[ruby/prism] Fix nested default value error

https://github.com/ruby/prism/commit/ef26b283de

3 files changed, 91 insertions, 37 deletions

diff --git a/prism/prism.c b/prism/prism.c
index 96725b1ee0..570b86ab1d 100644
--- a/prism/prism.c
+++ b/prism/prism.c
@@ -5933,6 +5933,33 @@ pm_parser_scope_push(pm_parser_t *parser, bool closed) {
 }
 
 /**
+ * Save the current param name as the return value and set it to the given
+ * constant id.
+ */
+static inline pm_constant_id_t
+pm_parser_current_param_name_set(pm_parser_t *parser, pm_constant_id_t current_param_name) {
+    pm_constant_id_t saved_param_name = parser->current_param_name;
+    parser->current_param_name = current_param_name;
+    return saved_param_name;
+}
+
+/**
+ * Save the current param name as the return value and clear it.
+ */
+static inline pm_constant_id_t
+pm_parser_current_param_name_unset(pm_parser_t *parser) {
+    return pm_parser_current_param_name_set(parser, PM_CONSTANT_ID_UNSET);
+}
+
+/**
+ * Restore the current param name from the given value.
+ */
+static inline void
+pm_parser_current_param_name_restore(pm_parser_t *parser, pm_constant_id_t saved_param_name) {
+    parser->current_param_name = saved_param_name;
+}
+
+/**
  * Check if any of the currently visible scopes contain a local variable
  * described by the given constant id.
  */
@@ -11715,8 +11742,8 @@ parse_parameters(
                 if (accept1(parser, PM_TOKEN_EQUAL)) {
                     pm_token_t operator = parser->previous;
                     context_push(parser, PM_CONTEXT_DEFAULT_PARAMS);
-                    pm_constant_id_t old_param_name = parser->current_param_name;
-                    parser->current_param_name = pm_parser_constant_id_token(parser, &name);
+
+                    pm_constant_id_t saved_param_name = pm_parser_current_param_name_set(parser, pm_parser_constant_id_token(parser, &name));
                     pm_node_t *value = parse_value_expression(parser, binding_power, false, PM_ERR_PARAMETER_NO_DEFAULT);
 
                     pm_optional_parameter_node_t *param = pm_optional_parameter_node_create(parser, &name, &operator, value);
@@ -11725,7 +11752,7 @@ parse_parameters(
                     }
                     pm_parameters_node_optionals_append(params, param);
 
-                    parser->current_param_name = old_param_name;
+                    pm_parser_current_param_name_restore(parser, saved_param_name);
                     context_pop(parser);
 
                     // If parsing the value of the parameter resulted in error recovery,
@@ -11793,11 +11820,13 @@ parse_parameters(
 
                         if (token_begins_expression_p(parser->current.type)) {
                             context_push(parser, PM_CONTEXT_DEFAULT_PARAMS);
-                            pm_constant_id_t old_param_name = parser->current_param_name;
-                            parser->current_param_name = pm_parser_constant_id_token(parser, &local);
+
+                            pm_constant_id_t saved_param_name = pm_parser_current_param_name_set(parser, pm_parser_constant_id_token(parser, &local));
                             pm_node_t *value = parse_value_expression(parser, binding_power, false, PM_ERR_PARAMETER_NO_DEFAULT_KW);
-                            parser->current_param_name = old_param_name;
+
+                            pm_parser_current_param_name_restore(parser, saved_param_name);
                             context_pop(parser);
+
                             param = (pm_node_t *) pm_optional_keyword_parameter_node_create(parser, &name, value);
                         }
                         else {
@@ -12142,8 +12171,10 @@ parse_block(pm_parser_t *parser) {
     pm_token_t opening = parser->previous;
     accept1(parser, PM_TOKEN_NEWLINE);
 
