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.c b/lexer.c
index cc35d66..95acfe6 100644
--- a/lexer.c
+++ b/lexer.c
@@ -152,6 +152,7 @@ static const struct keyword reserved_words[] = {
 	{ TK_WHILE,		"while", 5, { 0 } },
 	{ TK_BREAK,		"break", 5, { 0 } },
 	{ TK_CATCH,		"catch", 5, { 0 } },
+	{ TK_CONST,		"const", 5, { 0 } },
 	{ TK_BOOL,		"false", 5, { .b = false } },
 	{ TK_BOOL,		"true",  4, { .b = true } },
 	{ TK_ELIF,		"elif",  4, { 0 } },