在下面的代码片段中，两个代码块有什么区别？
如果我检查println(name==it)，则返回 true，因此它们必须引用同一个对象，对吗？
但是，当 name 变量有值时，一切正常，但是一旦我将其设置为 null，代码块 1 就可以工作（这意味着 let 块根本不会被执行），但代码块 2 会抛出错误。为什么 kotlin 不只是跳过/忽略 Codeblock 2，什么时候name为空？
fun main() {
var name:String? = "Cedric"
//name = null
//Codeblock 1
name?.let{
println("The length of name is ${name.length}")
}
//Codeblock 1
name?.let{
println("The length of name is ${it.length}")
}
}
非常感谢，任何帮助表示赞赏。
代码块 2 实际上给出了编译时错误，而代码块 1 没有。我认为这只是一个奇怪的 linting bug，因为这两种情况应该被同等对待。
据我了解，您在编译器中发现了错误。我在 Android Studio 和 IntelliJ 中有两种不同的行为。如果在编译时，编译后的代码会被优化，反编译时看起来像这样：
public final void main() {
Object name = "Cedric";
name = (String)null;
}
如果未编译，我会收到错误消息：
org.jetbrains.kotlin.codegen.CompilationException: Back-end (JVM) Internal error: Failed to generate expression: KtNameReferenceExpression
File being compiled: (12,45) in D:/Projekti/kotlin playground/src/Main.kt
The root cause java.lang.AssertionError was thrown at: org.jetbrains.kotlin.codegen.ExpressionCodegen.visitSimpleNameExpression(ExpressionCodegen.java:1797)
at org.jetbrains.kotlin.codegen.ExpressionCodegen.genQualified(ExpressionCodegen.java:326)
at org.jetbrains.kotlin.codegen.ExpressionCodegen.genQualified(ExpressionCodegen.java:286)
at org.jetbrains.kotlin.codegen.ExpressionCodegen.visitDotQualifiedExpression(ExpressionCodegen.java:3258)
at org.jetbrains.kotlin.codegen.ExpressionCodegen.visitDotQualifiedExpression(ExpressionCodegen.java:112)
at org.jetbrains.kotlin.psi.KtDotQualifiedExpression.accept(KtDotQualifiedExpression.kt:32)
at org.jetbrains.kotlin.codegen.CodegenStatementVisitor.visitKtElement(CodegenStatementVisitor.java:31)
at org.jetbrains.kotlin.codegen.CodegenStatementVisitor.visitKtElement(CodegenStatementVisitor.java:22)
at org.jetbrains.kotlin.psi.KtVisitor.visitExpression(KtVisitor.java:182)
at org.jetbrains.kotlin.psi.KtVisitor.visitQualifiedExpression(KtVisitor.java:286)
at org.jetbrains.kotlin.psi.KtVisitor.visitDotQualifiedExpression(KtVisitor.java:302)
at org.jetbrains.kotlin.psi.KtDotQualifiedExpression.accept(KtDotQualifiedExpression.kt:32)
at org.jetbrains.kotlin.codegen.ExpressionCodegen.genQualified(ExpressionCodegen.java:304)
at org.jetbrains.kotlin.codegen.ExpressionCodegen.genStatement(ExpressionCodegen.java:409)
at org.jetbrains.kotlin.codegen.ExpressionCodegen.gen(ExpressionCodegen.java:366)
at org.jetbrains.kotlin.codegen.ExpressionCodegen.invokeAppend(ExpressionCodegen.java:4108)
at org.jetbrains.kotlin.codegen.ExpressionCodegen.invokeAppendForEntries(ExpressionCodegen.java:874)
at org.jetbrains.kotlin.codegen.ExpressionCodegen.lambda$visitStringTemplateExpression$6(ExpressionCodegen.java:864)
at org.jetbrains.kotlin.codegen.OperationStackValue.putSelector(StackValue.kt:79)
at org.jetbrains.kotlin.codegen.StackValue.put(StackValue.java:122)
at org.jetbrains.kotlin.codegen.StackValue.put(StackValue.java:115)
at org.jetbrains.kotlin.codegen.CallGenerator$DefaultCallGenerator.genValueAndPut(CallGenerator.kt:71)
at org.jetbrains.kotlin.codegen.CallBasedArgumentGenerator.generateExpression(CallBasedArgumentGenerator.kt:42)
at org.jetbrains.kotlin.codegen.ArgumentGenerator.generate(ArgumentGenerator.kt:68)
at org.jetbrains.kotlin.codegen.ExpressionCodegen.invokeMethodWithArguments(ExpressionCodegen.java:2534)
