add divergences section to README.md and fixed reversed and noop arguments

CLAUDE.md

@@ -61,6 +61,15 @@ that place it:
   order but never twice. Used by `translate` and `include`; keyword arguments are guarded by the scanner
   instead. Grows as `Σ C(n,k)·k!` (65 for four names), which is
   why it is only used for signatures that name their arguments.
+- `wordAsValueRules(word)` / `wordAsValue($, word, continued)` — a tag's own keyword written where a value
+  goes. Django tells its flag from a variable by comparing the whole bit, so `reversed` is the flag of
+  `{% for %}` while `reversed.x` and `reversed|last` are lookups; `continued` selects that second group.
+  Needed because keyword extraction hands the parser the keyword wherever both it and `identifier` are
+  valid, so the reading in which the word names a variable has to be built back out of it. The rules are
+  hidden and aliased at the use site, one per level (`variable_attribute`, `value`, `filtered_value`),
+  because an alias renames the node its own rule makes and **cannot nest one inside another** — writing
+  it as nested inline `alias(alias(...))` calls silently yields a flat, partly zero-width tree that still
+  generates and still parses. Check the tree, not just the accept.
 
 Consequences worth knowing before editing a rule:
 
@@ -229,6 +238,19 @@ too if it were spelled the same way. `queries/exports.scm` names it for a tool t
 bind in the scope around the block, which a locals query cannot do: it places a definition in the innermost
 scope containing it and offers no way out again.
 
+`queries/conditionals.scm` is data for a tool too: `@conditional.group` / `@conditional.branch` /
+`@conditional.default` say which bodies render on only some passes, so a checker can tell that
+`{% if a %}{% now "Y" as n %}{% endif %}{{ n }}` may reach `{{ n }}` with nothing bound. A locals query
+cannot: it matches a reference to the definition whose scope contains it and has no notion of a path not
+taken. A group is exhaustive iff it has a `@conditional.default`, so each pattern captures the group
+alongside one of its parts and a tool needs no list of which clause belongs to which group. Adding a tag
+group whose body may be skipped means adding it there — `{% cache %}` is the non-obvious one, since a
+cache hit skips the body outright and `CacheNode` pushes no context.
+
+A branch that is also a `@local.scope` confines its bindings whichever way the branch goes, which is why
+`{% for %}` is inert for that check: `ForNode` renders `nodelist_empty` **inside** the same
+`context.push()` as the loop body, so `empty_clause` is a scope alongside `for_clause`.
+
 ## Testing
 
 Corpus tests live in `test/corpus/*.txt`, one file per tag.
@@ -264,6 +286,12 @@ documentation or memory. Both checks are worth repeating whenever tags, filters
 
 - Django has no number token: `[\w.]+` is one lexeme and `int()`/`float()` decides whether it is a literal,
   so `1a`, `1e`, `0x1f`, `1.2.3`, `1__0` and `1.` are variable _lookups_ there and errors here.
+- Django has no boolean or `None` token either. `True`, `False` and `None` are lookups, which resolve
+  because `BaseContext._reset_dicts` seeds every context with `{"True": True, "False": False, "None": None}`.
+  They are `boolean` and `none` literals here, so that a tool reading `queries/locals.scm` does not count
+  them as references to something the template never defines. Shadowing still parses — `{% with True=1 %}`
+  binds an `identifier`, because the keyword is not valid where a binding name is — but `{{ True.x }}` is
+  an error here and an ordinary two-part lookup in Django, which renders `string_if_invalid`.
 - A `with` binding written twice (`{% with a=1 a=2 %}`, and the same in `{% include %}` and
   `{% blocktranslate %}`) is an error here and not in Django, where `token_kwargs` builds a dict and the
   later value wins. It has no use, so it is treated as the mistake it almost certainly is.
@@ -286,11 +314,5 @@ documentation or memory. Both checks are worth repeating whenever tags, filters
   `{% cache 500 sidebar.name %}` names a fragment there, `{% cache 500 using="c" %}` names a fragment
   called `using="c"` rather than choosing a cache, and `{% cache 500 sidebar using= %}` takes an empty
   name. All three are errors here.
-- `do_for` reads `reversed` off the end of the tag before it looks for `in`, so `{% for x in reversed %}`
-  is an error there and a loop over a variable named `reversed` here. Writing the flag as well
-  (`{% for x in reversed reversed %}`) is accepted by both, which is why the name is not simply reserved
-  in that position.
-- `do_translate` refuses `as` and `noop` as the value of its `context` option, so
-  `{% trans "hi" context noop %}` is an error there and a context named by the variable `noop` here.
 - `partial`/`partialdef` are Django builtins as of Django 6; `elif`/`else`/`empty` are modelled as parts of
   their enclosing tag rather than as separate tags.

