patch 8.2.1712: Vim9: leaking memory when calling a lambda

Problem:    Vim9: leaking memory when calling a lambda.
Solution:   Decrement function reference from ISN_DCALL.

src/proto/userfunc.pro

@@ -12,6 +12,7 @@ char_u *fname_trans_sid(char_u *name, char_u *fname_buf, char_u **tofree, int *e
 ufunc_T *find_func_even_dead(char_u *name, int is_global, cctx_T *cctx);
 ufunc_T *find_func(char_u *name, int is_global, cctx_T *cctx);
 int func_is_global(ufunc_T *ufunc);
+int func_name_refcount(char_u *name);
 void copy_func(char_u *lambda, char_u *global);
 int call_user_func_check(ufunc_T *fp, int argcount, typval_T *argvars, typval_T *rettv, funcexe_T *funcexe, dict_T *selfdict);
 void save_funccal(funccal_entry_T *entry);

src/userfunc.c

@@ -1058,7 +1058,7 @@ cleanup_function_call(funccall_T *fc)
  * using function() does not count as a reference, because the function is
  * looked up by name.
  */
-    static int
+    int
 func_name_refcount(char_u *name)
 {
     return isdigit(*name) || *name == '<';
@@ -1176,8 +1176,9 @@ func_clear(ufunc_T *fp, int force)
  * Free a function and remove it from the list of functions.  Does not free
  * what a function contains, call func_clear() first.
  * When "force" is TRUE we are exiting.
+ * Returns OK when the function was actually freed.
  */
-    static void
+    static int
 func_free(ufunc_T *fp, int force)
 {
     // Only remove it when not done already, otherwise we would remove a newer
@@ -1191,7 +1192,9 @@ func_free(ufunc_T *fp, int force)
 	    unlink_def_function(fp);
 	VIM_CLEAR(fp->uf_name_exp);
 	vim_free(fp);
+	return OK;
     }
+    return FAIL;
 }
 
 /*
@@ -1890,9 +1893,13 @@ free_all_functions(void)
 		    ++skipped;
 		else
 		{
-		    func_free(fp, FALSE);
-		    skipped = 0;
-		    break;
+		    if (func_free(fp, FALSE) == OK)
+		    {
+			skipped = 0;
+			break;
+		    }
+		    // did not actually free it
+		    ++skipped;
 		}
 	    }
     }

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1712,
 /**/
     1711,
 /**/

src/vim9compile.c

@@ -1452,7 +1452,7 @@ generate_CALL(cctx_T *cctx, ufunc_T *ufunc, int pushed_argcount)
 		    ufunc->uf_def_status != UF_NOT_COMPILED ? ISN_DCALL
 							 : ISN_UCALL)) == NULL)
 	return FAIL;
-    if (ufunc->uf_def_status != UF_NOT_COMPILED)
+    if (isn->isn_type == ISN_DCALL)
     {
 	isn->isn_arg.dfunc.cdf_idx = ufunc->uf_dfunc_idx;
 	isn->isn_arg.dfunc.cdf_argcount = argcount;
@@ -2634,8 +2634,8 @@ compile_lambda_call(char_u **arg, cctx_T *cctx)
     clear_tv(&rettv);
     ga_init2(&ufunc->uf_type_list, sizeof(type_T *), 10);
 
-    // The function will have one line: "return {expr}".
-    // Compile it into instructions.
+    // The function will have one line: "return {expr}".  Compile it into
+    // instructions so that we get any errors right now.
     compile_def_function(ufunc, TRUE, cctx);
 
     // compile the arguments
@@ -7285,7 +7285,19 @@ delete_instr(isn_T *isn)
 	    {
 		dfunc_T *dfunc = ((dfunc_T *)def_functions.ga_data)
 					       + isn->isn_arg.funcref.fr_func;
-		func_ptr_unref(dfunc->df_ufunc);
+
+		if (func_name_refcount(dfunc->df_ufunc->uf_name))
+		    func_ptr_unref(dfunc->df_ufunc);
+	    }
+	    break;
+
+	case ISN_DCALL:
+	    {
+		dfunc_T *dfunc = ((dfunc_T *)def_functions.ga_data)
+					       + isn->isn_arg.dfunc.cdf_idx;
+
+		if (func_name_refcount(dfunc->df_ufunc->uf_name))
+		    func_ptr_unref(dfunc->df_ufunc);
 	    }
 	    break;
 
@@ -7333,7 +7345,6 @@ delete_instr(isn_T *isn)
 	case ISN_COMPARESPECIAL:
 	case ISN_COMPARESTRING:
 	case ISN_CONCAT:
-	case ISN_DCALL:
 	case ISN_DROP:
 	case ISN_ECHO:
 	case ISN_ECHOERR: