Update docs

Author: odersky

compiler/src/dotty/tools/dotc/transform/CacheAliasImplicits.scala

@@ -25,7 +25,7 @@ object CacheAliasImplicits {
 
 /** This phase ensures that the right hand side of parameterless alias implicits
  *  is cached. It applies to all alias implicits that have neither type parameters
- *  not a given clause. Example: The alias
+ *  nor a given clause. Example: The alias
  *
  *      implicit a for TC = rhs
  *

docs/docs/reference/contextual-implicit/relationship-implicits.md

@@ -41,20 +41,21 @@ Implicit instances can be mapped to combinations of implicit objects and implici
       implicit global for ExecutionContext = new ForkJoinContext()
       implicit config for Config = default.config
 
-      def ctx: Context
+      val ctx: Context
       implicit for Context = ctx
     ```
     would map to
     ```scala
-      private[this] var global$cache: ExecutionContext | Null = null
+      private[this] var global$_cache: ExecutionContext | Null = null
       final implicit def global: ExecutionContext = {
-        if (global$cache == null) global$cache = new ForkJoinContext()
-        global$cache
+        if (global$_cache == null) global$_cache = new ForkJoinContext()
+        global$_cache
       }
 
       final implicit val config: Config = default.config
 
-      final implicit def Context_repr = ctx
+      val ctx: Context
+      final implicit def Context_ev = ctx
     ```
 
 ### Anonymous Implicit Instances