patch 8.2.3029: Vim9: crash when using operator and list unpack assignment

Problem:    Vim9: crash when using operator and list unpack assignment.
            (Naohiro Ono)
Solution:   Get variable value before operation. (closes #8416)

src/ex_docmd.c

@@ -3485,6 +3485,8 @@ find_ex_command(
 	    // can't be an assignment.
 	    if (*eap->cmd == '[')
 	    {
+		char_u	    *eq;
+
 		p = to_name_const_end(eap->cmd);
 		if (p == eap->cmd && *p == '[')
 		{
@@ -3493,12 +3495,19 @@ find_ex_command(
 
 		    p = skip_var_list(eap->cmd, TRUE, &count, &semicolon, TRUE);
 		}
-		if (p == NULL || p == eap->cmd || *skipwhite(p) != '=')
+		eq = p;
+		if (eq != NULL)
+		{
+		    eq = skipwhite(eq);
+		    if (vim_strchr((char_u *)"+-*/%", *eq) != NULL)
+			++eq;
+		}
+		if (p == NULL || p == eap->cmd || *eq != '=')
 		{
 		    eap->cmdidx = CMD_eval;
 		    return eap->cmd;
 		}
-		if (p > eap->cmd && *skipwhite(p) == '=')
+		if (p > eap->cmd && *eq == '=')
 		{
 		    eap->cmdidx = CMD_var;
 		    return eap->cmd;

src/testdir/test_vim9_assign.vim

@@ -283,6 +283,29 @@ def Test_assign_unpack()
     [v1, v2; _] = [1, 2, 3, 4, 5]
     assert_equal(1, v1)
     assert_equal(2, v2)
+
+    var a = 1
+    var b = 3
+    [a, b] += [2, 4]
+    assert_equal(3, a)
+    assert_equal(7, b)
+
+    [a, b] -= [1, 2]
+    assert_equal(2, a)
+    assert_equal(5, b)
+
+    [a, b] *= [3, 2]
+    assert_equal(6, a)
+    assert_equal(10, b)
+
+    [a, b] /= [2, 4]
+    assert_equal(3, a)
+    assert_equal(2, b)
+
+    [a, b] = [17, 15]
+    [a, b] %= [5, 3]
+    assert_equal(2, a)
+    assert_equal(0, b)
   END
   CheckDefAndScriptSuccess(lines)
 

src/testdir/test_vim9_disassemble.vim

@@ -452,6 +452,37 @@ def Test_disassemble_list_assign()
         res)
 enddef
 
+def s:ListAssignWithOp()
+  var a = 2
+  var b = 3
+  [a, b] += [4, 5]
+enddef
+
+def Test_disassemble_list_assign_with_op()
+  var res = execute('disass s:ListAssignWithOp')
+  assert_match('<SNR>\d*_ListAssignWithOp\_s*' ..
+        'var a = 2\_s*' ..
+        '\d STORE 2 in $0\_s*' ..
+        'var b = 3\_s*' ..
+        '\d STORE 3 in $1\_s*' ..
+        '\[a, b\] += \[4, 5\]\_s*' ..
+        '\d\+ PUSHNR 4\_s*' ..
+        '\d\+ PUSHNR 5\_s*' ..
+        '\d\+ NEWLIST size 2\_s*' ..
+        '\d\+ CHECKLEN 2\_s*' ..
+        '\d\+ LOAD $0\_s*' ..
+        '\d\+ ITEM 0 with op\_s*' ..
+        '\d\+ OPNR +\_s*' ..
+        '\d\+ STORE $0\_s*' ..
+        '\d\+ LOAD $1\_s*' ..
+        '\d\+ ITEM 1 with op\_s*' ..
+        '\d\+ OPNR +\_s*' ..
+        '\d\+ STORE $1\_s*' ..
+        '\d\+ DROP\_s*' ..
+        '\d\+ RETURN void',
+        res)
+enddef
+
 def s:ListAdd()
   var l: list<number> = []
   add(l, 123)

src/version.c

@@ -755,6 +755,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    3029,
 /**/
     3028,
 /**/

src/vim9.h

@@ -209,6 +209,12 @@ typedef struct {
     int	    cuf_argcount;   // number of arguments on top of stack
 } cufunc_T;
 
+// arguments to ISN_GETITEM
+typedef struct {
+    varnumber_T	gi_index;
+    int		gi_with_op;
+} getitem_T;
+
 typedef enum {
     JUMP_ALWAYS,
     JUMP_IF_FALSE,		// pop and jump if false
@@ -432,6 +438,7 @@ struct isn_S {
 	isn_T		    *instr;
 	tostring_T	    tostring;
 	tobool_T	    tobool;
+	getitem_T	    getitem;
     } isn_arg;
 };
 

src/vim9compile.c

@@ -1240,13 +1240,16 @@ generate_PUSHFUNC(cctx_T *cctx, char_u *name, type_T *type)
 
