[ruby/prism] Support ItParametersNode

So that compilers know they need to add to add an anonymous
variable to the local table.

ruby/prism@7f1aadd057

prism/config.yml

@@ -1948,6 +1948,12 @@ nodes:
 
           `foo #{bar} baz`
           ^^^^^^^^^^^^^^^^
+  - name: ItParametersNode
+    comment: |
+      Represents an implicit set of parameters through the use of the `it` keyword within a block or lambda.
+
+          -> { it + it }
+          ^^^^^^^^^^^^^^
   - name: KeywordHashNode
     fields:
       - name: flags

prism/diagnostic.c

@@ -202,8 +202,14 @@ static const pm_diagnostic_data_t diagnostic_messages[PM_DIAGNOSTIC_ID_LEN] = {
     [PM_ERR_INVALID_MULTIBYTE_CHARACTER]        = { "invalid multibyte character 0x%X", PM_ERROR_LEVEL_FATAL },
     [PM_ERR_INVALID_PRINTABLE_CHARACTER]        = { "invalid character `%c`", PM_ERROR_LEVEL_FATAL },
     [PM_ERR_INVALID_PERCENT]                    = { "invalid `%` token", PM_ERROR_LEVEL_FATAL }, // TODO WHAT?
+<<<<<<< HEAD:prism/diagnostic.c
     [PM_ERR_INVALID_VARIABLE_GLOBAL]            = { "'%.*s' is not allowed as a global variable name", PM_ERROR_LEVEL_FATAL },
     [PM_ERR_IT_NOT_ALLOWED]                     = { "`it` is not allowed when an ordinary parameter is defined", PM_ERROR_LEVEL_FATAL },
+=======
+    [PM_ERR_INVALID_VARIABLE_GLOBAL]            = { "`%.*s' is not allowed as a global variable name", PM_ERROR_LEVEL_FATAL },
+    [PM_ERR_IT_NOT_ALLOWED_NUMBERED]            = { "`it` is not allowed when an numbered parameter is defined", PM_ERROR_LEVEL_FATAL },
+    [PM_ERR_IT_NOT_ALLOWED_ORDINARY]            = { "`it` is not allowed when an ordinary parameter is defined", PM_ERROR_LEVEL_FATAL },
+>>>>>>> 7f1aadd057 (Support ItParametersNode):src/diagnostic.c
     [PM_ERR_LAMBDA_OPEN]                        = { "expected a `do` keyword or a `{` to open the lambda block", PM_ERROR_LEVEL_FATAL },
     [PM_ERR_LAMBDA_TERM_BRACE]                  = { "expected a lambda block beginning with `{` to end with `}`", PM_ERROR_LEVEL_FATAL },
     [PM_ERR_LAMBDA_TERM_END]                    = { "expected a lambda block beginning with `do` to end with `end`", PM_ERROR_LEVEL_FATAL },
@@ -225,7 +231,8 @@ static const pm_diagnostic_data_t diagnostic_messages[PM_DIAGNOSTIC_ID_LEN] = {
     [PM_ERR_NOT_EXPRESSION]                     = { "expected an expression after `not`", PM_ERROR_LEVEL_FATAL },
     [PM_ERR_NO_LOCAL_VARIABLE]                  = { "%.*s: no such local variable", PM_ERROR_LEVEL_FATAL },
     [PM_ERR_NUMBER_LITERAL_UNDERSCORE]          = { "number literal ending with a `_`", PM_ERROR_LEVEL_FATAL },
-    [PM_ERR_NUMBERED_PARAMETER_NOT_ALLOWED]     = { "numbered parameters are not allowed when an ordinary parameter is defined", PM_ERROR_LEVEL_FATAL },
+    [PM_ERR_NUMBERED_PARAMETER_IT]              = { "numbered parameters are not allowed when an 'it' parameter is defined", PM_ERROR_LEVEL_FATAL },
+    [PM_ERR_NUMBERED_PARAMETER_ORDINARY]        = { "numbered parameters are not allowed when an ordinary parameter is defined", PM_ERROR_LEVEL_FATAL },
     [PM_ERR_NUMBERED_PARAMETER_OUTER_SCOPE]     = { "numbered parameter is already used in outer scope", PM_ERROR_LEVEL_FATAL },
     [PM_ERR_OPERATOR_MULTI_ASSIGN]              = { "unexpected operator for a multiple assignment", PM_ERROR_LEVEL_FATAL },
     [PM_ERR_OPERATOR_WRITE_ARGUMENTS]           = { "unexpected operator after a call with arguments", PM_ERROR_LEVEL_FATAL },