+    pm_constant_id_t saved_param_name = pm_parser_current_param_name_unset(parser);
     pm_accepts_block_stack_push(parser, true);
     pm_parser_scope_push(parser, false);
+
     pm_block_parameters_node_t *block_parameters = NULL;
 
     if (accept1(parser, PM_TOKEN_PIPE)) {
@@ -12207,6 +12238,8 @@ parse_block(pm_parser_t *parser) {
     pm_constant_id_list_t locals = parser->current_scope->locals;
     pm_parser_scope_pop(parser);
     pm_accepts_block_stack_pop(parser);
+    pm_parser_current_param_name_restore(parser, saved_param_name);
+
     return pm_block_node_create(parser, &locals, locals_body_index, &opening, parameters, statements, &parser->previous);
 }
 
@@ -14910,8 +14943,7 @@ parse_expression_prefix(pm_parser_t *parser, pm_binding_power_t binding_power, b
                 pm_token_t operator = parser->previous;
                 pm_node_t *expression = parse_value_expression(parser, PM_BINDING_POWER_NOT, true, PM_ERR_EXPECT_EXPRESSION_AFTER_LESS_LESS);
 
-                pm_constant_id_t old_param_name = parser->current_param_name;
-                parser->current_param_name = 0;
+                pm_constant_id_t saved_param_name = pm_parser_current_param_name_unset(parser);
                 pm_parser_scope_push(parser, true);
                 accept2(parser, PM_TOKEN_NEWLINE, PM_TOKEN_SEMICOLON);
 
@@ -14928,11 +14960,12 @@ parse_expression_prefix(pm_parser_t *parser, pm_binding_power_t binding_power, b
                 }
 
                 expect1(parser, PM_TOKEN_KEYWORD_END, PM_ERR_CLASS_TERM);
-
                 pm_constant_id_list_t locals = parser->current_scope->locals;
+
                 pm_parser_scope_pop(parser);
-                parser->current_param_name = old_param_name;
                 pm_do_loop_stack_pop(parser);
+                pm_parser_current_param_name_restore(parser, saved_param_name);
+
                 return (pm_node_t *) pm_singleton_class_node_create(parser, &locals, &class_keyword, &operator, expression, statements, &parser->previous);
             }
 
@@ -14958,9 +14991,9 @@ parse_expression_prefix(pm_parser_t *parser, pm_binding_power_t binding_power, b
                 superclass = NULL;
             }
 
-            pm_constant_id_t old_param_name = parser->current_param_name;
-            parser->current_param_name = 0;
+            pm_constant_id_t saved_param_name = pm_parser_current_param_name_unset(parser);
             pm_parser_scope_push(parser, true);
+
             if (inheritance_operator.type != PM_TOKEN_NOT_PROVIDED) {
                 expect2(parser, PM_TOKEN_NEWLINE, PM_TOKEN_SEMICOLON, PM_ERR_CLASS_UNEXPECTED_END);
             } else {
@@ -14986,9 +15019,10 @@ parse_expression_prefix(pm_parser_t *parser, pm_binding_power_t binding_power, b
             }
 
             pm_constant_id_list_t locals = parser->current_scope->locals;
+
             pm_parser_scope_pop(parser);
-            parser->current_param_name = old_param_name;
             pm_do_loop_stack_pop(parser);
+            pm_parser_current_param_name_restore(parser, saved_param_name);
 
             if (!PM_NODE_TYPE_P(constant_path, PM_CONSTANT_PATH_NODE) && !(PM_NODE_TYPE_P(constant_path, PM_CONSTANT_READ_NODE))) {
                 pm_parser_err_node(parser, constant_path, PM_ERR_CLASS_NAME);
@@ -15003,18 +15037,21 @@ parse_expression_prefix(pm_parser_t *parser, pm_binding_power_t binding_power, b
             pm_token_t operator = not_provided(parser);
             pm_token_t name = (pm_token_t) { .type = PM_TOKEN_MISSING, .start = def_keyword.end, .end = def_keyword.end };
 
