rust-fmt: Store parsed string in Pieces struct

gcc/rust/ChangeLog:

	* ast/rust-fmt.cc (Pieces::collect): Fix signature to take ownership
	of the given string.
	* ast/rust-fmt.h (struct Pieces): Store parsed string in the struct.

libgrust/ChangeLog:

	* libformat_parser/src/lib.rs: Add debug prompt.

gcc/rust/ast/rust-fmt.cc

@@ -23,7 +23,7 @@ namespace Rust {
 namespace Fmt {
 
 Pieces
-Pieces::collect (const std::string &to_parse)
+Pieces::collect (std::string &&to_parse)
 {
   auto piece_slice = collect_pieces (to_parse.c_str ());
 
@@ -34,7 +34,7 @@ Pieces::collect (const std::string &to_parse)
   auto pieces = std::vector (piece_slice.base_ptr,
 			     piece_slice.base_ptr + piece_slice.len);
 
-  return Pieces (piece_slice);
+  return Pieces (piece_slice, std::move (to_parse));
 }
 
 Pieces::~Pieces () { destroy_pieces (slice); }

gcc/rust/ast/rust-fmt.h

@@ -251,13 +251,16 @@ void destroy_pieces (PieceSlice);
 
 struct Pieces
 {
-  static Pieces collect (const std::string &to_parse);
+  static Pieces collect (std::string &&to_parse);
   ~Pieces ();
 
 private:
-  Pieces (PieceSlice slice) : slice (slice) {}
+  Pieces (PieceSlice slice, std::string &&to_parse)
+    : slice (slice), to_parse (std::move (to_parse))
+  {}
 
   PieceSlice slice;
+  std::string to_parse;
 };
 
 } // namespace Fmt

libgrust/libformat_parser/src/lib.rs

@@ -340,6 +340,7 @@ pub struct PieceSlice {
 pub extern "C" fn collect_pieces(input: *const libc::c_char) -> PieceSlice {
     // FIXME: Add comment
     let str = unsafe { CStr::from_ptr(input) };
+    dbg!(str);
 
     // FIXME: No unwrap
     let pieces: Vec<ffi::Piece<'_>> = rust::collect_pieces(str.to_str().unwrap())