isnull, is distinct from

corpus/plpgsql/if_statement.txt

@@ -154,3 +154,71 @@ end $$;
             (return_statement
               (number)))))
       (dollar_quote))))
+
+================================================================================
+if is not null
+================================================================================
+do $$ begin
+if foo is not null then select 1; end if;
+end $$;
+--------------------------------------------------------------------------------
+
+(source_file
+  (do_block
+    (block
+      (dollar_quote)
+      (body
+        (if_statement
+          (op_expression
+            (identifier)
+            (comparison_null))
+          (select_statement
+            (select_item
+              (number)))))
+      (dollar_quote))))
+
+================================================================================
+if is not distinct from
+================================================================================
+do $$ begin
+if foo is not distinct from bar then select 1; end if;
+end $$;
+--------------------------------------------------------------------------------
+
+(source_file
+  (do_block
+    (block
+      (dollar_quote)
+      (body
+        (if_statement
+          (op_expression
+            (identifier)
+            (comparison_kw)
+            (identifier))
+          (select_statement
+            (select_item
+              (number)))))
+      (dollar_quote))))
+
+================================================================================
+if is distinct from
+================================================================================
+do $$ begin
+if foo is distinct from bar then select 1; end if;
+end $$;
+--------------------------------------------------------------------------------
+
+(source_file
+  (do_block
+    (block
+      (dollar_quote)
+      (body
+        (if_statement
+          (op_expression
+            (identifier)
+            (comparison_kw)
+            (identifier))
+          (select_statement
+            (select_item
+              (number)))))
+      (dollar_quote))))

grammar.js

@@ -757,7 +757,8 @@ module.exports = grammar({
       prec.left(6, seq($._value_expression, $.other_op, $._value_expression)),
       // between in like ilike similar
       prec.left(4, seq($._value_expression, $.comparison_op, $._value_expression,)),
-      // is isnull notnull
+      prec.left(3, seq($._value_expression, $.comparison_kw, $._value_expression,)),
+      prec.left(3, seq($._value_expression, $.comparison_null)),
       prec.right(2, seq($.not, $._value_expression)),
       prec.left(1, seq($._value_expression, choice($.and, $.or), $._value_expression,)),
     ),
@@ -766,8 +767,19 @@ module.exports = grammar({
 
     // TODO(chrde): https://www.postgresql.org/docs/13/sql-syntax-lexical.html
     comparison_op: $ => choice("<", ">", "=", "<=", ">=", "<>", "!="),
+    comparison_null: $ => choice(
+      kw("is null"),
+      kw("isnull"),
+      kw("is not null"),
+      kw("notnull"),
+    ),
+    comparison_kw: $ => choice(
+      kw("is"),
+      kw("is distinct from"),
+      kw("is not distinct from")
+    ),
     // TODO(chrde): this should be a regex
-    other_op: $ => choice("||"),
+    other_op: $ => choice("||", "<@", "@>", "<<", ">>", "&&", "&<", "&>", "-|-"),
     cast: $ => "::",
     minus: $ => "-",
     plus: $ => "+",