-            // This context is necessary for lexing `...` in a bare params correctly.
-            // It must be pushed before lexing the first param, so it is here.
+            // This context is necessary for lexing `...` in a bare params
+            // correctly. It must be pushed before lexing the first param, so it
+            // is here.
             context_push(parser, PM_CONTEXT_DEF_PARAMS);
+            pm_constant_id_t saved_param_name;
+
             parser_lex(parser);
-            pm_constant_id_t old_param_name = parser->current_param_name;
 
             switch (parser->current.type) {
                 case PM_CASE_OPERATOR:
+                    saved_param_name = pm_parser_current_param_name_unset(parser);
                     pm_parser_scope_push(parser, true);
-                    parser->current_param_name = 0;
                     lex_state_set(parser, PM_LEX_STATE_ENDFN);
                     parser_lex(parser);
+
                     name = parser->previous;
                     break;
                 case PM_TOKEN_IDENTIFIER: {
@@ -15023,17 +15060,18 @@ parse_expression_prefix(pm_parser_t *parser, pm_binding_power_t binding_power, b
                     if (match2(parser, PM_TOKEN_DOT, PM_TOKEN_COLON_COLON)) {
                         receiver = parse_variable_call(parser);
 
+                        saved_param_name = pm_parser_current_param_name_unset(parser);
                         pm_parser_scope_push(parser, true);
-                        parser->current_param_name = 0;
                         lex_state_set(parser, PM_LEX_STATE_FNAME);
                         parser_lex(parser);
 
                         operator = parser->previous;
                         name = parse_method_definition_name(parser);
                     } else {
+                        saved_param_name = pm_parser_current_param_name_unset(parser);
                         pm_refute_numbered_parameter(parser, parser->previous.start, parser->previous.end);
                         pm_parser_scope_push(parser, true);
-                        parser->current_param_name = 0;
+
                         name = parser->previous;
                     }
 
@@ -15050,9 +15088,10 @@ parse_expression_prefix(pm_parser_t *parser, pm_binding_power_t binding_power, b
                 case PM_TOKEN_KEYWORD___FILE__:
                 case PM_TOKEN_KEYWORD___LINE__:
                 case PM_TOKEN_KEYWORD___ENCODING__: {
+                    saved_param_name = pm_parser_current_param_name_unset(parser);
                     pm_parser_scope_push(parser, true);
-                    parser->current_param_name = 0;
                     parser_lex(parser);
+
                     pm_token_t identifier = parser->previous;
 
                     if (match2(parser, PM_TOKEN_DOT, PM_TOKEN_COLON_COLON)) {
@@ -15124,8 +15163,8 @@ parse_expression_prefix(pm_parser_t *parser, pm_binding_power_t binding_power, b
                     operator = parser->previous;
                     receiver = (pm_node_t *) pm_parentheses_node_create(parser, &lparen, expression, &rparen);
 
+                    saved_param_name = pm_parser_current_param_name_unset(parser);
                     pm_parser_scope_push(parser, true);
-                    parser->current_param_name = 0;
 
                     // To push `PM_CONTEXT_DEF_PARAMS` again is for the same reason as described the above.
                     context_push(parser, PM_CONTEXT_DEF_PARAMS);
@@ -15133,8 +15172,9 @@ parse_expression_prefix(pm_parser_t *parser, pm_binding_power_t binding_power, b
                     break;
                 }
                 default:
+                    saved_param_name = pm_parser_current_param_name_unset(parser);
                     pm_parser_scope_push(parser, true);
-                    parser->current_param_name = 0;
+
                     name = parse_method_definition_name(parser);
                     break;
             }
@@ -15249,8 +15289,9 @@ parse_expression_prefix(pm_parser_t *parser, pm_binding_power_t binding_power, b
             }
 
             pm_constant_id_list_t locals = parser->current_scope->locals;
-            parser->current_param_name = old_param_name;
+
             pm_parser_scope_pop(parser);
+            pm_parser_current_param_name_restore(parser, saved_param_name);
 
             return (pm_node_t *) pm_def_node_create(
                 parser,
@@ -15478,9 +15519,9 @@ parse_expression_prefix(pm_parser_t *parser, pm_binding_power_t binding_power, b
                 pm_parser_err_token(parser, &name, PM_ERR_MODULE_NAME);
             }
 