at org.jetbrains.kotlin.codegen.ExpressionCodegen.invokeMethodWithArguments(ExpressionCodegen.java:2506)
at org.jetbrains.kotlin.codegen.Callable$invokeMethodWithArguments$1.invoke(Callable.kt:41)
at org.jetbrains.kotlin.codegen.Callable$invokeMethodWithArguments$1.invoke(Callable.kt:13)
at org.jetbrains.kotlin.codegen.OperationStackValue.putSelector(StackValue.kt:79)
at org.jetbrains.kotlin.codegen.StackValueWithLeaveTask.putSelector(StackValue.kt:67)
at org.jetbrains.kotlin.codegen.StackValue.put(StackValue.java:122)
at org.jetbrains.kotlin.codegen.StackValue.put(StackValue.java:115)
at org.jetbrains.kotlin.codegen.ExpressionCodegen.putStackValue(ExpressionCodegen.java:386)
at org.jetbrains.kotlin.codegen.ExpressionCodegen.gen(ExpressionCodegen.java:367)
at org.jetbrains.kotlin.codegen.ExpressionCodegen.returnExpression(ExpressionCodegen.java:1731)
at org.jetbrains.kotlin.codegen.FunctionGenerationStrategy$FunctionDefault.doGenerateBody(FunctionGenerationStrategy.java:64)
at org.jetbrains.kotlin.codegen.ClosureGenerationStrategy.doGenerateBody(ClosureGenerationStrategy.kt:35)
at org.jetbrains.kotlin.codegen.FunctionGenerationStrategy$CodegenBased.generateBody(FunctionGenerationStrategy.java:84)
at org.jetbrains.kotlin.codegen.FunctionCodegen.generateMethodBody(FunctionCodegen.java:654)
at org.jetbrains.kotlin.codegen.FunctionCodegen.generateMethodBody(FunctionCodegen.java:479)
at org.jetbrains.kotlin.codegen.FunctionCodegen.generateMethod(FunctionCodegen.java:261)
at org.jetbrains.kotlin.codegen.FunctionCodegen.generateMethod(FunctionCodegen.java:177)
at org.jetbrains.kotlin.codegen.ClosureCodegen.generateClosureBody(ClosureCodegen.java:181)
at org.jetbrains.kotlin.codegen.ClosureCodegen.generateBody(ClosureCodegen.java:169)
at org.jetbrains.kotlin.codegen.MemberCodegen.generate(MemberCodegen.java:129)
at org.jetbrains.kotlin.codegen.ExpressionCodegen.genClosure(ExpressionCodegen.java:1038)
at org.jetbrains.kotlin.codegen.ExpressionCodegen.genClosure(ExpressionCodegen.java:1008)
at org.jetbrains.kotlin.codegen.ExpressionCodegen.visitLambdaExpression(ExpressionCodegen.java:999)
at org.jetbrains.kotlin.codegen.ExpressionCodegen.visitLambdaExpression(ExpressionCodegen.java:112)
at org.jetbrains.kotlin.psi.KtLambdaExpression.accept(KtLambdaExpression.java:40)
at org.jetbrains.kotlin.codegen.ExpressionCodegen.genQualified(ExpressionCodegen.java:304)
at org.jetbrains.kotlin.codegen.ExpressionCodegen.genQualified(ExpressionCodegen.java:286)
at org.jetbrains.kotlin.codegen.ExpressionCodegen.gen(ExpressionCodegen.java:358)
at org.jetbrains.kotlin.codegen.CallGenerator$DefaultCallGenerator.genValueAndPut(CallGenerator.kt:70)
at org.jetbrains.kotlin.codegen.CallBasedArgumentGenerator.generateExpression(CallBasedArgumentGenerator.kt:42)
at org.jetbrains.kotlin.codegen.ArgumentGenerator.generate(ArgumentGenerator.kt:68)
at org.jetbrains.kotlin.codegen.ExpressionCodegen.invokeMethodWithArguments(ExpressionCodegen.java:2534)
at org.jetbrains.kotlin.codegen.ExpressionCodegen.invokeMethodWithArguments(ExpressionCodegen.java:2506)
at org.jetbrains.kotlin.codegen.Callable$invokeMethodWithArguments$1.invoke(Callable.kt:41)
at org.jetbrains.kotlin.codegen.Callable$invokeMethodWithArguments$1.invoke(Callable.kt:13)