README.md

@@ -11,3 +11,28 @@ npm run parser-test      # run the corpus tests in test/corpus
 npm run parser-build     # build the WASM binary
 npm run playground       # interactively explore the grammar
 ```
+
+## Divergences from Django
+
+The grammar aims to accept what Django accepts, with one deliberate exception. Where Django takes an
+input without complaint but the input is almost certainly a mistake — it parses, and then silently
+renders nothing or quietly ignores half of what was written — the grammar reports an error instead.
+Every case below is input Django itself accepts:
+
+- **Number-shaped names.** Django has no number token: a word is a literal if `int()` or `float()` parses
+  it and a variable lookup otherwise, so `0x1f`, `1a`, `1.`, `1.2.3` and `1__0` look up a variable of that
+  name and render nothing.
+- **An attribute of `True`, `False` or `None`.** Every Django context is seeded with those three names, so
+  `{{ True.x }}` is an ordinary two-part lookup that can never resolve.
+- **A keyword argument written twice.** `{% with a=1 a=2 %}`, and the same in `{% include %}` and
+  `{% blocktranslate %}`, where Django builds a dict and lets the last value win.
+- **Anything after a `{% static %}` path.** `StaticNode.handle_token` looks for `as` two words from the end
+  and ignores the rest, so `{% static "a" junk %}` and `{% static "a" as url junk %}` render as if the
+  extra words were not there.
+- **A `{% cache %}` argument meant as something other than the fragment name.** Django takes the raw word
+  in that position, so `{% cache 500 using="c" %}` names a fragment called `using="c"` rather than choosing
+  a cache, and `{% cache 500 sidebar.name %}` names one with a dot in it.
+
+In the other direction the grammar is more permissive only where it cannot know better: the names a
+`{% load %}` brings in live in Python, so `{{ x|lenght }}` cannot be told from a filter some library
+registered, and an unknown tag's arguments are assumed to have the shape `simple_tag` gives them.

grammar.js

@@ -64,6 +64,56 @@ function asVariable($) {
   return part("as", field("variable", $.identifier));
 }
 
+/**
+ * A tag's own keyword written where a value goes, with the tree an ordinary
+ * lookup would have so that a tool sees no difference. Where a keyword and an
+ * identifier are both valid, tree-sitter hands the parser the keyword, so the
+ * reading in which the word names a variable has to be built back out of it —
+ * and out of hidden rules, because an alias only renames the node its rule
+ * makes and cannot nest one inside another.
+ *
+ * Django tells such a keyword from a variable by comparing the whole bit, so
+ * "reversed" is its flag while "reversed.x" and "reversed|last" are lookups.
+ * That second group is what `continued` selects.
+ *
+ * @param {string} word
+ * @returns {Record<string, RuleBuilder<string>>}
+ */
+function wordAsValueRules(word) {
+  return {
+    [`_${word}_lookup`]: ($) => alias(word, $.identifier),
+    [`_${word}_dotted_lookup`]: ($) =>
+      seq(alias(word, $.identifier), ".", $.attribute),
+    [`_${word}_value`]: ($) =>
+      alias($[`_${word}_lookup`], $.variable_attribute),
+    [`_${word}_dotted_value`]: ($) =>
+      alias($[`_${word}_dotted_lookup`], $.variable_attribute),
+    [`_${word}_bare`]: ($) => alias($[`_${word}_value`], $.value),
+    [`_${word}_continued`]: ($) =>
+      choice(
+        seq(
+          alias($[`_${word}_dotted_value`], $.value),
+          optional(seq("|", $.filter_expression)),
+        ),
+        seq(alias($[`_${word}_value`], $.value), "|", $.filter_expression),
+      ),
+  };
+}
+
+/**
+ * The rules wordAsValueRules() built, where a value goes.
+ * @param {GrammarSymbols<string>} $
+ * @param {string} word
+ * @param {boolean} continued whether a "." or a "|" has to follow the word
+ * @returns {RuleOrLiteral}
+ */
+function wordAsValue($, word, continued) {
+  return alias(
+    $[`_${word}_${continued ? "continued" : "bare"}`],
+    $.filtered_value,
+  );
+}
+
 /**
  * @param {RuleOrLiteral[]} chosen
  * @param {RuleOrLiteral[]} rest
@@ -342,7 +392,8 @@ const django = grammar({
       seq($.value, optional(seq("|", $.filter_expression))),
     filter_expression: ($) => seq($.filter, repeat(seq("|", $.filter))),
     value: ($) => choice($.literal, $.variable_attribute),
-    literal: ($) => choice($.number, $.string, $.translated_string),
+    literal: ($) =>
+      choice($.number, $.string, $.translated_string, $.boolean, $.none),
     // digits, with single underscores allowed between them, as Python's
     // int() and float() accept ("1_000") and Django's Variable relies on
     number: ($) =>
@@ -354,6 +405,12 @@ const django = grammar({
      * string: "_( 'a' )" is a syntax error there, not a translated literal.
