Install valgrind for Linux github runners

.github/workflows/run-tests.yml

@@ -17,7 +17,7 @@ jobs:
     steps:
     - name: Install dependencies (Linux)
       if: runner.os == 'Linux'
-      run: sudo apt-get update && sudo apt-get install -y gcc gdc ldc
+      run: sudo apt-get update && sudo apt-get install -y gcc gdc ldc valgrind
 
     - name: Install dependencies (macOS)
       if: runner.os == 'macOS'

CHANGELOG.md

@@ -1,3 +1,24 @@
+## v4.7.0
+
+### New Features
+
+- Support parser rule user code blocks in tree generation mode.
+
+### Fixes
+
+- propane.vim: do not highlight rule components as propane keywords
+
+## v4.6.0
+
+### New Features
+
+- Add lexer user code API to access matched input text positions
+- Track rule component text positions and add parser user code API to access
+
+### Fixes
+
+- Fixed a few user guide and source comments related to text input positions
+
 ## v4.5.0
 
 ### New Features
@@ -9,6 +30,7 @@
 
 - Fix #line reset directives
 - Update keyword list in extra/vim/syntax/propane.vim
+- Fix propane.vim keyword detection
 
 ## v4.4.0
 

assets/parser.c.erb

@@ -486,6 +486,22 @@ static size_t attempt_lex_token(<%= @grammar.prefix %>context_t * context, <%= @
     case P_SUCCESS:
         {
         <%= @grammar.prefix %>token_t token_to_accept = match_info.accepting_state->token;
+        /* Calculate the token length and start/end positions before invoking
+         * the lexer user code so that the user code can access them. The
+         * context input text position tracking is not updated until after the
+         * user code has run so that it is left unchanged if the user code
+         * requests to terminate the lexer. */
+        token_info.length = match_info.length;
+        if (match_info.end_delta_position.row != 0u)
+        {
+            token_info.end_position.row = token_info.position.row + match_info.end_delta_position.row;
+            token_info.end_position.col = match_info.end_delta_position.col;
+        }
+        else
+        {
+            token_info.end_position.row = token_info.position.row;
+            token_info.end_position.col = token_info.position.col + match_info.end_delta_position.col;
+        }
         if (match_info.accepting_state->code_id != INVALID_USER_CODE_ID)
         {
             uint8_t const * match = &context->input[context->input_index];
@@ -524,17 +540,6 @@ static size_t attempt_lex_token(<%= @grammar.prefix %>context_t * context, <%= @
             return P_DROP;
         }
         token_info.token = token_to_accept;
-        token_info.length = match_info.length;
-        if (match_info.end_delta_position.row != 0u)
-        {
-            token_info.end_position.row = token_info.position.row + match_info.end_delta_position.row;
-            token_info.end_position.col = match_info.end_delta_position.col;
-        }
-        else
-        {
-            token_info.end_position.row = token_info.position.row;
-            token_info.end_position.col = token_info.position.col + match_info.end_delta_position.col;
-        }
         *out_token_info = token_info;
         }
         return P_SUCCESS;
@@ -707,12 +712,14 @@ typedef struct
     /** Parser state ID. */
     size_t state_id;
 
-    /** Parser value from this state. */
-    <%= @grammar.prefix %>value_t pvalue;
-
 <% if @grammar.tree %>
     /** tree node. */
     void * tree_node;
+<% else %>
+    <%= @grammar.prefix %>position_t position;
+    <%= @grammar.prefix %>position_t end_position;
+    /** Parser value from this state. */
+    <%= @grammar.prefix %>value_t pvalue;
 <% end %>
 } state_value_t;
 
@@ -866,6 +873,59 @@ static void state_values_stack_free(state_values_stack_t * stack)
 }
 
