Reset constraint when one of several implicit arguments is not found.

odersky · odersky · commit df53e4da02b7 · 2015-12-05T18:21:20.000+01:00
diff --git a/src/dotty/tools/dotc/typer/Typer.scala b/src/dotty/tools/dotc/typer/Typer.scala
@@ -1415,7 +1415,13 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
                 implicitArgError(d"no implicit argument of type $formal found for $where" + failure.postscript)
             }
           }
-          if (args.exists(_.isEmpty)) { assert(constr eq ctx.typerState.constraint); tree }
+          if (args.exists(_.isEmpty)) {
+            // If there are several arguments, some arguments might already
+            // have influenced the context, binfing variables, but later ones
+            // might fail. In that case the constraint needs to be reset.
+            ctx.typerState.constraint = constr
+            tree
+          }
           else adapt(tpd.Apply(tree, args), pt)
         }
         if ((pt eq WildcardType) || original.isEmpty) addImplicitArgs

Original file line number	Diff line number	Diff line change
`@@ -1415,7 +1415,13 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit`
`1415`	`1415`	`implicitArgError(d"no implicit argument of type $formal found for $where" + failure.postscript)`
`1416`	`1416`	`}`
`1417`	`1417`	`}`
`1418`		`- if (args.exists(_.isEmpty)) { assert(constr eq ctx.typerState.constraint); tree }`
	`1418`	`+ if (args.exists(_.isEmpty)) {`
	`1419`	`+ // If there are several arguments, some arguments might already`
	`1420`	`+ // have influenced the context, binfing variables, but later ones`
	`1421`	`+ // might fail. In that case the constraint needs to be reset.`
	`1422`	`+ ctx.typerState.constraint = constr`
	`1423`	`+ tree`
	`1424`	`+ }`
`1419`	`1425`	`else adapt(tpd.Apply(tree, args), pt)`
`1420`	`1426`	`}`
`1421`	`1427`	`if ((pt eq WildcardType) \|\| original.isEmpty) addImplicitArgs`