feat: implement goto statement

5 files changed, 202 insertions, 0 deletions

diff --git a/src/ast.h b/src/ast.h
index c5171d7..4ca2e1b 100644
--- a/src/ast.h
+++ b/src/ast.h
@@ -106,10 +106,12 @@ typedef enum {
     AstNodeKind_func_call,
     AstNodeKind_func_decl,
     AstNodeKind_func_def,
+    AstNodeKind_goto_stmt,
     AstNodeKind_gvar,
     AstNodeKind_gvar_decl,
     AstNodeKind_if_stmt,
     AstNodeKind_int_expr,
+    AstNodeKind_label_stmt,
     AstNodeKind_list,
     AstNodeKind_logical_expr,
     AstNodeKind_lvar,
diff --git a/src/codegen.c b/src/codegen.c
index f02a38c..4387449 100644
--- a/src/codegen.c
+++ b/src/codegen.c
@@ -578,6 +578,15 @@ static void codegen_continue_stmt(CodeGen* g, AstNode* ast) {
     fprintf(g->out, "  jmp .Lcontinue%d\n", label);
 }
 
+static void codegen_goto_stmt(CodeGen* g, AstNode* ast) {
+    fprintf(g->out, "  jmp .L%s__%s\n", g->current_func->name, ast->name);
+}
+
+static void codegen_label_stmt(CodeGen* g, AstNode* ast) {
+    fprintf(g->out, ".L%s__%s:\n", g->current_func->name, ast->name);
+    codegen_stmt(g, ast->node_body);
+}
+
 // Helper to collect case values from the switch body
 static void collect_cases(AstNode* stmt, int* case_values, int* case_labels, int* n_cases) {
     if (!stmt)
@@ -694,6 +703,10 @@ static void codegen_stmt(CodeGen* g, AstNode* ast) {
         codegen_break_stmt(g, ast);
     } else if (ast->kind == AstNodeKind_continue_stmt) {
         codegen_continue_stmt(g, ast);
+    } else if (ast->kind == AstNodeKind_goto_stmt) {
+        codegen_goto_stmt(g, ast);
+    } else if (ast->kind == AstNodeKind_label_stmt) {
+        codegen_label_stmt(g, ast);
     } else if (ast->kind == AstNodeKind_expr_stmt) {
         codegen_expr_stmt(g, ast);
     } else if (ast->kind == AstNodeKind_lvar_decl) {
diff --git a/src/parse.c b/src/parse.c
index b82c45d..1ad11bd 100644
--- a/src/parse.c
+++ b/src/parse.c
@@ -1331,12 +1331,30 @@ static AstNode* parse_stmt(Parser* p) {
         return parse_break_stmt(p);
     } else if (t->kind == TokenKind_keyword_continue) {
         return parse_continue_stmt(p);
+    } else if (t->kind == TokenKind_keyword_goto) {
+        expect(p, TokenKind_keyword_goto);
+        Token* label_token = expect(p, TokenKind_ident);
+        expect(p, TokenKind_semicolon);
+
+        AstNode* goto_stmt = ast_new(AstNodeKind_goto_stmt);
+        goto_stmt->name = label_token->value.string;
+        return goto_stmt;
     } else if (t->kind == TokenKind_brace_l) {
         return parse_block_stmt(p);
     } else if (t->kind == TokenKind_semicolon) {
         return parse_empty_stmt(p);
     } else if (is_type_token(p, t)) {
         return parse_var_decl(p);
+    } else if (t->kind == TokenKind_ident && peek_token2(p)->kind == TokenKind_colon) {
+        // Label statement
+        Token* label_token = expect(p, TokenKind_ident);
+        expect(p, TokenKind_colon);
+        AstNode* stmt = parse_stmt(p);
+
+        AstNode* label_stmt = ast_new(AstNodeKind_label_stmt);
+        label_stmt->name = label_token->value.string;
+        label_stmt->node_body = stmt;
+        return label_stmt;
     } else {
         return parse_expr_stmt(p);
     }
diff --git a/tests/helpers.sh b/tests/helpers.sh
index adc9511..6e0c51c 100644
--- a/tests/helpers.sh
+++ b/tests/helpers.sh
@@ -43,6 +43,7 @@ function test_compile_error() {
 
     if [[ $exit_code -eq 0 ]]; then
         echo "expected to fail" >&2
+        cat expected >&2
         exit 1
     fi
 
diff --git a/tests/test_goto.sh b/tests/test_goto.sh
new file mode 100644
index 0000000..1e28a51
--- /dev/null
+++ b/tests/test_goto.sh
@@ -0,0 +1,168 @@
+touch expected
+test_diff <<'EOF'
+int main() {
+    goto end;
+    return 1;
+end:
+    return 0;
+}
+EOF
+
+cat <<'EOF' > expected
+1
+2
+3
+EOF
+test_diff <<'EOF'
+int printf(const char*, ...);
+
+int main() {
+    int i = 0;
+loop:
+    i++;
+    printf("%d\n", i);
+    if (i < 3)
+        goto loop;
+    return 0;
+}
+EOF
+
+cat < /dev/null > expected
+test_diff <<'EOF'
+int main() {
+    goto skip;
+    int x = 5;
+skip:
+    return 0;
+}
+EOF
+
+cat <<'EOF' > expected
+start
+middle
+end
+EOF
+test_diff <<'EOF'
+int printf(const char*, ...);
+
+int main() {
+    printf("start\n");
+    goto middle;
+first:
+    printf("first\n");
+    goto end;
+middle:
+    printf("middle\n");
+    goto end;
+last:
+    printf("last\n");
+end:
+    printf("end\n");
+    return 0;
+}
+EOF
+
+cat <<'EOF' > expected
+before
+after
+EOF
+test_diff <<'EOF'
+int printf(const char*, ...);
+
+int main() {
+    printf("before\n");
+    {
+        {
+            goto out;
+            printf("inside\n");
+        }
+        printf("middle\n");
+    }
+out:
+    printf("after\n");
+    return 0;
+}
+EOF
+
+cat <<'EOF' > expected
+x is 5
+x is 10
+EOF
+test_diff <<'EOF'
+int printf(const char*, ...);
+
+int main() {
+    int x = 5;
+    if (x == 5) {
+        printf("x is 5\n");
+        goto next;
+    }
+    printf("x is not 5\n");
+next:
+    x = 10;
+    printf("x is %d\n", x);
+    return 0;
+}
+EOF
+
+cat <<'EOF' > expected
+case 2
+done
+EOF
+test_diff <<'EOF'
+int printf(const char*, ...);
+
+int main() {
+    int x = 2;
+    switch (x) {
+    case 1:
+        printf("case 1\n");
+        break;
+    case 2:
+        printf("case 2\n");
+        goto done;
+    case 3:
+        printf("case 3\n");
+        break;
+    }
+    printf("after switch\n");
+done:
+    printf("done\n");
+    return 0;
+}
+EOF
+
+# cat <<'EOF' > expected
+# error: use of undeclared label 'undefined'
+# EOF
+# test_compile_error <<'EOF'
+# int main() {
+#     goto undefined;
+#     return 0;
+# }
+# EOF
+
+# cat <<'EOF' > expected
+# error: redefinition of label 'duplicate'
+# EOF
+# test_compile_error <<'EOF'
+# int main() {
+# duplicate:
+#     ;
+# duplicate:
+#     return 0;
+# }
+# EOF
+
+# cat <<'EOF' > expected
+# error: label at end of compound statement
+# EOF
+# test_compile_error <<'EOF'
+# int main() {
+#     {
+#         goto end;
+#     end:
+#     }
+#     return 0;
+# }
+# EOF