-            pm_constant_id_t old_param_name = parser->current_param_name;
-            parser->current_param_name = 0;
+            pm_constant_id_t saved_param_name = pm_parser_current_param_name_unset(parser);
             pm_parser_scope_push(parser, true);
+
             accept2(parser, PM_TOKEN_SEMICOLON, PM_TOKEN_NEWLINE);
             pm_node_t *statements = NULL;
 
@@ -15497,7 +15538,7 @@ parse_expression_prefix(pm_parser_t *parser, pm_binding_power_t binding_power, b
 
             pm_constant_id_list_t locals = parser->current_scope->locals;
             pm_parser_scope_pop(parser);
-            parser->current_param_name = old_param_name;
+            pm_parser_current_param_name_restore(parser, saved_param_name);
 
             expect1(parser, PM_TOKEN_KEYWORD_END, PM_ERR_MODULE_TERM);
 
@@ -16164,7 +16205,9 @@ parse_expression_prefix(pm_parser_t *parser, pm_binding_power_t binding_power, b
             parser_lex(parser);
 
             pm_token_t operator = parser->previous;
+            pm_constant_id_t saved_param_name = pm_parser_current_param_name_unset(parser);
             pm_parser_scope_push(parser, false);
+
             pm_block_parameters_node_t *block_parameters;
 
             switch (parser->current.type) {
@@ -16243,8 +16286,11 @@ parse_expression_prefix(pm_parser_t *parser, pm_binding_power_t binding_power, b
             }
 
             pm_constant_id_list_t locals = parser->current_scope->locals;
+
             pm_parser_scope_pop(parser);
             pm_accepts_block_stack_pop(parser);
+            pm_parser_current_param_name_restore(parser, saved_param_name);
+
             return (pm_node_t *) pm_lambda_node_create(parser, &locals, locals_body_index, &operator, &opening, &parser->previous, parameters, body);
         }
         case PM_TOKEN_UPLUS: {
diff --git a/prism/util/pm_constant_pool.c b/prism/util/pm_constant_pool.c
index e06682eb48..7b8ed0654d 100644
--- a/prism/util/pm_constant_pool.c
+++ b/prism/util/pm_constant_pool.c
@@ -124,13 +124,13 @@ pm_constant_pool_resize(pm_constant_pool_t *pool) {
 
         // If an id is set on this constant, then we know we have content here.
         // In this case we need to insert it into the next constant pool.
-        if (bucket->id != 0) {
+        if (bucket->id != PM_CONSTANT_ID_UNSET) {
             uint32_t next_index = bucket->hash & mask;
 
             // This implements linear scanning to find the next available slot
             // in case this index is already taken. We don't need to bother
             // comparing the values since we know that the hash is unique.
-            while (next_buckets[next_index].id != 0) {
+            while (next_buckets[next_index].id != PM_CONSTANT_ID_UNSET) {
                 next_index = (next_index + 1) & mask;
             }
 
@@ -177,7 +177,7 @@ pm_constant_pool_init(pm_constant_pool_t *pool, uint32_t capacity) {
  */
 pm_constant_t *
 pm_constant_pool_id_to_constant(const pm_constant_pool_t *pool, pm_constant_id_t constant_id) {
-    assert(constant_id > 0 && constant_id <= pool->size);
+    assert(constant_id != PM_CONSTANT_ID_UNSET && constant_id <= pool->size);
     return &pool->constants[constant_id - 1];
 }
 