      */
     translated_string: ($) => seq("_(", $.string, ")"),
+    // the flags of "for" and "trans", spelled as the variable names they
+    // also are; see wordAsValueRules()
+    ...wordAsValueRules("reversed"),
+    ...wordAsValueRules("noop"),
+    boolean: ($) => choice("True", "False"),
+    none: ($) => "None",
     attribute: ($) => /[a-zA-Z0-9][a-zA-Z0-9_]*(?:\.[a-zA-Z0-9][a-zA-Z0-9_]*)*/,
     variable_attribute: ($) =>
       seq($.identifier, optional(seq(".", $.attribute))),
@@ -648,10 +705,19 @@ const django = grammar({
             ),
           ),
           part("in"),
-          part($.filtered_value),
+          // do_for reads the flag off the end and takes the sequence from the
-          // do_for reads this off the end and takes the sequence from the bit
+          // bit before it, so the flag comes last or not at all. A bare
-          // before it, so it comes last or not at all
+          // "reversed" in the sequence position leaves nothing to iterate,
-          optional(part("reversed")),
+          // naming a sequence only when a lookup or filter continues it or
+          // when the flag follows it as well
+          choice(
+            seq(part($.filtered_value), optional(part("reversed"))),
+            seq(
+              part(wordAsValue($, "reversed", true)),
+              optional(part("reversed")),
+            ),
+            seq(part(wordAsValue($, "reversed", false)), part("reversed")),
+          ),
         ),
         optional($.template),
       ),
@@ -811,7 +877,12 @@ const django = grammar({
         optional(
           arrangements([
             part("noop"),
-            part("context", $.filtered_value),
+            // do_translate refuses "as" and "noop" as the context, comparing
+            // the whole bit, so a lookup that only begins with one is fine
+            part(
+              "context",
+              choice($.filtered_value, wordAsValue($, "noop", true)),
+            ),
             asVariable($),
           ]),
         ),

queries/conditionals.scm

@@ -0,0 +1,76 @@
+; Which parts of a template render conditionally, for a tool checking that a
+; variable is defined on every path that reaches a use of it.
+;
+; Django binds an "as" target straight into the context, and a tag that pushes
+; no context leaves that binding visible after its group closes. So
+;
+;     {% if a %}{% now "Y" as n %}{% endif %}{{ n }}
+;
+; renders the year when a is truthy and string_if_invalid ("" by default) when
+; it is not — a silent empty string, not an error. queries/locals.scm cannot
+; see that: a locals query matches a reference to the definition whose scope
+; contains it and has no notion of a path that may not be taken.
+;
+; The halves a tool joins, by grouping matches on the @conditional.group node:
+;
+;   @conditional.group    the whole construct
+;   @conditional.branch   one alternative; at most one of a group's branches
+;                         renders on any given pass
+;   @conditional.default  the branch that renders when no other one does
+;
+; A group is exhaustive iff one of its matches carries a @conditional.default.
+; If it is not, some pass through it binds nothing, so every definition inside
+; is conditional. If it is, a definition escapes only when every branch makes
+; it. Each capture names both halves of the pair, so no ancestor walk is needed
+; and no clause has to be attributed to a group by name.
+;
+; Branches nest, so the same test applies again to a group inside a branch.
+;
+; A branch that is also a @local.scope in queries/locals.scm confines its
+; bindings whether or not it renders; the two queries compose and the scope
+; decides first.
+
+; if/elif are alternatives tested in order; else runs when none matched. None
+; of the three pushes a context, so this is the case the check exists for.
+(if_group
+  [
+    (if_clause)
+    (elif_clause)
+  ] @conditional.branch) @conditional.group
+
+(if_group
+  (else_clause) @conditional.default) @conditional.group
+
+; ifchanged renders its body only when the watched value differs from the
+; previous pass, and its else otherwise. It pushes no context either.
+(ifchanged_group
+  (ifchanged_clause) @conditional.branch) @conditional.group
+
+(ifchanged_group
+  (else_clause) @conditional.default) @conditional.group
+
+; The loop body runs once per item and empty runs when there are none, so the
+; two partition every render. Both are inside ForNode's context.push() — the
+; empty branch included, which is easy to miss — so locals.scm scopes both and
+; nothing escapes either way. Named here because the construct does branch, and
+; because a tool reading only this file should not have to infer that it does.
+(for_group
+  (for_clause) @conditional.branch) @conditional.group
+
+(for_group
+  (empty_clause) @conditional.default) @conditional.group
+
+; A cache body is skipped entirely on a cache hit, and CacheNode pushes no
+; context, so a binding made inside it reaches the rest of the template on the
+; first render and is gone on the next. One branch and no default: never
+; exhaustive, which is the right answer.
