feat: partially implement static_assert (parsing only)

3 files changed, 36 insertions, 8 deletions

diff --git a/docs/c_grammar.md b/docs/c_grammar.md
index 3bde591..807db1a 100644
--- a/docs/c_grammar.md
+++ b/docs/c_grammar.md
@@ -18,7 +18,7 @@
 * `{ A |? S }*`: 1 or more repetitions of A separated by S, allowing optional trailing S
     * Equivalent to `{ A |? S }+?`
 * `( A )`: Grouping
-* `# ...`: Additional constraints
+* `/* ... */`: Additional constraints
 
 
 ## Expressions
@@ -429,10 +429,6 @@ translation-unit:
     { external-declaration }+
 
 external-declaration:
-    function-definition
-    declaration
-
-external-declaration:
     static_assert-declaration
     attribute-specifier-sequence ';'
     attribute-specifier-sequence function-definition-or-declaration-rest
@@ -441,6 +437,6 @@ external-declaration:
 function-definition-or-declaration-rest:
     declaration-specifiers init-declarator-list ';'
     declaration-specifiers init-declarator-list compound-stmt
-        # Each item of init-declarator-list must not have initializer.
-        # The length of init-declarator-list must be one.
+        /* Each item of init-declarator-list must not have initializer. */
+        /* The length of init-declarator-list must be one. */
 ```
diff --git a/src/parse.c b/src/parse.c
index 494e4a2..f703f17 100644
--- a/src/parse.c
+++ b/src/parse.c
@@ -2607,8 +2607,26 @@ static AstNode* parse_return_stmt(Parser* p) {
     return ast_new_return_stmt(expr);
 }
 
+// static_assert-declaration:
+//     'static_assert' '(' constant-expr ( ',' string-literal )? ')' ';'
+static AstNode* parse_static_assert_declaration(Parser* p) {
+    expect(p, TokenKind_keyword_static_assert);
+    expect(p, TokenKind_paren_l);
+    AstNode* predicate = parse_constant_expr(p);
+    Token* message = NULL;
+    if (consume_token_if(p, TokenKind_comma)) {
+        message = expect(p, TokenKind_literal_str);
+    }
+    // TODO: validate the assertion.
+    (void)predicate;
+    (void)message;
+    expect(p, TokenKind_paren_r);
+    expect(p, TokenKind_semicolon);
+    return NULL;
+}
+
 // external-declaration:
-//     TODO static_assert-declaration
+//     static_assert-declaration
 //     TODO attribute-specifier-sequence ';'
 //     TODO attribute-specifier-sequence function-definition-or-declaration-rest
 //     function-definition-or-declaration-rest
@@ -2617,6 +2635,10 @@ static AstNode* parse_return_stmt(Parser* p) {
 //     declaration-specifiers init-declarator-list ';'
 //     declaration-specifiers init-declarator-list compound-stmt
 static AstNode* parse_external_declaration(Parser* p) {
+    if (peek_token(p)->kind == TokenKind_keyword_static_assert) {
+        return parse_static_assert_declaration(p);
+    }
+
     Type* ty = parse_declaration_specifiers(p);
     if (consume_token_if(p, TokenKind_semicolon)) {
         // Type declaration.
diff --git a/tests/assert.c b/tests/assert.c
new file mode 100644
index 0000000..e57f3e3
--- /dev/null
+++ b/tests/assert.c
@@ -0,0 +1,10 @@
+#include <helpers.h>
+
+static_assert(1);
+static_assert(1, "always true");
+static_assert(1 + 1);
+static_assert(123 == 123);
+static_assert(sizeof(int) == sizeof(unsigned int));
+
+int main() {
+}