fix crash when passing void to var args function

closes #235

src/all_types.hpp

@@ -1262,6 +1262,7 @@ struct CodeGen {
     LLVMValueRef err_name_table;
 
     IrInstruction *invalid_instruction;
+    ConstExprValue const_void_val;
 };
 
 // TODO after merging IR branch, we can probably delete some of these fields

src/codegen.cpp

@@ -3738,6 +3738,9 @@ static void init(CodeGen *g, Buf *source_path) {
 
     g->invalid_instruction = allocate<IrInstruction>(1);
     g->invalid_instruction->value.type = g->builtin_types.entry_invalid;
+
+    g->const_void_val.special = ConstValSpecialStatic;
+    g->const_void_val.type = g->builtin_types.entry_void;
 }
 
 void codegen_parseh(CodeGen *g, Buf *src_dirname, Buf *src_basename, Buf *source_code) {

src/ir.cpp

@@ -7397,7 +7397,7 @@ static TypeTableEntry *ir_analyze_array_cat(IrAnalyze *ira, IrInstructionBinOp *
         op2_array_end = op2_array_val->data.x_array.size - 1;
     } else {
         ir_add_error(ira, op2,
-            buf_sprintf("expected array or C string literal, found '%s'", buf_ptr(&op1->value.type->name)));
+            buf_sprintf("expected array or C string literal, found '%s'", buf_ptr(&op2->value.type->name)));
         // TODO if meta_type is type decl, add note pointing to type decl declaration
         return ira->codegen->builtin_types.entry_invalid;
     }
@@ -8511,6 +8511,23 @@ static TypeTableEntry *ir_analyze_instruction_var_ptr(IrAnalyze *ira, IrInstruct
     return ir_analyze_var_ptr(ira, &var_ptr_instruction->base, var, var_ptr_instruction->is_const, false);
 }
 
+static VariableTableEntry *get_fn_var_by_index(FnTableEntry *fn_entry, size_t index) {
+    size_t next_var_i = 0;
+    FnGenParamInfo *gen_param_info = fn_entry->type_entry->data.fn.gen_param_info;
+    for (size_t param_i = 0; param_i < index; param_i += 1) {
+        FnGenParamInfo *info = &gen_param_info[param_i];
+        if (info->gen_index == SIZE_MAX)
+            continue;
+
+        next_var_i += 1;
+    }
+    FnGenParamInfo *info = &gen_param_info[index];
+    if (info->gen_index == SIZE_MAX)
+        return nullptr;
+
+    return fn_entry->variable_list.at(next_var_i);
+}
+
 static TypeTableEntry *ir_analyze_instruction_elem_ptr(IrAnalyze *ira, IrInstructionElemPtr *elem_ptr_instruction) {
     IrInstruction *array_ptr = elem_ptr_instruction->array_ptr->other;
     if (array_ptr->value.type->id == TypeTableEntryIdInvalid)
@@ -8560,10 +8577,15 @@ static TypeTableEntry *ir_analyze_instruction_elem_ptr(IrAnalyze *ira, IrInstruc
         size_t abs_index = start + index;
         FnTableEntry *fn_entry = exec_fn_entry(ira->new_irb.exec);
         assert(fn_entry);
-        VariableTableEntry *var = fn_entry->variable_list.at(abs_index);
+        VariableTableEntry *var = get_fn_var_by_index(fn_entry, abs_index);
         bool depends_on_compile_var = array_ptr->value.depends_on_compile_var ||
             elem_index->value.depends_on_compile_var;
+        if (var) {
             return ir_analyze_var_ptr(ira, &elem_ptr_instruction->base, var, true, depends_on_compile_var);
+        } else {
+            return ir_analyze_const_ptr(ira, &elem_ptr_instruction->base, &ira->codegen->const_void_val,
+                    ira->codegen->builtin_types.entry_void, depends_on_compile_var, ConstPtrSpecialNone, true);
+        }
     } else {
         ir_add_error_node(ira, elem_ptr_instruction->base.source_node,
                 buf_sprintf("array access of non-array type '%s'", buf_ptr(&array_type->name)));
@@ -10445,16 +10467,13 @@ static TypeTableEntry *ir_analyze_instruction_type_name(IrAnalyze *ira, IrInstru
     if (type_entry->id == TypeTableEntryIdInvalid)
         return ira->codegen->builtin_types.entry_invalid;
 
-    TypeTableEntry *str_type = get_slice_type(ira->codegen, ira->codegen->builtin_types.entry_u8, true);
     if (!type_entry->cached_const_name_val) {
-        ConstExprValue *array_val = create_const_str_lit(ira->codegen, &type_entry->name);
+        type_entry->cached_const_name_val = create_const_str_lit(ira->codegen, &type_entry->name);
-        type_entry->cached_const_name_val = create_const_slice(ira->codegen,
-                array_val, 0, buf_len(&type_entry->name), true);
     }
     ConstExprValue *out_val = ir_build_const_from(ira, &instruction->base,
         type_value->value.depends_on_compile_var);
     *out_val = *type_entry->cached_const_name_val;
-    return str_type;
+    return out_val->type;
 }
 
 static TypeTableEntry *ir_analyze_instruction_c_import(IrAnalyze *ira, IrInstructionCImport *instruction) {

std/io.zig

@@ -165,6 +165,8 @@ pub const OutStream = struct {
         } else if (@canImplicitCast([]const u8, value)) {
             const casted_value = ([]const u8)(value);
             return self.write(casted_value);
+        } else if (T == void) {
+            return self.write("void");
         } else {
             @compileError("Unable to print type '" ++ @typeName(T) ++ "'");
         }

test/cases/var_args.zig

@@ -15,3 +15,13 @@ fn testAddArbitraryArgs() {
     assert(add(i32(1234)) == 1234);
     assert(add() == 0);
 }
+
+fn readFirstVarArg(args: ...) {
+    const value = args[0];
+}
+
+fn sendVoidArgToVarArgs() {
+    @setFnTest(this);
+
+    readFirstVarArg({});
+}