diff options
Diffstat (limited to 'src/mir/from_hir_match.cpp')
| -rw-r--r-- | src/mir/from_hir_match.cpp | 29 |
1 files changed, 21 insertions, 8 deletions
diff --git a/src/mir/from_hir_match.cpp b/src/mir/from_hir_match.cpp index db347081..d1dbfd4d 100644 --- a/src/mir/from_hir_match.cpp +++ b/src/mir/from_hir_match.cpp @@ -81,16 +81,21 @@ void MIR_LowerHIR_Match( MirBuilder& builder, MirConverter& conv, ::HIR::ExprNod // 1. Stop the current block so we can generate code // > TODO: Can this goto be avoided while still being defensive? (Avoiding incomplete blocks) auto first_cmp_block = builder.new_bb_unlinked(); - builder.end_block( ::MIR::Terminator::make_Goto(next_block) ); + builder.end_block( ::MIR::Terminator::make_Goto(first_cmp_block) ); + + auto match_scope = builder.new_scope(node.span()); // Map of arm index to ruleset ::std::vector< ArmCode> arm_code; t_arm_rules arm_rules; for(unsigned int arm_idx = 0; arm_idx < node.m_arms.size(); arm_idx ++) { + /*const*/ auto& arm = node.m_arms[arm_idx]; ArmCode ac; - /*const*/ auto& arm = node.m_arms[arm_idx]; + // Register introduced bindings to be dropped on return/diverge within this scope + auto drop_scope = builder.new_scope( arm.m_code->span(), true ); + unsigned int pat_idx = 0; for( const auto& pat : arm.m_patterns ) { @@ -102,23 +107,31 @@ void MIR_LowerHIR_Match( MirBuilder& builder, MirConverter& conv, ::HIR::ExprNod pat_idx += 1; } - - // TODO: Register introduced bindings to be dropped on return/diverge within this scope - //auto drop_scope = builder.new_drop_scope( arm.m_patterns[0] ); // Code ac.code = builder.new_bb_unlinked(); builder.set_cur_block( ac.code ); conv.visit_node_ptr( arm.m_code ); if( !builder.block_active() && !builder.has_result() ) { + 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$(drop_scope); } else { + DEBUG("Arm result"); + // - Set result builder.push_stmt_assign( result_val.clone(), builder.get_result(arm.m_code->span()) ); + // - Drop all non-moved values from this scope + builder.terminate_scope( arm.m_code->span(), mv$(drop_scope) ); + // - Go to the next block builder.end_block( ::MIR::Terminator::make_Goto(next_block) ); } // Condition + // NOTE: The condition isn't covered by the drop scope, because the only values that can be used within it are + // Copy (otherwise they'd move out and invalidate on failure). + // - The above is rustc E0008 "cannot bind by-move into a pattern guard" if(arm.m_cond) { ac.has_condition = true; @@ -130,9 +143,8 @@ void MIR_LowerHIR_Match( MirBuilder& builder, MirConverter& conv, ::HIR::ExprNod builder.pause_cur_block(); // NOTE: Paused so that later code (which knows what the false branch will be) can end it correctly - // TODO: What to do with contidionals? - // > Could fall back on a sequential comparison model. - // > OR split the match on each conditional. + // TODO: What to do with contidionals in the fast model? + // > Could split the match on each conditional - separating such that if a conditional fails it can fall into the other compatible branches. fall_back_on_simple = true; } else @@ -157,6 +169,7 @@ void MIR_LowerHIR_Match( MirBuilder& builder, MirConverter& conv, ::HIR::ExprNod builder.set_cur_block( next_block ); builder.set_result( node.span(), mv$(result_val) ); + builder.terminate_scope( node.span(), mv$(match_scope) ); } // -------------------------------------------------------------------- |