 /*
  * Generate an ISN_GETITEM instruction with "index".
+ * "with_op" is TRUE for "+=" and other operators, the stack has the current
+ * value below the list with values.
  */
     static int
-generate_GETITEM(cctx_T *cctx, int index)
+generate_GETITEM(cctx_T *cctx, int index, int with_op)
 {
     isn_T	*isn;
     garray_T	*stack = &cctx->ctx_type_stack;
-    type_T	*type = ((type_T **)stack->ga_data)[stack->ga_len - 1];
+    type_T	*type = ((type_T **)stack->ga_data)[stack->ga_len
+							  - (with_op ? 2 : 1)];
     type_T	*item_type = &t_any;
 
     RETURN_OK_IF_SKIP(cctx);
@@ -1260,7 +1263,8 @@ generate_GETITEM(cctx_T *cctx, int index)
     item_type = type->tt_member;
     if ((isn = generate_instr(cctx, ISN_GETITEM)) == NULL)
 	return FAIL;
-    isn->isn_arg.number = index;
+    isn->isn_arg.getitem.gi_index = index;
+    isn->isn_arg.getitem.gi_with_op = with_op;
 
     // add the item type to the type stack
     if (ga_grow(stack, 1) == FAIL)
@@ -6746,19 +6750,17 @@ compile_assignment(char_u *arg, exarg_T *eap, cmdidx_T cmdidx, cctx_T *cctx)
 		int	is_const = FALSE;
 		char_u	*wp;
 
+		// for "+=", "*=", "..=" etc. first load the current value
+		if (*op != '='
+			&& compile_load_lhs_with_index(&lhs, var_start,
+								 cctx) == FAIL)
+		    goto theend;
+
 		// For "var = expr" evaluate the expression.
 		if (var_count == 0)
 		{
 		    int	r;
 
-		    // for "+=", "*=", "..=" etc. first load the current value
-		    if (*op != '=')
-		    {
-			if (compile_load_lhs_with_index(&lhs, var_start,
-								 cctx) == FAIL)
-			    goto theend;
-		    }
-
 		    // Compile the expression.
 		    instr_count = instr->ga_len;
 		    if (incdec)
@@ -6795,7 +6797,7 @@ compile_assignment(char_u *arg, exarg_T *eap, cmdidx_T cmdidx, cctx_T *cctx)
 		{
 		    // For "[var, var] = expr" get the "var_idx" item from the
 		    // list.
-		    if (generate_GETITEM(cctx, var_idx) == FAIL)
+		    if (generate_GETITEM(cctx, var_idx, *op != '=') == FAIL)
 			goto theend;
 		}
 

src/vim9execute.c

@@ -3832,12 +3832,12 @@ exec_instructions(ectx_T *ectx)
 	    case ISN_GETITEM:
 		{
 		    listitem_T	*li;
-		    int		index = iptr->isn_arg.number;
+		    getitem_T	*gi = &iptr->isn_arg.getitem;
 
 		    // Get list item: list is at stack-1, push item.
 		    // List type and length is checked for when compiling.
-		    tv = STACK_TV_BOT(-1);
-		    li = list_find(tv->vval.v_list, index);
+		    tv = STACK_TV_BOT(-1 - gi->gi_with_op);
+		    li = list_find(tv->vval.v_list, gi->gi_index);
 
 		    if (GA_GROW(&ectx->ec_stack, 1) == FAIL)
 			goto theend;
@@ -3846,7 +3846,7 @@ exec_instructions(ectx_T *ectx)
 
 		    // Useful when used in unpack assignment.  Reset at
 		    // ISN_DROP.
-		    ectx->ec_where.wt_index = index + 1;
+		    ectx->ec_where.wt_index = gi->gi_index + 1;
 		    ectx->ec_where.wt_variable = TRUE;
 		}
 		break;
@@ -5376,8 +5376,10 @@ list_instructions(char *pfx, isn_T *instr, int instr_count, ufunc_T *ufunc)
 	    case ISN_ANYSLICE: smsg("%s%4d ANYSLICE", pfx, current); break;
 	    case ISN_SLICE: smsg("%s%4d SLICE %lld",
 					 pfx, current, iptr->isn_arg.number); break;
-	    case ISN_GETITEM: smsg("%s%4d ITEM %lld",
-					 pfx, current, iptr->isn_arg.number); break;
+	    case ISN_GETITEM: smsg("%s%4d ITEM %lld%s", pfx, current,
+					 iptr->isn_arg.getitem.gi_index,
+					 iptr->isn_arg.getitem.gi_with_op ?
+						       " with op" : ""); break;
 	    case ISN_MEMBER: smsg("%s%4d MEMBER", pfx, current); break;
 	    case ISN_STRINGMEMBER: smsg("%s%4d MEMBER %s", pfx, current,
 						  iptr->isn_arg.string); break;