MIR Gen - Drop InnerMoved early for cleaner logic

4 files changed, 41 insertions, 10 deletions

diff --git a/src/mir/from_hir.cpp b/src/mir/from_hir.cpp
index 9b9ddf5c..b8085cdb 100644
--- a/src/mir/from_hir.cpp
+++ b/src/mir/from_hir.cpp
@@ -523,8 +523,8 @@ namespace {
                 this->visit_node_ptr(node.m_true);
                 if( m_builder.block_active() || m_builder.has_result() ) {
                     m_builder.push_stmt_assign( node.span(), result_val.clone(), m_builder.get_result(node.m_true->span()) );
-                    m_builder.end_block( ::MIR::Terminator::make_Goto(next_block) );
                     m_builder.end_split_arm(node.span(), scope, true);
+                    m_builder.end_block( ::MIR::Terminator::make_Goto(next_block) );
                 }
                 else {
                     m_builder.end_split_arm(node.span(), scope, false);
diff --git a/src/mir/from_hir.hpp b/src/mir/from_hir.hpp
index 66877913..e7492df6 100644
--- a/src/mir/from_hir.hpp
+++ b/src/mir/from_hir.hpp
@@ -38,14 +38,17 @@ public:
     ~ScopeHandle();
 };
 
+// TODO: Replace the first three states with just one (and flags for init/moved)
 enum class VarState {
     Uninit, // No value assigned yet
-    Init,   // Initialised and valid at this point
-    MaybeMoved, // Possibly has been moved
-    //MaybeMovedInner,  // Inner possibly has been moved
     Moved,  // Definitely moved
-    InnerMoved, // The inner has been moved, but the container needs to be dropped
     Dropped,    // Dropped (out of scope)
+    
+    InnerMoved, // The inner has been moved, but the container needs to be dropped
+    //MaybeMovedInner,  // Inner possibly has been moved
+    MaybeMoved, // Possibly has been moved
+    
+    Init,   // Initialised and valid at this point
 };
 extern ::std::ostream& operator<<(::std::ostream& os, VarState x);
 
@@ -88,6 +91,7 @@ class MirBuilder
     ::MIR::RValue   m_result;
     bool    m_result_valid;
     
+    // TODO: Extra information.
     //::std::vector<VarState>   m_arg_states;
     ::std::vector<VarState> m_variable_states;
     ::std::vector<VarState> m_temporary_states;
diff --git a/src/mir/from_hir_match.cpp b/src/mir/from_hir_match.cpp
index 6ad2cd95..5cf5ff1e 100644
--- a/src/mir/from_hir_match.cpp
+++ b/src/mir/from_hir_match.cpp
@@ -178,10 +178,10 @@ void MIR_LowerHIR_Match( MirBuilder& builder, MirConverter& conv, ::HIR::ExprNod
             builder.push_stmt_assign( arm.m_code->span(), result_val.clone(), builder.get_result(arm.m_code->span()) );
             // - Drop all non-moved values from this scope
             builder.terminate_scope( arm.m_code->span(), mv$(drop_scope) );
+            // - Split end match scope
+            builder.end_split_arm( arm.m_code->span(), match_scope, true );
             // - Go to the next block
             builder.end_block( ::MIR::Terminator::make_Goto(next_block) );
-            
-            builder.end_split_arm( arm.m_code->span(), match_scope, true );
         }
 
         arm_code.push_back( mv$(ac) );
diff --git a/src/mir/mir_builder.cpp b/src/mir/mir_builder.cpp
index c2667025..24972b10 100644
--- a/src/mir/mir_builder.cpp
+++ b/src/mir/mir_builder.cpp
@@ -480,7 +480,21 @@ void MirBuilder::end_split_arm(const Span& sp, const ScopeHandle& handle, bool r
     
     sd_split.arms.back().always_early_terminated = /*sd_split.arms.back().has_early_terminated &&*/ !reachable;
     
-    // TODO: Undo moves from within the other scope
+    // HACK: If this arm's end is reachable, convert InnerMoved (shallow drop) variable states to Moved
+    // - I'm not 100% sure this is the correct place for calling drop.
+    if( reachable )
+    {
+        for(unsigned int i = 0; i < sd_split.arms.back().var_states.size(); i ++ )
+        {
+            auto& vs = sd_split.arms.back().var_states[i];
+            if( vs == VarState::InnerMoved ) {
+                // Emit the shallow drop
+                push_stmt_drop_shallow( sp, ::MIR::LValue::make_Variable(i) );
+                vs = VarState::Moved;
+            }
+        }
+    }
+    
     sd_split.arms.push_back( {} );
 }
 void MirBuilder::end_split_arm_early(const Span& sp)
@@ -500,6 +514,16 @@ void MirBuilder::end_split_arm_early(const Span& sp)
         auto& sd = m_scopes[ m_scope_stack.back() ];
         auto& sd_split = sd.data.as_Split();
         sd_split.arms.back().has_early_terminated = true;
+        
+        for(unsigned int i = 0; i < sd_split.arms.back().var_states.size(); i ++ )
+        {
+            auto& vs = sd_split.arms.back().var_states[i];
+            if( vs == VarState::InnerMoved ) {
+                // Emit the shallow drop
+                push_stmt_drop_shallow( sp, ::MIR::LValue::make_Variable(i) );
+                //vs = VarState::Dropped;
+            }
+        }
     }
 }
 void MirBuilder::complete_scope(ScopeDef& sd)
@@ -546,7 +570,7 @@ void MirBuilder::complete_scope(ScopeDef& sd)
                 assert(i < changed.size());
                 if( changed[i] )
                 {
-                    DEBUG("("<<new_states[i]<<","<<arm.var_states[i]<<")");
+                    DEBUG(i << " ("<<new_states[i]<<","<<arm.var_states[i]<<")");
                     switch(new_states[i])
                     {
                     case VarState::Uninit:
@@ -581,7 +605,9 @@ void MirBuilder::complete_scope(ScopeDef& sd)
                         }
                         break;
                     case VarState::InnerMoved:
-                        TODO(sd.span, "Handle InnerMoved in Split scope (new_states)");
+                        // Need to tag for conditional shallow drop? Or just do that at the end of the split?
+                        // - End of the split means that the only optional state is outer drop.
+                        TODO(sd.span, "Handle InnerMoved in Split scope (new_states) - " << i << " " << m_output.named_variables[i]);
                         break;
                     case VarState::MaybeMoved:
                         // Already optional, don't change
@@ -623,6 +649,7 @@ void MirBuilder::complete_scope(ScopeDef& sd)
                 }
                 else if( arm.changed_var_states[i] )
                 {
+                    DEBUG(i << " (_,"<<arm.var_states[i]<<")");
                     changed[i] = true;
                     new_states[i] = arm.var_states[i];
                 }