icore

name	icore
description	Use when reading, writing, or reviewing `.icore` JSON files. Covers the Core IR JSON format with icoreVersion, decls arrays, function/struct/class declarations, body statements, boundary ABI layouts, and symbol exports. Triggers: .icore file, icore format, Core IR JSON, icoreVersion, boundary ABI, layout, symbol export.

.icore Skill

Guide for the inauguration .icore JSON format — Core IR serialized as JSON, consumed by compiler::icore front.

Triggers

• Writing or reviewing .icore files
• in build --parser icore on .icore sources
• Core IR JSON structure questions
• Boundary ABI layouts and symbol exports
• icoreVersion, decls, boundary fields

File Extension

.icore — resolved by parser_registry.rs via extension map or #!in parser=icore magic line.

Format Reference

Minimal valid .icore

{
  "icoreVersion": 2,
  "decls": [
    {
      "kind": "function",
      "name": "main",
      "params": [],
      "return": "Void",
      "body": [
        { "kind": "return" }
      ]
    }
  ]
}

Top-level keys

Key	Type	Required	Description
icoreVersion	int	yes	Format version (2 = current, 3 = with boundary)
decls	array	yes	Declaration list, processed in order
boundary	object	no	ABI layout info (version 3 only)

Declaration kinds

Function

{
  "kind": "function",
  "name": "helper",
  "params": [],
  "return": "Int",
  "body": [
    { "kind": "return", "value": { "kind": "int", "value": 7 } }
  ]
}

Field	Type	Description
kind	string	"function"
name	string	Function symbol name
params	array	[{ "name": "p", "type": "Type" }] or []
return	string	Return type: "Int", "String", "Bool", "Void", named struct
body	array	Statement list (optional — empty/absent = declaration only)

Struct

{
  "kind": "struct",
  "name": "Point",
  "fields": [
    { "name": "x", "type": "Int" },
    { "name": "y", "type": "Int" }
  ]
}

Field	Type	Description
kind	string	"struct"
name	string	Struct type name
fields	array	[{ "name": "f", "type": "T" }]

Types

Type string	Meaning
"Int"	64-bit integer
"String"	String
"Bool"	Boolean
"Void"	No return
"Array"	Dynamic array
"Named"	Named struct (use struct name directly)

Statement kinds

Return

{ "kind": "return" }
{ "kind": "return", "value": { "kind": "int", "value": 42 } }

Let binding

{ "kind": "let", "name": "x", "value": { "kind": "int", "value": 10 } }

Assignment

{ "kind": "assign", "target": "x", "value": { "kind": "int", "value": 20 } }

If expression

{
  "kind": "if",
  "cond": { "kind": "binary", "op": "==", "left": { "kind": "ident", "name": "x" }, "right": { "kind": "int", "value": 0 } },
  "then": [ { "kind": "return", "value": { "kind": "int", "value": 1 } } ],
  "else": [ { "kind": "return", "value": { "kind": "int", "value": 0 } } ]
}

While loop

{
  "kind": "while",
  "cond": { "kind": "binary", "op": "<", "left": { "kind": "ident", "name": "i" }, "right": { "kind": "int", "value": 10 } },
  "body": [
    { "kind": "assign", "target": "i", "value": { "kind": "binary", "op": "+", "left": { "kind": "ident", "name": "i" }, "right": { "kind": "int", "value": 1 } } }
  ]
}

Expression statement

{ "kind": "expr", "value": { "kind": "call", "callee": "print", "args": [ { "kind": "string", "value": "hello" } ] } }

Expression kinds

Literals

{ "kind": "int", "value": 42 }
{ "kind": "string", "value": "hello" }
{ "kind": "bool", "value": true }
{ "kind": "null" }

Identifier

{ "kind": "ident", "name": "x" }

Binary operation

{ "kind": "binary", "op": "+", "left": { "kind": "ident", "name": "a" }, "right": { "kind": "ident", "name": "b" } }

Ops: +, -, *, /, %, &, |, ^, <<, >>, ==, !=, <, >, <=, >=, &&, ||

Call

{ "kind": "call", "callee": "function_name", "args": [ { "kind": "ident", "name": "x" } ] }

Struct init

{
  "kind": "struct_init",
  "name": "Point",
  "fields": [
    { "name": "x", "value": { "kind": "int", "value": 1 } },
    { "name": "y", "value": { "kind": "int", "value": 2 } }
  ]
}

Field access

{ "kind": "field", "object": { "kind": "ident", "name": "p" }, "field": "x" }

Array init

{ "kind": "array_init", "elements": [ { "kind": "int", "value": 1 }, { "kind": "int", "value": 2 } ] }

Array access

{ "kind": "array_access", "object": { "kind": "ident", "name": "a" }, "index": { "kind": "int", "value": 0 } }

Closure

{
  "kind": "closure",
  "params": [ { "name": "x", "type": "Int" } ],
  "return": "Int",
  "body": [ { "kind": "return", "value": { "kind": "ident", "name": "x" } } ]
}

Boundary (version 3)

{
  "icoreVersion": 3,
  "decls": [ ... ],
  "boundary": {
    "abi_version": 1,
    "module": "sample.person",
    "layouts": [
      {
        "name": "Person",
        "kind": "struct",
        "repr": "c",
        "size": 24,
        "align": 8,
        "stride": 24,
        "fields": [
          { "name": "name", "offset": 0, "type": "InSliceU8", "transfer": "borrow" },
          { "name": "age", "offset": 16, "type": "u32", "transfer": "copy" }
        ]
      }
    ],
    "symbols": [
      {
        "name": "person_new",
        "signature_hash": "person_new_v1",
        "ownership": "returns-owned-handle",
        "calling_convention": "c"
      }
    ],
    "allocators": [
      { "id": 1, "kind": "host_arena", "free_with": "host" }
    ]
  }
}

Layout entry

Field	Type	Description
name	string	Type name
kind	string	"struct"
repr	string	ABI representation: "c" for C layout
size	int	Size in bytes
align	int	Alignment in bytes
stride	int	Stride (including padding)
fields	array	Field layout entries

Field layout

Field	Type	Description
name	string	Field name
offset	int	Byte offset from struct start
type	string	ABI type: "InSliceU8", "u32", "u64", etc.
transfer	string	Ownership transfer: "borrow", "copy", "move"

Symbol entry

Field	Type	Description
name	string	Symbol name
signature_hash	string	Versioned signature hash
ownership	string	"returns-owned-handle", "borrows", etc.
calling_convention	string	"c", "rust", etc.

Allocator entry

Field	Type	Description
id	int	Allocator ID
kind	string	"host_arena", etc.
free_with	string	"host", "guest", etc.

Pipeline

.icore JSON → compiler::icore → UnifiedModule → family_typecheck → Core IR → SIL → bytecode → VM

Key files

File	Role
in-cli/src/compiler/icore.rs	.icore JSON parser
in-cli/src/core_ir.rs	Core IR data structures
in-cli/src/lower_core.rs	Core IR → textual SIL

See also

• agents/skills/in-lang/SKILL.md — .in source language
• docs/core-ir-extensions.md — classes, interfaces, closures, exceptions
• docs/multi-frontend-ir.md — UnifiedModule, parser resolution