CODEWITHSUNDEEP
scalasuppress-warningsscala-macrosscala-quasiquotes
steinybot
steinybot

Reputation: 6104

How do I ignore unused warnings in quasiquotes?

I have a macro that is using quasiquotes like:

    accessor.tree match {
      // FIXME: Get rid of the unused warning here.
      case q"($source) => $rhs" => validate(rhs, hasSelect = false)
      case t                    => c.abort(c.enclosingPosition, s"Invalid function expression ${show(t)}")
    }

This gives me the following warnings:

[warn] /Users/jason/source/goodcover/core/macros/src/main/scala/webm/react/syntax/StableFieldOpsImpl.scala:36:12: pattern var qq$macro$1 in method unapply is never used: use a wildcard `_` or suppress this warning with `qq$macro$1@_`
[warn]       case q"($source) => $rhs" => validate(rhs, hasSelect = false)
[warn]            ^
[warn] /Users/jason/source/goodcover/core/macros/src/main/scala/webm/react/syntax/StableFieldOpsImpl.scala:36:16: pattern var source in method validateSelection is never used: use a wildcard `_` or suppress this warning with `source@_`
[warn]       case q"($source) => $rhs" => validate(rhs, hasSelect = false)
[warn]                ^
[warn] two warnings found

Using a wildcard doesn't work:

    accessor.tree match {
      // FIXME: Get rid of the unused warning here.
      case q"(_) => $rhs" => validate(rhs, hasSelect = false)
      case t              => c.abort(c.enclosingPosition, s"Invalid function expression ${show(t)}")
    }

That fails with:

[error] /Users/jason/source/goodcover/core/macros/src/main/scala/webm/react/syntax/StableFieldOpsImpl.scala:36:18: ';' expected but '=>' found.
[error]       case q"(_) => $rhs" => validate(rhs, hasSelect = false)
[error]                  ^
[error] /Users/jason/source/goodcover/core/macros/src/main/scala/webm/react/syntax/StableFieldOpsImpl.scala:36:12: extractor macros can only expand into extractor calls
[error]       case q"(_) => $rhs" => validate(rhs, hasSelect = false)
[error]            ^
[error] two errors found

I don't know what suppress this warning with `source@_` means.

If I take it literally as in:

    accessor.tree match {
      // FIXME: Get rid of the unused warning here.
      case q"(source@_) => $rhs" => validate(rhs, hasSelect = false)
      case t                     => c.abort(c.enclosingPosition, s"Invalid function expression ${show(t)}")
    }

Then I get:

[error] /Users/jason/source/goodcover/core/macros/src/main/scala/webm/react/syntax/StableFieldOpsImpl.scala:36:21: ')' expected but '@' found.
[error]       case q"(source@_) => $rhs" => validate(rhs, hasSelect = false)
[error]                     ^
[error] /Users/jason/source/goodcover/core/macros/src/main/scala/webm/react/syntax/StableFieldOpsImpl.scala:36:12: extractor macros can only expand into extractor calls
[error]       case q"(source@_) => $rhs" => validate(rhs, hasSelect = false)
[error]            ^
[error] two errors found

How do I ignore these warnings?

Upvotes: 0

Views: 291

Answers (1)

pishen
pishen

Reputation: 419

Not sure why but adding

scalacOptions += "-Ywarn-macros:after"

makes the warning disappeared in my case.

Upvotes: 0

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