Elm.TypeInference

Type inference for elm-syntax ASTs.

Optimized for lazy queries Range -> Maybe Type.

The process:

Convert elm.json and dependencies' elm.json + docs.json into DependencyEnv.
Load the Files into a Project.
(When it's clear you need it) Infer a module with inferModule, producing TypeLookupTable.
(When it's clear you need it) Get a Type for a given AST Node's Range with get.

dependencyEnv :

{ directDependencies : List PackageName

, allDependencies : List Dependency

, sourcesToResolveAmbiguity : Dict PackageName (List File)

}

-> DependencyEnvOutcome

Build a DependencyEnv.

Initially you can run with sourcesToResolveAmbiguity = Dict.empty. If you get NeedPackageSources back, read and parse those Elm files from the dependencies in your ELM_HOME (usually ~/.elm) and supply them in sourcesToResolveAmbiguity in the next call.

type DependencyEnvOutcome

= Ready DependencyEnv

| NeedPackageSources (Dict PackageName (List String))

| Failed Error

Possible outcomes of running dependencyEnv.

An example NeedPackageSources:

Dict.fromList
    [ ( "example/css", [ "src/Css/Internal.elm" ] ) ]

type DependencyEnv

Data parsed from dependencies' docs.json files.

This cache doesn't change as user's project code changes - only invalidate it and Project when elm.json changes.

type alias Dependency =

{ name : PackageName

, dependencies : List PackageName

, modules : List Module

}

Input to dependencyEnv.

A dependency package with its type information, parsed from the dependency's elm.json (via Elm.Project.decoder) and docs.json (via elm/project-metadata-utils Elm.Docs.decoder):

name: the package identifier (e.g. "elm/html").
dependencies: names of the package's immediate elm.json dependencies (eg. "elm/virtual-dom").
modules: the decoded docs.json modules.

project :

Maybe PackageName

-> DependencyEnv

-> Dict ModuleName File

-> Result Error Project

Analyze the import graph of the project source code, producing a Project.

type Project

An indexed project: every file has been assigned a ModuleId and its imports resolved, but nothing has been solved yet. Cheap to build.

inferModule : ModuleName -> Project -> ( Result Error TypeLookupTable, Project )

Infer types in the given module.

inferModules :

Dict ModuleName File