better debug position for class merging default case

Summary: We generate default block that's just invoke-super on common overriden method. But this code block don't have debug position and will cause merged class appear in stack frame that is causing confusion.

Reviewed By: NTillmann

Differential Revision: D66139527

fbshipit-source-id: 42ed11934676c7111e55a22d6e54cee1f18ae40e

libredex/Creators.cpp

@@ -558,6 +558,10 @@ void MethodBlock::push_instruction(IRInstruction* insn) {
   curr = mc->push_instruction(curr, insn);
 }
 
+void MethodBlock::push_position(std::unique_ptr<DexPosition> pos) {
+  curr = mc->push_position(curr, std::move(pos));
+}
+
 IRList::iterator MethodCreator::push_instruction(const IRList::iterator& curr,
                                                  IRInstruction* insn) {
   if (curr == meth_code->end()) {
@@ -568,6 +572,16 @@ IRList::iterator MethodCreator::push_instruction(const IRList::iterator& curr,
   }
 }
 
+IRList::iterator MethodCreator::push_position(
+    const IRList::iterator& curr, std::unique_ptr<DexPosition> pos) {
+  if (curr == meth_code->end()) {
+    meth_code->push_back(std::move(pos));
+    return std::prev(meth_code->end());
+  } else {
+    return meth_code->insert_after(curr, std::move(pos));
+  }
+}
+
 MethodBlock* MethodBlock::make_if_block(IRInstruction* insn) {
   IRList::iterator false_block;
   curr = mc->make_if_block(curr, insn, &false_block);

libredex/Creators.h

@@ -357,6 +357,8 @@ struct MethodBlock {
   MethodBlock* switch_op(Location test,
                          std::map<SwitchIndices, MethodBlock*>& cases);
 
+  void push_position(std::unique_ptr<DexPosition> pos);
+
  private:
   MethodBlock(const IRList::iterator& iterator, MethodCreator* creator);
 
@@ -483,6 +485,8 @@ struct MethodCreator {
 
   IRList::iterator push_instruction(const IRList::iterator& curr,
                                     IRInstruction* insn);
+  IRList::iterator push_position(const IRList::iterator& curr,
+                                 std::unique_ptr<DexPosition> pos);
   IRList::iterator make_if_block(IRList::iterator curr,
                                  IRInstruction* insn,
                                  IRList::iterator* false_block);

service/switch-dispatch/SwitchDispatch.cpp

@@ -126,6 +126,10 @@ void handle_default_block(
                       SHOW(spec.overridden_meth));
     // Note that the overridden can be an default interface or external default
     // interface method.
+    auto artificial_pos = std::make_unique<DexPosition>(
+        DexString::make_string(show_deobfuscated(spec.overridden_meth)),
+        DexString::make_string("UnknownSource"), 0);
+    def_block->push_position(std::move(artificial_pos));
     emit_call(spec, OPCODE_INVOKE_SUPER, args, ret_loc, spec.overridden_meth,
               def_block);
   } else if (!spec.proto->is_void()) {