Changes in src/Tuples/Explode.cc [c6b4432:bccd70a]

File:

• src/Tuples/Explode.cc (modified) (1 diff)

src/Tuples/Explode.cc

@@ -15 +15 @@
 
 #include "Explode.h"
+#include <list>                  // for list
 
 #include "AST/Pass.hpp"          // for Pass
+#include "SynTree/Mutator.h"     // for Mutator
+#include "Common/PassVisitor.h"  // for PassVisitor
 
 namespace Tuples {
+        namespace {
+                // remove one level of reference from a reference type -- may be useful elsewhere.
+                Type * getReferenceBase( Type * t ) {
+                        if ( ReferenceType * refType = dynamic_cast<ReferenceType *>( t ) ) {
+                                return refType->get_base();
+                        } else {
+                                // for the moment, I want to know immediately if a non-reference type is ever passed in here.
+                                assertf( false, "getReferenceBase for non-ref: %s", toString( refType ).c_str() );
+                                return nullptr;
+                        }
+                }
+
+                struct CastExploder {
+                        bool castAdded = false;
+                        bool foundUniqueExpr = false;
+                        Expression * applyCast( Expression * expr, bool first = true ) {
+                                if ( TupleExpr * tupleExpr = dynamic_cast< TupleExpr * >( expr ) ){
+                                        foundUniqueExpr = true;
+                                        std::list< Expression * > exprs;
+                                        for ( Expression *& expr : tupleExpr->get_exprs() ) {
+                                                // move cast into tuple exprs
+                                                exprs.push_back( applyCast( expr, false ) );
+                                        }
+                                        // want the top-level expression to be cast to reference type, but not nested
+                                        // tuple expressions
+                                        if ( first ) {
+                                                castAdded = true;
+                                                Expression * tupleExpr = new TupleExpr( exprs );
+                                                return new CastExpr( tupleExpr, new ReferenceType( Type::Qualifiers(), tupleExpr->result->clone() ) );
+                                        } else {
+                                                return new TupleExpr( exprs );
+                                        }
+                                }
+                                if ( dynamic_cast<ReferenceType*>( expr->result ) ) {
+                                        // don't need to cast reference type to another reference type
+                                        return expr->clone();
+                                } else {
+                                        // anything else should be cast to reference as normal
+                                        castAdded = true;
+                                        return new CastExpr( expr->clone(), new ReferenceType( Type::Qualifiers(), expr->result->clone() ) );
+                                }
+                        }
+
+                        Expression * postmutate( UniqueExpr * uniqueExpr ) {
+                                // move cast into unique expr so that the unique expr has type T& rather than
+                                // type T. In particular, this transformation helps with generating the
+                                // correct code for reference-cast member tuple expressions, since the result
+                                // should now be a tuple of references rather than a reference to a tuple.
+                                // Still, this code is a bit awkward, and could use some improvement.
+                                UniqueExpr * newUniqueExpr = new UniqueExpr( applyCast( uniqueExpr->get_expr() ), uniqueExpr->get_id() );
+                                delete uniqueExpr;
+                                if ( castAdded ) {
+                                        // if a cast was added by applyCast, then unique expr now has one more layer of reference
+                                        // than it had coming into this function. To ensure types still match correctly, need to cast
+                                        //  to reference base so that outer expressions are still correct.
+                                        castAdded = false;
+                                        Type * toType = getReferenceBase( newUniqueExpr->result );
+                                        return new CastExpr( newUniqueExpr, toType->clone() );
+                                }
+                                return newUniqueExpr;
+                        }
+
+
+                        Expression * postmutate( TupleIndexExpr * tupleExpr ) {
+                                // tuple index expr needs to be rebuilt to ensure that the type of the
+                                // field is consistent with the type of the tuple expr, since the field
+                                // may have changed from type T to T&.
+                                Expression * expr = tupleExpr->get_tuple();
+                                tupleExpr->set_tuple( nullptr );
+                                TupleIndexExpr * ret = new TupleIndexExpr( expr, tupleExpr->get_index() );
+                                delete tupleExpr;
+                                return ret;
+                        }
+                };
+        } // namespace
+
+        Expression * distributeReference( Expression * expr ) {
+                PassVisitor<CastExploder> exploder;
+                expr = expr->acceptMutator( exploder );
+                if ( ! exploder.pass.foundUniqueExpr ) {
+                        // if a UniqueExpr was found, then the cast has already been added inside the UniqueExpr as appropriate
+                        expr = new CastExpr( expr, new ReferenceType( Type::Qualifiers(), expr->result->clone() ) );
+                }
+                return expr;
+        }
 
 namespace {