Merge #956

956: Substitute repetitions r=CohenArthur a=CohenArthur

Needs #955 

This PR splits up the `substitute_tokens` function into multiple smaller functions. Still a draft until I can get repetitions working.

Closes #960 
Closes #961 

Co-authored-by: Arthur Cohen <arthur.cohen@embecosm.com>

Author: bors[bot]

gcc/rust/ast/rust-ast.h

@@ -204,6 +204,7 @@ class Token : public TokenTree, public MacroMatch
   std::vector<std::unique_ptr<Token> > to_token_stream () const override;
 
   TokenId get_id () const { return tok_ref->get_id (); }
+  const std::string &get_str () const { return tok_ref->get_str (); }
 
   Location get_locus () const { return tok_ref->get_locus (); }
 

gcc/rust/expand/rust-macro-expand.cc

@@ -3118,7 +3118,7 @@ MacroExpander::expand_decl_macro (Location invoc_locus,
 
   // find matching arm
   AST::MacroRule *matched_rule = nullptr;
-  std::map<std::string, MatchedFragment> matched_fragments;
+  std::map<std::string, std::vector<MatchedFragment>> matched_fragments;
   for (auto &rule : rules_def.get_rules ())
     {
       sub_stack.push ();
@@ -3127,9 +3127,9 @@ MacroExpander::expand_decl_macro (Location invoc_locus,
 
       if (did_match_rule)
 	{
-	  for (auto &frag : matched_fragments)
-	    rust_debug ("matched fragment: %s",
-			frag.second.as_string ().c_str ());
+	  for (auto &kv : matched_fragments)
+	    rust_debug ("[fragment]: %s (%ld)", kv.first.c_str (),
+			kv.second.size ());
 
 	  matched_rule = &rule;
 	  break;
@@ -3535,9 +3535,8 @@ MacroExpander::match_matcher (Parser<MacroInvocLexer> &parser,
 
 	    // matched fragment get the offset in the token stream
 	    size_t offs_end = source.get_offs ();
-	    sub_stack.peek ().insert (
-	      {fragment->get_ident (),
-	       MatchedFragment (fragment->get_ident (), offs_begin, offs_end)});
+	    sub_stack.insert_fragment (
+	      MatchedFragment (fragment->get_ident (), offs_begin, offs_end));
 	  }
 	  break;
 
@@ -3611,7 +3610,6 @@ MacroExpander::match_n_matches (
   match_amount = 0;
 
   const MacroInvocLexer &source = parser.get_token_source ();
-  std::vector<std::string> fragment_identifiers;
   while (true)
     {
       // If the current token is a closing macro delimiter, break away.
@@ -3633,12 +3631,9 @@ MacroExpander::match_n_matches (
 
 		// matched fragment get the offset in the token stream
 		size_t offs_end = source.get_offs ();
-		sub_stack.peek ().insert (
-		  {fragment->get_ident (),
-		   MatchedFragment (fragment->get_ident (), offs_begin,
-				    offs_end)});
-
-		fragment_identifiers.emplace_back (fragment->get_ident ());
+		sub_stack.insert_fragment (
+		  MatchedFragment (fragment->get_ident (), offs_begin,
+				   offs_end));
 	      }
 	      break;
 
@@ -3677,21 +3672,10 @@ MacroExpander::match_n_matches (
 
   // Check if the amount of matches we got is valid: Is it more than the lower
   // bound and less than the higher bound?
-  auto result = hi_bound ? match_amount >= lo_bound && match_amount <= hi_bound
-			 : match_amount >= lo_bound;
-
-  // We can now set the amount to each fragment we matched in the substack
-  auto &stack_map = sub_stack.peek ();
-  for (auto &fragment_id : fragment_identifiers)
-    {
-      auto it = stack_map.find (fragment_id);
-
-      rust_assert (it != stack_map.end ());
+  bool did_meet_lo_bound = match_amount >= lo_bound;
+  bool did_meet_hi_bound = hi_bound ? match_amount <= hi_bound : true;
 
