More section on changes

Author: odersky

docs/docs/reference/changed/implicit-resolution.md

@@ -0,0 +1,46 @@
+---
+layout: doc-page
+title: "Changes in Implicit Resolution"
+---
+
+Implicit resolution uses a new algorithm which caches implicit results
+more aggressively for perforance. There are also some changes that
+affect implicits on the language level.
+
+ 1. Types of implicit values and result types of implicit methods
+    must be explicitly declared. Excepted are only values in local blocks
+    where the type may still be inferred:
+
+        class C {
+
+          val ctx: Context = ...        // ok
+
+          /*!*/ implicit val x = ...    // error: type must be given explicitly
+
+          /*!*/ next(): Context = ...   // error: type must be given explicitly
+
+          val y = {
+            implicit val ctx = this.ctx // ok
+            ...
+          }
+
+ 2. Implicit parameters may not have singleton types.
+
+        /*!*/ def f(implicit x: y.type) // error `y.type` not allowed as type of implicit
+
+ 3. Nesting is now taken into account for selecting an implicit.
+    Consider for instance the following scenario
+
+        def f(implicit i: C) = {
+          def g(implicit j: C) = {
+            implicitly[C]
+          }
+        }
+
+    This will now resolve the `implicitly` call to `j`, because `j` is nested
+    more deeply than `i`. Previously, this would have resulted in an
+    ambiguity error.
+
+[//] # todo: expand with precise rules
+
+

docs/docs/reference/changed/type-checking.md

@@ -0,0 +1,6 @@
+---
+layout: doc-page
+title: "Changes in Type Checking"
+---
+
+[//] # todo: fill in

docs/docs/reference/changed/type-inference.md

@@ -0,0 +1,7 @@
+---
+layout: doc-page
+title: "Changes in Type Inference"
+---
+
+[//] # todo: fill in
+

docs/sidebar.yml

@@ -27,7 +27,7 @@ sidebar:
           url: docs/reference/multiversal-equality.html
         - title: Inline
           url: docs/reference/inline.html
-        - title: Smaller Changes
+        - title: Smaller Additions
           subsection:
             - title: By-Name Implicits
               url: docs/reference/implicit-by-name-parameters.html
@@ -41,6 +41,12 @@ sidebar:
               url: docs/reference/changed/lazy-vals.md
             - title: Structural Types
               url: docs/reference/changed/structural-types.md
+            - title: Type Checking
+              url: docs/reference/changed/type-checking.md
+            - title: Type Inference
+              url: docs/reference/changed/type-inference.md
+            - title: Implicit Resolution
+              url: docs/reference/changed/implicit-resolution.md
         - title: Dropped Features
           subsection:
             - title: DelayedInit