MIR Gen - Alter handling of scopes to support diverging expressions

3 files changed, 24 insertions, 25 deletions

diff --git a/src/mir/from_hir.cpp b/src/mir/from_hir.cpp
index 52e53cde..40e43f3b 100644
--- a/src/mir/from_hir.cpp
+++ b/src/mir/from_hir.cpp
@@ -383,16 +383,14 @@ namespace {
 
                     auto stmt_scope = m_builder.new_scope_temp(sp);
                     this->visit_node_ptr(subnode);
-                    if( m_builder.has_result() ) {
-                        // TODO: Drop.
-                        m_builder.get_result(sp);
-                    }
 
-                    if( m_builder.block_active() ) {
+                    if( m_builder.block_active() || m_builder.has_result() ) {
+                        // TODO: Emit a drop
+                        m_builder.get_result(sp);
                         m_builder.terminate_scope(sp, mv$(stmt_scope));
                     }
                     else {
-                        auto _ = mv$(stmt_scope);
+                        m_builder.terminate_scope(sp, mv$(stmt_scope), false);
 
                         m_builder.set_cur_block( m_builder.new_bb_unlinked() );
                         diverged = true;
@@ -422,8 +420,8 @@ namespace {
                     }
                     else
                     {
-                        { auto _ = mv$(stmt_scope); }
-                        { auto _ = mv$(scope); }
+                        m_builder.terminate_scope( node.span(), mv$(stmt_scope), false );
+                        m_builder.terminate_scope( node.span(), mv$(scope), false );
                         // Block diverged in final node.
                     }
                 }
@@ -431,7 +429,7 @@ namespace {
                 {
                     if( diverged )
                     {
-                        auto _ = mv$(scope);
+                        m_builder.terminate_scope( node.span(), mv$(scope), false );
                         m_builder.end_block( ::MIR::Terminator::make_Diverge({}) );
                         // Don't set a result if there's no block.
                     }
@@ -617,8 +615,8 @@ namespace {
                     m_builder.terminate_scope( node.span(), mv$(scope) );
                 }
                 else {
-                    { auto _ = mv$(tmp_scope); }
-                    { auto _ = mv$(scope); }
+                    m_builder.terminate_scope( node.span(), mv$(tmp_scope), false );
+                    m_builder.terminate_scope( node.span(), mv$(scope), false );
                 }
             }
             else {
@@ -726,7 +724,7 @@ namespace {
                     m_builder.end_block( ::MIR::Terminator::make_Goto(next_block) );
                 }
                 else {
-                    { auto _ = mv$(stmt_scope); }
+                    m_builder.terminate_scope(node.span(), mv$(stmt_scope), false);
                     m_builder.end_split_arm(node.span(), scope, false);
                 }
             }
@@ -745,7 +743,7 @@ namespace {
                     m_builder.end_block( ::MIR::Terminator::make_Goto(next_block) );
                 }
                 else {
-                    { auto _ = mv$(stmt_scope); }
+                    m_builder.terminate_scope(node.span(), mv$(stmt_scope), false);
                     m_builder.end_split_arm(node.span(), scope, false);
                 }
             }
diff --git a/src/mir/from_hir_match.cpp b/src/mir/from_hir_match.cpp
index 43b60816..a657ffd5 100644
--- a/src/mir/from_hir_match.cpp
+++ b/src/mir/from_hir_match.cpp
@@ -310,8 +310,8 @@ void MIR_LowerHIR_Match( MirBuilder& builder, MirConverter& conv, ::HIR::ExprNod
             DEBUG("Arm diverged");
             // Nothing need be done, as the block diverged.
             // - Drops were handled by the diverging block (if not, the below will panic)
-            { auto _ = mv$(tmp_scope); }
-            { auto _ = mv$(drop_scope); }
+            builder.terminate_scope( arm.m_code->span(), mv$(tmp_scope), false );
+            builder.terminate_scope( arm.m_code->span(), mv$(drop_scope), false );
             builder.end_split_arm( arm.m_code->span(), match_scope, false );
         }
         else {
diff --git a/src/mir/mir_builder.cpp b/src/mir/mir_builder.cpp
index d9899dc8..16b0fd80 100644
--- a/src/mir/mir_builder.cpp
+++ b/src/mir/mir_builder.cpp
@@ -616,9 +616,11 @@ void MirBuilder::terminate_scope(const Span& sp, ScopeHandle scope, bool emit_cl
     }
 
     auto& scope_def = m_scopes.at(scope.idx);
-    ASSERT_BUG( sp, scope_def.complete == false, "Terminating scope which is already terminated" );
+    //if( emit_cleanup ) {
+    //    ASSERT_BUG( sp, scope_def.complete == false, "Terminating scope which is already terminated" );
+    //}
 
-    if( emit_cleanup )
+    if( emit_cleanup && scope_def.complete == false )
     {
         // 2. Emit drops for all non-moved variables (share with below)
         drop_scope_values(scope_def);
@@ -663,7 +665,6 @@ void MirBuilder::terminate_scope_early(const Span& sp, const ScopeHandle& scope,
         if( !is_conditional ) {
             DEBUG("Complete scope " << idx);
             drop_scope_values(scope_def);
-            m_scope_stack.pop_back();
             complete_scope(scope_def);
         }
         else {
@@ -1029,23 +1030,23 @@ void MirBuilder::end_split_arm(const Span& sp, const ScopeHandle& handle, bool r
 void MirBuilder::end_split_arm_early(const Span& sp)
 {
     TRACE_FUNCTION_F("");
+    size_t i = m_scope_stack.size();
     // Terminate all scopes until a split is found.
-    while( ! m_scope_stack.empty() && ! (m_scopes.at( m_scope_stack.back() ).data.is_Split() || m_scopes.at( m_scope_stack.back() ).data.is_Loop()) )
+    while( i -- && ! (m_scopes.at(m_scope_stack[i]).data.is_Split() || m_scopes.at(m_scope_stack[i]).data.is_Loop()) )
     {
-        auto& scope_def = m_scopes[m_scope_stack.back()];
+        auto& scope_def = m_scopes[m_scope_stack[i]];
         // Fully drop the scope
-        DEBUG("Complete scope " << m_scope_stack.back());
+        DEBUG("Complete scope " << m_scope_stack[i]);
         drop_scope_values(scope_def);
-        m_scope_stack.pop_back();
         complete_scope(scope_def);
     }
 
-    if( !m_scope_stack.empty() )
+    if( i < m_scope_stack.size() )
     {
-        if( m_scopes.at( m_scope_stack.back() ).data.is_Split() )
+        if( m_scopes.at( m_scope_stack[i] ).data.is_Split() )
         {
             DEBUG("Early terminate split scope " << m_scope_stack.back());
-            auto& sd = m_scopes[ m_scope_stack.back() ];
+            auto& sd = m_scopes[ m_scope_stack[i] ];
             auto& sd_split = sd.data.as_Split();
             sd_split.arms.back().has_early_terminated = true;