This was trickier than expected as the expression parser, and in particular the bin-op parser will interpret negative patterns as a continuation of a binary operation and eventually choke on the next right-arrow symbol. This is due to how we actually completely erase newlines once we're done with the lexer. The newline separating when clause is actually semantically important. In principle, we could only parse an expression until the next newline.
Ideally, we would keep that newline in the list of token but it's difficult to figure out which newline to keep between two right arrows since a clause guard can be written over multiple lines. Though, since we know that this is only truly a problem for negative integers, we can use the same trick as for tuples and define a new 'NewLineMinus' token. That token CANNOT be part of a binop expression. That means it's impossible to write a binary operation with a minus over multiple lines, or more specifically, with the '-' symbol on a newline. This sounds like a fair limitation. What we get in exchange is less ambiguity when parsing patterns following expressions in when clause cases.
Another more cumbersome option could be to preserve the first newline encountered after a 'right-arrow' symbol and before any parenthesis or curly brace is found (which would otherwise signal the beginning of a new block). That requires to traverse, at least partially, the list of tokens twice. This feels unnecessary for now and until we do face a similar issue with a binary operator.
The main goal is to make the parser more reusable to be used for when-clauses, instead of the expression parser. A side goal has been to make it more readable by moving the construction of some untyped expression as method on UntypedExpr. Doing so, I got rid of the extra temporary 'ParseArg' type and re-used the generic 'CallArg' instead by simply using an Option<UntypedExpr> as value to get the same semantic as 'ParseArg' (which would distinguish between plain call args and holes). Now the chained parser is in a bit more reusable state.
We do not actually every parse negative values in there, as a negative value is a combination of a 'Negate' and 'UInt' expression.
However, for patterns and constant, it'll be simpler to parse whole Int values as there's no ambiguity with arithmetic operations
there. To avoid confusion of having some 'Int' constructors containing only non-negative values, and some being on the whole range,
I've renamed the constructor to 'UInt' to make this more obvious.
This was a bit more tricky than anticipated but played out nicely in
the end. Now we have one holistic way of parsing todos and errors
instead of it being duplicated between when/clause and sequence. The
error/todo parser has been moved up to the expression part rather than
being managed when parsing sequences. Not sure what motivated that to
begin with.
Fixes#621.
Alleviate a bit more the top-level expression parser. Note that we
probably need a bit more disciplined in what we export and at what level
because there doesn't seem to be much logic as for whether a parser is
private, exported to the crate only or to the wide open. I'd be in favor
of exporting everything by default.
Also moved the logic for 'int' and 'string' there though it is trivial. Yet, for bytearray, it tidies things nicely by removing them from the 'utils' module.
Equality on a union-type is potentially dangerous as the compiler won't
complain if we add a new case that we don't cover. Reversing the
assignment by yielding a `Token` for a given `AssignmentKind`. This way
we can use a pattern-match that got us covered for future cases.
The 'public' util was arguably not really adding much except a layer of indirection.
In the end, one useful parsing behavior to abstract is the idea of 'optional flag' that we use for both 'pub' and 'opaque' keywords.
Somehow, miette doesn't play well with spans when using chars indices.
So we have to count the number of bytes in strings / chars, so that
spans align accordingly.
Rules are now as follows:
- If a pipeline contains a newline, then the entire pipeline is formatted over multiple lines.
- If it doesn't, then it's formatted as a single-line UNLESS it cannot fit; in which case, we fallback to multiline again.
This has been bothering me and the more I thought of it the more I
disliked the idea of a warning. The rationale being that in this very
context, there's absolutely no ambiguity. So it is only frustrating
that the parser is even able to make the exact suggestion of what
should be fixed, but still fails.
I can imagine it is going to be very common for people to type:
```
trace "foo"
```
...yet terribly frustrating if they have to remember each time that
this should actually be a string. Because of the `trace`, `todo` and
`error` keywords, we know exactly the surrounding context and what to
expect here. So we can work it nicely.
However, the formatter will re-format it to:
```
trace @"foo"
```
Just for the sake of remaining consistent with the type-system. This
way, we still only manipulate `String` in the AST, but we conveniently
parse a double-quote utf-8 literal when coupled with one of the
specific keywords.
I believe that's the best of both worlds.
The core observation is that **in the context of Aiken** (i.e. on-chain logic)
people do not generally want to use String. Instead, they want
bytearrays.
So, it should be easy to produce bytearrays when needed and it should
be the default. Before this commit, `"foo"` would parse as a `String`.
Now, it parses as a `ByteArray`, whose bytes are the UTF-8 bytes
encoding of "foo".
Now, to make this change really "fool-proof", we now want to:
- [ ] Emit a parse error if we parse a UTF-8 bytearray literal in
place where we would expect a `String`. For example, `trace`,
`error` and `todo` can only be followed by a `String`.
So when we see something like:
```
trace "foo"
```
we know it's a mistake and we can suggest users to use:
```
trace @"foo"
```
instead.
- [ ] Emit a warning if we ever see a bytearray literals UTF-8, which
is either 56 or 64 character long and is a valid hexadecimal string.
For example:
```
let policy_id = "29d222ce763455e3d7a09a665ce554f00ac89d2e99a1a83d267170c6"
```
This is _most certainly_ a mistake, as this generates a ByteArray of
56 bytes, which is effectively the hex-encoding of the provided string.
In this scenario, we want to warn the user and inform them they probably meant to use:
```
let policy_id = #"29d222ce763455e3d7a09a665ce554f00ac89d2e99a1a83d267170c6"
```
Interestingly enough, chumsky seems to fail when given a 'choice' with
more than 25 elements. That's why this commit groups together some of
the choices as another nested 'choice'.
With pretty parse errors on failures. The type-checker was already
implemented for those, so it now only requires some work in the code
generation.
Fixes#297.
This changes allow to use parenthesis `(` `)` to encapsulate
expressions in addition to braces `{` `}` used to define blocks.
The main use-case is for arithmetic and boolean expressions for which
developers are used to using parenthesis. For example:
```
{ 14 + 42 } * 1337
```
can now be written as:
```
( 14 + 42 ) * 1337
```
This may sound straightforward at first but wasn't necessarily trivial
in Aiken given that (a) everything is an expression, (b) whitespaces
do not generally matter and (c) there's no symbol indicating the end
of a 'statement' (because there's no statement).
Thus, we have to properly disambiguate between:
```
let foo = bar(14 + 42)
```
and
```
let foo = bar
(14 + 42)
```
Before this commit, the latter would be interpreted as a function call
and would lead to a somewhat puzzling error. Now, the newline serves
as a delimiting symbol. The trade-off being that for a function call,
the left parenthesis has to be on the same line as the function name
identifier -- which is a fair trade off. So this is still allowed:
```
let foo = bar(
14 + 42
)
```
As there's very little ambiguity about it.
This fixes#236 and would seemingly allow us to get rid of the leading
`#` in front of tuples.
* add unary op
* parse, typecheck, and code gen it
* express boolean not as unary op as well, previously called negate
Co-authored-by: rvcas <x@rvcas.dev>
rvcas