+(cache_group
+  (cache_clause) @conditional.branch) @conditional.group
+
+; Not here, deliberately: block and partialdef bodies may also fail to render —
+; a child template overrides the block, and a partial renders only where
+; {% partial %} names it — but both clauses are @local.scope in locals.scm, so
+; nothing they bind escapes to be checked. Bodies that always render once
+; (with, filter, autoescape, spaceless, language, localize, localtime,
+; timezone) are not conditional at all, and comment, verbatim and
+; blocktranslate bodies hold no tags to bind anything.

queries/highlights.scm

@@ -41,6 +41,8 @@ variable: (identifier) @variable.parameter
 
 (number) @number
 (string) @string
+(boolean) @constant.builtin
+(none) @constant.builtin
 
 (library
     (identifier) @module)

queries/locals.scm

@@ -11,6 +11,13 @@ variable: (identifier) @local.definition
 (block_clause) @local.scope
 (partialdef_clause) @local.scope
 
+; ForNode renders nodelist_empty inside the same context.push() as the loop
+; body, so "{% empty %}" is part of the loop's scope even though it is a
+; separate clause: "{% for x in ys %}a{% empty %}{% now "Y" as n %}{% endfor %}{{ n }}"
+; is empty. queries/conditionals.scm names both clauses as branches of the
+; same group and relies on this.
+(empty_clause) @local.scope
+
 ; blocktranslate pushes a context for its "with" and "count" bindings. Its
 ; asvar target is not one of them: it is written in the same tag but assigned
 ; outside it, and carries an "asvar" field rather than "variable" so that this

src/grammar.json

@@ -122,6 +122,14 @@
         {
           "type": "SYMBOL",
           "name": "translated_string"
+        },
+        {
+          "type": "SYMBOL",
+          "name": "boolean"
+        },
+        {
+          "type": "SYMBOL",
+          "name": "none"
         }
       ]
     },
@@ -150,6 +158,263 @@
         }
       ]
     },
+    "_reversed_lookup": {
+      "type": "ALIAS",
+      "content": {
+        "type": "STRING",
+        "value": "reversed"
+      },
+      "named": true,
+      "value": "identifier"
+    },
+    "_reversed_dotted_lookup": {
+      "type": "SEQ",
+      "members": [
+        {
+          "type": "ALIAS",
+          "content": {
+            "type": "STRING",
+            "value": "reversed"
+          },
+          "named": true,
+          "value": "identifier"
+        },
+        {
+          "type": "STRING",
+          "value": "."
+        },
+        {
+          "type": "SYMBOL",
+          "name": "attribute"
+        }
+      ]
+    },
+    "_reversed_value": {
+      "type": "ALIAS",
+      "content": {
+        "type": "SYMBOL",
+        "name": "_reversed_lookup"
+      },
+      "named": true,
+      "value": "variable_attribute"
+    },
+    "_reversed_dotted_value": {
+      "type": "ALIAS",
+      "content": {
+        "type": "SYMBOL",
+        "name": "_reversed_dotted_lookup"
+      },
+      "named": true,
+      "value": "variable_attribute"
+    },
+    "_reversed_bare": {
+      "type": "ALIAS",
+      "content": {
+        "type": "SYMBOL",
+        "name": "_reversed_value"
+      },
+      "named": true,
+      "value": "value"
+    },
+    "_reversed_continued": {
+      "type": "CHOICE",
+      "members": [
+        {
+          "type": "SEQ",
+          "members": [
+            {
+              "type": "ALIAS",
+              "content": {
+                "type": "SYMBOL",
+                "name": "_reversed_dotted_value"
+              },
+              "named": true,
+              "value": "value"
+            },
+            {
+              "type": "CHOICE",
+              "members": [
+                {
+                  "type": "SEQ",
+                  "members": [
+                    {
+                      "type": "STRING",
+                      "value": "|"
+                    },
+                    {
+                      "type": "SYMBOL",
+                      "name": "filter_expression"
+                    }
+                  ]
+                },
+                {
+                  "type": "BLANK"
+                }
+              ]
+            }
+          ]
+        },
+        {
+          "type": "SEQ",
+          "members": [
+            {
+              "type": "ALIAS",
+              "content": {
+                "type": "SYMBOL",
+                "name": "_reversed_value"
+              },
+              "named": true,
+              "value": "value"
+            },
+            {
+              "type": "STRING",
+              "value": "|"
+            },
+            {
+              "type": "SYMBOL",
+              "name": "filter_expression"
+            }
+          ]
+        }
+      ]
+    },
+    "_noop_lookup": {
+      "type": "ALIAS",
+      "content": {
+        "type": "STRING",
+        "value": "noop"
+      },
+      "named": true,
+      "value": "identifier"
+    },
+    "_noop_dotted_lookup": {
+      "type": "SEQ",
+      "members": [
+        {
+          "type": "ALIAS",
+          "content": {
+            "type": "STRING",
+            "value": "noop"
+          },
+          "named": true,
+          "value": "identifier"
+        },
+        {
+          "type": "STRING",
+          "value": "."
