Add an UNUSED_SHOWN_NAMES hint to the analyzer

pkg/analyzer/lib/src/generated/error.dart

Index: pkg/analyzer/lib/src/generated/error.dart
diff --git a/pkg/analyzer/lib/src/generated/error.dart b/pkg/analyzer/lib/src/generated/error.dart
index b6ae9c74d08c08293ce358594c0ac440a7db04b3..685788bfc6666287df6e5b0cad4f1150c7fd806f 100644
--- a/pkg/analyzer/lib/src/generated/error.dart
+++ b/pkg/analyzer/lib/src/generated/error.dart
@@ -2707,6 +2707,7 @@ abstract class ErrorCode {
     HintCode.UNUSED_CATCH_CLAUSE,
     HintCode.UNUSED_CATCH_STACK,
     HintCode.UNUSED_LOCAL_VARIABLE,
+    HintCode.UNUSED_SHOWN_NAME,
     HintCode.USE_OF_VOID_RESULT,
     HintCode.FILE_IMPORT_INSIDE_LIB_REFERENCES_FILE_OUTSIDE,
     HintCode.FILE_IMPORT_OUTSIDE_LIB_REFERENCES_FILE_INSIDE,
@@ -3779,6 +3780,12 @@ class HintCode extends ErrorCode {
       "The value of the local variable '{0}' is not used");
 
   /**
+   * Unused shown names are names shown on imports which are never used.
+   */
+  static const HintCode UNUSED_SHOWN_NAME =
+      const HintCode('UNUSED_SHOWN_NAME', "The name {0} is shown, but not used.");
+
+  /**
    * Hint for cases where the source expects a method or function to return a
    * non-void result, but the method or function signature returns void.
    *