Merge pull request #4191 from Vexu/non-exhaustive-enums

Implement non-exhaustive enums

1 files changed, 31 insertions, 7 deletions

diff --git a/src/analyze.cpp b/src/analyze.cpp
index b7838003c8..e064677a09 100644
--- a/src/analyze.cpp
+++ b/src/analyze.cpp
@@ -2569,15 +2569,8 @@ static Error resolve_enum_zero_bits(CodeGen *g, ZigType *enum_type) {
         return ErrorSemanticAnalyzeFail;
     }
 
-    enum_type->data.enumeration.src_field_count = field_count;
-    enum_type->data.enumeration.fields = allocate<TypeEnumField>(field_count);
-    enum_type->data.enumeration.fields_by_name.init(field_count);
-
     Scope *scope = &enum_type->data.enumeration.decls_scope->base;
 
-    HashMap<BigInt, AstNode *, bigint_hash, bigint_eql> occupied_tag_values = {};
-    occupied_tag_values.init(field_count);
-
     ZigType *tag_int_type;
     if (enum_type->data.enumeration.layout == ContainerLayoutExtern) {
         tag_int_type = get_c_int_type(g, CIntTypeInt);
@@ -2619,6 +2612,7 @@ static Error resolve_enum_zero_bits(CodeGen *g, ZigType *enum_type) {
         }
     }
 
+    enum_type->data.enumeration.non_exhaustive = false;
     enum_type->data.enumeration.tag_int_type = tag_int_type;
     enum_type->size_in_bits = tag_int_type->size_in_bits;
     enum_type->abi_size = tag_int_type->abi_size;
@@ -2627,6 +2621,31 @@ static Error resolve_enum_zero_bits(CodeGen *g, ZigType *enum_type) {
     BigInt bi_one;
     bigint_init_unsigned(&bi_one, 1);
 
+    AstNode *last_field_node = decl_node->data.container_decl.fields.at(field_count - 1);
+    if (buf_eql_str(last_field_node->data.struct_field.name, "_")) {
+        field_count -= 1;
+        if (field_count > 1 && log2_u64(field_count) == enum_type->size_in_bits) {
+            add_node_error(g, last_field_node, buf_sprintf("non-exhaustive enum specifies every value"));
+            enum_type->data.enumeration.resolve_status = ResolveStatusInvalid;
+        }
+        if (decl_node->data.container_decl.init_arg_expr == nullptr) {
+            add_node_error(g, last_field_node, buf_sprintf("non-exhaustive enum must specify size"));
+            enum_type->data.enumeration.resolve_status = ResolveStatusInvalid;
+        }
+        if (last_field_node->data.struct_field.value != nullptr) {
+            add_node_error(g, last_field_node, buf_sprintf("value assigned to '_' field of non-exhaustive enum"));
+            enum_type->data.enumeration.resolve_status = ResolveStatusInvalid;
+        }
+        enum_type->data.enumeration.non_exhaustive = true;
+    }
+
+    enum_type->data.enumeration.src_field_count = field_count;
+    enum_type->data.enumeration.fields = allocate<TypeEnumField>(field_count);
+    enum_type->data.enumeration.fields_by_name.init(field_count);
+
+    HashMap<BigInt, AstNode *, bigint_hash, bigint_eql> occupied_tag_values = {};
+    occupied_tag_values.init(field_count);
+
     TypeEnumField *last_enum_field = nullptr;
 
     for (uint32_t field_i = 0; field_i < field_count; field_i += 1) {
@@ -2648,6 +2667,11 @@ static Error resolve_enum_zero_bits(CodeGen *g, ZigType *enum_type) {
                     buf_sprintf("consider 'union(enum)' here"));
         }
 
+        if (buf_eql_str(type_enum_field->name, "_")) {
+            add_node_error(g, field_node, buf_sprintf("'_' field of non-exhaustive enum must be last"));
+            enum_type->data.enumeration.resolve_status = ResolveStatusInvalid;
+        }
+
         auto field_entry = enum_type->data.enumeration.fields_by_name.put_unique(type_enum_field->name, type_enum_field);
         if (field_entry != nullptr) {
             ErrorMsg *msg = add_node_error(g, field_node,