Merge pull request #214 from tree-sitter/object_is

Support predefined types in type predicates

Author: aryx

common/corpus/types.txt

@@ -876,6 +876,30 @@ function isT(t: T): t is T {
         (type_identifier)))
     (statement_block (return_statement (true)))))
 
+==================================
+Type predicate and predefined types
+==================================
+
+function isFish(pet: Fish): pet is Fish {
+}
+
+function isFish(object: Fish): object is Fish {
+}
+
+---
+(program
+  (function_declaration (identifier)
+    (formal_parameters
+       (required_parameter (identifier) (type_annotation (type_identifier))))
+    (type_predicate_annotation (type_predicate (identifier) (type_identifier)))
+    (statement_block))
+  (function_declaration (identifier)
+    (formal_parameters
+      (required_parameter (identifier) (type_annotation (type_identifier))))
+    (type_predicate_annotation (type_predicate (identifier) (type_identifier)))
+    (statement_block))
+)
+
 ==================================
 Read-only arrays
 ==================================

common/define-grammar.js

@@ -687,7 +687,16 @@ module.exports = function defineGrammar(dialect) {
       )),
 
       type_predicate: $ => seq(
-        field('name', choice($.identifier, $.this)),
+          field('name', choice(
+	      $.identifier,
+	      $.this,
+	      // Sometimes tree-sitter contextual lexing is not good enough to know
+	      // that 'object' in ':object is foo' is really an identifier and not
+	      // a predefined_type, so we must explicitely list all possibilities.
+	      // TODO: should we use '_reserved_identifier'? Should all the element in
+	      // 'predefined_type' be added to '_reserved_identifier'?
+	      alias($.predefined_type, $.identifier)
+	  )),
         'is',
         field('type', $._type)
       ),

tsx/src/grammar.json

@@ -8815,6 +8815,15 @@
               {
                 "type": "SYMBOL",
                 "name": "this"
+              },
+              {
+                "type": "ALIAS",
+                "content": {
+                  "type": "SYMBOL",
+                  "name": "predefined_type"
+                },
+                "named": true,
+                "value": "identifier"
               }
             ]
           }

tsx/src/node-types.json

@@ -2742,6 +2742,11 @@
       }
     }
   },
+  {
+    "type": "identifier",
+    "named": true,
+    "fields": {}
+  },
   {
     "type": "if_statement",
     "named": true,
@@ -6111,10 +6116,6 @@
     "type": "hash_bang_line",
     "named": true
   },
-  {
-    "type": "identifier",
-    "named": true
-  },
   {
     "type": "if",
     "named": false