Fix container type extraction of tuple members

Author: tamasvajk

csharp/extractor/Semmle.Extraction.CSharp/Entities/CachedSymbol.cs

@@ -16,7 +16,11 @@ protected CachedSymbol(Context cx, T init)
         {
         }
 
-        public virtual Type? ContainingType => Symbol.ContainingType is not null ? Type.Create(Context, Symbol.ContainingType) : null;
+        public virtual Type? ContainingType => Symbol.ContainingType is not null
+            ? Symbol.ContainingType.IsTupleType
+                ? NamedType.CreateNamedTypeFromTupleType(Context, Symbol.ContainingType)
+                : Type.Create(Context, Symbol.ContainingType)
+            : null;
 
         public void PopulateModifiers(TextWriter trapFile)
         {

csharp/ql/src/semmle/code/csharp/dataflow/LibraryTypeDataFlow.qll

@@ -1848,8 +1848,15 @@ class SystemTupleFlow extends LibraryTypeDataFlow, ValueOrRefType {
         c.(Constructor).getDeclaringType() = this and
         t = this
         or
-        c = this.getAMethod(any(string name | name.regexpMatch("Create(<,*>)?"))) and
-        t = c.getReturnType().getUnboundDeclaration()
+        exists(ValueOrRefType namedType |
+          namedType = this or namedType = this.(TupleType).getUnderlyingType()
+        |
+          c = namedType.getAMethod(any(string name | name.regexpMatch("Create(<,*>)?"))) and
+          (
+            t = c.getReturnType().getUnboundDeclaration() or
+            t = c.getReturnType().(TupleType).getUnderlyingType().getUnboundDeclaration()
+          )
+        )
       )
       or
       c =

csharp/ql/test/library-tests/csharp7/TupleTypes.expected

@@ -3,8 +3,8 @@
 | (Int32,Double) | (int, double) | ValueTuple<Int32, Double> | 2 | 0 | CSharp7.cs:215:6:215:8 | Item1 |
 | (Int32,Double) | (int, double) | ValueTuple<Int32, Double> | 2 | 1 | CSharp7.cs:215:11:215:16 | Item2 |
 | (Int32,Int32) | (int, int) | ValueTuple<Int32, Int32> | 2 | 0 | CSharp7.cs:64:10:64:10 | Item1 |
-| (Int32,Int32) | (int, int) | ValueTuple<Int32, Int32> | 2 | 1 | file://:0:0:0:0 | Item2 |
+| (Int32,Int32) | (int, int) | ValueTuple<Int32, Int32> | 2 | 1 | CSharp7.cs:64:17:64:17 | Item2 |
 | (String,Int32) | (string, int) | ValueTuple<String, Int32> | 2 | 0 | CSharp7.cs:84:17:84:17 | Item1 |
-| (String,Int32) | (string, int) | ValueTuple<String, Int32> | 2 | 1 | file://:0:0:0:0 | Item2 |
+| (String,Int32) | (string, int) | ValueTuple<String, Int32> | 2 | 1 | CSharp7.cs:84:23:84:23 | Item2 |
 | (String,String) | (string, string) | ValueTuple<String, String> | 2 | 0 | CSharp7.cs:89:19:89:27 | Item1 |
 | (String,String) | (string, string) | ValueTuple<String, String> | 2 | 1 | CSharp7.cs:89:30:89:33 | Item2 |