Show and test implicit conversions using SAM types.

Author: odersky

docs/docs/reference/contextual/conversions.md

@@ -14,6 +14,10 @@ implied for Conversion[String, Token] {
   def apply(str: String): Token = new KeyWord(str)
 }
 ```
+Using an implied alias this can be expressed more concisely as:
+```scala
+implied for Conversion[String, Token] = new KeyWord(_)
+```
 An implicit conversion is applied automatically by the compiler in three situations:
 
 1. If an expression `e` has type `T`, and `T` does not conform to the expression's expected type `S`.
@@ -33,9 +37,8 @@ If such an instance `C` is found, the expression `e` is replaced by `C.apply(e)`
 primitive number types to subclasses of `java.lang.Number`. For instance, the
 conversion from `Int` to `java.lang.Integer` can be defined as follows:
 ```scala
-implied int2Integer for Conversion[Int, java.lang.Integer] {
-  def apply(x: Int) = new java.lang.Integer(x)
-}
+implied int2Integer for Conversion[Int, java.lang.Integer] =
+  new java.lang.Integer(x)
 ```
 
 2. The "magnet" pattern is sometimes used to express many variants of a method. Instead of defining overloaded versions of the method, one can also let the method take one or more arguments of specially defined "magnet" types, into which various argument types can be converted. E.g.
@@ -56,15 +59,9 @@ object Completions {
     //
     //   CompletionArg.fromStatusCode(statusCode)
 
-    implied fromString for Conversion[String, CompletionArg] {
-      def apply(s: String) = CompletionArg.Error(s)
-    }
-    implied fromFuture for Conversion[Future[HttpResponse], CompletionArg] {
-      def apply(f: Future[HttpResponse]) = CompletionArg.Response(f)
-    }
-    implied fromStatusCode for Conversion[Future[StatusCode], CompletionArg] {
-      def apply(code: Future[StatusCode]) = CompletionArg.Status(code)
-    }
+    implied fromString for Conversion[String, CompletionArg] = Error(_)
+    implied fromFuture for Conversion[Future[HttpResponse], CompletionArg] = Response(_)
+    implied fromStatusCode for Conversion[Future[StatusCode], CompletionArg] = Status(_)
   }
   import CompletionArg._
 

tests/pos/reference/instances.scala

@@ -274,15 +274,9 @@ object Completions {
     //
     //   CompletionArg.from(statusCode)
 
-    implied fromString for Conversion[String, CompletionArg] {
-      def apply(s: String) = CompletionArg.Error(s)
-    }
-    implied fromFuture for Conversion[Future[HttpResponse], CompletionArg] {
-      def apply(f: Future[HttpResponse]) = CompletionArg.Response(f)
-    }
-    implied fromStatusCode for Conversion[Future[StatusCode], CompletionArg] {
-      def apply(code: Future[StatusCode]) = CompletionArg.Status(code)
-    }
+    implied fromString for Conversion[String, CompletionArg] = Error(_)
+    implied fromFuture for Conversion[Future[HttpResponse], CompletionArg] = Response(_)
+    implied fromStatusCode for Conversion[Future[StatusCode], CompletionArg] = Status(_)
   }
   import CompletionArg._