 <% unless @grammar.tree %>
+/**
+ * Get the rule position (start or end) for the currently matched rule.
+ */
+static <%= @grammar.prefix %>position_t get_rule_position(state_values_stack_t * statevalues, size_t i, size_t n_states, bool get_end)
+{
+    if (n_states > 0u)
+    {
+        if (i == 0u)
+        {
+            if (get_end)
+            {
+                int stack_index = -1;
+                for (size_t j = 0u; j < n_states; j++)
+                {
+                    state_value_t * sv = state_values_stack_index(statevalues, stack_index - (int)j);
+                    if (<%= @grammar.prefix %>position_valid(sv->end_position))
+                    {
+                        return sv->end_position;
+                    }
+                }
+            }
+            else
+            {
+                int stack_index = -(int)n_states;
+                for (size_t j = 0u; j < n_states; j++)
+                {
+                    state_value_t * sv = state_values_stack_index(statevalues, stack_index + (int)j);
+                    if (<%= @grammar.prefix %>position_valid(sv->position))
+                    {
+                        return sv->position;
+                    }
+                }
+            }
+        }
+        else
+        {
+            if (get_end)
+            {
+                return state_values_stack_index(statevalues, -1 - (int)n_states + (int)i)->end_position;
+            }
+            else
+            {
+                return state_values_stack_index(statevalues, -1 - (int)n_states + (int)i)->position;
+            }
+        }
+    }
+    <%= @grammar.prefix %>position_t empty_pos;
+    memset(&empty_pos, 0, sizeof(empty_pos));
+    return empty_pos;
+}
+<% end %>
+
+<% if !@grammar.tree || @grammar.parser_user_code_used? %>
 /**
  * Execute user code associated with a parser rule.
  *
@@ -876,7 +936,7 @@ static void state_values_stack_free(state_values_stack_t * stack)
  * @retval P_USER_TERMINATED
  *   User requested to terminate parsing.
  */
-static size_t parser_user_code(<%= @grammar.prefix %>value_t * _pvalue, uint32_t rule, state_values_stack_t * statevalues, uint32_t n_states, <%= @grammar.prefix %>context_t * context)
+static size_t parser_user_code(<%= @grammar.tree ? "void" : "#{@grammar.prefix}value_t" %> * _pvalue, uint32_t rule, state_values_stack_t * statevalues, uint32_t n_states, <%= @grammar.prefix %>context_t * context)
 {
     switch (rule)
     {
@@ -971,6 +1031,8 @@ static size_t parse_from(<%= @grammar.prefix %>context_t * context, size_t start
 <% if @grammar.tree %>
     void * reduced_parser_node;
 <% else %>
+    <%= @grammar.prefix %>position_t reduced_position;
+    <%= @grammar.prefix %>position_t reduced_end_position;
     <%= @grammar.prefix %>value_t reduced_parser_value;
 <% end %>
     state_values_stack_init(&statevalues);
@@ -1013,7 +1075,8 @@ static size_t parse_from(<%= @grammar.prefix %>context_t * context, size_t start
         {
             /* We have something to shift. */
             state_values_stack_push(&statevalues);
-            state_values_stack_index(&statevalues, -1)->state_id = shift_state;
+            state_value_t * new_state_info = state_values_stack_index(&statevalues, -1);
+            new_state_info->state_id = shift_state;
             if (reduced_rule_set == INVALID_ID)
             {
                 /* We shifted a token, mark it consumed. */
@@ -1030,9 +1093,11 @@ static size_t parse_from(<%= @grammar.prefix %>context_t * context, size_t start
                 token_tree_node->token = token;
                 token_tree_node->pvalue = token_info.pvalue;
 <%= expand_code(@grammar.on_token_node, false, nil, nil) %>
-                state_values_stack_index(&statevalues, -1)->tree_node = token_tree_node;
+                new_state_info->tree_node = token_tree_node;
 <% else %>
-                state_values_stack_index(&statevalues, -1)->pvalue = token_info.pvalue;
+                new_state_info->position = token_info.position;
+                new_state_info->end_position = token_info.end_position;
+                new_state_info->pvalue = token_info.pvalue;
 <% end %>
                 token = INVALID_TOKEN_ID;
             }
@@ -1040,9 +1105,11 @@ static size_t parse_from(<%= @grammar.prefix %>context_t * context, size_t start
             {
                 /* We shifted a RuleSet. */
 <% if @grammar.tree %>
-                state_values_stack_index(&statevalues, -1)->tree_node = reduced_parser_node;
+                new_state_info->tree_node = reduced_parser_node;
 <% else %>
-                state_values_stack_index(&statevalues, -1)->pvalue = reduced_parser_value;
+                new_state_info->pvalue = reduced_parser_value;
+                new_state_info->position = reduced_position;
+                new_state_info->end_position = reduced_end_position;
                 <%= @grammar.prefix %>value_t new_parse_result;
                 memset(&new_parse_result, 0, sizeof(new_parse_result));
                 reduced_parser_value = new_parse_result;
@@ -1104,6 +1171,13 @@ static size_t parse_from(<%= @grammar.prefix %>context_t * context, size_t start
             {
                 reduced_parser_node = NULL;
             }
+<%   if @grammar.parser_user_code_used? %>
+            if (parser_user_code(reduced_parser_node, parser_reduce_table[reduce_index].rule, &statevalues, parser_reduce_table[reduce_index].n_states, context) == P_USER_TERMINATED)
+            {
+                state_values_stack_free(&statevalues);
+                return P_USER_TERMINATED;
+            }
+<%   end %>
 <% else %>
             <%= @grammar.prefix %>value_t reduced_parser_value2;
             memset(&reduced_parser_value2, 0, sizeof(reduced_parser_value2));
@@ -1113,6 +1187,16 @@ static size_t parse_from(<%= @grammar.prefix %>context_t * context, size_t start
                 return P_USER_TERMINATED;
             }
             reduced_parser_value = reduced_parser_value2;
+            if (parser_reduce_table[reduce_index].n_states > 0u)
+            {
+                reduced_position = get_rule_position(&statevalues, 0u, parser_reduce_table[reduce_index].n_states, false);
+                reduced_end_position = get_rule_position(&statevalues, 0u, parser_reduce_table[reduce_index].n_states, true);
+            }
+            else
+            {
+                memset(&reduced_position, 0, sizeof(reduced_position));
+                memset(&reduced_end_position, 0, sizeof(reduced_end_position));
+            }
 <% end %>
             reduced_rule_set = parser_reduce_table[reduce_index].rule_set;
             state_values_stack_pop(&statevalues, parser_reduce_table[reduce_index].n_states);

assets/parser.d.erb

@@ -59,10 +59,10 @@ public alias <%= @grammar.prefix %>code_point_t = uint;
  */
 public struct <%= @grammar.prefix %>position_t
 {
-    /** Input text row (0-based). */
+    /** Input text row (1-based). */
     uint row;
 
-    /** Input text column (0-based). */
+    /** Input text column (1-based). */
     uint col;
 
     /** Invalid position value. */
@@ -665,6 +665,22 @@ private size_t attempt_lex_token(<%= @grammar.prefix %>context_t * context, <%=
     {
     case P_SUCCESS:
         <%= @grammar.prefix %>token_t token_to_accept = match_info.accepting_state.token;
+        /* Calculate the token length and start/end positions before invoking
+         * the lexer user code so that the user code can access them. The
+         * context input text position tracking is not updated until after the
+         * user code has run so that it is left unchanged if the user code
+         * requests to terminate the lexer. */
+        token_info.length = match_info.length;
+        if (match_info.end_delta_position.row != 0u)
+        {
+            token_info.end_position.row = token_info.position.row + match_info.end_delta_position.row;
+            token_info.end_position.col = match_info.end_delta_position.col;
+        }
+        else
+        {
+            token_info.end_position.row = token_info.position.row;
+            token_info.end_position.col = token_info.position.col + match_info.end_delta_position.col;
+        }
         if (match_info.accepting_state.code_id != INVALID_USER_CODE_ID)
         {
             string match = context.input[context.input_index..(context.input_index + match_info.length)];
@@ -703,17 +719,6 @@ private size_t attempt_lex_token(<%= @grammar.prefix %>context_t * context, <%=
             return P_DROP;
         }
         token_info.token = token_to_accept;
-        token_info.length = match_info.length;
-        if (match_info.end_delta_position.row != 0u)
-        {
-            token_info.end_position.row = token_info.position.row + match_info.end_delta_position.row;
-            token_info.end_position.col = match_info.end_delta_position.col;
-        }
-        else
-        {
-            token_info.end_position.row = token_info.position.row;
-            token_info.end_position.col = token_info.position.col + match_info.end_delta_position.col;
-        }
         *out_token_info = token_info;
         return P_SUCCESS;
 
@@ -882,12 +887,14 @@ private struct state_value_t
     /** Parser state ID. */
     size_t state_id;
 
-    /** Parser value from this state. */
-    <%= @grammar.prefix %>value_t pvalue;
-
 <% if @grammar.tree %>
     /** Tree node. */
     void * tree_node;
+<% else %>
+    <%= @grammar.prefix %>position_t position;
+    <%= @grammar.prefix %>position_t end_position;
+    /** Parser value from this state. */
+    <%= @grammar.prefix %>value_t pvalue;
 <% end %>
 
     this(size_t state_id)
@@ -941,6 +948,55 @@ private immutable parser_state_t[] parser_state_table = [
 ];
 
