolveResult getEnumeratorCall, IType collectionType, IType enumeratorType, IType elementType, IProperty currentProperty, IMethod moveNextMethod, IType voidType)
 			: base(voidType)
 		{
 			if (getEnumeratorCall == null)
@@ -76,13 +71,10 @@ namespace ICSharpCode.Decompiler.Semantics
 				throw new ArgumentNullException("enumeratorType");
 			if (elementType == null)
 				throw new ArgumentNullException("elementType");
-			if (elementVariable == null)
-				throw new ArgumentNullException("elementVariable");
 			this.GetEnumeratorCall = getEnumeratorCall;
 			this.CollectionType = collectionType;
 			this.EnumeratorType = enumeratorType;
 			this.ElementType = elementType;
-			this.ElementVariable = elementVariable;
 			this.CurrentProperty = currentProperty;
 			this.MoveNextMethod = moveNextMethod;
 		}

ILSpy/Controls/CustomDialog.cs

@@ -100,6 +100,8 @@ namespace ICSharpCode.ILSpy.Controls
 		{
 			if (cancelButton == -1 && e.KeyCode == Keys.Escape) {
 				this.Close();
+			} else if (e.KeyCode == Keys.C && e.Control) {
+				Clipboard.SetText(this.Text + Environment.NewLine + label.Text);
 			}
 		}
 
@@ -156,5 +158,10 @@ namespace ICSharpCode.ILSpy.Controls
 			this.AutoScaleMode = AutoScaleMode.Dpi;
 			this.AutoScaleDimensions = new SizeF(96, 96);
 		}
+
+		private void CustomDialog_KeyDown(object sender, KeyEventArgs e)
+		{
+			throw new NotImplementedException();
+		}
 	}
 }