-      it->second.set_match_amount (match_amount);
-    }
-
-  return result;
+  return did_meet_lo_bound && did_meet_hi_bound;
 }
 
 bool
@@ -3733,14 +3717,41 @@ MacroExpander::match_repetition (Parser<MacroInvocLexer> &parser,
   rust_debug_loc (rep.get_match_locus (), "%s matched %lu times",
 		  res ? "successfully" : "unsuccessfully", match_amount);
 
+  // We can now set the amount to each fragment we matched in the substack
+  auto &stack_map = sub_stack.peek ();
+  for (auto &match : rep.get_matches ())
+    {
+      if (match->get_macro_match_type ()
+	  == AST::MacroMatch::MacroMatchType::Fragment)
+	{
+	  auto fragment = static_cast<AST::MacroMatchFragment *> (match.get ());
+	  auto it = stack_map.find (fragment->get_ident ());
+
+	  // If we can't find the fragment, but the result was valid, then
+	  // it's a zero-matched fragment and we can insert it
+	  if (it == stack_map.end ())
+	    {
+	      sub_stack.insert_fragment (
+		MatchedFragment::zero (fragment->get_ident ()));
+	    }
+	  else
+	    {
+	      // We can just set the repetition amount on the first match
+	      // FIXME: Make this more ergonomic and similar to what we fetch
+	      // in `substitute_repetition`
+	      it->second[0].set_match_amount (match_amount);
+	    }
+	}
+    }
+
   return res;
 }
 
 AST::ASTFragment
 MacroExpander::transcribe_rule (
   AST::MacroRule &match_rule, AST::DelimTokenTree &invoc_token_tree,
-  std::map<std::string, MatchedFragment> &matched_fragments, bool semicolon,
-  ContextType ctx)
+  std::map<std::string, std::vector<MatchedFragment>> &matched_fragments,
+  bool semicolon, ContextType ctx)
 {
   // we can manipulate the token tree to substitute the dollar identifiers so
   // that when we call parse its already substituted for us
@@ -3874,11 +3885,193 @@ MacroExpander::transcribe_rule (
   return AST::ASTFragment (std::move (nodes));
 }
 