 <% unless @grammar.tree %>
+/**
+ * Get the rule position (start or end) for the currently matched rule.
+ */
+private <%= @grammar.prefix %>position_t get_rule_position(state_value_t[] statevalues, size_t i, size_t n_states, bool get_end)
+{
+    if (n_states > 0u)
+    {
+        if (i == 0u)
+        {
+            if (get_end)
+            {
+                for (size_t j = 0u; j < n_states; j++)
+                {
+                    state_value_t * sv = &statevalues[$-1-j];
+                    if (sv.end_position.valid)
+                    {
+                        return sv.end_position;
+                    }
+                }
+            }
+            else
+            {
+                for (size_t j = 0u; j < n_states; j++)
+                {
+                    state_value_t * sv = &statevalues[$-n_states+j];
+                    if (sv.position.valid)
+                    {
+                        return sv.position;
+                    }
+                }
+            }
+        }
+        else
+        {
+            if (get_end)
+            {
+                return statevalues[$-1-n_states+i].end_position;
+            }
+            else
+            {
+                return statevalues[$-1-n_states+i].position;
+            }
+        }
+    }
+    return <%= @grammar.prefix %>position_t.INVALID;
+}
+<% end %>
+
+<% if !@grammar.tree || @grammar.parser_user_code_used? %>
 /**
  * Execute user code associated with a parser rule.
  *
@@ -951,7 +1007,7 @@ private immutable parser_state_t[] parser_state_table = [
  * @retval P_USER_TERMINATED
  *   User requested to terminate parsing.
  */
-private size_t parser_user_code(<%= @grammar.prefix %>value_t * _pvalue, uint rule, state_value_t[] statevalues, uint n_states, <%= @grammar.prefix %>context_t * context)
+private size_t parser_user_code(<%= @grammar.tree ? "void" : "#{@grammar.prefix}value_t" %> * _pvalue, uint rule, state_value_t[] statevalues, uint n_states, <%= @grammar.prefix %>context_t * context)
 {
     switch (rule)
     {
@@ -1047,6 +1103,8 @@ private size_t parse_from(<%= @grammar.prefix %>context_t * context, size_t star
 <% if @grammar.tree %>
     void * reduced_parser_node;
 <% else %>
+    <%= @grammar.prefix %>position_t reduced_position;
+    <%= @grammar.prefix %>position_t reduced_end_position;
     <%= @grammar.prefix %>value_t reduced_parser_value;
 <% end %>
     for (;;)
@@ -1091,6 +1149,8 @@ private size_t parse_from(<%= @grammar.prefix %>context_t * context, size_t star
 <%= expand_code(@grammar.on_token_node, false, nil, nil) %>
                 statevalues[$-1].tree_node = token_tree_node;
 <% else %>
+                statevalues[$-1].position = token_info.position;
+                statevalues[$-1].end_position = token_info.end_position;
                 statevalues[$-1].pvalue = token_info.pvalue;
 <% end %>
                 token = INVALID_TOKEN_ID;
@@ -1102,6 +1162,8 @@ private size_t parse_from(<%= @grammar.prefix %>context_t * context, size_t star
                 statevalues[$-1].tree_node = reduced_parser_node;
 <% else %>
                 statevalues[$-1].pvalue = reduced_parser_value;
+                statevalues[$-1].position = reduced_position;
+                statevalues[$-1].end_position = reduced_end_position;
                 <%= @grammar.prefix %>value_t new_parse_result;
                 reduced_parser_value = new_parse_result;
 <% end %>
@@ -1167,6 +1229,12 @@ private size_t parse_from(<%= @grammar.prefix %>context_t * context, size_t star
             {
                 reduced_parser_node = null;
             }
+<%   if @grammar.parser_user_code_used? %>
+            if (parser_user_code(reduced_parser_node, parser_reduce_table[reduce_index].rule, statevalues, parser_reduce_table[reduce_index].n_states, context) == P_USER_TERMINATED)
+            {
+                return P_USER_TERMINATED;
+            }
+<%   end %>
 <% else %>
             <%= @grammar.prefix %>value_t reduced_parser_value2;
             if (parser_user_code(&reduced_parser_value2, parser_reduce_table[reduce_index].rule, statevalues, parser_reduce_table[reduce_index].n_states, context) == P_USER_TERMINATED)
@@ -1174,6 +1242,16 @@ private size_t parse_from(<%= @grammar.prefix %>context_t * context, size_t star
                 return P_USER_TERMINATED;
             }
             reduced_parser_value = reduced_parser_value2;
+            if (parser_reduce_table[reduce_index].n_states > 0u)
+            {
+                reduced_position = get_rule_position(statevalues, 0u, parser_reduce_table[reduce_index].n_states, false);
+                reduced_end_position = get_rule_position(statevalues, 0u, parser_reduce_table[reduce_index].n_states, true);
+            }
+            else
+            {
+                reduced_position = <%= @grammar.prefix %>position_t.INVALID;
+                reduced_end_position = <%= @grammar.prefix %>position_t.INVALID;
+            }
 <% end %>
             reduced_rule_set = parser_reduce_table[reduce_index].rule_set;
             statevalues.length -= parser_reduce_table[reduce_index].n_states;

assets/parser.h.erb

@@ -45,10 +45,10 @@ typedef uint32_t <%= @grammar.prefix %>code_point_t;
  */
 typedef struct
 {
-    /** Input text row (0-based). */
+    /** Input text row (1-based). */
     uint32_t row;
 
-    /** Input text column (0-based). */
+    /** Input text column (1-based). */
     uint32_t col;
 } <%= @grammar.prefix %>position_t;
 

doc/user_guide.md

@@ -151,12 +151,37 @@ needed by a `ptype` directive, for example:
 
 ### Lexer pattern code blocks
 
-#### C/C++
+Lexer code blocks appear between `<<` and `>>` markers following a `drop`,
+`token`, or pattern expression.
+User code in a lexer code block will be executed when the lexer matches the
+given pattern.
+Assignment to the `$$` symbol will associate a parser value with the lexed
+token.
+This parser value can then be used later in a parser rule.
+
+The input text positions of the matched token can also be accessed from within
+a lexer code block.
+Each of these positions is an instance of the `p_position_t` structure (see
+`${#p_position_t}`), which contains 1-based `row` and `col` fields.
+The start position of the matched token is accessed with `${position}`, and
+the end position of the matched token is accessed with `${end_position}`.
+
+Example:
+
+```
+token integer /\d+/ <<
+  printf("integer token on row %d, col %d\n",
+      ${position}.row, ${position}.col);
+  $$ = parse_integer(match, match_length);
+>>
+```
+
+#### C/C++ lexer code block arguments
 
 The lexer code block is passed the following arguments:
 
-  * `match` - a pointer points to the text matched by the lexer pattern.
+  * `match` (`uint8_t const`) - the pointer points to the text matched by the lexer pattern.
-  * `match_length` - length of the matched text.
+  * `match_length` (`size_t`) - length of the matched text.
 
 Example:
 
@@ -174,11 +199,11 @@ token integer /\d+/ <<
 >>
 ```
 
-#### D
+#### D lexer code block arguments
 
 The lexer code block is passed the following arguments:
 
-  * `match` - a slice containing the text matched by the lexer pattern.
+  * `match` (`string`) - a slice containing the text matched by the lexer pattern.
 
