implement undefined literal

src/all_types.hpp

@@ -62,6 +62,7 @@ struct ConstPtrValue {
 struct ConstExprValue {
     bool ok; // true if constant expression evalution worked
     bool depends_on_compile_var;
+    bool undef;
 
     union {
         BigNum x_bignum;
@@ -808,6 +809,7 @@ enum TypeTableEntryId {
     TypeTableEntryIdStruct,
     TypeTableEntryIdNumLitFloat,
     TypeTableEntryIdNumLitInt,
+    TypeTableEntryIdUndefLit,
     TypeTableEntryIdMaybe,
     TypeTableEntryIdError,
     TypeTableEntryIdEnum,
@@ -949,6 +951,7 @@ struct CodeGen {
         TypeTableEntry *entry_invalid;
         TypeTableEntry *entry_num_lit_int;
         TypeTableEntry *entry_num_lit_float;
+        TypeTableEntry *entry_undef;
     } builtin_types;
 
     LLVMTargetDataRef target_data_ref;

src/analyze.cpp

@@ -111,6 +111,7 @@ TypeTableEntry *new_type_table_entry(TypeTableEntryId id) {
         case TypeTableEntryIdMaybe:
         case TypeTableEntryIdFn:
         case TypeTableEntryIdError:
+        case TypeTableEntryIdUndefLit:
             // nothing to init
             break;
         case TypeTableEntryIdStruct:
@@ -1063,6 +1064,7 @@ static bool type_has_codegen_value(TypeTableEntryId id) {
         case TypeTableEntryIdUnreachable:
         case TypeTableEntryIdNumLitFloat:
         case TypeTableEntryIdNumLitInt:
+        case TypeTableEntryIdUndefLit:
             return false;
 
         case TypeTableEntryIdBool:
@@ -2481,10 +2483,9 @@ static TypeTableEntry *analyze_undefined_literal_expr(CodeGen *g, ImportTableEnt
     ConstExprValue *const_val = &expr->const_val;
 
     const_val->ok = true;
+    const_val->undef = true;
 
-    zig_panic("TODO");
-
-    return expected_type;
+    return expected_type ? expected_type : g->builtin_types.entry_undef;
 }
 
 

src/codegen.cpp

@@ -1725,8 +1725,16 @@ static LLVMValueRef gen_var_decl_raw(CodeGen *g, AstNode *source_node, AstNodeVa
     }
     if (variable->type->size_in_bits == 0) {
         return nullptr;
-    } else {
+    }
+
+    bool have_init_expr = false;
     if (var_decl->expr) {
+        ConstExprValue *const_val = &get_resolved_expr(var_decl->expr)->const_val;
+        if (!const_val->ok || !const_val->undef) {
+            have_init_expr = true;
+        }
+    }
+    if (have_init_expr) {
         TypeTableEntry *expr_type = get_expr_type(var_decl->expr);
         LLVMValueRef value;
         if (unwrap_maybe) {
@@ -1802,7 +1810,6 @@ static LLVMValueRef gen_var_decl_raw(CodeGen *g, AstNode *source_node, AstNodeVa
     LLVMZigInsertDeclareAtEnd(g->dbuilder, variable->value_ref, variable->di_loc_var, debug_loc,
             LLVMGetInsertBlock(g->builder));
     return nullptr;
-    }
 }
 
 static LLVMValueRef gen_var_decl_expr(CodeGen *g, AstNode *node) {
@@ -2035,6 +2042,10 @@ static void build_label_blocks(CodeGen *g, AstNode *block_node) {
 static LLVMValueRef gen_const_val(CodeGen *g, TypeTableEntry *type_entry, ConstExprValue *const_val) {
     assert(const_val->ok);
 
+    if (const_val->undef) {
+        return LLVMConstNull(type_entry->type_ref);
+    }
+
     if (type_entry->id == TypeTableEntryIdInt) {
         return LLVMConstInt(type_entry->type_ref, bignum_to_twos_complement(&const_val->data.x_bignum), false);
     } else if (type_entry->id == TypeTableEntryIdFloat) {
@@ -2389,6 +2400,11 @@ static void define_builtin_types(CodeGen *g) {
         buf_init_from_str(&entry->name, "(integer literal)");
         g->builtin_types.entry_num_lit_int = entry;
     }
+    {
+        TypeTableEntry *entry = new_type_table_entry(TypeTableEntryIdUndefLit);
+        buf_init_from_str(&entry->name, "(undefined)");
+        g->builtin_types.entry_undef = entry;
+    }
 
     for (int i = 0; i < array_length(int_sizes_in_bits); i += 1) {
         int size_in_bits = int_sizes_in_bits[i];