+std::vector<std::unique_ptr<AST::Token>>
+MacroExpander::substitute_metavar (
+  std::vector<std::unique_ptr<AST::Token>> &input,
+  std::map<std::string, std::vector<MatchedFragment>> &fragments,
+  std::unique_ptr<AST::Token> &metavar)
+{
+  auto metavar_name = metavar->get_str ();
+
+  std::vector<std::unique_ptr<AST::Token>> expanded;
+  auto it = fragments.find (metavar_name);
+  if (it == fragments.end ())
+    {
+      // Return a copy of the original token
+      expanded.push_back (metavar->clone_token ());
+    }
+  else
+    {
+      // Replace
+      // We only care about the vector when expanding repetitions. Just access
+      // the first element of the vector.
+      // FIXME: Clean this up so it makes more sense
+      auto &frag = it->second[0];
+      for (size_t offs = frag.token_offset_begin; offs < frag.token_offset_end;
+	   offs++)
+	{
+	  auto &tok = input.at (offs);
+	  expanded.push_back (tok->clone_token ());
+	}
+    }
+
+  return expanded;
+}
+
+std::vector<std::unique_ptr<AST::Token>>
+MacroExpander::substitute_repetition (
+  std::vector<std::unique_ptr<AST::Token>> &input,
+  std::vector<std::unique_ptr<AST::Token>> &macro,
+  std::map<std::string, std::vector<MatchedFragment>> &fragments,
+  size_t pattern_start, size_t pattern_end)
+{
+  rust_assert (pattern_end < macro.size ());
+
+  rust_debug ("pattern start: %lu", pattern_start);
+  rust_debug ("pattern end: %lu", pattern_end);
+
+  std::vector<std::unique_ptr<AST::Token>> expanded;
+
+  // Find the first fragment and get the amount of repetitions that we should
+  // perform
+  size_t repeat_amount = 0;
+  for (size_t i = pattern_start; i < pattern_end; i++)
+    {
+      if (macro.at (i)->get_id () == DOLLAR_SIGN)
+	{
+	  auto &frag_token = macro.at (i + 1);
+	  if (frag_token->get_id () == IDENTIFIER)
+	    {
+	      auto it = fragments.find (frag_token->get_str ());
+	      if (it == fragments.end ())
+		{
+		  // If the repetition is not anything we know (ie no declared
+		  // metavars, or metavars which aren't present in the
+		  // fragment), we can just error out. No need to paste the
+		  // tokens as if nothing had happened.
+		  rust_error_at (frag_token->get_locus (),
+				 "metavar %s used in repetition does not exist",
+				 frag_token->get_str ().c_str ());
+		  // FIXME:
+		  return expanded;
+		}
+
+	      // FIXME: Refactor, ugly
+	      repeat_amount = it->second[0].match_amount;
+	    }
+	}
+    }
+
+  rust_debug ("repetition amount to use: %lu", repeat_amount);
+  std::vector<std::unique_ptr<AST::Token>> new_macro;
+
+  // We want to generate a "new macro" to substitute with. This new macro
+  // should contain only the tokens inside the pattern
+  for (size_t tok_idx = pattern_start; tok_idx < pattern_end; tok_idx++)
+    new_macro.emplace_back (macro.at (tok_idx)->clone_token ());
+
+  // Then, we want to create a subset of the matches so that
+  // `substitute_tokens()` can only see one fragment per metavar. Let's say we
+  // have the following user input: (1 145 'h')
+  // on the following match arm: ($($lit:literal)*)
+  // which causes the following matches: { "lit": [1, 145, 'h'] }
+  //
+  // The pattern (new_macro) is `$lit:literal`
+  // The first time we expand it, we want $lit to have the following token: 1
+  // The second time, 145
+  // The third and final time, 'h'
+  //
+  // In order to do so we must create "sub maps", which only contain parts of
+  // the original matches
+  // sub-maps: [ { "lit": 1 }, { "lit": 145 }, { "lit": 'h' } ]
+  //
+  // and give them to `substitute_tokens` one by one.
+
+  for (size_t i = 0; i < repeat_amount; i++)
+    {
+      std::map<std::string, std::vector<MatchedFragment>> sub_map;
+      for (auto &kv_match : fragments)
+	{
+	  std::vector<MatchedFragment> sub_vec;
+	  sub_vec.emplace_back (kv_match.second[i]);
+
+	  sub_map.insert ({kv_match.first, sub_vec});
+	}
+
+      auto new_tokens = substitute_tokens (input, new_macro, sub_map);
+
+      for (auto &new_token : new_tokens)
+	expanded.emplace_back (new_token->clone_token ());
+    }
+
+  // FIXME: We also need to make sure that all subsequent fragments
+  // contain the same amount of repetitions as the first one
+
+  return expanded;
+}
+
+std::pair<std::vector<std::unique_ptr<AST::Token>>, size_t>
+MacroExpander::substitute_token (
+  std::vector<std::unique_ptr<AST::Token>> &input,
+  std::vector<std::unique_ptr<AST::Token>> &macro,
+  std::map<std::string, std::vector<MatchedFragment>> &fragments,
+  size_t token_idx)
+{
+  auto &token = macro.at (token_idx);
+  switch (token->get_id ())
+    {
+    case IDENTIFIER:
+      rust_debug ("expanding metavar: %s", token->get_str ().c_str ());
+      return {substitute_metavar (input, fragments, token), 1};
+      case LEFT_PAREN: {
+	// We need to parse up until the closing delimiter and expand this
+	// fragment->n times.
+	rust_debug ("expanding repetition");
+	std::vector<std::unique_ptr<AST::Token>> repetition_pattern;
+	size_t pattern_start = token_idx + 1;
+	size_t pattern_end = pattern_start;
+	for (; pattern_end < macro.size ()
+	       && macro.at (pattern_end)->get_id () != RIGHT_PAREN;
+	     pattern_end++)
+	  ;
+
+	// FIXME: This skips whitespaces... Is that okay??
+	// FIXME: Is there any existing parsing function that allows us to parse
+	// a macro pattern?
+
+	// FIXME: Add error handling in the case we haven't found a matching
+	// closing delimiter
+
+	// FIXME: We need to parse the repetition token now
+
+	return {
+	  substitute_repetition (input, macro, fragments, pattern_start,
+				 pattern_end),
+	  // + 2 for the opening and closing parentheses which are mandatory
+	  // + 1 for the repetitor (+, *, ?)
+	  pattern_end - pattern_start + 3};
+      }
+      // TODO: We need to check if the $ was alone. In that case, do
+      // not error out: Simply act as if there was an empty identifier
+      // with no associated fragment and paste the dollar sign in the
+      // transcription. Unsure how to do that since we always have at
+      // least the closing curly brace after an empty $...
+    default:
+      rust_error_at (token->get_locus (),
+		     "unexpected token in macro transcribe: expected "
+		     "%<(%> or identifier after %<$%>, got %<%s%>",
+		     get_token_description (token->get_id ()));
+    }
+
+  // FIXME: gcc_unreachable() error case?
+  return {std::vector<std::unique_ptr<AST::Token>> (), 0};
+}
+
 std::vector<std::unique_ptr<AST::Token>>
 MacroExpander::substitute_tokens (
   std::vector<std::unique_ptr<AST::Token>> &input,
   std::vector<std::unique_ptr<AST::Token>> &macro,
-  std::map<std::string, MatchedFragment> &fragments)
+  std::map<std::string, std::vector<MatchedFragment>> &fragments)
 {
   std::vector<std::unique_ptr<AST::Token>> replaced_tokens;
 
