perf: fix polynomial decoding induced by `#import`s

Motivation and Context

Related issue: #2153

Related slack thread: https://tezos-dev.slack.com/archives/C04EM6W78A0/p1710346643230689

Currently we have the following build process:

• The build system builds each file independently (ordered topologically based on the dep graph)
• The preprocessor expands #import "<file>" "<name>" to module <name> = Mangled_module_<file>
• The build system links modules by defining module Mangled_module_<file> = struct <file contents> end as a 'header', creating a single large Ast_typed module

For every module <name> = Mangled_module_<file>, the type checker has to encode the signature of <file> to be added into the Context and then must decode the signature of <file> from the typer's IR signature to Ast_typed.signature.

The problem is that module aliases are by default public, meaning that the signature of the #import is exported. This can result in nasty polynomial behaviour in larger projects where files are nested by depth d and have common / repeated imports: O(N^d L) where N is the number of files in the project and L is the upper bound on lengths of signatures

Description

The fix is to:

• Adding a D_import declaration to Ast_core.declaration
• Modifying the nanopasses to transpile:
  • JsLIGO: import = <Mangled_module> ~> D_import (Name, Mangled_module)
  • CameLIGO module = <Mangled_module> ~> D_import (Name, Mangled_module)
• The type checker will type the import just like a module, but it won't add the alias to the signature of the module nor will it need the decode the signature of the Mangled_module
• Add a linking phase to the build system that converts imports to module aliases

This is a breaking change on the current behaviour (imports are exported by default). To mitigate this, imports can be exported:

(* cameligo *)
[@public]
#import "foobar.mligo" "Foobar"

// jsligo
export #import "foobar.jsligo" "Foobar"

For reviewers: I've tried to mostly split commits by:

• compiler changes
• lsp changes
• test changes

Once approved, I'll squash and merge :)

Component

• compiler
• website
• webide
• vscode-plugin
• debugger

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Performance improvement (non-breaking change that improves performance)
• None (change with no changelog)

Changelog

perf!: fix polynomial decoding induced by #imports

Checklist:

• If a new syntax has been introduced, put a message on slack ligo-lsp
• Changes follow the existing coding style (use dune @fmt to check).
• Tests for the changes have been added (for bug fixes / feature).
• Documentation has been updated.
• Changelog description has been added (if appropriate).
• Start titles under ## Changelog section with #### (if appropriate).
• There is no image or uploaded file in changelog
• Examples in changed behaviour have been added to the changelog (for breaking change / feature).