Update theory rewriter ownership, add stats to strings (#4202)

This commit adds statistics for string rewrites. This is work towards proof     
support in the string solver. At a high level, this commit adds a pointer to a  
`SequenceStatistics` in the rewriters and modifies                              
`SequencesRewriter::returnRewrite()` to count the rewrites done. In practice,   
to make this work requires a couple of changes, some of them temporary:         
                                                                                
- We can't have a single `Rewriter` instance shared between different           
  `SmtEngine` instances anymore. Thus the `Rewriter` is now owned by the        
  `SmtEngine` and calling the rewriter retrieves the rewriter associated with   
  the current `SmtEngine`. This is a temporary workaround before we get rid of  
  singletons.                                                                   
- Methods in the `SequencesRewriter` and the `StringsRewriter` are made         
  non-`static` because they need access to the statistics instance.             
- `StringsEntail` now has non-`static` methods because it needs a reference to  
  the sequences rewriter that it can call.                                      
- The interaction between the `StringsRewriter` and the `SequencesRewriter`     
  changed: the `StringsRewriter` is now a proper `TheoryRewriter` that inherits 
  from `SequencesRewriter` and calls its `postRewrite()` before applying its    
  own rewrites (this is essentially a reversal of roles from before: the        
  `SequencesRewriter` used to call `static` methods in the `StringsRewriter`).  
- The theory rewriters are now owned by the individual theories. This design    
  mirrors the `EqualityEngine`s owned by the individual theories.

1 files changed, 0 insertions, 38 deletions

diff --git a/src/theory/quantifiers/candidate_rewrite_database.h b/src/theory/quantifiers/candidate_rewrite_database.h
index b68b20998..a9ca659e1 100644
--- a/src/theory/quantifiers/candidate_rewrite_database.h
+++ b/src/theory/quantifiers/candidate_rewrite_database.h
@@ -103,44 +103,6 @@ class CandidateRewriteDatabase : public ExprMiner
   bool d_silent;
 };
 
-/**
- * This class generates and stores candidate rewrite databases for multiple
- * types as needed.
- */
-class CandidateRewriteDatabaseGen
-{
- public:
-  /** constructor
-   *
-   * vars : the variables we are testing substitutions for, for all types,
-   * nsamples : number of sample points this class will test for all types.
-   */
-  CandidateRewriteDatabaseGen(std::vector<Node>& vars, unsigned nsamples);
-  /** add term
-   *
-   * This registers term n with this class. We generate the candidate rewrite
-   * database of the appropriate type (if not allocated already), and register
-   * n with this database. This may result in "candidate-rewrite" being
-   * printed on the output stream out. We return true if the term sol is
-   * distinct (up to equivalence) with all previous terms added to this class.
-   */
-  bool addTerm(Node n, std::ostream& out);
-
- private:
-  /** reference to quantifier engine */
-  QuantifiersEngine* d_qe;
-  /** the variables */
-  std::vector<Node> d_vars;
-  /** sygus sampler object for each type */
-  std::map<TypeNode, SygusSampler> d_sampler;
-  /** the number of samples */
-  unsigned d_nsamples;
-  /** candidate rewrite databases for each type */
-  std::map<TypeNode, CandidateRewriteDatabase> d_cdbs;
-  /** an extended rewriter object */
-  ExtendedRewriter d_ext_rewrite;
-};
-
 } /* CVC4::theory::quantifiers namespace */
 } /* CVC4::theory namespace */
 } /* CVC4 namespace */