@@ -187,7 +187,7 @@ pm_constant_pool_id_to_constant(const pm_constant_pool_t *pool, pm_constant_id_t
 static inline pm_constant_id_t
 pm_constant_pool_insert(pm_constant_pool_t *pool, const uint8_t *start, size_t length, pm_constant_pool_bucket_type_t type) {
     if (pool->size >= (pool->capacity / 4 * 3)) {
-        if (!pm_constant_pool_resize(pool)) return 0;
+        if (!pm_constant_pool_resize(pool)) return PM_CONSTANT_ID_UNSET;
     }
 
     assert(is_power_of_two(pool->capacity));
@@ -197,7 +197,7 @@ pm_constant_pool_insert(pm_constant_pool_t *pool, const uint8_t *start, size_t l
     uint32_t index = hash & mask;
     pm_constant_pool_bucket_t *bucket;
 
-    while (bucket = &pool->buckets[index], bucket->id != 0) {
+    while (bucket = &pool->buckets[index], bucket->id != PM_CONSTANT_ID_UNSET) {
         // If there is a collision, then we need to check if the content is the
         // same as the content we are trying to insert. If it is, then we can
         // return the id of the existing constant.
@@ -248,8 +248,8 @@ pm_constant_pool_insert(pm_constant_pool_t *pool, const uint8_t *start, size_t l
 }
 
 /**
- * Insert a constant into a constant pool. Returns the id of the constant, or 0
- * if any potential calls to resize fail.
+ * Insert a constant into a constant pool. Returns the id of the constant, or
+ * PM_CONSTANT_ID_UNSET if any potential calls to resize fail.
  */
 pm_constant_id_t
 pm_constant_pool_insert_shared(pm_constant_pool_t *pool, const uint8_t *start, size_t length) {
@@ -258,8 +258,8 @@ pm_constant_pool_insert_shared(pm_constant_pool_t *pool, const uint8_t *start, s
 
 /**
  * Insert a constant into a constant pool from memory that is now owned by the
- * constant pool. Returns the id of the constant, or 0 if any potential calls to
- * resize fail.
+ * constant pool. Returns the id of the constant, or PM_CONSTANT_ID_UNSET if any
+ * potential calls to resize fail.
  */
 pm_constant_id_t
 pm_constant_pool_insert_owned(pm_constant_pool_t *pool, const uint8_t *start, size_t length) {
@@ -268,7 +268,8 @@ pm_constant_pool_insert_owned(pm_constant_pool_t *pool, const uint8_t *start, si
 
 /**
  * Insert a constant into a constant pool from memory that is constant. Returns
- * the id of the constant, or 0 if any potential calls to resize fail.
+ * the id of the constant, or PM_CONSTANT_ID_UNSET if any potential calls to
+ * resize fail.
  */
 pm_constant_id_t
 pm_constant_pool_insert_constant(pm_constant_pool_t *pool, const uint8_t *start, size_t length) {
@@ -286,7 +287,7 @@ pm_constant_pool_free(pm_constant_pool_t *pool) {
         pm_constant_pool_bucket_t *bucket = &pool->buckets[index];
 
         // If an id is set on this constant, then we know we have content here.
-        if (bucket->id != 0 && bucket->type == PM_CONSTANT_POOL_BUCKET_OWNED) {
+        if (bucket->id != PM_CONSTANT_ID_UNSET && bucket->type == PM_CONSTANT_POOL_BUCKET_OWNED) {
             pm_constant_t *constant = &pool->constants[bucket->id - 1];
             free((void *) constant->start);
         }
diff --git a/prism/util/pm_constant_pool.h b/prism/util/pm_constant_pool.h
index ae5a88fbde..3743d9f58d 100644
--- a/prism/util/pm_constant_pool.h
+++ b/prism/util/pm_constant_pool.h
@@ -19,6 +19,13 @@
 #include <string.h>
 
 /**
+ * When we allocate constants into the pool, we reserve 0 to mean that the slot
+ * is not yet filled. This constant is reused in other places to indicate the
+ * lack of a constant id.
+ */
+#define PM_CONSTANT_ID_UNSET 0
+
+/**
  * A constant id is a unique identifier for a constant in the constant pool.
  */
 typedef uint32_t pm_constant_id_t;