Don't eta expand in Pattern mode.

odersky · odersky · commit 1ee79345f45e · 2017-06-14T16:53:43.000+02:00
diff --git a/compiler/src/dotty/tools/dotc/typer/Typer.scala b/compiler/src/dotty/tools/dotc/typer/Typer.scala
@@ -2012,7 +2012,7 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
             else -1 // no eta expansion in this case
           }
 
-        if (arity >= 0 && !tree.symbol.isConstructor)
+        if (arity >= 0 && !tree.symbol.isConstructor && !ctx.mode.is(Mode.Pattern))
           typed(etaExpand(tree, wtp, arity), pt)
         else if (wtp.paramInfos.isEmpty)
           adaptInterpolated(tpd.Apply(tree, Nil), pt, EmptyTree)

Original file line number	Diff line number	Diff line change
`@@ -2012,7 +2012,7 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit`
`2012`	`2012`	`else -1 // no eta expansion in this case`
`2013`	`2013`	`}`
`2014`	`2014`
`2015`		`- if (arity >= 0 && !tree.symbol.isConstructor)`
	`2015`	`+ if (arity >= 0 && !tree.symbol.isConstructor && !ctx.mode.is(Mode.Pattern))`
`2016`	`2016`	`typed(etaExpand(tree, wtp, arity), pt)`
`2017`	`2017`	`else if (wtp.paramInfos.isEmpty)`
`2018`	`2018`	`adaptInterpolated(tpd.Apply(tree, Nil), pt, EmptyTree)`