content: /*
   * Copyright 2016 HuntBugs contributors
   * 
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   * 
   *     http://www.apache.org/licenses/LICENSE-2.0
   * 
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package one.util.huntbugs.detect;
  
  import java.util.Set;
  
  import com.strobel.assembler.metadata.MethodDefinition;
  import com.strobel.assembler.metadata.MethodReference;
  import com.strobel.decompiler.ast.AstCode;
  import com.strobel.decompiler.ast.Expression;
  
  import one.util.huntbugs.flow.Inf;
  import one.util.huntbugs.registry.MethodContext;
  import one.util.huntbugs.registry.anno.AstNodes;
  import one.util.huntbugs.registry.anno.AstVisitor;
  import one.util.huntbugs.registry.anno.WarningDefinition;
  import one.util.huntbugs.warning.Roles;
  
  /**
   * @author Tagir Valeev
   *
   */
  @WarningDefinition(category="Performance", name="StringConstructor", maxScore=50)
  @WarningDefinition(category="Performance", name="StringConstructorEmpty", maxScore=55)
  @WarningDefinition(category="RedundantCode", name="StringToString", maxScore=40)
  public class StringUsage {
      @AstVisitor(nodes=AstNodes.EXPRESSIONS)
      public void visit(Expression node, MethodContext mc, MethodDefinition md) {
          if(node.getCode() == AstCode.InitObject) {
              MethodReference mr = (MethodReference) node.getOperand();
              if(mr.getDeclaringType().getInternalName().equals("java/lang/String")) {
                  int priority = 0;
                  if(md.isTypeInitializer()) {
                      // Static field initializer: only one object is created
                      // not a big performance problem and probably intended
                      Set<Expression> usages = Inf.BACKLINK.findUsages(node);
                      if(usages.size() == 1 && usages.iterator().next().getCode() == AstCode.PutStatic) {
                          priority = 15;
                          node = usages.iterator().next();
                      }
                  }
                  if(mr.getSignature().equals("()V")) {
                      mc.report("StringConstructorEmpty", priority, node);
                  } else if(mr.getSignature().equals("(Ljava/lang/String;)V")) {
                      mc.report("StringConstructor", priority, node);
                  }
              }
          } else if(node.getCode() == AstCode.InvokeVirtual) {
              MethodReference mr = (MethodReference) node.getOperand();
              if(mr.getDeclaringType().getInternalName().equals("java/lang/String") && mr.getName().equals("toString")) {
                  mc.report("StringToString", 0, node.getArguments().get(0), Roles.CALLED_METHOD.create(mr));
              }
          }
      }
  }
  