Scala

Iulian Dragos

Overview

Static checker tool

Based on type-checked ASTs

Easy to use and write rules

Goals

Unify existing approaches in one platform

Easy to write rules

Easy to use other peoples rules

Reasonable performance

Good integrations

Abide

Rules are decoupled from the tool

rule packages

project-specific rules

Integrates with Sbt

planned: Maven, Eclipse

Examples Core package

Unused members

Vars that are never re-assigned

Renamed arguments with defaults

Akka

sender method called inside future

Architecture

Abide

abide-plugin

scalac

core rules

extra rules

project-specific

. . .

Use

addSbtPlugin("com.typesafe" % "sbt-abide" % "0.1.0")

libraryDependencies += "com.typesafe" %% "abide-core" % 0.1.0 % "abide"

libraryDependencies += "com.typesafe" %% "abide-extra" % 0.1.0 % "abide"

Project(...).dependsOn(rules % "abide")

Anatomy

Traversers

Fused: one-pass for all rules

Optimised: rules are filtered on what they match

Directives

Shared context between rules

compiler universe

user-defined mix-ins

Rules

val step = { case varDef @ q"$mods var $name : $tpt = $value" => nok(varDef.symbol, Warning(varDef)) case q"$rcv = $expr" => ok(rcv.symbol) }

quasi-quote

state helpers

Replace `var` with `val`

Rules

partial function Tree => Unit

collect keys that can do one transition

nok (not ok)

ok (stable state)

Rules existential rules (what weve seen)

scoping rules

helpers to maintain nesting

enter (no need for removing, handled by the library)

path rules

like scoping, but richer state checks

Coding a rule

For example..

Mutation inside iteration

Lets forbid mutating the underlying collection while iterating

for (x xs -= x }

ys foreach { case (k, v) => ys remove 1 }

for (p

Simplifying assumptions

purely syntactical matching (no points-to analysis)

name-based

xs map { x => xs -= x }

Lets code

Future

Next

SupressWarning support

Integrations: maven and IDEs

More rules

Contribute!

The value is in rules

Contribute to scala/scala-abide

..or write your own rule package

Acknowledgements

Nicolas Voirol (@samarion) did all the work during his internship at Typesafe Switzerland

Thank you