Factor adding lines to a block out of basic blocks constructor

So that additional code can be added to this part in the following
commit without increasing the size of the constructor.

Author: thomasspriggs

src/goto-instrument/cover_basic_blocks.cpp

@@ -58,13 +58,7 @@ cover_basic_blockst::cover_basic_blockst(const goto_programt &goto_program)
 
     block_map[it] = current_block;
 
-    // update lines belonging to block
-    const irep_idt &line = it->source_location.get_line();
-    if(!line.empty())
-    {
-      block_info.lines.insert(unsafe_string2unsigned(id2string(line)));
-      block_info.source_lines.insert(it->source_location);
-    }
+    add_block_lines(block_info, *it);
 
     // set representative program location to instrument
     if(
@@ -155,6 +149,18 @@ void cover_basic_blockst::output(std::ostream &out) const
         << '\n';
 }
 
+void cover_basic_blockst::add_block_lines(
+  cover_basic_blockst::block_infot &block,
+  const goto_programt::instructiont &instruction)
+{
+  const irep_idt &line = instruction.source_location.get_line();
+  if(!line.empty())
+  {
+    block.lines.insert(unsafe_string2unsigned(id2string(line)));
+    block.source_lines.insert(instruction.source_location);
+  }
+}
+
 void cover_basic_blockst::update_covered_lines(block_infot &block_info)
 {
   if(block_info.source_location.is_nil())

src/goto-instrument/cover_basic_blocks.h

@@ -119,6 +119,11 @@ class cover_basic_blockst final : public cover_blocks_baset
   /// map block numbers to block information
   std::vector<block_infot> block_infos;
 
+  /// Adds the lines which \param instruction spans to \param block.
+  static void add_block_lines(
+    cover_basic_blockst::block_infot &block,
+    const goto_programt::instructiont &instruction);
+
   /// create list of covered lines as CSV string and set as property of source
   /// location of basic block, compress to ranges if applicable
   static void update_covered_lines(block_infot &block_info);