+        },
+        {
+          "type": "SYMBOL",
+          "name": "attribute"
+        }
+      ]
+    },
+    "_noop_value": {
+      "type": "ALIAS",
+      "content": {
+        "type": "SYMBOL",
+        "name": "_noop_lookup"
+      },
+      "named": true,
+      "value": "variable_attribute"
+    },
+    "_noop_dotted_value": {
+      "type": "ALIAS",
+      "content": {
+        "type": "SYMBOL",
+        "name": "_noop_dotted_lookup"
+      },
+      "named": true,
+      "value": "variable_attribute"
+    },
+    "_noop_bare": {
+      "type": "ALIAS",
+      "content": {
+        "type": "SYMBOL",
+        "name": "_noop_value"
+      },
+      "named": true,
+      "value": "value"
+    },
+    "_noop_continued": {
+      "type": "CHOICE",
+      "members": [
+        {
+          "type": "SEQ",
+          "members": [
+            {
+              "type": "ALIAS",
+              "content": {
+                "type": "SYMBOL",
+                "name": "_noop_dotted_value"
+              },
+              "named": true,
+              "value": "value"
+            },
+            {
+              "type": "CHOICE",
+              "members": [
+                {
+                  "type": "SEQ",
+                  "members": [
+                    {
+                      "type": "STRING",
+                      "value": "|"
+                    },
+                    {
+                      "type": "SYMBOL",
+                      "name": "filter_expression"
+                    }
+                  ]
+                },
+                {
+                  "type": "BLANK"
+                }
+              ]
+            }
+          ]
+        },
+        {
+          "type": "SEQ",
+          "members": [
+            {
+              "type": "ALIAS",
+              "content": {
+                "type": "SYMBOL",
+                "name": "_noop_value"
+              },
+              "named": true,
+              "value": "value"
+            },
+            {
+              "type": "STRING",
+              "value": "|"
+            },
+            {
+              "type": "SYMBOL",
+              "name": "filter_expression"
+            }
+          ]
+        }
+      ]
+    },
+    "boolean": {
+      "type": "CHOICE",
+      "members": [
+        {
+          "type": "STRING",
+          "value": "True"
+        },
+        {
+          "type": "STRING",
+          "value": "False"
+        }
+      ]
+    },
+    "none": {
+      "type": "STRING",
+      "value": "None"
+    },
     "attribute": {
       "type": "PATTERN",
       "value": "[a-zA-Z0-9][a-zA-Z0-9_]*(?:\\.[a-zA-Z0-9][a-zA-Z0-9_]*)*"
@@ -3401,19 +3666,6 @@
                 }
               ]
             },
-            {
-              "type": "SEQ",
-              "members": [
-                {
-                  "type": "PATTERN",
-                  "value": "[ \\t\\r\\n]+"
-                },
-                {
-                  "type": "SYMBOL",
-                  "name": "filtered_value"
-                }
-              ]
-            },
             {
               "type": "CHOICE",
               "members": [
@@ -3421,17 +3673,120 @@
                   "type": "SEQ",
                   "members": [
                     {
-                      "type": "PATTERN",
+                      "type": "SEQ",
-                      "value": "[ \\t\\r\\n]+"
+                      "members": [
+                        {
+                          "type": "PATTERN",
+                          "value": "[ \\t\\r\\n]+"
+                        },
+                        {
+                          "type": "SYMBOL",
+                          "name": "filtered_value"
+                        }
+                      ]
                     },
                     {
-                      "type": "STRING",
+                      "type": "CHOICE",
-                      "value": "reversed"
+                      "members": [
+                        {
+                          "type": "SEQ",
+                          "members": [
+                            {
+                              "type": "PATTERN",
+                              "value": "[ \\t\\r\\n]+"
+                            },
+                            {
+                              "type": "STRING",
+                              "value": "reversed"
+                            }
+                          ]
+                        },
+                        {
+                          "type": "BLANK"
+                        }
+                      ]
                     }
                   ]
                 },
                 {
-                  "type": "BLANK"
+                  "type": "SEQ",
+                  "members": [
+                    {
+                      "type": "SEQ",
+                      "members": [
+                        {
+                          "type": "PATTERN",
+                          "value": "[ \\t\\r\\n]+"
+                        },
+                        {
+                          "type": "ALIAS",
+                          "content": {
+                            "type": "SYMBOL",
+                            "name": "_reversed_continued"
+                          },
+                          "named": true,
+                          "value": "filtered_value"
+                        }
+                      ]
+                    },
+                    {
+                      "type": "CHOICE",
+                      "members": [
+                        {
+                          "type": "SEQ",
+                          "members": [
+                            {
+                              "type": "PATTERN",
+                              "value": "[ \\t\\r\\n]+"
+                            },
+                            {
+                              "type": "STRING",
+                              "value": "reversed"
+                            }
+                          ]
+                        },
+                        {
+                          "type": "BLANK"
+                        }
+                      ]
+                    }
+                  ]
+                },
+                {
+                  "type": "SEQ",
+                  "members": [
+                    {
+                      "type": "SEQ",
