stage1: Fix for generic fn monomorphization

Don't use the instantiation argument types to build the function
parameter array.

f416535768fc30195cad6cd481f73fd1e80082aa worked around the problem, this
commit solves it.

1 files changed, 7 insertions, 1 deletions

diff --git a/src/stage1/ir.cpp b/src/stage1/ir.cpp
index fb94762b05..0e1c659642 100644
--- a/src/stage1/ir.cpp
+++ b/src/stage1/ir.cpp
@@ -20226,9 +20226,12 @@ static bool ir_analyze_fn_call_generic_arg(IrAnalyze *ira, AstNode *fn_proto_nod
     bool is_var_args = param_decl_node->data.param_decl.is_var_args;
     bool arg_part_of_generic_id = false;
     IrInstGen *casted_arg;
+
+    ZigType *param_info_type = nullptr;
     if (is_var_args) {
         arg_part_of_generic_id = true;
         casted_arg = arg;
+        param_info_type = arg->value->type;
     } else {
         if (param_decl_node->data.param_decl.anytype_token == nullptr) {
             AstNode *param_type_node = param_decl_node->data.param_decl.type;
@@ -20239,9 +20242,12 @@ static bool ir_analyze_fn_call_generic_arg(IrAnalyze *ira, AstNode *fn_proto_nod
             casted_arg = ir_implicit_cast2(ira, arg_src, arg, param_type);
             if (type_is_invalid(casted_arg->value->type))
                 return false;
+
+            param_info_type = param_type;
         } else {
             arg_part_of_generic_id = true;
             casted_arg = arg;
+            param_info_type = arg->value->type;
         }
     }
 
@@ -20298,7 +20304,7 @@ static bool ir_analyze_fn_call_generic_arg(IrAnalyze *ira, AstNode *fn_proto_nod
     if (!comptime_arg) {
         casted_args[fn_type_id->param_count] = casted_arg;
         FnTypeParamInfo *param_info = &fn_type_id->param_info[fn_type_id->param_count];
-        param_info->type = casted_arg->value->type;
+        param_info->type = param_info_type;
         param_info->is_noalias = param_decl_node->data.param_decl.is_noalias;
         impl_fn->param_source_nodes[fn_type_id->param_count] = param_decl_node;
         fn_type_id->param_count += 1;