grammar: open subsystem keys to arbitrary identifiers (closes #64)

CHANGELOG.md

@@ -8,6 +8,10 @@ Prose references a version as `v0.X.Y`; headings stay bare `[0.X.Y]`.
 
 ### Added
 
+- Subsystem keys in the chain manifest accept arbitrary identifiers, not just the five stdlib axes (`consensus`, `gas`, `state`, `exec`, `da`). A chain can declare any axis it cares about as a first-class subsystem: `privacy: GrothProver<curve=BN254>`, `mev: FlashbotsBundler`, etc. Lifts the parser-layer gatekeeping that was blocking third-party protocol extensions at the chain layer. Closes #64.
+- Parser test reworked: `test_error_unknown_subsystem_key` (which asserted "unknown:" was rejected) replaced by `test_arbitrary_subsystem_key_parses` (asserts `privacy: ...` works) plus `test_subsystem_key_can_still_be_stdlib_keyword` (regression guard that `consensus:`, `state:`, etc. still parse the same way).
+- `spec/grammar.ebnf` updated: `SubsystemKey = IDENT` instead of the enumerated five names; comment explains the stdlib axes are still conventions, just not parser-level requirements.
+- Tree-sitter grammar updated in lockstep: `subsystem_key` is now `$.identifier` instead of a fixed-choice rule.
 - Solidity toolchain integration. Real `solc`-compiled Solidity contracts now run end-to-end on the EVM engine. `runtime/tests/solidity.rs` shells out to `solc --bin --optimize` to compile `runtime/tests/fixtures/MiniERC20.sol`, deploys via `Evm::deploy` with a 32-byte ABI-encoded constructor arg (`initial supply`), then exercises `balanceOf` and `transfer` via hand-rolled ABI encoding of the standard selectors (`0x70a08231 balanceOf(address)`, `0xa9059cbb transfer(address,uint256)`, `0x18160ddd totalSupply()`). Closes #52.
 - 2 new integration tests:
   - `erc20_deploys_and_transfers`: deploys MiniERC20 with 1M supply to alice, asserts `totalSupply == 1M`, asserts `balanceOf(alice) == 1M` and `balanceOf(bob) == 0`, transfers 100 from alice to bob, asserts both balances post-transfer

compiler/src/parser.c

@@ -7,7 +7,9 @@
  *   top_level        := chain_decl | module_decl | protocol_decl
  *
  *   chain_decl       := "chain" IDENT "{" subsystem_assign* "}"
- *   subsystem_assign := SUBSYSTEM_KEY ":" type_expr (";"|",")?
+ *   subsystem_assign := IDENT ":" type_expr (";"|",")?     -- key is any
+ *                                                            identifier
+ *                                                            since issue #64
  *
  *   module_decl      := "module" IDENT "{" module_item* "}"
  *   module_item      := state_decl | gas_decl | event_decl | fn_decl | effect_decl
@@ -59,10 +61,23 @@
 
 #include "parser.h"
 
-/* Subsystem keys are lexed as their own keyword tokens (see lexer.c). The
- * parser accepts any of these as a chain-block field key. */
+/* Subsystem keys are arbitrary identifiers (issue #64). The five names
+ * `consensus`, `gas`, `state`, `exec`, `da` are still keyword tokens
+ * for other reasons (state/gas double as module-item declaration
+ * keywords), so we accept both the reserved keyword tokens AND plain
+ * identifiers in chain-block field-key position. A chain manifest can
+ * now declare any axis it cares about as a first-class subsystem:
+ *
+ *     chain MyZkChain {
+ *         consensus: Tendermint
+ *         privacy:   GrothProver<curve=BN254>
+ *     }
+ *
+ * Third-party protocol implementations (RFC #65) hang off this
+ * relaxation; the parser stops being the gatekeeper. */
 static int is_subsystem_key(TokenKind k) {
     switch (k) {
+    case TK_IDENT:
     case TK_KW_CONSENSUS:
     case TK_KW_GAS:
     case TK_KW_STATE:
@@ -347,11 +362,13 @@ static AstNode *parse_type_expr(Parser *p) {
 }
 