 ```
 ptype ulong;
@@ -194,13 +219,6 @@ token integer /\d+/ <<
 >>
 ```
 
-Lexer code blocks appear following a `drop`, `token`, or pattern expression.
-User code in a lexer code block will be executed when the lexer matches the
-given pattern.
-Assignment to the `$$` symbol will associate a parser value with the lexed
-token.
-This parser value can then be used later in a parser rule.
-
 ### Parser rule code blocks
 
 Example:
@@ -217,9 +235,73 @@ rule.
 Parser values for the rules or tokens in the rule pattern can be accessed
 positionally with tokens `$1`, `$2`, `$3`, etc...
 
-Parser rule code blocks are not available in tree generation mode.
+The input text positions for the reduced rule and for the individual rule
+components can also be accessed from within a parser rule code block.
+Each of these positions is an instance of the `p_position_t` structure (see
+`${#p_position_t}`), which contains 1-based `row` and `col` fields.
+
+The start position of the overall reduced rule is accessed with
+`${$.position}`, and the end position of the overall reduced rule is accessed
+with `${$.end_position}`.
+
+The start and end positions of an individual rule component are accessed
+positionally with `${N.position}` and `${N.end_position}`, where `N` is the
+1-based index of the component (`${1.position}` for the first component,
+`${2.position}` for the second, and so on).
+
+Example:
+
+```
+Assignment -> ident equals Expr <<
+    printf("assignment on row %d, col %d\n",
+        ${$.position}.row, ${$.position}.col);
+    printf("target identifier ends on row %d, col %d\n",
+        ${1.end_position}.row, ${1.end_position}.col);
+    printf("expression starts on row %d, col %d\n",
+        ${3.position}.row, ${3.position}.col);
+>>
+```
+
+A rule or rule component that allows for an empty match may not have valid
+positions.
+In this case the position should be checked for validity before its `row` and
+`col` fields are used (see `${#p_position_valid}`).
+For C targets this can be accomplished with
+`if (p_position_valid(${$.position}))` and for D targets this can be
+accomplished with `if (${$.position}.valid)`.
+
 In tree generation mode, a full parse tree is automatically constructed in
 memory for user code to traverse after parsing is complete.
+Parser rule code blocks are still supported in tree generation mode, but they
+behave differently than when tree generation mode is not active.
+The code block for a rule is executed after the rule has been matched and its
+tree node has been fully formed.
+Within the code block, `$$` refers to the tree node for the reduced rule, typed
+as a pointer to that rule's generated tree node structure.
+The tree nodes for the rule components are accessed positionally with `$1`,
+`$2`, `$3`, etc..., each typed as a pointer to the generated tree node structure
+for that component (a rule node or a `Token` node).
+Field aliases (see the "Specifying parser rules" section) may also be used to
+reference a component tree node by name; a field alias behaves identically to
+the positional reference for that component.
+The positional position expansions (`${$.position}`, `${N.position}`, etc...)
+are not available in tree generation mode; the `position` and `end_position`
+fields of the tree nodes can be accessed directly instead.
+
+Example:
+
+```
+tree;
+
+Assignment -> ident equals Expr <<
+    /* $$ is the Assignment tree node, $1 is the ident Token node, and $3 is
+     * the Expr rule node. */
+    printf("assignment on row %d, col %d\n",
+        $$->position.row, $$->position.col);
+    printf("target identifier ends on row %d, col %d\n",
+        $1->end_position.row, $1->end_position.col);
+>>
+```
 
 ##> `context_user_fields` statement - adding custom fields to the context
 
@@ -657,7 +739,9 @@ It is recommended to place this statement early in the grammar.
 In tree generation mode various aspects of propane's behavior are changed:
 
   * Only one `ptype` is allowed.
-  * Parser user code blocks are not supported.
+  * Parser user code blocks execute after the rule's tree node has been formed
+  and access the tree nodes via `$$`, `$1`, `$2`, etc... (see the "Parser rule
+  code blocks" section).
   * Structure types are generated to represent the parsed tokens and rules as
   defined in the grammar.
   * The parse result from `p_result()` points to a `Start` struct containing
@@ -1006,8 +1090,12 @@ The `$$` symbol accesses the output parser value for this rule.
 The above examples demonstrate how the parser values for the rule components
 can be used to produce the parser value for the accepted rule.
 
-Parser rule code blocks are not allowed and not used when tree generation mode
+In tree generation mode, parser rule code blocks access the reduced rule tree
-is active.
+node and its component tree nodes via `$$`, `$1`, `$2`, etc... (see the "Parser
+rule code blocks" section).
+Field aliases may still be used in tree generation mode to reference a component
+tree node by name, behaving identically to the corresponding positional
+reference.
 
 ##> User termination of the lexer or parser
 
@@ -1346,7 +1434,7 @@ if (p_parse(context) == P_UNEXPECTED_TOKEN)
 {
     p_position_t error_position = p_position(context);
     fprintf(stderr, "Error: unexpected token at row %u column %u\n",
-        error_position.row + 1, error_position.col + 1);
+        error_position.row, error_position.col);
 }
 ```
 
