patch 8.2.1865: Vim9: add() does not check type of argument

Problem:    Vim9: add() does not check type of argument.
Solution:   Inline the add() call. (closes #7160)

src/errors.h

@@ -282,4 +282,6 @@ EXTERN char e_endblock_without_block[]
 	INIT(= N_("E1128: } without {"));
 EXTERN char e_throw_with_empty_string[]
 	INIT(= N_("E1129: Throw with empty string"));
+EXTERN char e_cannot_add_to_null_list[]
+	INIT(= N_("E1130: Cannot add to null list"));
 #endif

src/testdir/test_vim9_disassemble.vim

@@ -273,6 +273,34 @@ def Test_disassemble_list_assign()
         res)
 enddef
 
+def s:ListAdd()
+  var l: list<number> = []
+  add(l, 123)
+  add(l, g:aNumber)
+enddef
+
+def Test_disassemble_list_add()
+  var res = execute('disass s:ListAdd')
+  assert_match('<SNR>\d*_ListAdd\_s*' ..
+        'var l: list<number> = []\_s*' ..
+        '\d NEWLIST size 0\_s*' ..
+        '\d STORE $0\_s*' ..
+        'add(l, 123)\_s*' ..
+        '\d LOAD $0\_s*' ..
+        '\d PUSHNR 123\_s*' ..
+        '\d LISTAPPEND\_s*' ..
+        '\d DROP\_s*' ..
+        'add(l, g:aNumber)\_s*' ..
+        '\d LOAD $0\_s*' ..
+        '\d\+ LOADG g:aNumber\_s*' ..
+        '\d\+ CHECKTYPE number stack\[-1\]\_s*' ..
+        '\d\+ LISTAPPEND\_s*' ..
+        '\d\+ DROP\_s*' ..
+        '\d\+ PUSHNR 0\_s*' ..
+        '\d\+ RETURN',
+        res)
+enddef
+
 def s:ScriptFuncUnlet()
   g:somevar = "value"
   unlet g:somevar
@@ -803,7 +831,7 @@ def Test_disassemble_for_loop()
         'res->add(i)\_s*' ..
         '\d LOAD $0\_s*' ..
         '\d LOAD $2\_s*' ..
-        '\d\+ BCALL add(argc 2)\_s*' ..
+        '\d\+ LISTAPPEND\_s*' ..
         '\d\+ DROP\_s*' ..
         'endfor\_s*' ..
         '\d\+ JUMP -> \d\+\_s*' ..

src/testdir/test_vim9_func.vim

@@ -1772,6 +1772,24 @@ def Test_list2str_str2list_utf8()
   list2str(l, true)->assert_equal(s)
 enddef
 
+def Test_list_add()
+  var l: list<number>  # defaults to empty list
+  add(l, 9)
+  assert_equal([9], l)
+
+  var lines =<< trim END
+      var l: list<number>
+      add(l, "x")
+  END
+  CheckDefFailure(lines, 'E1012:', 2)
+
+  lines =<< trim END
+      var l: list<number> = test_null_list()
+      add(l, 123)
+  END
+  CheckDefExecFailure(lines, 'E1130:', 2)
+enddef
+
 def SID(): number
   return expand('<SID>')
           ->matchstr('<SNR>\zs\d\+\ze_$')

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1865,
 /**/
     1864,
 /**/

src/vim9.h

@@ -96,8 +96,8 @@ typedef enum {
     ISN_ENDTRY,	    // take entry off from ec_trystack
 
     // more expression operations
-    ISN_ADDLIST,
+    ISN_ADDLIST,    // add two lists
-    ISN_ADDBLOB,
+    ISN_ADDBLOB,    // add two blobs
 
     // operation with two arguments; isn_arg.op.op_type is exptype_T
     ISN_OPNR,
@@ -120,6 +120,7 @@ typedef enum {
     ISN_CONCAT,
     ISN_STRINDEX,   // [expr] string index
     ISN_STRSLICE,   // [expr:expr] string slice
+    ISN_LISTAPPEND, // append to a list, like add()
     ISN_LISTINDEX,  // [expr] list index
     ISN_LISTSLICE,  // [expr:expr] list slice
     ISN_ANYINDEX,   // [expr] runtime index

src/vim9compile.c

@@ -1494,6 +1494,32 @@ generate_BCALL(cctx_T *cctx, int func_idx, int argcount, int method_call)
     return OK;
 }
 
