C#: Apply closed-world assumption for type-parameter qualifiers in dynamic calls

Author: hvitved

csharp/ql/lib/semmle/code/csharp/Unification.qll

@@ -538,23 +538,26 @@ module Unification {
      *
      * Note: This predicate is inlined.
      */
-    bindingset[t]
+    bindingset[this]
+    pragma[inline_late]
     predicate unifiable(Type t) { none() }
 
     /**
      * Holds if this type parameter subsumes type `t`
      *
      * Note: This predicate is inlined.
      */
-    bindingset[t]
+    bindingset[this]
+    pragma[inline_late]
     predicate subsumes(Type t) { none() }
   }
 
   /** A type parameter that has a single constraint. */
   private class SingleConstraintTypeParameter extends ConstrainedTypeParameter {
     SingleConstraintTypeParameter() { constraintCount = 1 }
 
-    bindingset[t]
+    bindingset[this]
+    pragma[inline_late]
     override predicate unifiable(Type t) {
       exists(TTypeParameterConstraint ttc | ttc = getATypeConstraint(this) |
         ttc = TRefTypeConstraint() and
@@ -567,7 +570,8 @@ module Unification {
       )
     }
 
-    bindingset[t]
+    bindingset[this]
+    pragma[inline_late]
     override predicate subsumes(Type t) {
       exists(TTypeParameterConstraint ttc | ttc = getATypeConstraint(this) |
         ttc = TRefTypeConstraint() and
@@ -585,9 +589,13 @@ module Unification {
   private class MultiConstraintTypeParameter extends ConstrainedTypeParameter {
     MultiConstraintTypeParameter() { constraintCount > 1 }
 
-    bindingset[t]
+    pragma[nomagic]
+    TTypeParameterConstraint getATypeConstraint() { result = getATypeConstraint(this) }
+
+    bindingset[this]
+    pragma[inline_late]
     override predicate unifiable(Type t) {
-      forex(TTypeParameterConstraint ttc | ttc = getATypeConstraint(this) |
+      forex(TTypeParameterConstraint ttc | ttc = this.getATypeConstraint() |
         ttc = TRefTypeConstraint() and
         t.isRefType()
         or
@@ -598,9 +606,10 @@ module Unification {
       )
     }
 
-    bindingset[t]
+    bindingset[this]
+    pragma[inline_late]
     override predicate subsumes(Type t) {
-      forex(TTypeParameterConstraint ttc | ttc = getATypeConstraint(this) |
+      forex(TTypeParameterConstraint ttc | ttc = this.getATypeConstraint() |
         ttc = TRefTypeConstraint() and
         t.isRefType()
         or

csharp/ql/lib/semmle/code/csharp/dispatch/Dispatch.qll

@@ -862,9 +862,7 @@ private module Internal {
         or
         Unification::subsumes(t, qualifierType)
         or
-        t.(Unification::ConstrainedTypeParameter).unifiable(qualifierType)
-        or
-        qualifierType = t.(Unification::UnconstrainedTypeParameter).getAnUltimatelySuppliedType()
+        qualifierType = t.(TypeParameter).getAnUltimatelySuppliedType()
       )
     }