@@ -1474,7 +1562,7 @@ if (p_parse(context) == P_UNEXPECTED_TOKEN)
     p_position_t error_position = p_position(context);
     fprintf(stderr, "Error: unexpected token `%s' at row %u column %u\n",
         p_token_names[context->token],
-        error_position.row + 1, error_position.col + 1);
+        error_position.row, error_position.col);
 }
 ```
 

extra/vim/syntax/propane.vim

@@ -20,18 +20,32 @@ exe "syn include @propaneTarget syntax/".b:propane_subtype.".vim"
 syn region propaneTarget matchgroup=propaneDelimiter start="<<" end=">>$" contains=@propaneTarget keepend
 
 syn match propaneComment "#.*"
-syn match propaneOperator "->"
 syn match propaneFieldAlias ":[a-zA-Z0-9_]\+" contains=propaneFieldOperator
 syn match propaneFieldOperator ":" contained
 syn match propaneOperator "?"
-syn keyword propaneKeyword context_user_fields drop free_token_node lex_fn module noline on_token_node prefix ptype start token token_user_fields tokenid tree tree_prefix tree_suffix
+" The right-hand side of a rule (after '->' up to '<<' or ';') lists symbol
+" names that may coincide with propane keywords (e.g. 'start', 'token',
+" 'tree'). Wrap it in a region that excludes keyword matches so those names
+" are not highlighted as keywords. The '<<' is left unconsumed so the
+" propaneTarget region can still match it.
+syn region propaneRuleRhs matchgroup=propaneOperator start="->" end="\ze<<" end=";" contains=propaneFieldAlias,propaneRuleOperator,propaneComment keepend
+syn match propaneRuleOperator "?" contained
+" Keywords that introduce a user-defined name. The name is consumed by
+" propaneName via nextgroup so a name matching a keyword (e.g. 'token start')
+" is not highlighted as a keyword. These must be a match (not syn keyword)
+" because a syn keyword always wins over a contained nextgroup match.
+syn match propaneNameDecl "\<\%(tokenid\|token\|lex_fn\|module\|start\|tree_prefix\|tree_suffix\)\>" nextgroup=propaneName skipwhite
+syn match propaneName "\<\h\w*\>" contained
+syn match propaneKeyword "\<\%(context_user_fields\|drop\|free_token_node\|noline\|on_token_node\|prefix\|ptype\|token_user_fields\|tree\)\>"
 
 syn region propaneRegex start="/" end="/" skip="\v\\\\|\\/"
 
 hi def link propaneComment Comment
 hi def link propaneKeyword Keyword
+hi def link propaneNameDecl Keyword
 hi def link propaneRegex String
 hi def link propaneOperator Operator
+hi def link propaneRuleOperator Operator
 hi def link propaneFieldOperator Operator
 hi def link propaneDelimiter Delimiter
 hi def link propaneFieldAlias Identifier

lib/propane/generator.rb

@@ -185,7 +185,8 @@ class Propane
                 end
               end
               @grammar.rules << Rule.new(component, [], nil, ptypename, rule.line_number)
-              @grammar.rules << Rule.new(component, [c], "$$ = $1;\n", ptypename, rule.line_number)
+              optcode = @grammar.tree ? nil : "$$ = $1;\n"
+              @grammar.rules << Rule.new(component, [c], optcode, ptypename, rule.line_number)
               optional_rules_added << component
             end
           end
@@ -296,6 +297,14 @@ class Propane
       end
       if parser
         code = code.gsub(/\$\$/) do |match|
+          if @grammar.tree
+            case @language
+            when "c"
+              "((#{@grammar.tree_prefix}#{rule.name}#{@grammar.tree_suffix} *)_pvalue)"
+            when "d"
+              "(cast(#{@grammar.tree_prefix}#{rule.name}#{@grammar.tree_suffix} *)_pvalue)"
+            end
+          else
             case @language
             when "c"
               "_pvalue->v_#{rule.ptypename}"
@@ -303,24 +312,26 @@ class Propane
               "_pvalue.v_#{rule.ptypename}"
             end
           end
-        code = code.gsub(/\$(\d+)/) do |match|
-          index = $1.to_i
-          case @language
-          when "c"
-            "state_values_stack_index(statevalues, -1 - (int)n_states + #{index})->pvalue.v_#{rule.components[index - 1].ptypename}"
-          when "d"
-            "statevalues[$-1-n_states+#{index}].pvalue.v_#{rule.components[index - 1].ptypename}"
         end
+        code = code.gsub(/\$(\d+)/) do |match|
+          parser_component_reference(rule, $1.to_i)
+        end
+        code = code.gsub(/\$\{(\$|\d+)\.position\}/) do |match|
+          index = $1.to_i
+          "get_rule_position(statevalues, #{index}, n_states, false)"
+        end
+        code = code.gsub(/\$\{(\$|\d+)\.end_position\}/) do |match|
+          index = $1.to_i
+          "get_rule_position(statevalues, #{index}, n_states, true)"
         end
         code = code.gsub(/\$\{(\w+)\}/) do |match|
           aliasname = $1
           if index = rule.aliases[aliasname]
-            case @language
+            # Field aliases are just a named reference to a positional rule
-            when "c"
+            # component, so reuse the same expansion as `$1', `$2', etc. Note
-              "state_values_stack_index(statevalues, -(int)n_states + #{index})->pvalue.v_#{rule.components[index].ptypename}"
+            # that rule.aliases stores a 0-based component index, so add 1 to
-            when "d"
+            # convert it to the 1-based index used for positional references.
-              "statevalues[$-n_states+#{index}].pvalue.v_#{rule.components[index].ptypename}"
+            parser_component_reference(rule, index + 1)
-            end
           else
             raise Error.new("Field alias '#{aliasname}' not found")
           end
@@ -343,6 +354,22 @@ class Propane
             end
           end
         end
+        code = code.gsub(/\$\{position\}/) do |match|
+          case @language
+          when "c"
+            "out_token_info->position"
+          when "d"
+            "out_token_info.position"
+          end
+        end
+        code = code.gsub(/\$\{end_position\}/) do |match|
+          case @language
+          when "c"
+            "out_token_info->end_position"
+          when "d"
+            "out_token_info.end_position"
+          end
+        end
         code = code.gsub(/\$mode\(([a-zA-Z_][a-zA-Z_0-9]*)\)/) do |match|
           mode_name = $1
           mode_id = @lexer.mode_id(mode_name)
@@ -360,6 +387,45 @@ class Propane
       code
     end
 
+    # Expand a positional reference to a parser rule component.
+    #
+    # This is used to expand `$1', `$2', etc. as well as field aliases (which
