Changeset caa649b for src/SynTree/TypeSubstitution.cc

Timestamp:

Mar 6, 2018, 12:11:11 PM (6 years ago)

Author:

Thierry Delisle <tdelisle@…>

Branches:

ADT, aaron-thesis, arm-eh, ast-experimental, cleanup-dtors, deferred_resn, demangler, enum, forall-pointer-decay, jacob/cs343-translation, jenkins-sandbox, master, new-ast, new-ast-unique-expr, new-env, no_list, persistent-indexer, pthread-emulation, qualifiedEnum, resolv-new, with_gc

Children:

520145b, e5d4e5c, e6c5e79

Parents:

094476d (diff), 1feb535f (diff)
Note: this is a merge changeset, the changes displayed below correspond to the merge itself.
Use the (diff) links above to see all the changes relative to each parent.

Message:

Merge branch 'master' of plg.uwaterloo.ca:software/cfa/cfa-cc

File:

• src/SynTree/TypeSubstitution.cc (modified) (1 diff)

src/SynTree/TypeSubstitution.cc

@@ -104 +104 @@
 bool TypeSubstitution::empty() const {
         return typeEnv.empty() && varEnv.empty();
+}
+
+namespace {
+        struct EnvTrimmer {
+                TypeSubstitution * env, * newEnv;
+                EnvTrimmer( TypeSubstitution * env, TypeSubstitution * newEnv ) : env( env ), newEnv( newEnv ){}
+                void previsit( TypeDecl * tyDecl ) {
+                        // transfer known bindings for seen type variables
+                        if ( Type * t = env->lookup( tyDecl->name ) ) {
+                                newEnv->add( tyDecl->name, t );
+                        }
+                }
+        };
+} // namespace
+
+/// reduce environment to just the parts that are referenced in a given expression
+TypeSubstitution * TypeSubstitution::newFromExpr( Expression * expr, TypeSubstitution * env ) {
+        if ( env ) {
+                TypeSubstitution * newEnv = new TypeSubstitution();
+                PassVisitor<EnvTrimmer> trimmer( env, newEnv );
+                expr->accept( trimmer );
+                return newEnv;
+        }
+        return nullptr;
 }