@@ -3887,54 +4080,20 @@ MacroExpander::substitute_tokens (
       auto &tok = macro.at (i);
       if (tok->get_id () == DOLLAR_SIGN)
 	{
-	  std::vector<std::unique_ptr<AST::Token>> parsed_toks;
+	  // Aaaaah, if only we had C++17 :)
+	  // auto [expanded, tok_to_skip] = ...
+	  auto p = substitute_token (input, macro, fragments, i + 1);
+	  auto expanded = std::move (p.first);
+	  auto tok_to_skip = p.second;
 
-	  std::string ident;
-	  for (size_t offs = i; i < macro.size (); offs++)
-	    {
-	      auto &tok = macro.at (offs);
-	      if (tok->get_id () == DOLLAR_SIGN && offs == i)
-		{
-		  parsed_toks.push_back (tok->clone_token ());
-		}
-	      else if (tok->get_id () == IDENTIFIER)
-		{
-		  rust_assert (tok->as_string ().size () == 1);
-		  ident.push_back (tok->as_string ().at (0));
-		  parsed_toks.push_back (tok->clone_token ());
-		}
-	      else
-		{
-		  break;
-		}
-	    }
+	  i += tok_to_skip;
 
-	  // lookup the ident
-	  auto it = fragments.find (ident);
-	  if (it == fragments.end ())
-	    {
-	      // just leave the tokens in
-	      for (auto &tok : parsed_toks)
-		{
-		  replaced_tokens.push_back (tok->clone_token ());
-		}
-	    }
-	  else
-	    {
-	      // replace
-	      MatchedFragment &frag = it->second;
-	      for (size_t offs = frag.token_offset_begin;
-		   offs < frag.token_offset_end; offs++)
-		{
-		  auto &tok = input.at (offs);
-		  replaced_tokens.push_back (tok->clone_token ());
-		}
-	    }
-	  i += parsed_toks.size () - 1;
+	  for (auto &token : expanded)
+	    replaced_tokens.emplace_back (token->clone_token ());
 	}
       else
 	{
-	  replaced_tokens.push_back (tok->clone_token ());
+	  replaced_tokens.emplace_back (tok->clone_token ());
 	}
     }