+                      "members": [
+                        {
+                          "type": "PATTERN",
+                          "value": "[ \\t\\r\\n]+"
+                        },
+                        {
+                          "type": "ALIAS",
+                          "content": {
+                            "type": "SYMBOL",
+                            "name": "_reversed_bare"
+                          },
+                          "named": true,
+                          "value": "filtered_value"
+                        }
+                      ]
+                    },
+                    {
+                      "type": "SEQ",
+                      "members": [
+                        {
+                          "type": "PATTERN",
+                          "value": "[ \\t\\r\\n]+"
+                        },
+                        {
+                          "type": "STRING",
+                          "value": "reversed"
+                        }
+                      ]
+                    }
+                  ]
                 }
               ]
             },
@@ -6709,8 +7064,22 @@
                               "value": "[ \\t\\r\\n]+"
                             },
                             {
-                              "type": "SYMBOL",
+                              "type": "CHOICE",
-                              "name": "filtered_value"
+                              "members": [
+                                {
+                                  "type": "SYMBOL",
+                                  "name": "filtered_value"
+                                },
+                                {
+                                  "type": "ALIAS",
+                                  "content": {
+                                    "type": "SYMBOL",
+                                    "name": "_noop_continued"
+                                  },
+                                  "named": true,
+                                  "value": "filtered_value"
+                                }
+                              ]
                             }
                           ]
                         }
@@ -6753,8 +7122,22 @@
                               "value": "[ \\t\\r\\n]+"
                             },
                             {
-                              "type": "SYMBOL",
+                              "type": "CHOICE",
-                              "name": "filtered_value"
+                              "members": [
+                                {
+                                  "type": "SYMBOL",
+                                  "name": "filtered_value"
+                                },
+                                {
+                                  "type": "ALIAS",
+                                  "content": {
+                                    "type": "SYMBOL",
+                                    "name": "_noop_continued"
+                                  },
+                                  "named": true,
+                                  "value": "filtered_value"
+                                }
+                              ]
                             }
                           ]
                         }
@@ -6905,8 +7288,22 @@
                               "value": "[ \\t\\r\\n]+"
                             },
                             {
-                              "type": "SYMBOL",
+                              "type": "CHOICE",
-                              "name": "filtered_value"
+                              "members": [
+                                {
+                                  "type": "SYMBOL",
+                                  "name": "filtered_value"
+                                },
+                                {
+                                  "type": "ALIAS",
+                                  "content": {
+                                    "type": "SYMBOL",
+                                    "name": "_noop_continued"
+                                  },
+                                  "named": true,
+                                  "value": "filtered_value"
+                                }
+                              ]
                             }
                           ]
                         }
@@ -6933,8 +7330,22 @@
                           "value": "[ \\t\\r\\n]+"
                         },
                         {
-                          "type": "SYMBOL",
+                          "type": "CHOICE",
-                          "name": "filtered_value"
+                          "members": [
+                            {
+                              "type": "SYMBOL",
+                              "name": "filtered_value"
+                            },
+                            {
+                              "type": "ALIAS",
+                              "content": {
+                                "type": "SYMBOL",
+                                "name": "_noop_continued"
+                              },
+                              "named": true,
+                              "value": "filtered_value"
+                            }
+                          ]
                         }
                       ]
                     }
@@ -6962,8 +7373,22 @@
                               "value": "[ \\t\\r\\n]+"
                             },
                             {
-                              "type": "SYMBOL",
+                              "type": "CHOICE",
-                              "name": "filtered_value"
+                              "members": [
+                                {
+                                  "type": "SYMBOL",
+                                  "name": "filtered_value"
+                                },
+                                {
+                                  "type": "ALIAS",
+                                  "content": {
+                                    "type": "SYMBOL",
+                                    "name": "_noop_continued"
+                                  },
+                                  "named": true,
+                                  "value": "filtered_value"
+                                }
+                              ]
                             }