prism/diagnostic.h

@@ -201,7 +201,8 @@ typedef enum {
     PM_ERR_INVALID_PRINTABLE_CHARACTER,
     PM_ERR_INVALID_PERCENT,
     PM_ERR_INVALID_VARIABLE_GLOBAL,
-    PM_ERR_IT_NOT_ALLOWED,
+    PM_ERR_IT_NOT_ALLOWED_NUMBERED,
+    PM_ERR_IT_NOT_ALLOWED_ORDINARY,
     PM_ERR_LAMBDA_OPEN,
     PM_ERR_LAMBDA_TERM_BRACE,
     PM_ERR_LAMBDA_TERM_END,
@@ -223,7 +224,8 @@ typedef enum {
     PM_ERR_NOT_EXPRESSION,
     PM_ERR_NO_LOCAL_VARIABLE,
     PM_ERR_NUMBER_LITERAL_UNDERSCORE,
-    PM_ERR_NUMBERED_PARAMETER_NOT_ALLOWED,
+    PM_ERR_NUMBERED_PARAMETER_IT,
+    PM_ERR_NUMBERED_PARAMETER_ORDINARY,
     PM_ERR_NUMBERED_PARAMETER_OUTER_SCOPE,
     PM_ERR_OPERATOR_MULTI_ASSIGN,
     PM_ERR_OPERATOR_WRITE_ARGUMENTS,

prism/parser.h

@@ -450,37 +450,31 @@ typedef struct {
  * into their parent scopes, while others cannot.
  */
 typedef struct pm_scope {
-    /** The IDs of the locals in the given scope. */
-    pm_constant_id_list_t locals;
-
     /** A pointer to the previous scope in the linked list. */
     struct pm_scope *previous;
 
-    /**
-     * A boolean indicating whether or not this scope can see into its parent.
-     * If closed is true, then the scope cannot see into its parent.
-     */
-    bool closed;
-
-    /**
-     * A boolean indicating whether or not this scope has explicit parameters.
-     * This is necessary to determine whether or not numbered parameters are
-     * allowed.
-     */
-    bool explicit_params;
+    /** The IDs of the locals in the given scope. */
+    pm_constant_id_list_t locals;
 
     /**
-     * Booleans indicating whether the parameters for this scope have declared
-     * forwarding parameters.
+     * This is a bitfield that indicates the parameters that are being used in
+     * this scope. It is a combination of the PM_SCOPE_PARAMS_* constants. There
+     * are three different kinds of parameters that can be used in a scope:
+     *
+     * - Ordinary parameters (e.g., def foo(bar); end)
+     * - Numbered parameters (e.g., def foo; _1; end)
+     * - The it parameter (e.g., def foo; it; end)
+     *
+     * If ordinary parameters are being used, then certain parameters can be
+     * forwarded to another method/structure. Those are indicated by four
+     * additional bits in the params field. For example, some combinations of:
      *
-     * For example, some combinations of:
-     *   def foo(*); end
-     *   def foo(**); end
-     *   def foo(&); end
-     *   def foo(...); end
+     * - def foo(*); end
+     * - def foo(**); end
+     * - def foo(&); end
+     * - def foo(...); end
      */
-
-    uint8_t forwarding_params;
+    uint8_t parameters;
 
     /**
      * An integer indicating the number of numbered parameters on this scope.
@@ -489,13 +483,27 @@ typedef struct pm_scope {
      * about how many numbered parameters exist.
      */
     int8_t numbered_parameters;
+
+    /**
+     * A boolean indicating whether or not this scope can see into its parent.
+     * If closed is true, then the scope cannot see into its parent.
+     */
+    bool closed;
 } pm_scope_t;
 
-static const uint8_t PM_FORWARDING_POSITIONALS = 0x1;
-static const uint8_t PM_FORWARDING_KEYWORDS = 0x2;
-static const uint8_t PM_FORWARDING_BLOCK = 0x4;
-static const uint8_t PM_FORWARDING_ALL = 0x8;
-static const int8_t PM_NUMBERED_PARAMETERS_DISALLOWED = -1;
+static const uint8_t PM_SCOPE_PARAMETERS_NONE = 0x0;
+static const uint8_t PM_SCOPE_PARAMETERS_ORDINARY = 0x1;
+static const uint8_t PM_SCOPE_PARAMETERS_NUMBERED = 0x2;
+static const uint8_t PM_SCOPE_PARAMETERS_IT = 0x4;
+static const uint8_t PM_SCOPE_PARAMETERS_TYPE_MASK = 0x7;
+
+static const uint8_t PM_SCOPE_PARAMETERS_FORWARDING_POSITIONALS = 0x8;
+static const uint8_t PM_SCOPE_PARAMETERS_FORWARDING_KEYWORDS = 0x10;
+static const uint8_t PM_SCOPE_PARAMETERS_FORWARDING_BLOCK = 0x20;
+static const uint8_t PM_SCOPE_PARAMETERS_FORWARDING_ALL = 0x40;
+
+static const int8_t PM_SCOPE_NUMBERED_PARAMETERS_DISALLOWED = -1;
+static const int8_t PM_SCOPE_NUMBERED_PARAMETERS_NONE = 0;
 
 /**
  * This struct represents the overall parser. It contains a reference to the