Report HintCode.UNUSED_LOCAL_VARIABLE for local variables whose value is never used.

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

Index: pkg/analyzer/lib/src/generated/element.dart
diff --git a/pkg/analyzer/lib/src/generated/element.dart b/pkg/analyzer/lib/src/generated/element.dart
index 7962858113fac3e11d9dcab10b0b13aacef82c9a..5c3d4d035fe1cdbb7858196d3b270a35bfc50e14 100644
--- a/pkg/analyzer/lib/src/generated/element.dart
+++ b/pkg/analyzer/lib/src/generated/element.dart
@@ -8275,6 +8275,9 @@ class LocalVariableElementImpl extends VariableElementImpl implements LocalVaria
   @override
   bool get isPotentiallyMutatedInScope => hasModifier(Modifier.POTENTIALLY_MUTATED_IN_SCOPE);
 
+  @override
+  bool get isUsed => hasModifier(Modifier.IS_USED_VARIABLE);
+
   /**
    * Specifies that this variable is potentially mutated somewhere in closure.
    */
@@ -8290,6 +8293,13 @@ class LocalVariableElementImpl extends VariableElementImpl implements LocalVaria
   }
 
   /**
+   * Specifies that the value of this variable is used.
+   */
+  void markUsed() {
+    setModifier(Modifier.IS_USED_VARIABLE, true);
+  }
+
+  /**
    * Set the toolkit specific information objects attached to this variable.
    *
    * @param toolkitObjects the toolkit objects attached to this variable
@@ -8750,47 +8760,52 @@ class Modifier extends Enum<Modifier> {
   static const Modifier HAS_EXT_URI = const Modifier('HAS_EXT_URI', 9);
 
   /**
+   * Indicates that the value of a variable is used - read or invoked.
+   */
+  static const Modifier IS_USED_VARIABLE = const Modifier('IS_USED_VARIABLE', 10);
+
+  /**
    * Indicates that a class can validly be used as a mixin.
    */
-  static const Modifier MIXIN = const Modifier('MIXIN', 10);
+  static const Modifier MIXIN = const Modifier('MIXIN', 11);
 
   /**
    * Indicates that the value of a parameter or local variable might be mutated within the context.
    */
-  static const Modifier POTENTIALLY_MUTATED_IN_CONTEXT = const Modifier('POTENTIALLY_MUTATED_IN_CONTEXT', 11);
+  static const Modifier POTENTIALLY_MUTATED_IN_CONTEXT = const Modifier('POTENTIALLY_MUTATED_IN_CONTEXT', 12);
 
   /**
    * Indicates that the value of a parameter or local variable might be mutated within the scope.
    */
-  static const Modifier POTENTIALLY_MUTATED_IN_SCOPE = const Modifier('POTENTIALLY_MUTATED_IN_SCOPE', 12);
+  static const Modifier POTENTIALLY_MUTATED_IN_SCOPE = const Modifier('POTENTIALLY_MUTATED_IN_SCOPE', 13);
 
   /**
    * Indicates that a class contains an explicit reference to 'super'.
    */
-  static const Modifier REFERENCES_SUPER = const Modifier('REFERENCES_SUPER', 13);
+  static const Modifier REFERENCES_SUPER = const Modifier('REFERENCES_SUPER', 14);
 
   /**
    * Indicates that the pseudo-modifier 'set' was applied to the element.
    */
-  static const Modifier SETTER = const Modifier('SETTER', 14);
+  static const Modifier SETTER = const Modifier('SETTER', 15);
 
   /**
    * Indicates that the modifier 'static' was applied to the element.
    */
-  static const Modifier STATIC = const Modifier('STATIC', 15);
+  static const Modifier STATIC = const Modifier('STATIC', 16);
 
   /**
    * Indicates that the element does not appear in the source code but was implicitly created. For
    * example, if a class does not define any constructors, an implicit zero-argument constructor
    * will be created and it will be marked as being synthetic.
    */
-  static const Modifier SYNTHETIC = const Modifier('SYNTHETIC', 16);
+  static const Modifier SYNTHETIC = const Modifier('SYNTHETIC', 17);
 
   /**
    * Indicates that a class was defined using an alias. TODO(brianwilkerson) This should be renamed
    * to 'ALIAS'.
    */
-  static const Modifier TYPEDEF = const Modifier('TYPEDEF', 17);
+  static const Modifier TYPEDEF = const Modifier('TYPEDEF', 18);
 
   static const List<Modifier> values = const [
       ABSTRACT,
@@ -8803,6 +8818,7 @@ class Modifier extends Enum<Modifier> {
       GENERATOR,
       GETTER,
       HAS_EXT_URI,
+      IS_USED_VARIABLE,
       MIXIN,
       POTENTIALLY_MUTATED_IN_CONTEXT,
       POTENTIALLY_MUTATED_IN_SCOPE,
@@ -11585,6 +11601,14 @@ abstract class VariableElementImpl extends ElementImpl implements VariableElemen
   bool get isFinal => hasModifier(Modifier.FINAL);
 
   /**
+   * Return `true` if this variable is used (i.e. purely read or invoked)
+   * somewhere in its scope. This information is only available for local
+   * variables (including parameters) and only after the compilation unit
+   * containing the variable has been resolved.
+   */
+  bool get isUsed => false;
+
+  /**
    * Return `true` if this variable is potentially mutated somewhere in a closure. This
    * information is only available for local variables (including parameters) and only after the
    * compilation unit containing the variable has been resolved.