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Update text format for descriptor and describes clauses #46

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90 changes: 45 additions & 45 deletions proposals/custom-descriptors/Overview.md
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Original file line number Diff line number Diff line change
Expand Up @@ -40,8 +40,8 @@ what type their custom descriptors have.

```wasm
(rec
(type $foo (descriptor $foo.rtt (struct (field ...))))
(type $foo.rtt (describes $foo (struct (field ...))))
(type $foo (descriptor $foo.rtt) (struct (field ...)))
(type $foo.rtt (describes $foo) (struct (field ...)))
)
```

Expand All @@ -59,13 +59,13 @@ but type `$C` is different.

```wasm
(rec
(type $A (descriptor $A.rtt (struct (field i32))))
(type $A.rtt (describes $A (struct (field i32))))
(type $A (descriptor $A.rtt) (struct (field i32)))
(type $A.rtt (describes $A) (struct (field i32)))
)

(rec
(type $B (descriptor $B.rtt (struct (field i32))))
(type $B.rtt (describes $B (struct (field i32))))
(type $B (descriptor $B.rtt) (struct (field i32)))
(type $B.rtt (describes $B) (struct (field i32)))
)

(rec
Expand All @@ -80,9 +80,9 @@ creating arbitrarily long chains of meta-descriptors:

```wasm
(rec
(type $foo (descriptor $foo.rtt (struct)))
(type $foo.rtt (describes $foo (descriptor $foo.meta-rtt (struct))))
(type $foo.meta-rtt (describes $foo.rtt (struct)))
(type $foo (descriptor $foo.rtt) (struct))
(type $foo.rtt (describes $foo) (descriptor $foo.meta-rtt) (struct))
(type $foo.meta-rtt (describes $foo.rtt) (struct))
)
```

Expand All @@ -97,8 +97,8 @@ which in turn must have a `descriptor` clause referring to the describing type.
```wasm
(rec
(type $A (struct))
(type $B (descriptor $C (struct)))
(type $C (describes $A (struct))) ;; Invalid: must be 'describes $B'
(type $B (descriptor $C) (struct))
(type $C (describes $A) (struct)) ;; Invalid: must be 'describes $B'
)
```

Expand All @@ -116,15 +116,15 @@ This is the same strategy we use for ensuring supertype chains do not have cycle
```wasm
(rec
;; Invalid describes clause: $self is not a previously defined type.
(type $self (describes $self (descriptor $self (struct))))
(type $self (describes $self) (descriptor $self) (struct))

;; Invalid describes clause: $pong is not a previously defined type.
(type $ping (describes $pong (descriptor $pong (struct))))
(type $pong (describes $ping (descriptor $ping (struct))))
(type $ping (describes $pong) (descriptor $pong) (struct))
(type $pong (describes $ping) (descriptor $ping) (struct))

;; Invalid describes clause: $foo is not a previously defined type.
(type $foo.rtt (describes $foo (struct)))
(type $foo (descriptor $foo.rtt (struct)))
(type $foo.rtt (describes $foo) (struct))
(type $foo (descriptor $foo.rtt) (struct))
)
```

Expand Down Expand Up @@ -164,34 +164,34 @@ might be laid out after the engine-managed RTT for the type they describe.

```wasm
(rec
(type $super (sub (descriptor $super.rtt (struct))))
(type $super.rtt (sub (describes $super (struct))))
(type $super (sub (descriptor $super.rtt) (struct)))
(type $super.rtt (sub (describes $super) (struct)))

;; Ok
(type $sub (sub $super (descriptor $sub.rtt (struct))))
(type $sub.rtt (sub $super.rtt (describes $sub (struct))))
(type $sub (sub $super (descriptor $sub.rtt) (struct)))
(type $sub.rtt (sub $super.rtt (describes $sub) (struct)))
)

(rec
(type $super (sub (struct)))

;; Ok
(type $sub (sub $super (descriptor $sub.rtt (struct))))
(type $sub.rtt (describes $sub (struct)))
(type $sub (sub $super (descriptor $sub.rtt) (struct)))
(type $sub.rtt (describes $sub) (struct))
)

(rec
(type $super (sub (descriptor $super.rtt (struct ))))
(type $super.rtt (sub (describes $super (struct))))
(type $super (sub (descriptor $super.rtt) (struct )))
(type $super.rtt (sub (describes $super) (struct)))

