Implement C interop foundation: AST, parser, and type system

[Copilot]

Implements the C interoperability foundation per docs/CINTEROP.md, enabling Shortcake to call C functions, declare C structs, and load C libraries.

Changes

AST Layer

• Added 6 node types: c_load, c_include, c_import, c_from_import, c_struct_decl, c_callback_reg
• Added corresponding data structures in extra union with helper methods
• Memory management in deinit() for new node types

Parser Layer (src/parser.zig)

• parseCStructDecl(): Parse $struct $Name do ... end with field declarations
• parseCType(): Parse C types ($int, $char*, $int[10])
• parseCFunctionCall(): Parse C function invocations
• parseCRegisterDecl(): Parse callback registration
• Dollar token handling in parseDeclaration() and parsePrimaryExpression()

Type System (src/c_types.zig)

• CPrimitiveType: 19 C primitive types with Shortcake/MLIR mappings
• CType: Union type supporting primitive, pointer, array, function pointer, struct, custom
• CTypeMapping: Parse C type strings, convert to Shortcake/MLIR types, compatibility checking

Codegen (src/codegen.zig)

• Integrated C interop into generateExpr() switch
• Placeholder MLIR generation for $load, $struct, C function calls
• mapCTypeToMLIR(): Type conversion helper

Tests & Examples

• 10 parser tests covering all C interop syntax
• 6 type system unit tests
• Example programs: c_math_example.sho, c_structs_example.sho

Example Usage

$load "libm.so"
$from <math.h> $import sin, cos, sqrt

$struct $Point do
  x: $int
  y: $int
end

fn main() do
  local result = $sqrt(16.0)
  $printf("Result: %f\n", result)
end

Scope

Parser and type system are complete. MLIR codegen and runtime (dlopen/dlsym, symbol registry, callbacks) deferred to future PRs.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• ziglang.org
  • Triggering command: curl -L REDACTED -o /tmp/zig.tar.xz (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Implement CInterop</issue_title>
<issue_description>Implement the module system in Shortcake. Following the plan from docs/CINTEROP.md</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Implement CInterop #3

---

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.