syntax: introduce `const` support

Introduce support for declaring constant variables through the `const`
keyword. Variables declared with `const` follow the same scoping rules
as `let` declared ones.

In contrast to normal variables, `const` ones may not be assigned to
after their declaration. Any attempt to do so will result in a syntax
error during compilation.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

1 files changed, 1 insertions, 0 deletions

diff --git a/lexer.h b/lexer.h
index e31f78a..96cdff8 100644
--- a/lexer.h
+++ b/lexer.h
@@ -104,6 +104,7 @@ typedef enum {
 	TK_NULL,
 	TK_THIS,
 	TK_DELETE,
+	TK_CONST,
 
 	TK_EOF,
 	TK_ERROR