fix parser errors

the new keywords 'add', 'del', and 'rewrite' caused some tests involving
these identifiers to fail
the solution was, similarly to the abstract keyword in libadalang, to
use an exact identifier match in the nanopass parser and remove the
keywords from the lexer

Author: Killian Perlin

lkql/lkql.lkt

@@ -63,9 +63,6 @@ lexer lkql_lexer {
     @symbol() New <- "new"
     @symbol() Class <- "class"
     @symbol() Pass <- "pass"
-    @symbol() Del <- "del"
-    @symbol() Add <- "add"
-    @symbol() Rewrite <- "rewrite"
     @symbol() RunPass <- "run_pass"
     Integer <- p"[0-9]+"
     @symbol() Identifier <- p"[a-z][A-Za-z0-9_]*"
@@ -292,9 +289,9 @@ grammar lkql_grammar {
         ))
     "}" )
     prefix_field <- DotAccess(upper_id "." id)
-    pass_del_block <- DelBlock("del" "{" list*(or(prefix_field | Identifier(@UpperIdentifier))) "}")
-    pass_add_block <- AddBlock("add" "{" list*(or(prefix_field_decl | class_decl)) "}")
-    pass_rewrite_block <- RewriteBlock("rewrite" "{" list*(match_arm) "}")
+    pass_del_block <- DelBlock(@Identifier("del") "{" list*(or(prefix_field | Identifier(@UpperIdentifier))) "}")
+    pass_add_block <- AddBlock(@Identifier("add") "{" list*(or(prefix_field_decl | class_decl)) "}")
+    pass_rewrite_block <- RewriteBlock(@Identifier("rewrite") "{" list*(match_arm) "}")
     prefix_field_decl <- PrefixField(upper_id "." id ":" upper_id)
     class_field <- ClassField(id ":" upper_id)
     class_decl <- ClassDecl(