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Update validation for exact types #142

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Update validation for exact types #142

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14 changes: 7 additions & 7 deletions proposals/stack-switching/Explainer.md
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Original file line number Diff line number Diff line change
Expand Up @@ -543,7 +543,7 @@ The following instruction creates a *suspended continuation* from a
function.

```wast
cont.new $ct : [(ref null $ft)] -> [(ref $ct)]
cont.new $ct : [(ref null $ft)] -> [(ref (exact $ct))]
where:
- $ft = func [t1*] -> [t2*]
- $ct = cont $ft
Expand Down Expand Up @@ -617,7 +617,7 @@ switch.
switch $ct1 $e : [t1* (ref null $ct1)] -> [t2*]
where:
- $e : [] -> [t*]
- $ct1 = cont [t1* (ref $ct2)] -> [t*]
- $ct1 = cont [t1* (ref null? (exact? $ct2))] -> [t*]
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@rossberg rossberg Apr 7, 2026

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The missing null? here looks like an inconsistency independent from exact types. Perhaps make a PR fixing it separately?

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@tlively tlively Apr 7, 2026

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Opened #143

- $ct2 = cont [t2*] -> [t*]
```

Expand Down Expand Up @@ -655,7 +655,7 @@ A suspended continuation can be partially applied to a prefix of its
arguments yielding another suspended continuation.

```wast
cont.bind $ct1 $ct2 : [t1* (ref null $ct1)] -> [(ref $ct2)]
cont.bind $ct1 $ct2 : [t1* (ref null $ct1)] -> [(ref (exact $ct2))]
where:
- $ct1 = cont [t1* t3*] -> [t2*]
- $ct2 = cont [t3*] -> [t2*]
Expand Down Expand Up @@ -967,12 +967,12 @@ This abbreviation will be formalised with an auxiliary function or other means i

- `cont.new <typeidx>`
- Create a new continuation from a given typed funcref.
- `cont.new $ct : [(ref null $ft)] -> [(ref $ct)]`
- `cont.new $ct : [(ref null $ft)] -> [(ref (exact $ct))]`
- iff `C.types[$ct] ~~ cont [t1*] -> [t2*]`

- `cont.bind <typeidx> <typeidx>`
- Partially apply a continuation.
- `cont.bind $ct $ct' : [t3* (ref null $ct)] -> [(ref $ct')]`
- `cont.bind $ct $ct' : [t3* (ref null $ct)] -> [(ref (exact $ct'))]`
- iff `C.types[$ct] ~~ cont [t3* t1*] -> [t2*]`
- and `C.types[$ct'] ~~ cont [t1'*] -> [t2'*]`
- and `[t1*] -> [t2*] <: [t1'*] -> [t2'*]`
Expand Down Expand Up @@ -1004,7 +1004,7 @@ This abbreviation will be formalised with an auxiliary function or other means i
- Handlers attached to `resume` and `resume_throw`, handling control tags for `suspend` and `switch`, respectively.
- `(on tu $l) : t*`
- iff `tu : [t1*] -> [t2*]`
- and `C.labels[$l] = [t1'* (ref null? $ct)]`
- and `C.labels[$l] = [t1'* (ref null? (exact? $ct))]`
- and `t1* <: t1'*`
- and `C.types[$ct] ~~ cont [t2'*] -> [t'*]`
- and `[t2*] -> [t*] <: [t2'*] -> [t'*]`
Expand All @@ -1021,7 +1021,7 @@ This abbreviation will be formalised with an auxiliary function or other means i
- The suspension and switch are performed from the perspective of a parent `(on $e switch)` handler, determined by the annotated control tag.
- `switch $ct1 tu : [t1* (ref null $ct1)] -> [t2*]`
- iff `tu : [] -> [t*]`
- and `C.types[$ct1] ~~ cont [t1* (ref null? $ct2)] -> [te1*]`
- and `C.types[$ct1] ~~ cont [t1* (ref null? (exact? $ct2))] -> [te1*]`
- and `te1* <: t*`
- and `C.types[$ct2] ~~ cont [t2*] -> [te2*]`
- and `t* <: te2*`
Expand Down