Add support for C# 7 tuple types:

 * Use tuple literals instead of calling 'new ValueTuple<..>' constructor
 * Where available, use element names for field access
 * Make CallBuilder aware of tuple-name/dynamic type erasure, to avoid introducing casts when the types differ only in the tuple element names.
 * Make CallBuilder provide a ResolveResult with the correct C# return type for the resulting expression.
   Previously we were using the type-erased return type from the IL.
 * Fix a bug that caused us to introduce returning casts when accessing an indexer.

ICSharpCode.Decompiler.Tests/ICSharpCode.Decompiler.Tests.csproj

@@ -70,7 +70,7 @@
  <Compile Include="TestCases\Pretty\Issue1080.cs" />
  <Compile Include="TestCases\Pretty\QualifierTests.cs" />
  <Compile Include="TestCases\Pretty\RefLocalsAndReturns.cs" />
- <Compile Include="TestCases\Pretty\TupleTypes.cs" />
+ <Compile Include="TestCases\Pretty\TupleTests.cs" />
  <Compile Include="TestCases\Pretty\WellKnownConstants.cs" />
  <Compile Include="TypeSystem\TypeSystemHelper.cs" />
  <Compile Include="TypeSystem\TypeSystemLoaderTests.cs" />

ICSharpCode.Decompiler.Tests/PrettyTestRunner.cs

@@ -280,7 +280,7 @@ public void QualifierTests([ValueSource("defaultOptions")] CSharpCompilerOptions
  }
 
  [Test]
- public void TupleTypes([ValueSource("roslynOnlyOptions")] CSharpCompilerOptions cscOptions)
+ public void TupleTests([ValueSource("roslynOnlyOptions")] CSharpCompilerOptions cscOptions)
  {
  RunForLibrary(cscOptions: cscOptions);
  }

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

@@ -17,10 +17,12 @@
 // DEALINGS IN THE SOFTWARE.
 
 using System;
+using System.Collections.Generic;
+using System.Linq;
 
 namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 {
- public class TupleTypes
+ public class TupleTests
  {
  public ValueTuple VT0;
  public ValueTuple<int> VT1;
@@ -44,5 +46,34 @@ public class TupleTypes
  public ((object a, dynamic b), dynamic, (dynamic c, object d)) Nested2;
  public (ValueTuple a, (int x1, int x2), ValueTuple<int> b, (int y1, int y2), (int, int) c) Nested3;
  public (int a, int b, int c, int d, int e, int f, int g, int h, (int i, int j)) Nested4;
+
+ public Dictionary<(int a, string b), (string c, int d)> TupleDict;
+
+ public int VT1Member => VT1.Item1;
+ public int AccessUnnamed8 => Unnamed8.Item8;
+ public int AccessNamed8 => Named8.h;
+ public int AccessPartiallyNamed => PartiallyNamed.a + PartiallyNamed.Item3;
+
+ public ValueTuple<int> NewTuple1 => new ValueTuple<int>(1);
+ public (int a, int b) NewTuple2 => (1, 2);
+ public object BoxedTuple10 => (1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
+
+ public (uint, int) SwapUnnamed => (Unnamed2.Item2, Unnamed2.Item1);
+ public (uint, int) SwapNamed2 => (Named2.b, Named2.a);
+
+ public int TupleHash => (1, 2, 3).GetHashCode();
+ public int TupleHash2 => Named2.GetHashCode();
+
+ public void UseDict()
+ {
+ if (TupleDict.Count > 10) {
+ TupleDict.Clear();
+ }
+ // TODO: it would be nice if we could infer the name 'c' for the local
+ string item = TupleDict[(1, "abc")].c;
+ Console.WriteLine(item);
+ Console.WriteLine(item);
+ Console.WriteLine(TupleDict.Values.ToList().First().d);
+ }
  }
 }

ICSharpCode.Decompiler/CSharp/CSharpDecompiler.cs

@@ -1374,6 +1374,16 @@ static AstType ConvertType(TypeReference type, ICustomAttributeProvider typeAttr
  HasNullableSpecifier = true
  };
  }
+ if (CecilLoader.IsValueTuple(gType, out int tupleCardinality) && tupleCardinality > 1 && tupleCardinality < TupleType.RestPosition) {
+ var tupleType = new TupleAstType();
+ foreach (var typeArgument in gType.GenericArguments) {
+ typeIndex++;
+ tupleType.Elements.Add(new TupleTypeElement {
+ Type = ConvertType(typeArgument, typeAttributes, ref typeIndex, options)
+ });
+ }
+ return tupleType;
+ }
  AstType baseType = ConvertType(gType.ElementType, typeAttributes, ref typeIndex, options & ~ConvertTypeOptions.IncludeTypeParameterDefinitions);
  List<AstType> typeArguments = new List<AstType>();
  foreach (var typeArgument in gType.GenericArguments) {