Description
It seems that in some cases compiler does not recognize that "(foo" :: Symbol) ~ ("foo" :: Symbol) in presence of row types and their magic constraints.
To Reproduce
Consider the code
class TypeEquals a b | a -> b, b -> a
instance TypeEquals a a
fn :: forall label a r r'.
Cons label a r r' =>
Proxy label ->
Record r ->
Record r'
fn = unsafeThrow "not implemented"
These functions do not typecheck:
Cons "foo"; Proxy "foo"Cons foo; Proxy "foo"Cons "foo"; Proxy foo
bothLiterals :: forall a r r'.
Cons "foo" a r r' =>
Record r ->
Record r'
bothLiterals r =
fn (Proxy :: _ "foo") r -- fails
Type error
Could not match type
( foo :: t1
| r4
)
with type
r'5
proxyLiteral :: forall a r r' foo.
TypeEquals foo "foo" =>
Cons foo a r r' =>
Record r ->
Record r'
proxyLiteral r =
fn (Proxy :: _ "foo") r -- fails
Type error
Could not match type
( foo :: t1
| r4
)
with type
r'5
consLiteral :: forall a r r' foo.
TypeEquals foo "foo" =>
Cons "foo" a r r' =>
Record r ->
Record r'
consLiteral r = fn (Proxy :: _ foo) r -- fails
Type error
No type class instance was found for
Prim.Row.Cons foo4
t1
r5
r'6
And this one typechecks:
onlyTyVars :: forall a r r' foo.
TypeEquals foo "foo" =>
Cons foo a r r' =>
Record r ->
Record r'
onlyTyVars r = fn (Proxy :: _ foo) r
Expected behavior
Either all the examples cases typecheck well, or none of them do.
Additional context
Note, that if any of the functions was implemented, it would work well with foo ~ "foo". For instance this typechecks well:
f :: forall a r.
Record r ->
Record (foo :: a | r)
f = consLiteral -- using one of the functions that didn't typecheck
PureScript version
0.15.8
Description
It seems that in some cases compiler does not recognize that
"(foo" :: Symbol) ~ ("foo" :: Symbol)in presence of row types and their magic constraints.To Reproduce
Consider the code
These functions do not typecheck:
Cons "foo";Proxy "foo"Cons foo;Proxy "foo"Cons "foo";Proxy fooType error
Type error
Type error
And this one typechecks:
Cons foo;Proxy fooExpected behavior
Either all the examples cases typecheck well, or none of them do.
Additional context
Note, that if any of the functions was implemented, it would work well with
foo ~ "foo". For instance this typechecks well:PureScript version
0.15.8