+    # are just named references to a positional rule component).
+    #
+    # @param rule [Rule]
+    #   The Rule containing the user code.
+    # @param index [Integer]
+    #   1-based index of the rule component to reference.
+    #
+    # @return [String]
+    #   Expanded rule component reference.
+    def parser_component_reference(rule, index)
+      component = rule.components[index - 1]
+      if @grammar.tree
+        # In tree mode a component reference yields a pointer to that
+        # component's tree node. An optional component propagates its target
+        # node (or null), so use the optional target's node type.
+        if component.is_a?(RuleSet) && component.optional?
+          component = component.option_target
+        end
+        node_name = component.is_a?(Token) ? "Token" : component.name
+        typename = "#{@grammar.tree_prefix}#{node_name}#{@grammar.tree_suffix}"
+        case @language
+        when "c"
+          "((#{typename} *)state_values_stack_index(statevalues, -1 - (int)n_states + #{index})->tree_node)"
+        when "d"
+          "(cast(#{typename} *)statevalues[$-1-n_states+#{index}].tree_node)"
+        end
+      else
+        case @language
+        when "c"
+          "state_values_stack_index(statevalues, -1 - (int)n_states + #{index})->pvalue.v_#{component.ptypename}"
+        when "d"
+          "statevalues[$-1-n_states+#{index}].pvalue.v_#{component.ptypename}"
+        end
+      end
+    end
+
     # Get the lex function to use.
     #
     # @return [String]

lib/propane/grammar.rb

@@ -58,6 +58,10 @@ class Propane
       @tokens.size + 1
     end
 
+    def parser_user_code_used?
+      @rules.any? {|r| r.code}
+    end
+
     private
 
     def parse_grammar!
@@ -263,13 +267,9 @@ class Propane
         end
         md = consume!(/((?:#{IDENTIFIER_REGEX}\??(?::#{IDENTIFIER_REGEX})?\s*)*)\s*/, "expected rule component list")
         components = md[1].strip.split(/\s+/)
-        if @tree
-          consume!(/;/, "expected `;'")
-        else
         unless code = parse_code_block!
           consume!(/;/, "expected `;' or code block")
         end
-        end
         @rules << Rule.new(rule_name, components, code, ptypename, @line_number)
         @modeline = nil
         true

lib/propane/version.rb

@@ -1,3 +1,3 @@
 class Propane
-  VERSION = "4.4.0"
+  VERSION = "4.7.0"
 end

spec/propane_spec.rb

@@ -95,6 +95,9 @@ EOF
     File.binwrite("spec/run/.stdout", stdout)
     stderr.sub!(/^.*modules passed unittests\n/, "")
     results = Results.new(stdout, stderr, status)
+    # Valgrind is only reliably available on Linux, so limit the leak check to
+    # Linux platforms.
+    if RUBY_PLATFORM =~ /linux/
       stdout, stderr, status = Open3.capture3("valgrind --leak-check=full --show-leak-kinds=all --track-origins=yes --verbose spec/run/testparser")
       vgout = stdout + stderr
       File.binwrite("spec/run/.vgout", vgout)
@@ -104,6 +107,7 @@ EOF
           raise "Valgrind detected memory leak"
         end
       end
+    end
     results
   end
 
@@ -745,6 +749,78 @@ EOF
         ])
       end
 
+      it "executes user code associated with a parser rule in tree mode" do
+        case language
+        when "c", "cpp"
+          write_grammar <<EOF
+tree;
+context_user_fields <<
+    int start_n_fields;
+    int start_a_value;
+    int a_value;
+    int b_value;
+    p_token_t b_token;
+    int c_is_null;
+    int c_field_is_null;
+    int alias_a_value;
+    int alias_b_value;
+>>
+ptype int;
+token a << $$ = 11; >>
+token b << $$ = 22; >>
+Start -> A:ay B:bee C <<
+  ${context.start_n_fields} = $$->n_fields;
+  ${context.start_a_value} = $$->pA->pToken1->pvalue;
+  ${context.a_value} = $1->pToken1->pvalue;
+  ${context.b_value} = $2->pToken1->pvalue;
+  ${context.b_token} = $2->pToken1->token;
+  ${context.c_field_is_null} = ($$->pC == NULL) ? 1 : 0;
+  ${context.alias_a_value} = ${ay}->pToken1->pvalue;
+  ${context.alias_b_value} = ${bee}->pToken1->pvalue;
+>>
+A -> a;
+B -> b;
+C -> << ${context.c_is_null} = ($$ == NULL) ? 1 : 0; >>
+EOF
+        when "d"
+          write_grammar <<EOF
+tree;
+context_user_fields <<
+    int start_n_fields;
+    int start_a_value;
+    int a_value;
+    int b_value;
+    p_token_t b_token;
+    int c_is_null;
+    int c_field_is_null;
+    int alias_a_value;
+    int alias_b_value;
+>>
+ptype int;
+token a << $$ = 11; >>
+token b << $$ = 22; >>
+Start -> A:ay B:bee C <<
+  ${context.start_n_fields} = $$.n_fields;
+  ${context.start_a_value} = $$.pA.pToken1.pvalue;
+  ${context.a_value} = $1.pToken1.pvalue;
+  ${context.b_value} = $2.pToken1.pvalue;
+  ${context.b_token} = $2.pToken1.token;
+  ${context.c_field_is_null} = ($$.pC is null) ? 1 : 0;
+  ${context.alias_a_value} = ${ay}.pToken1.pvalue;
+  ${context.alias_b_value} = ${bee}.pToken1.pvalue;
+>>
+A -> a;
+B -> b;
+C -> << ${context.c_is_null} = ($$ is null) ? 1 : 0; >>
+EOF
+        end
+        run_propane(language: language)
+        compile("spec/test_parser_user_code_tree.#{language}", language: language)
+        results = run_test(language: language)
+        expect(results.stderr).to eq ""
+        expect(results.status).to eq 0
+      end
+
       it "parses lists" do
         write_grammar <<EOF
 ptype #{language == "d" ? "uint" : "uint32_t"};
@@ -910,6 +986,57 @@ EOF
         expect(results.status).to eq 0
       end
 
+      it "allows lexer code blocks to access the matched token positions" do
+        case language
+        when "c", "cpp"
+          write_grammar <<EOF
+<<
+#include <stdio.h>
+>>
+context_user_fields <<
+    p_position_t last_start;
+    p_position_t last_end;
+>>
+drop /\\s+/;
+token word /[a-z]+/ <<
+    ${context.last_start} = ${position};
+    ${context.last_end} = ${end_position};
+>>
+token stop /!/ <<
+    $terminate(42);
+>>
+Start -> Words;
+Words -> ;
+Words -> word Words;
+Words -> stop Words;
+EOF
+        when "d"
+          write_grammar <<EOF
+context_user_fields <<
+    p_position_t last_start;
+    p_position_t last_end;
+>>
+drop /\\s+/;
+token word /[a-z]+/ <<
+    ${context.last_start} = ${position};
+    ${context.last_end} = ${end_position};
+>>
+token stop /!/ <<
+    $terminate(42);
+>>
+Start -> Words;
+Words -> ;
+Words -> word Words;
+Words -> stop Words;
+EOF
+        end
+        run_propane(language: language)
+        compile("spec/test_lexer_positions.#{language}", language: language)
