Global compiler: unreachable code warning when using nullable in generic types #2780
Description
Here's the use case when compiling with --global:
class C[E]
var x: E
redef fun to_s
do
if x != null then
return "x is {x.as(not null)}"
end
return "x is null"
end
end
var c1 = new C[nullable Object](null)
var c2 = new C[nullable Int](null)
c1.x = "test"
c2.x = 100
The global compiler will try to inline the message sending when c1.x = .... However, this produce type_test which is unreachable :
$ nitc failing_example.nit --global
nitc__temp.nitgg.1.c: In function ‘nitc__temp___core__Sys___main’:
nitc__temp.nitgg.1.c:7419:6: warning: statement will never be executed [-Wswitch-unreachable]
var2 = 1;
~~~~~^~~
nitc__temp.nitgg.1.c:7474:6: warning: statement will never be executed [-Wswitch-unreachable]
var7 = 1;
~~~~~^~~
nitc__temp.nitgg.1.c:7577:7: warning: statement will never be executed [-Wswitch-unreachable]
var23 = 1;The generated C code :
switch(var->classid) {
default: /* test C[nullable Object] */
{ /* Inline temp$C$x= (var,((val*)NULL)) */
/* Covariant cast for argument 0 (x) <((val*)NULL):null> isa E */
/* isa nullable Object on <((val*)NULL):null> */
if (((val*)NULL) == NULL) {
var2 = 1; /* isa nullable Object */
} else
switch(((val*)NULL)->classid) {
var2 = 1;
break;
default:
var2 = 0;
}
if (unlikely(!var2)) {
{
struct catch_stack_t *catchStack = getCatchStack();
if(catchStack->cursor >= 0){
longjmp(catchStack->envs[catchStack->cursor], 1);
}
}
var_class_name = class_names[((val*)NULL)->classid];
PRINT_ERROR("Runtime error: Cast failed. Expected `%s`, got `%s`", "E", var_class_name);
PRINT_ERROR(" (%s:%d)\n", FILE_nitc__temp, 2);
fatal_exit(1);
}
/* write _x on <var:C[nullable Object] exact> */
switch(var->classid) {
default: /*ID_nitc__C__nullable__core__Object*/
((struct nitc__C__nullable__core__Object*)var)->nitc___nitc__C____x = ((val*)NULL);
break;
}
RET_LABEL1:(void)0;
}
break;
}