Rust: Use DerefExpr.

Author: geoffw0

rust/ql/lib/codeql/rust/elements/internal/VariableImpl.qll

@@ -610,7 +610,7 @@ module Impl {
     exists(Expr mid |
       assignmentExprDescendant(mid) and
       getImmediateParent(e) = mid and
-      not mid.(PrefixExpr).getOperatorName() = "*" and
+      not mid instanceof DerefExpr and
       not mid instanceof FieldExpr and
       not mid instanceof IndexExpr
     )

rust/ql/lib/codeql/rust/internal/TypeInference.qll

@@ -259,8 +259,7 @@ private predicate typeEqualityLeft(AstNode n1, TypePath path1, AstNode n2, TypeP
   typeEquality(n1, path1, n2, path2)
   or
   n2 =
-    any(PrefixExpr pe |
-      pe.getOperatorName() = "*" and
+    any(DerefExpr pe |
       pe.getExpr() = n1 and
       path1.isCons(TRefTypeParameter(), path2)
     )
@@ -271,8 +270,7 @@ private predicate typeEqualityRight(AstNode n1, TypePath path1, AstNode n2, Type
   typeEquality(n1, path1, n2, path2)
   or
   n2 =
-    any(PrefixExpr pe |
-      pe.getOperatorName() = "*" and
+    any(DerefExpr pe |
       pe.getExpr() = n1 and
       path1 = TypePath::cons(TRefTypeParameter(), path2)
     )

rust/ql/lib/codeql/rust/security/AccessInvalidPointerExtensions.qll

@@ -50,9 +50,7 @@ module AccessInvalidPointer {
    * A pointer access using the unary `*` operator.
    */
   private class DereferenceSink extends Sink {
-    DereferenceSink() {
-      exists(PrefixExpr p | p.getOperatorName() = "*" and p.getExpr() = this.asExpr().getExpr())
-    }
+    DereferenceSink() { exists(DerefExpr p | p.getExpr() = this.asExpr().getExpr()) }
   }
 
   /**