Match Ergonomics - Auto-deref in `ref` patterns to get `&T`

4 files changed, 26 insertions, 18 deletions

diff --git a/src/hir/pattern.hpp b/src/hir/pattern.hpp
index cd6c7422..d16fd942 100644
--- a/src/hir/pattern.hpp
+++ b/src/hir/pattern.hpp
@@ -32,19 +32,23 @@ struct PatternBinding
     ::std::string   m_name;
     unsigned int    m_slot;
 
+    unsigned m_implicit_deref_count = 0;
+
     bool is_valid() const { return m_name != ""; }
 
     PatternBinding():
         m_mutable(false),
         m_type(Type::Move),
         m_name(""),
-        m_slot(0)
+        m_slot(0),
+        m_implicit_deref_count(0)
     {}
     PatternBinding(bool mut, Type type, ::std::string name, unsigned int slot):
         m_mutable(mut),
         m_type(type),
         m_name( mv$(name) ),
-        m_slot( slot )
+        m_slot( slot ),
+        m_implicit_deref_count(0)
     {}
 };
 
diff --git a/src/hir_typeck/expr_cs.cpp b/src/hir_typeck/expr_cs.cpp
index a8e80a56..0b6b0089 100644
--- a/src/hir_typeck/expr_cs.cpp
+++ b/src/hir_typeck/expr_cs.cpp
@@ -4134,33 +4134,30 @@ void Context::handle_pattern(const Span& sp, ::HIR::Pattern& pat, const ::HIR::T
                         break;
                     case ::HIR::PatternBinding::Type::MutRef:
                         // NOTE: Needs to deref and borrow to get just `&mut T` (where T isn't a &mut T)
-                        //while( TU_TEST1(type_p->m_data, Borrow, .type >= ::HIR::BorrowType::Unique) )
-                        //{
-                        //    n_deref ++;
-                        //    type_p = &context.m_ivars.get_type(*type_p->m_data.as_Borrow().inner);
-                        //}
+                        while( TU_TEST1(type_p->m_data, Borrow, .type >= ::HIR::BorrowType::Unique) )
+                        {
+                            n_deref ++;
+                            type_p = &context.m_ivars.get_type(*type_p->m_data.as_Borrow().inner);
+                        }
                         DEBUG(n_deref << " from " << type << " to " << *type_p);
                         binding_type = &(tmp = ::HIR::TypeRef::new_borrow(::HIR::BorrowType::Unique, type_p->clone()));
                         break;
                     case ::HIR::PatternBinding::Type::Ref:
                         // NOTE: Needs to deref and borrow to get just `&mut T` (where T isn't a &mut T)
-                        //while( type_p->m_data.is_Borrow() )
-                        //{
-                        //    n_deref ++;
-                        //    type_p = &context.m_ivars.get_type(*type_p->m_data.as_Borrow().inner);
-                        //}
+                        while( type_p->m_data.is_Borrow() )
+                        {
+                            n_deref ++;
+                            type_p = &context.m_ivars.get_type(*type_p->m_data.as_Borrow().inner);
+                        }
                         DEBUG(n_deref << " from " << type << " to " << *type_p);
                         binding_type = &(tmp = ::HIR::TypeRef::new_borrow(::HIR::BorrowType::Shared, type_p->clone()));
                         break;
                     default:
                         TODO(sp, "Assign variable type using mode " << (int)binding_mode << " and " << type);
                     }
-                    if( n_deref > 0 ) {
-                        TODO(sp, "Handle autoderef of ref bindings in match ergonomics");
-                    }
                     assert(binding_type);
                     context.equate_types(sp, context.get_var(sp, pattern.m_binding.m_slot), *binding_type);
-                    //pattern.m_binding.n_deref = n_deref;
+                    pattern.m_binding.m_implicit_deref_count = n_deref;
                 }
 
                 // For `_` patterns, there's nothing to match, so they just succeed with no derefs
diff --git a/src/mir/check.cpp b/src/mir/check.cpp
index b2d86590..b5abdb0a 100644
--- a/src/mir/check.cpp
+++ b/src/mir/check.cpp
@@ -686,10 +686,12 @@ void MIR_Validate(const StaticTraitResolve& resolve, const ::HIR::ItemPath& path
                         // TODO: Check that the input type is Copy
                         ),
                     (Borrow,
-                        // TODO: Check return type
+                        ::HIR::TypeRef  tmp;
+                        check_types( dst_ty, ::HIR::TypeRef::new_borrow(e.type, state.get_lvalue_type(tmp, e.val).clone()) );
                         ),
                     (Cast,
-                        // TODO: Check return type
+                        // Check return type
+                        check_types( dst_ty, e.type );
                         // TODO: Check suitability of source type (COMPLEX)
                         ),
                     (BinOp,
diff --git a/src/mir/from_hir.cpp b/src/mir/from_hir.cpp
index 912b8c78..8d51bf55 100644
--- a/src/mir/from_hir.cpp
+++ b/src/mir/from_hir.cpp
@@ -174,6 +174,11 @@ namespace {
                     destructure_from_ex(sp, pat, lval.clone(), 3);
                 }
 
+                for(size_t i = 0; i < pat.m_binding.m_implicit_deref_count; i ++)
+                {
+                    lval = ::MIR::LValue::make_Deref({ box$(lval) });
+                }
+
                 switch( pat.m_binding.m_type )
                 {
                 case ::HIR::PatternBinding::Type::Move: