Rust: Remove restriction that blanket(-like) impls must have a constraint

Author: hvitved

rust/ql/lib/codeql/rust/internal/typeinference/BlanketImplementation.qll

@@ -126,7 +126,7 @@ module SatisfiesBlanketConstraint<
 
   /**
    * Holds if the argument type `at` satisfies the first non-trivial blanket
-   * constraint of `impl`.
+   * constraint of `impl`, or if there are no non-trivial constraints of `impl`.
    */
   pragma[nomagic]
   predicate satisfiesBlanketConstraint(ArgumentType at, ImplItemNode impl) {
@@ -135,6 +135,11 @@ module SatisfiesBlanketConstraint<
       SatisfiesBlanketConstraintInput::relevantConstraint(ato, impl, traitBound) and
       SatisfiesBlanketConstraint::satisfiesConstraintType(ato, TTrait(traitBound), _, _)
     )
+    or
+    exists(TypeParam blanketTypeParam |
+      hasBlanketCandidate(at, impl, _, blanketTypeParam) and
+      not hasFirstNonTrivialTraitBound(blanketTypeParam, _)
+    )
   }
 
   /**