Extract hints generation into a separte method and make is optional.

pkg/analyzer/lib/src/dart/analysis/analysis_impl.dart

 // Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import 'package:analyzer/context/declared_variables.dart';
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/error/error.dart';
 import 'package:analyzer/error/listener.dart';
 import 'package:analyzer/src/context/context.dart';
@@ skipping 72 matching lines @@
 
       _resolveDirectives(units);
 
       units.forEach((file, unit) {
         _resolveFile(file, unit);
       });
 
       _computeConstants();
 
       units.forEach((file, unit) {
-        {
-          var visitor = new GatherUsedLocalElementsVisitor(_libraryElement);
-          unit.accept(visitor);
-          _usedLocalElementsList.add(visitor.usedElements);
-        }
-        {
-          var visitor = new GatherUsedImportedElementsVisitor(_libraryElement);
-          unit.accept(visitor);
-          _usedImportedElementsList.add(visitor.usedElements);
-        }
+        _computeVerifyErrors(file, unit);
       });
 
-      units.forEach((file, unit) {
-        _computeVerifyErrorsAndHints(file, unit);
-      });
+      if (_analysisOptions.hint) {
+        units.forEach((file, unit) {
+          {
+            var visitor = new GatherUsedLocalElementsVisitor(_libraryElement);
+            unit.accept(visitor);
+            _usedLocalElementsList.add(visitor.usedElements);
+          }
+          {
+            var visitor =
+                new GatherUsedImportedElementsVisitor(_libraryElement);
+            unit.accept(visitor);
+            _usedImportedElementsList.add(visitor.usedElements);
+          }
+        });
+        units.forEach((file, unit) {
+          _computeHints(file, unit);
+        });
+      }
     } finally {
       _context.dispose();
     }
 
     // Return full results.
     Map<FileState, UnitAnalysisResult> results = {};
     units.forEach((file, unit) {
       List<AnalysisError> errors = _getErrorListener(file).errors;
       errors = _filterIgnoredErrors(file, errors);
       results[file] = new UnitAnalysisResult(file, unit, errors);
@@ skipping 17 matching lines @@
       nodeMap[constant] = node;
     }
 
     for (_ConstantNode node in nodes) {
       if (!node.isEvaluated) {
         new _ConstantWalker(evaluationEngine).walk(node);
       }
     }
   }
 
-  void _computeVerifyErrorsAndHints(FileState file, CompilationUnit unit) {
+  void _computeHints(FileState file, CompilationUnit unit) {
+    AnalysisErrorListener errorListener = _getErrorListener(file);
+    ErrorReporter errorReporter = _getErrorReporter(file);
+
+    unit.accept(
+        new DeadCodeVerifier(errorReporter, typeSystem: _context.typeSystem));
+
+    // Dart2js analysis.
+    if (_analysisOptions.dart2jsHint) {
+      unit.accept(new Dart2JSVerifier(errorReporter));
+    }
+
+    InheritanceManager inheritanceManager = new InheritanceManager(
+        _libraryElement,
+        includeAbstractFromSuperclasses: true);
+
+    unit.accept(new BestPracticesVerifier(
+        errorReporter, _typeProvider, _libraryElement, inheritanceManager,
+        typeSystem: _context.typeSystem));
+
+    unit.accept(new OverrideVerifier(errorReporter, inheritanceManager));
+
+    new ToDoFinder(errorReporter).findIn(unit);
+
+    // Verify imports.
+    {
+      ImportsVerifier verifier = new ImportsVerifier();
+      verifier.addImports(unit);
+      _usedImportedElementsList.forEach(verifier.removeUsedElements);
+      verifier.generateDuplicateImportHints(errorReporter);
+      verifier.generateUnusedImportHints(errorReporter);
+      verifier.generateUnusedShownNameHints(errorReporter);
+    }
+
+    // Unused local elements.
+    {
+      UsedLocalElements usedElements =
+          new UsedLocalElements.merge(_usedLocalElementsList);
+      UnusedLocalElementsVerifier visitor =
+          new UnusedLocalElementsVerifier(errorListener, usedElements);
+      unit.element.accept(visitor);
+    }
+  }
+
+  void _computeVerifyErrors(FileState file, CompilationUnit unit) {
     RecordingErrorListener errorListener = _getErrorListener(file);
     CompilationUnitElement unitElement = unit.element;
 