                           ]
                         }
@@ -7006,8 +7431,22 @@
                               "value": "[ \\t\\r\\n]+"
                             },
                             {
-                              "type": "SYMBOL",
+                              "type": "CHOICE",
-                              "name": "filtered_value"
+                              "members": [
+                                {
+                                  "type": "SYMBOL",
+                                  "name": "filtered_value"
+                                },
+                                {
+                                  "type": "ALIAS",
+                                  "content": {
+                                    "type": "SYMBOL",
+                                    "name": "_noop_continued"
+                                  },
+                                  "named": true,
+                                  "value": "filtered_value"
+                                }
+                              ]
                             }
                           ]
                         }
@@ -7080,8 +7519,22 @@
                               "value": "[ \\t\\r\\n]+"
                             },
                             {
-                              "type": "SYMBOL",
+                              "type": "CHOICE",
-                              "name": "filtered_value"
+                              "members": [
+                                {
+                                  "type": "SYMBOL",
+                                  "name": "filtered_value"
+                                },
+                                {
+                                  "type": "ALIAS",
+                                  "content": {
+                                    "type": "SYMBOL",
+                                    "name": "_noop_continued"
+                                  },
+                                  "named": true,
+                                  "value": "filtered_value"
+                                }
+                              ]
                             }
                           ]
                         }
@@ -7141,8 +7594,22 @@
                               "value": "[ \\t\\r\\n]+"
                             },
                             {
-                              "type": "SYMBOL",
+                              "type": "CHOICE",
-                              "name": "filtered_value"
+                              "members": [
+                                {
+                                  "type": "SYMBOL",
+                                  "name": "filtered_value"
+                                },
+                                {
+                                  "type": "ALIAS",
+                                  "content": {
+                                    "type": "SYMBOL",
+                                    "name": "_noop_continued"
+                                  },
+                                  "named": true,
+                                  "value": "filtered_value"
+                                }
+                              ]
                             }
                           ]
                         }
@@ -7336,8 +7803,22 @@
                               "value": "[ \\t\\r\\n]+"
                             },
                             {
-                              "type": "SYMBOL",
+                              "type": "CHOICE",
-                              "name": "filtered_value"
+                              "members": [
+                                {
+                                  "type": "SYMBOL",
+                                  "name": "filtered_value"
+                                },
+                                {
+                                  "type": "ALIAS",
+                                  "content": {
+                                    "type": "SYMBOL",
+                                    "name": "_noop_continued"
+                                  },
+                                  "named": true,
+                                  "value": "filtered_value"
+                                }
+                              ]
                             }
                           ]
                         }
@@ -7397,8 +7878,22 @@
                               "value": "[ \\t\\r\\n]+"
                             },
                             {
-                              "type": "SYMBOL",
+                              "type": "CHOICE",
-                              "name": "filtered_value"
+                              "members": [
+                                {
+                                  "type": "SYMBOL",
+                                  "name": "filtered_value"
+                                },
+                                {
+                                  "type": "ALIAS",
+                                  "content": {
+                                    "type": "SYMBOL",
+                                    "name": "_noop_continued"
+                                  },
+                                  "named": true,
+                                  "value": "filtered_value"
+                                }
+                              ]
                             }
                           ]
                         }
@@ -7458,8 +7953,22 @@
                               "value": "[ \\t\\r\\n]+"
                             },
                             {
-                              "type": "SYMBOL",
+                              "type": "CHOICE",
-                              "name": "filtered_value"
+                              "members": [
+                                {
+                                  "type": "SYMBOL",
+                                  "name": "filtered_value"
+                                },
+                                {
+                                  "type": "ALIAS",
+                                  "content": {
+                                    "type": "SYMBOL",
+                                    "name": "_noop_continued"
+                                  },
+                                  "named": true,
+                                  "value": "filtered_value"
