Fix 56 hints in pkg/compiler

pkg/compiler/lib/src/compiler.dart

Index: pkg/compiler/lib/src/compiler.dart
diff --git a/pkg/compiler/lib/src/compiler.dart b/pkg/compiler/lib/src/compiler.dart
index 6d8b6d0bee49ea805822bed401e8143ebc228862..8046c5b9642602cbbee9dfb6e16ffa05e849ea80 100644
--- a/pkg/compiler/lib/src/compiler.dart
+++ b/pkg/compiler/lib/src/compiler.dart
@@ -909,7 +909,7 @@ abstract class Compiler implements DiagnosticListener {
       }
       hasCrashed = true;
       rethrow;
-    } on StackOverflowError catch (ex) {
+    } on StackOverflowError {
       // We cannot report anything useful in this case, because we
       // do not have enough stack space.
       rethrow;
@@ -1763,9 +1763,7 @@ abstract class Compiler implements DiagnosticListener {
         resolved.remove(e);
       }
       if (identical(e.kind, ElementKind.GENERATIVE_CONSTRUCTOR)) {
-        ClassElement enclosingClass = e.enclosingClass;
         resolved.remove(e);
-
       }
       if (backend.isBackendLibrary(e.library)) {
         resolved.remove(e);
@@ -1901,7 +1899,6 @@ abstract class Compiler implements DiagnosticListener {
   void reportAssertionFailure(SpannableAssertionFailure ex) {
     String message = (ex.message != null) ? tryToString(ex.message)
                                           : tryToString(ex);
-    SourceSpan span = spanFromSpannable(ex.node);
     reportDiagnosticInternal(
         ex.node, MessageKind.GENERIC, {'text': message}, api.Diagnostic.CRASH);
   }