     //
     // Use the ErrorVerifier to compute errors.
     //
     List<PendingError> pendingErrors;
     {
       RequiredConstantsComputer computer =
           new RequiredConstantsComputer(file.source);
       unit.accept(computer);
       pendingErrors = computer.pendingErrors;
       List<ConstantEvaluationTarget> requiredConstants =
           computer.requiredConstants;
     }
 
     if (_analysisOptions.strongMode) {
       AnalysisOptionsImpl options = _analysisOptions as AnalysisOptionsImpl;
       CodeChecker checker = new CodeChecker(
           _typeProvider,
           new StrongTypeSystemImpl(_typeProvider,
               implicitCasts: options.implicitCasts,
               nonnullableTypes: options.nonnullableTypes),
           errorListener,
           options);
       checker.visitCompilationUnit(unit);
     }
 
-    var errorReporter = _getErrorReporter(file);
+    ErrorReporter errorReporter = _getErrorReporter(file);
 
     //
     // Validate the directives.
     //
     _validateUriBasedDirectives(file, unit);
 
     //
     // Use the ConstantVerifier to compute errors.
     //
     ConstantVerifier constantVerifier = new ConstantVerifier(
@@ skipping 10 matching lines @@
         new InheritanceManager(_libraryElement),
         _analysisOptions.enableSuperMixins);
     unit.accept(errorVerifier);
 
     //
     // Convert the pending errors into actual errors.
     //
     for (PendingError pendingError in pendingErrors) {
       errorListener.onError(pendingError.toAnalysisError());
     }
-
-    //
-    // Find dead code.
-    //
-    unit.accept(
-        new DeadCodeVerifier(errorReporter, typeSystem: _context.typeSystem));
-
-    // Dart2js analysis.
-    if (_analysisOptions.dart2jsHint) {
-      unit.accept(new Dart2JSVerifier(errorReporter));
-    }
-
-    InheritanceManager inheritanceManager = new InheritanceManager(
-        _libraryElement,
-        includeAbstractFromSuperclasses: true);
-
-    unit.accept(new BestPracticesVerifier(
-        errorReporter, _typeProvider, _libraryElement, inheritanceManager,
-        typeSystem: _context.typeSystem));
-
-    unit.accept(new OverrideVerifier(errorReporter, inheritanceManager));
-
-    new ToDoFinder(errorReporter).findIn(unit);
-
-    // Verify imports.
-    {
-      ImportsVerifier verifier = new ImportsVerifier();
-      verifier.addImports(unit);
-      _usedImportedElementsList.forEach(verifier.removeUsedElements);
-      ErrorReporter errorReporter = _getErrorReporter(file);
-      verifier.generateDuplicateImportHints(errorReporter);
-      verifier.generateUnusedImportHints(errorReporter);
-      verifier.generateUnusedShownNameHints(errorReporter);
-    }
-
-    {
-      GatherUsedLocalElementsVisitor visitor =
-          new GatherUsedLocalElementsVisitor(_libraryElement);
-      unit.accept(visitor);
-    }
-
-    // Unused local elements.
-    {
-      UsedLocalElements usedElements =
-          new UsedLocalElements.merge(_usedLocalElementsList);
-      UnusedLocalElementsVerifier visitor =
-          new UnusedLocalElementsVerifier(errorListener, usedElements);
-      unitElement.accept(visitor);
-    }
   }
 
   void _createAnalysisContext() {
     AnalysisContextImpl analysisContext =
         AnalysisEngine.instance.createAnalysisContext();
     analysisContext.analysisOptions = _analysisOptions;
     analysisContext.declaredVariables.addAll(_declaredVariables);
     analysisContext.sourceFactory = _sourceFactory.clone();
     analysisContext.contentCache = new _ContentCacheWrapper(_fsState);
     this._context = analysisContext;
@@ skipping 474 matching lines @@
 }
 
 /**
  * Either the name or the source associated with a part-of directive.
  */
 class _NameOrSource {
   final String name;
   final Source source;
   _NameOrSource(this.name, this.source);
 }