;; Ok (but strange)
(type $other (struct))
(type $sub.rtt (sub $super.rtt (describes $other (struct))))
(type $sub.rtt (sub $super.rtt (describes $other) (struct)))
)

(rec
(type $super (sub (descriptor $super.rtt (struct))))
(type $super.rtt (sub (describes $super (struct))))
(type $super (sub (descriptor $super.rtt) (struct)))
(type $super.rtt (sub (describes $super) (struct)))

;; Invalid: Must be described by an immediate subtype of $super.rtt.
(type $sub (sub $super (struct)))
Expand All @@ -201,12 +201,12 @@ might be laid out after the engine-managed RTT for the type they describe.
)

(rec
(type $super (sub (descriptor $super.rtt (struct))))
(type $super.rtt (sub (describes $super (struct))))
(type $super (sub (descriptor $super.rtt) (struct)))
(type $super.rtt (sub (describes $super) (struct)))

;; Invalid: $other.rtt must be a an immediate subtype of $super.rtt.
(type $sub (sub $super (descriptor $other.rtt (struct))))
(type $other.rtt (describes $sub (struct)))
(type $sub (sub $super (descriptor $other.rtt) (struct)))
(type $other.rtt (describes $sub) (struct))
)
```

Expand All @@ -226,10 +226,10 @@ This may be relaxed in the future.
```wasm
(rec
;; Invalid: descriptor clauses may only be used with structs.
(type $array (descriptor $array.rtt (array i8)))
(type $array (descriptor $array.rtt) (array i8))

;; Invalid: describes clauses may only be used with structs.
(type $array.rtt (describes $array (func)))
(type $array.rtt (describes $array) (func))
)
```

Expand All @@ -242,11 +242,11 @@ this could allow the following unsound program to validate and run:

```wasm
(rec
(type $foo (sub (descriptor $foo.rtt (struct))))
(type $foo.rtt (sub (describes $foo (struct))))
(type $foo (sub (descriptor $foo.rtt) (struct)))
(type $foo.rtt (sub (describes $foo) (struct)))

(type $bar (sub $foo (descriptor $bar.rtt (struct (field $bar-only i32)))))
(type $bar.rtt (sub $foo.rtt (describes $bar (struct))))
(type $bar (sub $foo (descriptor $bar.rtt) (struct (field $bar-only i32))))
(type $bar.rtt (sub $foo.rtt (describes $bar) (struct)))
)

(func $unsound (result i32)
Expand Down Expand Up @@ -486,12 +486,12 @@ WebAssembly.
;; counter.wasm
(module
(rec
(type $counter (descriptor $counter.vtable (struct (field $val (mut i32)))))
(type $counter.vtable (describes $counter (struct
(type $counter (descriptor $counter.vtable) (struct (field $val (mut i32))))
(type $counter.vtable (describes $counter) (struct
(field $proto (ref extern))
(field $get (ref $get_t))
(field $inc (ref $inc_t))
)))
))
(type $get_t (func (param (ref null $counter)) (result i32)))
(type $inc_t (func (param (ref null $counter))))
)
Expand Down Expand Up @@ -683,12 +683,12 @@ and additionally expose a constructor:

(module
(rec
(type $counter (descriptor $counter.vtable (struct (field $val (mut i32)))))
(type $counter.vtable (describes $counter (struct
(type $counter (descriptor $counter.vtable) (struct (field $val (mut i32))))
(type $counter.vtable (describes $counter) (struct
(field $proto (ref extern))
(field $get (ref $get_t))
(field $inc (ref $inc_t))
)))
))
(type $get_t (func (param (ref null $counter)) (result i32)))
(type $inc_t (func (param (ref null $counter))))
)
Expand Down Expand Up @@ -850,11 +850,11 @@ and is included below only to clarify the interaction between proposals.)

```
describedcomptype ::=
| 0x4D x:typeidx ct:comptype => (descriptor x ct)
| 0x4D x:typeidx ct:comptype => (descriptor x) ct
| ct:comptype => ct

describingcomptype ::=
| 0x4C x:typeidx ct:describedcomptype => (describes x ct)
| 0x4C x:typeidx ct:describedcomptype => (describes x) ct
| ct:describedcomptype => ct

sharecomptype ::=
Expand Down