Keep definitions when global-declarations enabled (#4572)

Fixes #4552. Fixes #4555. The SMT-LIB standard mandates that definitions
are kept when `:global-declarations` are enabled. Until now, CVC4 was
keeping track of the symbols of a definition correctly but lost the body
of the definition when the user context was popped. This commit fixes
the issue by adding a `global` parameter to
`SmtEngine::defineFunction()` and `SmtEngine::defineFunctionRec()`. If
that parameter is set, the definitions of functions are added at level 0
to `d_definedFunctions` and the lemmas for recursive function
definitions are kept in an additional list and asserted during each
`checkSat` call. The commit also updates new API, the commands, and the
parsers to reflect this change.

2 files changed, 19 insertions, 15 deletions

diff --git a/src/api/python/cvc4.pxd b/src/api/python/cvc4.pxd
index cc998306d..624b3c365 100644
--- a/src/api/python/cvc4.pxd
+++ b/src/api/python/cvc4.pxd
@@ -181,14 +181,14 @@ cdef extern from "api/cvc4cpp.h" namespace "CVC4::api":
         Term declareFun(const string& symbol, const vector[Sort]& sorts, Sort sort) except +
         Sort declareSort(const string& symbol, uint32_t arity) except +
         Term defineFun(const string& symbol, const vector[Term]& bound_vars,
-                       Sort sort, Term term) except +
-        Term defineFun(Term fun, const vector[Term]& bound_vars, Term term) except +
+                       Sort sort, Term term, bint glbl) except +
+        Term defineFun(Term fun, const vector[Term]& bound_vars, Term term, bint glbl) except +
         Term defineFunRec(const string& symbol, const vector[Term]& bound_vars,
-                          Sort sort, Term term) except +
+                          Sort sort, Term term, bint glbl) except +
         Term defineFunRec(Term fun, const vector[Term]& bound_vars,
-                          Term term) except +
+                          Term term, bint glbl) except +
         Term defineFunsRec(vector[Term]& funs, vector[vector[Term]]& bound_vars,
-                           vector[Term]& terms) except +
+                           vector[Term]& terms, bint glbl) except +
         vector[Term] getAssertions() except +
         vector[pair[Term, Term]] getAssignment() except +
         string getInfo(const string& flag) except +
diff --git a/src/api/python/cvc4.pxi b/src/api/python/cvc4.pxi
index 9dd9c1cde..b7593f6f1 100644
--- a/src/api/python/cvc4.pxi
+++ b/src/api/python/cvc4.pxi
@@ -797,13 +797,13 @@ cdef class Solver:
         sort.csort = self.csolver.declareSort(symbol.encode(), arity)
         return sort
 
-    def defineFun(self, sym_or_fun, bound_vars, sort_or_term, t=None):
+    def defineFun(self, sym_or_fun, bound_vars, sort_or_term, t=None, glbl=False):
         '''
         Supports two uses:
                 Term defineFun(str symbol, List[Term] bound_vars,
-                               Sort sort, Term term)
+                               Sort sort, Term term, bool glbl)
                 Term defineFun(Term fun, List[Term] bound_vars,
-                               Term term)
+                               Term term, bool glbl)
         '''
         cdef Term term = Term()
         cdef vector[c_Term] v
@@ -814,21 +814,23 @@ cdef class Solver:
             term.cterm = self.csolver.defineFun((<str?> sym_or_fun).encode(),
                                                 <const vector[c_Term] &> v,
                                                 (<Sort?> sort_or_term).csort,
-                                                (<Term?> t).cterm)
+                                                (<Term?> t).cterm,
+                                                <bint> glbl)
         else:
             term.cterm = self.csolver.defineFun((<Term?> sym_or_fun).cterm,
                                                 <const vector[c_Term]&> v,
-                                                (<Term?> sort_or_term).cterm)
+                                                (<Term?> sort_or_term).cterm,
+                                                <bint> glbl)
 
         return term
 
-    def defineFunRec(self, sym_or_fun, bound_vars, sort_or_term, t=None):
+    def defineFunRec(self, sym_or_fun, bound_vars, sort_or_term, t=None, glbl=False):
         '''
         Supports two uses:
                 Term defineFunRec(str symbol, List[Term] bound_vars,
-                               Sort sort, Term term)
+                               Sort sort, Term term, bool glbl)
                 Term defineFunRec(Term fun, List[Term] bound_vars,
-                               Term term)
+                               Term term, bool glbl)
         '''
         cdef Term term = Term()
         cdef vector[c_Term] v
@@ -839,11 +841,13 @@ cdef class Solver:
             term.cterm = self.csolver.defineFunRec((<str?> sym_or_fun).encode(),
                                                 <const vector[c_Term] &> v,
                                                 (<Sort?> sort_or_term).csort,
-                                                (<Term?> t).cterm)
+                                                (<Term?> t).cterm,
+                                                <bint> glbl)
         else:
             term.cterm = self.csolver.defineFunRec((<Term?> sym_or_fun).cterm,
                                                    <const vector[c_Term]&> v,
-                                                   (<Term?> sort_or_term).cterm)
+                                                   (<Term?> sort_or_term).cterm,
+                                                   <bint> glbl)
 
         return term