ponyc
ponyc copied to clipboard
Inconsistent compiler behavior for Array literals in field initialization
The compiler is inconsistent regarding how Array fields of an embedded class can be initalized using Array literals. The following compiles fine:
class Foo
embed _array: Array[I32] = []
actor Main
let env: Env
new create(env': Env) =>
env = env'
whereas when _array is initialized to a non-empty literal:
class Foo
embed _array: Array[I32] = [0]
actor Main
let env: Env
new create(env': Env) =>
env = env'
it complains:
Error:
main.pony:2:5: an embedded field must be assigned using a constructor
embed _array: Array[I32] = [0]
^
Info:
main.pony:2:32: the assigned expression is here
embed _array: Array[I32] = [0]
^
@jemc proposes that both forms of initialization should however be allowed. Since []
is sugar for Array.create()
and [0]
is sugar for Array.create(1).>push(0)
, the compiler should allow both instead of rejecting the second.
The Zulip discussion is here: https://ponylang.zulipchat.com/#narrow/stream/189934-general/topic/Inconsistent.20use.20of.20Array.20literals.20in.20field.20initialization
The first step would be to modify the following https://github.com/ponylang/ponyc/blob/99a1c6a83e2ba7acb179bbd51b27ee2cc462d745/src/libponyc/expr/operator.c#L212-L218
To deal with TK_FUNCHAIN
(which represents a series of calls with.>
):
diff --git a/src/libponyc/expr/operator.c b/src/libponyc/expr/operator.c
index e7863690..735681bf 100644
--- a/src/libponyc/expr/operator.c
+++ b/src/libponyc/expr/operator.c
@@ -215,7 +215,7 @@ static bool is_expr_constructor(ast_t* ast)
switch(ast_id(ast))
{
case TK_CALL:
- return ast_id(ast_child(ast)) == TK_NEWREF;
+ return (ast_id(ast_child(ast)) == TK_NEWREF) || (ast_id(ast_child(ast)) == TK_FUNCHAIN);
case TK_SEQ:
return is_expr_constructor(ast_childlast(ast));
case TK_IF:
But it seems like that doing only that isn't enough. See the results of changing only that:
class Foo
embed array: Array[U8] = []
new create() => None
class Bar
embed array: Array[U8] = [0]
new create() => None
actor Main
new create(env: Env) =>
env.out.print(Foo.array.size().string()) // Prints `0`
env.out.print(Bar.array.size().string()) // Prints `4508837504`
So there might be other parts during code generation that need to be adjusted.
@stefandd are you interested in tackling this?
@SeanTAllen As much as I'd like to, I still know far too little about the compiler as of yet to even know where to look for a solution. On the other hand, @ergl knew where to look and what to adjust, so I'd hope for him to succeed hunting this down all the way...