 /* subsystem_assign := SUBSYSTEM_KEY ":" type_expr
- * SUBSYSTEM_KEY is one of the keyword tokens (TK_KW_CONSENSUS, TK_KW_GAS, ...). */
+ * SUBSYSTEM_KEY is any identifier or one of the reserved subsystem
+ * keyword tokens (issue #64). The five stdlib names stay keywords
+ * because state/gas also introduce module-item declarations. */
 static AstNode *parse_subsystem_assign(Parser *p) {
     if (!is_subsystem_key(p->current.kind)) {
         error_at(p, &p->current,
-                 "expected a subsystem key (consensus, gas, state, exec, da)");
+                 "expected a subsystem key (an identifier)");
         return NULL;
     }
 

compiler/tests/parser_test.c

@@ -228,12 +228,33 @@ TEST(test_error_missing_colon_in_assignment) {
     free(err);
 }
 
-TEST(test_error_unknown_subsystem_key) {
-    /* `unknown:` lexes as IDENT, not one of the SUBSYSTEM keywords. */
+TEST(test_arbitrary_subsystem_key_parses) {
+    /* Issue #64: subsystem keys are no longer restricted to the five
+     * stdlib axes. Any identifier is a valid subsystem key so chains
+     * can declare custom axes (privacy, mev, da-variant, etc.). */
     char *err = NULL;
-    AstNode *root = parse_source("chain C { unknown: Tendermint }", &err);
-    ASSERT(root == NULL);
-    ASSERT(err && strstr(err, "expected a subsystem key") != NULL);
+    AstNode *root = parse_source(
+        "chain C { privacy: GrothProver<curve=BN254> }", &err);
+    ASSERT(root != NULL);
+    ASSERT_EQ_INT(root->kind, AST_CHAIN_DECL);
+    ASSERT_EQ_INT(root->as.chain.n_assignments, 1);
+    AstNode *sub = root->as.chain.assignments[0];
+    ASSERT_EQ_INT(sub->kind, AST_SUBSYSTEM_ASSIGN);
+    ASSERT_EQ_STR_LEN(sub->as.subsystem.key.start,
+                      sub->as.subsystem.key.length, "privacy");
+    free(err);
+}
+
+TEST(test_subsystem_key_can_still_be_stdlib_keyword) {
+    /* Regression guard: the five reserved keyword tokens still work
+     * as subsystem keys, since state/gas remain keywords for the
+     * module-item declarations elsewhere in the grammar. */
+    char *err = NULL;
+    AstNode *root = parse_source("chain C { consensus: Aura }", &err);
+    ASSERT(root != NULL);
+    AstNode *sub = root->as.chain.assignments[0];
+    ASSERT_EQ_STR_LEN(sub->as.subsystem.key.start,
+                      sub->as.subsystem.key.length, "consensus");
     free(err);
 }
 
@@ -590,7 +611,8 @@ int main(void) {
     RUN(test_error_missing_open_brace);
     RUN(test_error_missing_close_brace);
     RUN(test_error_missing_colon_in_assignment);
-    RUN(test_error_unknown_subsystem_key);
+    RUN(test_arbitrary_subsystem_key_parses);
+    RUN(test_subsystem_key_can_still_be_stdlib_keyword);
     RUN(test_error_missing_type_expr_after_colon);
     RUN(test_error_unterminated_generic_args);
 

spec/grammar.ebnf

@@ -39,8 +39,16 @@ SubsystemAssign
     = SubsystemKey, ":", TypeExpr
     ;
 
+(* Any identifier is a valid subsystem key (issue #64). The five names
+   below are the stdlib axes and remain reserved as keyword tokens for
+   reasons unrelated to the chain manifest (state and gas also start
+   module-item declarations). Chains can declare additional axes by
+   inventing new identifier names, which makes third-party protocol
+   extensions a first-class language feature. *)
+
 SubsystemKey
-    = "consensus" | "gas" | "state" | "exec" | "da"
+    = IDENT       (* includes the stdlib axes:
+                     "consensus", "gas", "state", "exec", "da" *)
     ;