+/*
+ * Generate an ISN_LISTAPPEND instruction.  Works like add().
+ * Argument count is already checked.
+ */
+    static int
+generate_LISTAPPEND(cctx_T *cctx)
+{
+    garray_T	*stack = &cctx->ctx_type_stack;
+    type_T	*list_type;
+    type_T	*item_type;
+    type_T	*expected;
+
+    // Caller already checked that list_type is a list.
+    list_type = ((type_T **)stack->ga_data)[stack->ga_len - 2];
+    item_type = ((type_T **)stack->ga_data)[stack->ga_len - 1];
+    expected = list_type->tt_member;
+    if (need_type(item_type, expected, -1, cctx, FALSE, FALSE) == FAIL)
+	return FAIL;
+
+    if (generate_instr(cctx, ISN_LISTAPPEND) == NULL)
+	return FAIL;
+
+    --stack->ga_len;	    // drop the argument
+    return OK;
+}
+
 /*
  * Generate an ISN_DCALL or ISN_UCALL instruction.
  * Return FAIL if the number of arguments is wrong.
@@ -2536,8 +2562,26 @@ compile_call(
 
 	// builtin function
 	idx = find_internal_func(name);
+	if (idx >= 0)
+	{
+	    if (STRCMP(name, "add") == 0 && argcount == 2)
+	    {
+		garray_T    *stack = &cctx->ctx_type_stack;
+		type_T	    *type = ((type_T **)stack->ga_data)[
+							    stack->ga_len - 2];
+
+		// TODO: also check for VAR_BLOB
+		if (type->tt_type == VAR_LIST)
+		{
+		    // inline "add(list, item)" so that the type can be checked
+		    res = generate_LISTAPPEND(cctx);
+		    idx = -1;
+		}
+	    }
+
 	    if (idx >= 0)
 		res = generate_BCALL(cctx, idx, argcount, argcount_init == 1);
+	}
 	else
 	    semsg(_(e_unknownfunc), namebuf);
 	goto theend;
@@ -7656,6 +7700,7 @@ delete_instr(isn_T *isn)
 	case ISN_FOR:
 	case ISN_GETITEM:
 	case ISN_JUMP:
+	case ISN_LISTAPPEND:
 	case ISN_LISTINDEX:
 	case ISN_LISTSLICE:
 	case ISN_LOAD:

src/vim9execute.c

@@ -2095,6 +2095,7 @@ call_def_function(
 				       || *skipwhite(tv->vval.v_string) == NUL)
 		{
 		    vim_free(tv->vval.v_string);
+		    SOURCING_LNUM = iptr->isn_lnum;
 		    emsg(_(e_throw_with_empty_string));
 		    goto failed;
 		}
@@ -2282,6 +2283,7 @@ call_def_function(
 		    typval_T *tv1 = STACK_TV_BOT(-2);
 		    typval_T *tv2 = STACK_TV_BOT(-1);
 
+		    // add two lists or blobs
 		    if (iptr->isn_type == ISN_ADDLIST)
 			eval_addlist(tv1, tv2);
 		    else
@@ -2291,6 +2293,25 @@ call_def_function(
 		}
 		break;
 
+	    case ISN_LISTAPPEND:
+		{
+		    typval_T	*tv1 = STACK_TV_BOT(-2);
+		    typval_T	*tv2 = STACK_TV_BOT(-1);
+		    list_T	*l = tv1->vval.v_list;
+
+		    // add an item to a list
+		    if (l == NULL)
+		    {
+			SOURCING_LNUM = iptr->isn_lnum;
+			emsg(_(e_cannot_add_to_null_list));
+			goto on_error;
+		    }
+		    if (list_append_tv(l, tv2) == FAIL)
+			goto failed;
+		    --ectx.ec_stack.ga_len;
+		}
+		break;
+
 	    // Computation with two arguments of unknown type
 	    case ISN_OPANY:
 		{
@@ -3410,6 +3431,7 @@ ex_disassemble(exarg_T *eap)
 	    case ISN_CONCAT: smsg("%4d CONCAT", current); break;
 	    case ISN_STRINDEX: smsg("%4d STRINDEX", current); break;
 	    case ISN_STRSLICE: smsg("%4d STRSLICE", current); break;
+	    case ISN_LISTAPPEND: smsg("%4d LISTAPPEND", current); break;
 	    case ISN_LISTINDEX: smsg("%4d LISTINDEX", current); break;
 	    case ISN_LISTSLICE: smsg("%4d LISTSLICE", current); break;
 	    case ISN_ANYINDEX: smsg("%4d ANYINDEX", current); break;