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Spectec for binary format of types and instructions #108

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8 changes: 6 additions & 2 deletions document/core/binary/types.rst
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Expand Up @@ -117,19 +117,23 @@ Composite Types
$${grammar: Bmut Bcomptype Bfieldtype Bstoragetype Bpacktype}


.. index:: recursive type, sub type, composite type
.. index:: recursive type, sub type, desctype, composite type
pair: binary format; recursive type
pair: binary format; sub type
pair: binary format; desctype
.. _binary-rectype:
.. _binary-subtype:
.. _binary-desctype:
.. _binary-describestype:
.. _binary-descriptortype:

Recursive Types
~~~~~~~~~~~~~~~

:ref:`Recursive types <syntax-rectype>` are encoded by the byte ${:0x4E} followed by a :ref:`list <binary-list>` of :ref:`sub types <syntax-subtype>`.
Additional shorthands are recognized for unary recursions and sub types without super types.

$${grammar: Brectype Bsubtype}
$${grammar: Brectype Bsubtype Bdesctype Bdescribestype Bdescriptortype}


.. index:: limits
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3 changes: 3 additions & 0 deletions document/core/util/macros.def
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Expand Up @@ -843,6 +843,9 @@
.. |Bstoragetype| mathdef:: \xref{binary/types}{binary-storagetype}{\B{storagetype}}
.. |Bpacktype| mathdef:: \xref{binary/types}{binary-packtype}{\B{packtype}}
.. |Bcomptype| mathdef:: \xref{binary/types}{binary-comptype}{\B{comptype}}
.. |Bdescribestype| mathdef:: \xref{binary/types}{binary-describestype}{\B{describestype}}
.. |Bdescriptortype| mathdef:: \xref{binary/types}{binary-descriptortype}{\B{descriptortype}}
.. |Bdesctype| mathdef:: \xref{binary/types}{binary-desctype}{\B{desctype}}
.. |Bsubtype| mathdef:: \xref{binary/types}{binary-subtype}{\B{subtype}}
.. |Brectype| mathdef:: \xref{binary/types}{binary-rectype}{\B{rectype}}
.. |Bglobaltype| mathdef:: \xref{binary/types}{binary-globaltype}{\B{globaltype}}
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19 changes: 16 additions & 3 deletions specification/wasm-latest/5.2-binary.types.spectec
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Expand Up @@ -29,6 +29,7 @@ grammar Babsheaptype : heaptype =

grammar Bheaptype : heaptype =
| ht:Babsheaptype => ht
| 0x62 x:Btypeidx => _HT EXACT (_IDX x)
| x33:Bs33 => _HT (_IDX $s33_to_u32(x33)) -- if x33 >= 0

grammar Breftype : reftype =
Expand Down Expand Up @@ -68,10 +69,22 @@ grammar Bcomptype : comptype =
| 0x5F ft*:Blist(Bfieldtype) => STRUCT ft*
| 0x60 t_1*:Bresulttype t_2*:Bresulttype => FUNC t_1* -> t_2*

grammar Bdescribestype : describestype =
| 0x4C x:Btypeidx => DESCRIBES (_IDX x)

grammar Bdescriptortype : descriptortype =
| 0x4D x:Btypeidx => DESCRIPTOR (_IDX x)

grammar Bdesctype : desctype =
| describestype:Bdescribestype descriptortype:Bdescriptortype ct:Bcomptype => describestype descriptortype ct

@tlively tlively Jul 16, 2026

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We probably want some other variable names here. I can use dt1 and dt2, but not dt_1 and dt_2 because dt is already taken by deftype. Any suggestions?

@rossberg rossberg Jul 22, 2026

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How about just d_1, d_2? I think d isn't taken globally.

Btw, how about dropping the type suffix on describes/descriptortype? These names are a mouthful, and they aren't really types in their own right anyway, more like modifiers.

| describestype:Bdescribestype ct:Bcomptype => describestype ct
| descriptortype:Bdescriptortype ct:Bcomptype => descriptortype ct
| ct:Bcomptype => ct

grammar Bsubtype : subtype =
| 0x4F x*:Blist(Btypeidx) ct:Bcomptype => SUB FINAL (_IDX x)* ct
| 0x50 x*:Blist(Btypeidx) ct:Bcomptype => SUB (_IDX x)* ct
| ct:Bcomptype => SUB FINAL eps ct
| 0x4F x*:Blist(Btypeidx) desctype:Bdesctype => SUB FINAL (_IDX x)* desctype
| 0x50 x*:Blist(Btypeidx) desctype:Bdesctype => SUB (_IDX x)* desctype
| desctype:Bdesctype => SUB FINAL eps desctype

grammar Brectype : rectype =
| 0x4E st*:Blist(Bsubtype) => REC st*
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9 changes: 9 additions & 0 deletions specification/wasm-latest/5.3-binary.instructions.spectec
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Expand Up @@ -56,6 +56,10 @@ grammar Binstr/control : instr = ...
l:Blabelidx ht_1:Bheaptype ht_2:Bheaptype => BR_ON_CAST l (REF null_1? ht_1) (REF null_2? ht_2)
| 0xFB 25:Bu32 (null_1?, null_2?):Bcastop
l:Blabelidx ht_1:Bheaptype ht_2:Bheaptype => BR_ON_CAST_FAIL l (REF null_1? ht_1) (REF null_2? ht_2)
| 0xFB 37:Bu32 (null_1?, null_2?):Bcastop
l:Blabelidx ht_1:Bheaptype ht_2:Bheaptype => BR_ON_CAST_DESC_EQ l (REF null_1? ht_1) (REF null_2? ht_2)
| 0xFB 38:Bu32 (null_1?, null_2?):Bcastop
l:Blabelidx ht_1:Bheaptype ht_2:Bheaptype => BR_ON_CAST_DESC_EQ_FAIL l (REF null_1? ht_1) (REF null_2? ht_2)
| ...

grammar Bcatch : catch =
Expand Down Expand Up @@ -146,6 +150,9 @@ grammar Binstr/ref : instr = ...
| 0xFB 21:Bu32 ht:Bheaptype => REF.TEST (REF NULL ht)
| 0xFB 22:Bu32 ht:Bheaptype => REF.CAST (REF ht)
| 0xFB 23:Bu32 ht:Bheaptype => REF.CAST (REF NULL ht)
| 0xFB 34:Bu32 x:Btypeidx => REF.GET_DESC x
| 0xFB 35:Bu32 ht:Bheaptype => REF.CAST_DESC_EQ (REF ht)
| 0xFB 36:Bu32 ht:Bheaptype => REF.CAST_DESC_EQ (REF NULL ht)
| ...

grammar Binstr/struct : instr = ...
Expand All @@ -155,6 +162,8 @@ grammar Binstr/struct : instr = ...
| 0xFB 3:Bu32 x:Btypeidx i:Bu32 => STRUCT.GET S x i
| 0xFB 4:Bu32 x:Btypeidx i:Bu32 => STRUCT.GET U x i
| 0xFB 5:Bu32 x:Btypeidx i:Bu32 => STRUCT.SET x i
| 0xFB 32:Bu32 x:Btypeidx => STRUCT.NEW_DESC x
| 0xFB 33:Bu32 x:Btypeidx => STRUCT.NEW_DEFAULT_DESC x
| ...

grammar Binstr/array : instr = ...
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