+                                }
+                              ]
                             }
                           ]
                         }

src/node-types.json

@@ -396,6 +396,11 @@
       ]
     }
   },
+  {
+    "type": "boolean",
+    "named": true,
+    "fields": {}
+  },
   {
     "type": "cache_clause",
     "named": true,
@@ -1699,6 +1704,14 @@
       "multiple": false,
       "required": true,
       "types": [
+        {
+          "type": "boolean",
+          "named": true
+        },
+        {
+          "type": "none",
+          "named": true
+        },
         {
           "type": "number",
           "named": true
@@ -2650,6 +2663,14 @@
     "type": ">=",
     "named": false
   },
+  {
+    "type": "False",
+    "named": false
+  },
+  {
+    "type": "True",
+    "named": false
+  },
   {
     "type": "_(",
     "named": false
@@ -3074,6 +3095,10 @@
     "type": "media",
     "named": false
   },
+  {
+    "type": "none",
+    "named": true
+  },
   {
     "type": "noop",
     "named": false

test/corpus/for.txt

@@ -455,3 +455,89 @@ For With Reversed Before In
 {% for x reversed in y %}a{% endfor %}
 
 ---
+
+==================
+For Over A Variable Named Reversed
+==================
+
+{% for x in reversed reversed %}a{% endfor %}
+
+---
+
+(template
+  (content)
+  (for_group
+    (for_clause
+      variable: (identifier)
+      (filtered_value
+        (value
+          (variable_attribute
+            (identifier))))
+      (template
+        (content))))
+  (content))
+
+==================
+For Over An Attribute Of A Variable Named Reversed
+==================
+
+{% for x in reversed.items %}a{% endfor %}
+
+---
+
+(template
+  (content)
+  (for_group
+    (for_clause
+      variable: (identifier)
+      (filtered_value
+        (value
+          (variable_attribute
+            (identifier)
+            (attribute))))
+      (template
+        (content))))
+  (content))
+
+==================
+For Over A Filtered Variable Named Reversed
+==================
+
+{% for x in reversed|last %}a{% endfor %}
+
+---
+
+(template
+  (content)
+  (for_group
+    (for_clause
+      variable: (identifier)
+      (filtered_value
+        (value
+          (variable_attribute
+            (identifier)))
+        (filter_expression
+          (filter)))
+      (template
+        (content))))
+  (content))
+
+==================
+For With Reversed As Its Whole Sequence
+:error
+==================
+
+{% for x in reversed %}a{% endfor %}
+
+---
+
+
+==================
+For With Reversed Three Times
+:error
+==================
+
+{% for x in reversed reversed reversed %}a{% endfor %}
+
+---
+

test/corpus/i18n.txt

@@ -488,3 +488,58 @@ Language Name Filter With An Argument
 {{ "de"|language_name:1 }}
 
 ---
+
+==================
+Translate With A Context Named After Noop
+:error
+==================
+
+{% trans "hi" context noop %}
+
+---
+
+
+==================
+Translate With A Context From An Attribute Of Noop
+==================
+
+{% trans "hi" context noop.x %}
+
+---
+
+(template
+  (content)
+  (translate
+    (filtered_value
+      (value
+        (literal
+          (string))))
+    (filtered_value
+      (value
+        (variable_attribute
+          (identifier)
+          (attribute)))))
+  (content))
+
+==================
+Translate With A Filtered Context Named After Noop
+==================
+
+{% trans "hi" context noop|upper %}
+
+---
+
+(template
+  (content)
+  (translate
+    (filtered_value
+      (value
+        (literal
+          (string))))
+    (filtered_value
+      (value
+        (variable_attribute
+          (identifier)))
+      (filter_expression
+        (filter))))
+  (content))

test/corpus/if.txt

@@ -156,3 +156,29 @@ If Operator Adjacent To Value
 {% if 1and 2 %}yes{% endif %}
 
 ---
+
+==================
+If Is Not None
+==================
+
+{% if status is not None %}yes{% endif %}
+
+---
+
+(template
+  (content)
+  (if_group
+    (if_clause
+      (predicate
+        (filtered_value
+          (value
+            (variable_attribute
+              (identifier))))
+        (binaryOperator)
+        (filtered_value
+          (value
+            (literal
+              (none)))))
+      (template
+        (content))))
+  (content))

test/corpus/template_variable.txt

@@ -361,3 +361,103 @@ Template Variable With Spaced Filter
       (filter_expression
         (filter))))
   (content))
+
+==================
+Template Variable True
+==================
+
+{{ True }}
+
+---
+
+(template
+  (content)
+  (template_variable
+    (filtered_value
+      (value
+        (literal
+          (boolean)))))
+  (content))
+
+==================
+Template Variable False
+==================
+
+{{ False }}
+
+---
+
+(template
+  (content)
+  (template_variable
+    (filtered_value
+      (value
+        (literal
+          (boolean)))))
+  (content))
+
+==================
+Template Variable None
+==================
+
+{{ None }}
+
+---
+
+(template
+  (content)
+  (template_variable
+    (filtered_value
+      (value
+        (literal
+          (none)))))
+  (content))
+
+==================
+Template Variable Boolean As Filter Argument
+==================
+
+{{ value|default:True }}
+
+---
+
+(template
+  (content)
+  (template_variable
+    (filtered_value
+      (value
+        (variable_attribute
+          (identifier)))
+      (filter_expression
+        (filter
+          argument: (value
+            (literal
+              (boolean)))))))
+  (content))
+
+==================
+Template Variable Name Beginning With A Literal
+==================
+
+{{ Truest }}
+
+---
+
+(template
+  (content)
+  (template_variable
+    (filtered_value
+      (value
+        (variable_attribute
+          (identifier)))))
+  (content))
+
+==================
+Template Variable Attribute Of A Literal
+:error
+==================
+
+{{ None.x }}
+
+---
+

test/corpus/with.txt

@@ -111,3 +111,24 @@ With Repeating A Binding Of The Tag Before It
       (template
         (content))))
   (content))
+
+==================
+With A Binding Named After A Literal
+==================
+
+{% with True=1 %}a{% endwith %}
+
+---
+
+(template
+  (content)
+  (with_group
+    (with_clause
+      variable: (identifier)
+      (filtered_value
+        (value
+          (literal
+            (number))))
+      (template
+        (content))))
+  (content))