+        results = run_test(language: language)
+        expect(results.stderr).to eq ""
+        expect(results.status).to eq 0
+      end
+
       it "allows the user to terminate the parser" do
         write_grammar <<EOF
 token a;
@@ -1814,6 +1941,132 @@ EOF
         expect(results.stderr).to eq ""
         expect(results.status).to eq 0
       end
+
+      it "allows accessing rule and component text positions" do
+        if language == "d"
+          write_grammar <<EOF
+<<
+import std.stdio;
+>>
+drop /\\s+/;
+token tok1;
+token tok2;
+token ident /[a-zA-Z_]\\w*/;
+token num /\\d+/;
+Num -> num;
+Start -> ident Num <<
+    writeln("ident start: ", ${1.position}.row, ", ", ${1.position}.col);
+    writeln("ident end: ", ${1.end_position}.row, ", ", ${1.end_position}.col);
+    writeln("Num start: ", ${2.position}.row, ", ", ${2.position}.col);
+    writeln("Num end: ", ${2.end_position}.row, ", ", ${2.end_position}.col);
+    writeln("Start start: ", ${$.position}.row, ", ", ${$.position}.col);
+    writeln("Start end: ", ${$.end_position}.row, ", ", ${$.end_position}.col);
+>>
+R -> Empty tok2 <<
+    writeln("Empty start: ", ${1.position}.row, ", ", ${1.position}.col);
+    writeln("Empty end: ", ${1.end_position}.row, ", ", ${1.end_position}.col);
+    writeln("tok2 start: ", ${2.position}.row, ", ", ${2.position}.col);
+    writeln("tok2 end: ", ${2.end_position}.row, ", ", ${2.end_position}.col);
+    writeln("R start: ", ${$.position}.row, ", ", ${$.position}.col);
+    writeln("R end: ", ${$.end_position}.row, ", ", ${$.end_position}.col);
+>>
+R -> tok1 Empty <<
+    writeln("tok1 start: ", ${1.position}.row, ", ", ${1.position}.col);
+    writeln("tok1 end: ", ${1.end_position}.row, ", ", ${1.end_position}.col);
+    writeln("Empty start: ", ${2.position}.row, ", ", ${2.position}.col);
+    writeln("Empty end: ", ${2.end_position}.row, ", ", ${2.end_position}.col);
+    writeln("R2 start: ", ${$.position}.row, ", ", ${$.position}.col);
+    writeln("R2 end: ", ${$.end_position}.row, ", ", ${$.end_position}.col);
+>>
+Empty -> ;
+Start -> R <<
+    writeln("StartR start: ", ${$.position}.row, ", ", ${$.position}.col);
+    writeln("StartR end: ", ${$.end_position}.row, ", ", ${$.end_position}.col);
+>>
+Start -> Empty <<
+    writeln("StartEmpty start: ", ${$.position}.row, ", ", ${$.position}.col);
+    writeln("StartEmpty end: ", ${$.end_position}.row, ", ", ${$.end_position}.col);
+>>
+EOF
+        else
+          write_grammar <<EOF
+<<
+#include <stdio.h>
+>>
+drop /\\s+/;
+token tok1;
+token tok2;
+token ident /[a-zA-Z_]\\w*/;
+token num /\\d+/;
+Num -> num;
+token pct /%/;
+Start -> ident Num <<
+    printf("ident start: %d, %d\\n", ${1.position}.row, ${1.position}.col);
+    printf("ident end: %d, %d\\n", ${1.end_position}.row, ${1.end_position}.col);
+    printf("Num start: %d, %d\\n", ${2.position}.row, ${2.position}.col);
+    printf("Num end: %d, %d\\n", ${2.end_position}.row, ${2.end_position}.col);
+    printf("Start start: %d, %d\\n", ${$.position}.row, ${$.position}.col);
+    printf("Start end: %d, %d\\n", ${$.end_position}.row, ${$.end_position}.col);
+>>
+R -> Empty tok2 <<
+    printf("Empty start: %d, %d\\n", ${1.position}.row, ${1.position}.col);
+    printf("Empty end: %d, %d\\n", ${1.end_position}.row, ${1.end_position}.col);
+    printf("tok2 start: %d, %d\\n", ${2.position}.row, ${2.position}.col);
+    printf("tok2 end: %d, %d\\n", ${2.end_position}.row, ${2.end_position}.col);
+    printf("R start: %d, %d\\n", ${$.position}.row, ${$.position}.col);
+    printf("R end: %d, %d\\n", ${$.end_position}.row, ${$.end_position}.col);
+>>
+R -> tok1 Empty <<
+    printf("tok1 start: %d, %d\\n", ${1.position}.row, ${1.position}.col);
+    printf("tok1 end: %d, %d\\n", ${1.end_position}.row, ${1.end_position}.col);
+    printf("Empty start: %d, %d\\n", ${2.position}.row, ${2.position}.col);
+    printf("Empty end: %d, %d\\n", ${2.end_position}.row, ${2.end_position}.col);
+    printf("R2 start: %d, %d\\n", ${$.position}.row, ${$.position}.col);
+    printf("R2 end: %d, %d\\n", ${$.end_position}.row, ${$.end_position}.col);
+>>
+Empty -> ;
+Start -> R <<
+    printf("StartR start: %d, %d\\n", ${$.position}.row, ${$.position}.col);
+    printf("StartR end: %d, %d\\n", ${$.end_position}.row, ${$.end_position}.col);
+>>
+Start -> Empty <<
+    printf("StartEmpty start: %d, %d\\n", ${$.position}.row, ${$.position}.col);
+    printf("StartEmpty end: %d, %d\\n", ${$.end_position}.row, ${$.end_position}.col);
+>>
+EOF
+        end
+        run_propane(language: language)
+        compile("spec/test_positions.#{language}", language: language)
+        results = run_test(language: language)
+        expect(results.stderr).to eq ""
+        expect(results.status).to eq 0
+        expect(results.stdout).to eq <<EOF
+ident start: 1, 5
+ident end: 1, 9
+Num start: 3, 9
+Num end: 3, 12
+Start start: 1, 5
+Start end: 3, 12
+
+Empty start: 0, 0
+Empty end: 0, 0
+tok2 start: 2, 2
+tok2 end: 2, 5
+R start: 2, 2
+R end: 2, 5
+StartR start: 2, 2
+StartR end: 2, 5
+
+tok1 start: 1, 3
+tok1 end: 1, 6
+Empty start: 0, 0
+Empty end: 0, 0
+R2 start: 1, 3
+R2 end: 1, 6
+StartR start: 1, 3
+StartR end: 1, 6
+EOF
+      end
     end
   end
 end

spec/test_lexer_positions.c

@@ -0,0 +1,50 @@
+#include "testparser.h"
+#include <assert.h>
+#include <string.h>
+
+int main()
+{
+    char const * input = "abc\n  defg hi\n!";
+    p_context_t * context = p_context_new((uint8_t const *)input, strlen(input));
+    p_token_info_t token_info;
+
+    /* First token "abc" on row 1, cols 1-3. */
+    assert(p_lex(context, &token_info) == P_SUCCESS);
+    assert(token_info.token == TOKEN_word);
+    assert(context->last_start.row == 1u);
+    assert(context->last_start.col == 1u);
+    assert(context->last_end.row == 1u);
+    assert(context->last_end.col == 3u);
+    /* The lexer code block observed the same positions reported to the caller. */
+    assert(context->last_start.row == token_info.position.row);
+    assert(context->last_start.col == token_info.position.col);
+    assert(context->last_end.row == token_info.end_position.row);
+    assert(context->last_end.col == token_info.end_position.col);
+
+    /* Second token "defg" on row 2, cols 3-6. */
+    assert(p_lex(context, &token_info) == P_SUCCESS);
+    assert(token_info.token == TOKEN_word);
