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, 2 insertions, 0 deletions

diff --git a/compiler.h b/compiler.h
index deec3d5..54f56c2 100644
--- a/compiler.h
+++ b/compiler.h
@@ -76,12 +76,14 @@ typedef struct {
 	ssize_t depth;
 	size_t from;
 	bool captured;
+	bool constant;
 } uc_local;
 
 typedef struct {
 	uc_value_t *name;
 	size_t index;
 	bool local;
+	bool constant;
 } uc_upval;
 
 uc_declare_vector(uc_locals, uc_local);