Implement linter options #15503
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itype:enhancement
Semester Project
Good project to be done by an MSc or strong Bsc computer science student in one semester
stat:taken
This project is already worked on by a student or as part of another volunteership program
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odersky
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itype:enhancement
Semester Project
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If this project is taken as a semester project, we would have to synchronize with the state when the project starts. reserving the project as a semester project should not hold up progress that could be made before. |
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Note that there is already a PR for unused imports: #14524 |
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Yes, @som-snytt what's the status on that? I notice it is still in draft state? |
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I can probably make some time to help with that one if needed. |
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I'll rebase |
odersky
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stat:taken
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Project reserved for Paul Cole. |
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See #15885 for another possible linter task. |
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szymon-rd
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Jan 9, 2023
…d support for unused imports (#16157) This PR, related to my **semester project** #15503 on adding **dotty's linter features**, adds the following: - [x] Add the `CheckUnused` front-end phase, which will check the the tree produced by the typer, for unused entites (imports, local defs, ...) - [x] Emit warning for `-Wunused:imports` including **given imports** and **wildcard imports** - [x] Emit warning for `-Wunused:locals` - [x] Emit warning for `-Wunused:privates` - [x] Emit warning for `-Wunused:params` - ~~Emit warning for `-Wunused:patvars`~~ - [x] Emit warning for `-Wunused:unsafe-warn-patvars` - [x] Emit warning for `-Wunused:linted` - [x] Add a simple _fatal-warning_ compilation-test suit - [x] _Fixes for the warning format_ - [x] Better help in CLI for `-Wunused` - [x] Add `-Wunused:givens` alias to `-Wunused:implicits` Here are a few examples: #### Unused Imports ```scala object Foo { import collection.mutable.{Set, Map} def main(args: Array[String]) = val bar = Set("this","set","is","used") println(s"Hello World: $bar") } ``` ``` sbt:scala3> scalac -Wunused:imports ../Foo.scala [...] -- Warning: ../scratch_files/Hello.scala:2:34 ---------------------------------- 2 | import collection.mutable.{Set, Map} | ^^^ | unused import 1 warning found ``` #### Unused local definitions ```scala class Foo { def bar = val a = 1 2 + 2 } ``` ``` sbt:scala3> scalac -Wunused:locals ../Foo.scala [...] -- Warning: ../scratch_files/MyHello.scala:3:8 --------------------------------- 3 | val a = 1 | ^^^^^^^^^ | unused local definition 1 warning found ``` #### Unused private members ```scala class Foo { private def a = 1 private def b = 2 def doSomething = b } ``` ``` sbt:scala3> scalac -Wunused:privates ../Foo.scala [...] -- Warning: ../scratch_files/MyHello.scala:2:14 -------------------------------- 2 | private def a = 1 | ^^^^^^^^^^^^^^^^^ | unused private member 1 warning found ``` #### Unused parameters ```scala def foo(a: String)(using Int) = bar ``` ``` sbt:scala3> scalac -Wunused:params ../scratch_files/Foo.scala [...] -- Warning: ../scratch_files/MyHello.scala:1:8 --------------------------------- 1 |def foo(a: String)(using Int) = bar | ^ | unused explicit parameter -- Warning: ../scratch_files/MyHello.scala:1:25 -------------------------------- 1 |def foo(a: String)(using Int) = bar | ^ | unused implicit parameter 2 warnings found ``` #### Unused pattern variables ```scala def foo(a: List[Int]) = a match case head :: tail => ??? case Nil => ??? ``` ``` sbt:scala3> scalac -Wunused:unsafe-warn-patvars ../scratch_files/Foo.scala [...] -- Warning: ../scratch_files/MyHello.scala:2:9 --------------------------------- 2 | case head :: tail => ??? | ^^^^ | unused pattern variable -- Warning: ../scratch_files/MyHello.scala:2:17 -------------------------------- 2 | case head :: tail => ??? | ^^^^ | unused pattern variable 2 warnings found ``` Please check the [test file](tests/neg-custom-args/fatal-warnings/i15503/i15503a.scala) for the handled cases. @odersky @anatoliykmetyuk
szymon-rd
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May 16, 2023
…7160) This PR is related to my Bachelor Semester Project, supervised by @anatoliykmetyuk. The latter consist in improving and implementing more Scala 3 linter options (see #15503), with #16639 as a starting issue fixed in this PR. - During the traversal in CheckUnused.scala (Miniphase & local TreeTraverser), when reaching an `Assign` case, symbols are collected as set, and then used to filter used locals and privates variable at reporting time. - Adapt test suit, and Add more test accordingly. - Note that for a same variable the unused warning always has priority and shadows the unset warning. That feature follows the Scala 2 `-Ywarn-unused:<args>` behavior.
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As of #16157 this is now implemented, so I'll go ahead and close! if there are any issues or specific follow-ups to this needed, please do create issues for them. |
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Scala 3 is currently missing several of Scala 2's linter options, including:
It would be great to add these.
We could also look out for other valuable options to add.
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