patch 8.2.3091: Vim9: default argument expr. cannot use previous argu…

…ment

Problem:    Vim9: default argument expression cannot use previous argument
Solution:   Correct argument index. (closes #8496)

src/structs.h

@@ -1610,6 +1610,8 @@ typedef struct
     int		uf_dfunc_idx;	// only valid if uf_def_status is UF_COMPILED
     garray_T	uf_args;	// arguments, including optional arguments
     garray_T	uf_def_args;	// default argument expressions
+    int		uf_args_visible; // normally uf_args.ga_len, less when
+				 // compiling default argument expression.
 
     // for :def (for :function uf_ret_type is NULL)
     type_T	**uf_arg_types;	// argument types (count == uf_args.ga_len)

src/testdir/test_vim9_func.vim

@@ -452,6 +452,12 @@ def Test_call_default_args()
       MyDefaultThird('->', 'xx', v:none)->assert_equal('->xxbb')
       MyDefaultThird('->', v:none, 'yy')->assert_equal('->aayy')
       MyDefaultThird('->', 'xx', 'yy')->assert_equal('->xxyy')
+
+      def DefArg(mandatory: any, optional = mandatory): string
+        return mandatory .. optional
+      enddef
+      DefArg(1234)->assert_equal('12341234')
+      DefArg("ok")->assert_equal('okok')
   END
   CheckDefAndScriptSuccess(lines)
 

src/version.c

@@ -755,6 +755,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    3091,
 /**/
     3090,
 /**/

src/vim9compile.c

@@ -274,7 +274,7 @@ arg_exists(
 
     if (len == 0)
 	return FAIL;
-    for (idx = 0; idx < cctx->ctx_ufunc->uf_args.ga_len; ++idx)
+    for (idx = 0; idx < cctx->ctx_ufunc->uf_args_visible; ++idx)
     {
 	char_u *arg = FUNCARG(cctx->ctx_ufunc, idx);
 
@@ -9172,7 +9172,6 @@ compile_def_function(
     {
 	int	count = ufunc->uf_def_args.ga_len;
 	int	first_def_arg = ufunc->uf_args.ga_len - count;
-	int	uf_args_len = ufunc->uf_args.ga_len;
 	int	i;
 	char_u	*arg;
 	int	off = STACK_FRAME_SIZE + (ufunc->uf_va_name != NULL ? 1 : 0);
@@ -9195,12 +9194,11 @@ compile_def_function(
 		goto erret;
 
 	    // Make sure later arguments are not found.
-	    ufunc->uf_args.ga_len = i;
+	    ufunc->uf_args_visible = arg_idx;
 
 	    arg = ((char_u **)(ufunc->uf_def_args.ga_data))[i];
 	    r = compile_expr0(&arg, &cctx);
 
-	    ufunc->uf_args.ga_len = uf_args_len;
 	    if (r == FAIL)
 		goto erret;
 
@@ -9230,6 +9228,7 @@ compile_def_function(
 	if (did_set_arg_type)
 	    set_function_type(ufunc);
     }
+    ufunc->uf_args_visible = ufunc->uf_args.ga_len;
 
     /*
      * Loop over all the lines of the function and generate instructions.