inferImplicit: narrow try...catch

Nested calls to `inferImplicit` have their own `try...catch`.

Author: Blaisorblade

compiler/src/dotty/tools/dotc/typer/Implicits.scala

@@ -840,13 +840,20 @@ trait Implicits { self: Typer =>
    *  !!! todo: catch potential cycles
    */
   def inferImplicit(pt: Type, argument: Tree, pos: Position)(implicit ctx: Context): SearchResult = track("inferImplicit") {
-    try {
       assert(ctx.phase.allowsImplicitSearch,
         if (argument.isEmpty) i"missing implicit parameter of type $pt after typer"
         else i"type error: ${argument.tpe} does not conform to $pt${err.whyNoMatchStr(argument.tpe, pt)}")
       trace(s"search implicit ${pt.show}, arg = ${argument.show}: ${argument.tpe.show}", implicits, show = true) {
         assert(!pt.isInstanceOf[ExprType])
-        val result = new ImplicitSearch(pt, argument, pos).bestImplicit(contextual = true)
+        val result =
+          try {
+            new ImplicitSearch(pt, argument, pos).bestImplicit(contextual = true)
+          } catch {
+            case ce: CyclicReference =>
+              ce.inImplicitSearch = true
+              throw ce
+          }
+
         result match {
           case result: SearchSuccess =>
             result.tstate.commit()
@@ -872,11 +879,6 @@ trait Implicits { self: Typer =>
             result
         }
       }
-    } catch {
-      case ce: CyclicReference =>
-        ce.inImplicitSearch = true
-        throw ce
-    }
   }
 
   /** An implicit search; parameters as in `inferImplicit` */