C#: Various C#8 features:

 - Async streams (test only)
 - Unmanaged generic structs (extractor support)
 - Alternate interpolated strings (test only)
 - static local function (test only)

Author: calumgrant

csharp/extractor/Semmle.Extraction.CSharp/Entities/Types/TypeParameter.cs

@@ -34,6 +34,9 @@ public override void Populate()
             if (symbol.HasConstructorConstraint)
                 Context.Emit(Tuples.general_type_parameter_constraints(constraints, 3));
 
+            if(symbol.HasUnmanagedTypeConstraint)
+                Context.Emit(Tuples.general_type_parameter_constraints(constraints, 4));
+
             ITypeSymbol baseType = symbol.HasValueTypeConstraint ?
                     Context.Compilation.GetTypeByMetadataName(valueTypeName) :
                     Context.Compilation.ObjectType;

csharp/ql/src/semmle/code/csharp/Generics.qll

@@ -223,6 +223,9 @@ class TypeParameterConstraints extends Element, @type_parameter_constraints {
   /** Holds if these constraints include a general value type constraint. */
   predicate hasValueTypeConstraint() { general_type_parameter_constraints(this, 2) }
 
+  /** Holds if these constraints include an unmanaged type constraint. */
+  predicate hasUnmanagedTypeConstraint() { general_type_parameter_constraints(this, 4) }
+
   /** Gets a textual representation of these constraints. */
   override string toString() { result = "where " + this.getTypeParameter().toString() + ": ..." }
 }

csharp/ql/test/library-tests/csharp8/AlternateInterpolatedStrings.cs

@@ -0,0 +1,7 @@
+using System;
+
+class AlternateInterpolatedStrings
+{
+    string s1 = $@"C:{12}";
+    string s2 = @$"C:{12}";
+}

csharp/ql/test/library-tests/csharp8/AlternateInterpolatedStrings.expected

@@ -0,0 +1,6 @@
+inserts
+| AlternateInterpolatedStrings.cs:5:17:5:26 | $"..." | 1 | AlternateInterpolatedStrings.cs:5:23:5:24 | 12 |
+| AlternateInterpolatedStrings.cs:6:17:6:26 | $"..." | 1 | AlternateInterpolatedStrings.cs:6:23:6:24 | 12 |
+text
+| AlternateInterpolatedStrings.cs:5:17:5:26 | $"..." | 0 | AlternateInterpolatedStrings.cs:5:20:5:21 | "C:" |
+| AlternateInterpolatedStrings.cs:6:17:6:26 | $"..." | 0 | AlternateInterpolatedStrings.cs:6:20:6:21 | "C:" |

csharp/ql/test/library-tests/csharp8/AlternateInterpolatedStrings.ql

@@ -0,0 +1,9 @@
+import csharp
+
+query predicate inserts(InterpolatedStringExpr expr, int i, Expr insert) {
+  insert = expr.getInsert(i)
+}
+
+query predicate text(InterpolatedStringExpr expr, int i, StringLiteral literal) {
+  literal = expr.getText(i)
+}

csharp/ql/test/library-tests/csharp8/AsyncStreams.cs

@@ -0,0 +1,44 @@
+// semmle-extractor-options: /r:System.Threading.Tasks.dll /r:System.Threading.Tasks.Extensions.dll /r:netstandard.dll
+
+using System;
+using System.Collections.Generic;
+using System.Threading;
+using System.Threading.Tasks;
+
+class AsyncStreams
+{
+    async IAsyncEnumerable<int> Items() {
+        yield return 1;
+        yield return 2;
+        await Task.Delay(1000);
+        yield return 3;
+    }
+
+    async void F()
+    {
+        await foreach(var item in Items())
+            Console.WriteLine(item);
+    }
+}
+
+namespace System
+{
+    interface IAsyncDisposable
+    {
+        System.Threading.Tasks.ValueTask DisposeAsync();
+    }
+}
+
+namespace System.Collections.Generic
+{
+    interface IAsyncEnumerable<out T>
+    {
+        public System.Collections.Generic.IAsyncEnumerator<T> GetAsyncEnumerator (System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken));
+    }
+
+    interface IAsyncEnumerator<out T> : IAsyncDisposable
+    {
+        T Current { get; }
+        System.Threading.Tasks.ValueTask<bool> MoveNextAsync();
+    }
+}

csharp/ql/test/library-tests/csharp8/DefaultInterfaceMethods.expected

@@ -0,0 +1,10 @@
+import csharp
+
+class DefaultInterfaceMethod extends Method {
+  DefaultInterfaceMethod() {
+    this.hasBody() and
+    this.getDeclaringType() instanceof Interface
+  }
+}
+
+query predicate defaultInterfaceMethods(DefaultInterfaceMethod m) { any() }

csharp/ql/test/library-tests/csharp8/DefaultInterfaceMethods.ql

@@ -0,0 +1,10 @@
+using System;
+
+class StaticLocalFunction
+{
+    int F()
+    {
+        static int G(int x) => x;
+        return G(12);
+    }
+}

csharp/ql/test/library-tests/csharp8/StaticLocalFunction.cs

@@ -0,0 +1,8 @@
+using System;
+
+struct S<T, U> where T: unmanaged
+{
+    int id;
+    T value1;
+    U value2;
+}