C#: Fix types of summary parameter nodes.

Author: aschackmull

csharp/ql/lib/semmle/code/csharp/dataflow/internal/DataFlowPrivate.qll

@@ -1136,16 +1136,6 @@ private module ParameterNodes {
     override predicate isParameterOf(DataFlowCallable c, ParameterPosition pos) {
       this.getSummarizedCallable() = c.asSummarizedCallable() and pos = this.getPosition()
     }
-
-    override Type getTypeImpl() {
-      exists(int i |
-        this.getPosition().getPosition() = i and
-        result = this.getSummarizedCallable().getParameter(i).getType()
-      )
-      or
-      this.getPosition().isThisParameter() and
-      result = this.getSummarizedCallable().getDeclaringType()
-    }
   }
 }
 

csharp/ql/lib/semmle/code/csharp/dataflow/internal/FlowSummaryImplSpecific.qll

@@ -41,6 +41,19 @@ DataFlowType getContentType(Content c) {
   )
 }
 
+/** Gets the type of the parameter at the given position. */
+DataFlowType getParameterType(SummarizedCallable c, ParameterPosition pos) {
+  exists(Type t | result = Gvn::getGlobalValueNumber(t) |
+    exists(int i |
+      pos.getPosition() = i and
+      t = c.getParameter(i).getType()
+    )
+    or
+    pos.isThisParameter() and
+    t = c.getDeclaringType()
+  )
+}
+
 private DataFlowType getReturnTypeBase(DotNet::Callable c, ReturnKind rk) {
   exists(Type t | result = Gvn::getGlobalValueNumber(t) |
     rk instanceof NormalReturnKind and