C#: Generalize pattern definition to not only include top level pattern definitions.

Author: michaelnebel

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

@@ -321,7 +321,7 @@ module AssignableInternal {
       TLocalVariableDefinition(LocalVariableDeclExpr lvde) {
         not lvde.hasInitializer() and
         not exists(getTupleSource(TTupleAssignmentDefinition(_, lvde))) and
-        not lvde instanceof TopLevelPatternDecl and
+        not lvde instanceof LocalVariablePatternDecl and
         not lvde.isOutArgument()
       } or
       TImplicitParameterDefinition(Parameter p) {
@@ -340,7 +340,7 @@ module AssignableInternal {
         default = p.getDefaultValue()
       } or
       TAddressOfDefinition(AddressOfExpr aoe) or
-      TPatternDefinition(TopLevelPatternDecl tlpd) or
+      TPatternDefinition(LocalVariablePatternDecl lvpd) or
       TAssignOperationDefinition(AssignOperation ao) {
         ao instanceof AssignCallExpr and not ao instanceof CompoundAssignmentOperatorCall
         or
@@ -753,18 +753,18 @@ module AssignableDefinitions {
   }
 
   /**
-   * A local variable definition in a pattern, for example `x is int i`.
+   * A local variable definition in a pattern, for example `int i` in `x is int i`.
    */
   class PatternDefinition extends AssignableDefinition, TPatternDefinition {
-    TopLevelPatternDecl tlpd;
+    LocalVariablePatternDecl lvpd;
 
-    PatternDefinition() { this = TPatternDefinition(tlpd) }
+    PatternDefinition() { this = TPatternDefinition(lvpd) }
 
     /** Gets the element matches against this pattern. */
-    PatternMatch getMatch() { result = tlpd.getMatch() }
+    PatternMatch getMatch() { result = lvpd.getMatch() }
 
     /** Gets the underlying local variable declaration. */
-    LocalVariableDeclExpr getDeclaration() { result = tlpd }
+    LocalVariableDeclExpr getDeclaration() { result = lvpd }
 
     override Expr getSource() { result = this.getMatch().getExpr() }