+    assert(context->last_start.row == 2u);
+    assert(context->last_start.col == 3u);
+    assert(context->last_end.row == 2u);
+    assert(context->last_end.col == 6u);
+
+    /* Third token "hi" on row 2, cols 8-9. */
+    assert(p_lex(context, &token_info) == P_SUCCESS);
+    assert(token_info.token == TOKEN_word);
+    assert(context->last_start.row == 2u);
+    assert(context->last_start.col == 8u);
+    assert(context->last_end.row == 2u);
+    assert(context->last_end.col == 9u);
+
+    /* The "!" stop token terminates the lexer. The context input text position
+     * must not be updated when the lexer user code requests termination, so it
+     * still points at the "!" token on row 3, col 1. */
+    assert(p_lex(context, &token_info) == P_USER_TERMINATED);
+    assert(p_user_terminate_code(context) == 42u);
+    assert(context->text_position.row == 3u);
+    assert(context->text_position.col == 1u);
+
+    p_context_delete(context);
+    return 0;
+}

spec/test_lexer_positions.d

@@ -0,0 +1,42 @@
+import testparser;
+import std.stdio;
+
+int main()
+{
+    return 0;
+}
+
+unittest
+{
+    string input = "abc\n  defg hi\n!";
+    p_context_t * context = p_context_new(input);
+    p_token_info_t token_info;
+
+    /* First token "abc" on row 1, cols 1-3. */
+    assert(p_lex(context, &token_info) == P_SUCCESS);
+    assert(token_info.token == TOKEN_word);
+    assert(context.last_start == p_position_t(1, 1));
+    assert(context.last_end == p_position_t(1, 3));
+    /* The lexer code block observed the same positions reported to the caller. */
+    assert(context.last_start == token_info.position);
+    assert(context.last_end == token_info.end_position);
+
+    /* Second token "defg" on row 2, cols 3-6. */
+    assert(p_lex(context, &token_info) == P_SUCCESS);
+    assert(token_info.token == TOKEN_word);
+    assert(context.last_start == p_position_t(2, 3));
+    assert(context.last_end == p_position_t(2, 6));
+
+    /* Third token "hi" on row 2, cols 8-9. */
+    assert(p_lex(context, &token_info) == P_SUCCESS);
+    assert(token_info.token == TOKEN_word);
+    assert(context.last_start == p_position_t(2, 8));
+    assert(context.last_end == p_position_t(2, 9));
+
+    /* The "!" stop token terminates the lexer. The context input text position
+     * must not be updated when the lexer user code requests termination, so it
+     * still points at the "!" token on row 3, col 1. */
+    assert(p_lex(context, &token_info) == P_USER_TERMINATED);
+    assert(p_user_terminate_code(context) == 42u);
+    assert(context.text_position == p_position_t(3, 1));
+}

spec/test_parser_user_code_tree.c

@@ -0,0 +1,39 @@
+#include "testparser.h"
+#include <assert.h>
+#include <string.h>
+#include "testutils.h"
+
+int main()
+{
+    char const * input = "ab";
+    p_context_t * context;
+    context = p_context_new((uint8_t const *)input, strlen(input));
+    assert_eq(P_SUCCESS, p_parse(context));
+
+    /* The parser user code recorded values accessed via $$, $1, and $2 while
+     * the tree node for the Start rule was being formed. */
+    assert_eq(3, context->start_n_fields);
+    assert_eq(11, context->start_a_value);
+    assert_eq(11, context->a_value);
+    assert_eq(22, context->b_value);
+    assert_eq(TOKEN_b, context->b_token);
+
+    /* The empty-matched rule C has a null $$ tree node, and its field in the
+     * Start node is null as well. */
+    assert_eq(1, context->c_is_null);
+    assert_eq(1, context->c_field_is_null);
+
+    /* Field aliases reference the same component tree nodes as the positional
+     * references. */
+    assert_eq(11, context->alias_a_value);
+    assert_eq(22, context->alias_b_value);
+
+    Start * start = p_result(context);
+    assert(start->pA != NULL);
+    assert(start->pB != NULL);
+    assert(start->pC == NULL);
+    p_tree_delete(start);
+    p_context_delete(context);
+
+    return 0;
+}

spec/test_parser_user_code_tree.d

@@ -0,0 +1,39 @@
+import testparser;
+import std.stdio;
+import testutils;
+
+int main()
+{
+    return 0;
+}
+
+unittest
+{
+    string input = "ab";
+    p_context_t * context = p_context_new(input);
+    assert_eq(P_SUCCESS, p_parse(context));
+
+    /* The parser user code recorded values accessed via $$, $1, and $2 while
+     * the tree node for the Start rule was being formed. */
+    assert_eq(3, context.start_n_fields);
+    assert_eq(11, context.start_a_value);
+    assert_eq(11, context.a_value);
+    assert_eq(22, context.b_value);
+    assert_eq(TOKEN_b, context.b_token);
+
+    /* The empty-matched rule C has a null $$ tree node, and its field in the
+     * Start node is null as well. */
+    assert_eq(1, context.c_is_null);
+    assert_eq(1, context.c_field_is_null);
+
+    /* Field aliases reference the same component tree nodes as the positional
+     * references. */
+    assert_eq(11, context.alias_a_value);
+    assert_eq(22, context.alias_b_value);
+
+    Start * start = p_result(context);
+    assert(start.pA !is null);
+    assert(start.pB !is null);
+    assert(start.pC is null);
+    p_tree_delete(start);
+}

spec/test_positions.c

@@ -0,0 +1,29 @@
+#include "testparser.h"
+#include <assert.h>
+#include <string.h>
+#include <stdio.h>
+
+int main()
+{
+    char const * input = "    Hello\n\n        4200\n";
+    p_context_t * context;
+    context = p_context_new((uint8_t const *)input, strlen(input));
+    assert(p_parse(context) == P_SUCCESS);
+    p_context_delete(context);
+
+    printf("\n");
+
+    input = "\n tok2";
+    context = p_context_new((uint8_t const *)input, strlen(input));
+    assert(p_parse(context) == P_SUCCESS);
+    p_context_delete(context);
+
+    printf("\n");
+
+    input = "  tok1";
+    context = p_context_new((uint8_t const *)input, strlen(input));
+    assert(p_parse(context) == P_SUCCESS);
+    p_context_delete(context);
+
+    return 0;
+}

spec/test_positions.d

@@ -0,0 +1,27 @@
+import testparser;
+import std.stdio;
+
+int main()
+{
+    return 0;
+}
+
+unittest
+{
+    string input = "    Hello\n\n        4200\n";
+    p_context_t * context;
+    context = p_context_new(input);
+    assert(p_parse(context) == P_SUCCESS);
+
+    writeln();
+
+    input = "\n tok2";
+    context = p_context_new(input);
+    assert(p_parse(context) == P_SUCCESS);
+
+    writeln();
+
+    input = "  tok1";
+    context = p_context_new(input);
+    assert(p_parse(context) == P_SUCCESS);
+}