at org.jetbrains.kotlin.codegen.OperationStackValue.putSelector(StackValue.kt:79)
at org.jetbrains.kotlin.codegen.CoercionValue.putSelector(StackValue.kt:31)
at org.jetbrains.kotlin.codegen.StackValue.put(StackValue.java:122)
at org.jetbrains.kotlin.codegen.StackValue.put(StackValue.java:115)
at org.jetbrains.kotlin.codegen.StackValue$StackValueWithSimpleReceiver.putReceiver(StackValue.java:2089)
at org.jetbrains.kotlin.codegen.StackValueWithLeaveTask.putReceiver(StackValue.kt:63)
at org.jetbrains.kotlin.codegen.StackValue.put(StackValue.java:120)
at org.jetbrains.kotlin.codegen.StackValue.put(StackValue.java:115)
at org.jetbrains.kotlin.codegen.ExpressionCodegen.putStackValue(ExpressionCodegen.java:386)
at org.jetbrains.kotlin.codegen.ExpressionCodegen.gen(ExpressionCodegen.java:367)
at org.jetbrains.kotlin.codegen.ExpressionCodegen.returnExpression(ExpressionCodegen.java:1731)
at org.jetbrains.kotlin.codegen.FunctionGenerationStrategy$FunctionDefault.doGenerateBody(FunctionGenerationStrategy.java:64)
at org.jetbrains.kotlin.codegen.FunctionGenerationStrategy$CodegenBased.generateBody(FunctionGenerationStrategy.java:84)
at org.jetbrains.kotlin.codegen.FunctionCodegen.generateMethodBody(FunctionCodegen.java:654)
at org.jetbrains.kotlin.codegen.FunctionCodegen.generateMethodBody(FunctionCodegen.java:479)
at org.jetbrains.kotlin.codegen.FunctionCodegen.generateMethod(FunctionCodegen.java:261)
at org.jetbrains.kotlin.codegen.FunctionCodegen.generateMethod(FunctionCodegen.java:177)
at org.jetbrains.kotlin.codegen.FunctionCodegen.gen(FunctionCodegen.java:148)
at org.jetbrains.kotlin.codegen.MemberCodegen.genSimpleMember(MemberCodegen.java:197)
at org.jetbrains.kotlin.codegen.PackagePartCodegen.generateBody(PackagePartCodegen.java:95)
at org.jetbrains.kotlin.codegen.MemberCodegen.generate(MemberCodegen.java:129)
at org.jetbrains.kotlin.codegen.PackageCodegenImpl.generateFile(PackageCodegenImpl.java:145)
at org.jetbrains.kotlin.codegen.PackageCodegenImpl.generate(PackageCodegenImpl.java:70)
at org.jetbrains.kotlin.codegen.DefaultCodegenFactory.generatePackage(CodegenFactory.kt:88)
at org.jetbrains.kotlin.codegen.DefaultCodegenFactory.generateModule(CodegenFactory.kt:67)
at org.jetbrains.kotlin.codegen.KotlinCodegenFacade.compileCorrectFiles(KotlinCodegenFacade.java:35)
at org.jetbrains.kotlin.idea.internal.KotlinBytecodeToolWindow$Companion.compileSingleFile(KotlinBytecodeToolWindow.kt:335)
at org.jetbrains.kotlin.idea.internal.KotlinBytecodeToolWindow$Companion.getBytecodeForFile(KotlinBytecodeToolWindow.kt:248)
at org.jetbrains.kotlin.idea.internal.KotlinBytecodeToolWindow$UpdateBytecodeToolWindowTask.processRequest(KotlinBytecodeToolWindow.kt:127)
at org.jetbrains.kotlin.idea.internal.KotlinBytecodeToolWindow$UpdateBytecodeToolWindowTask.processRequest(KotlinBytecodeToolWindow.kt:74)
at org.jetbrains.kotlin.idea.util.LongRunningReadTask$1$1.run(LongRunningReadTask.java:115)
at com.intellij.openapi.application.impl.ApplicationImpl.runReadAction(ApplicationImpl.java:869)
at org.jetbrains.kotlin.idea.util.LongRunningReadTask.lambda$runWithWriteActionPriority$0(LongRunningReadTask.java:235)
at com.intellij.openapi.progress.impl.CoreProgressManager.lambda$runProcess$2(CoreProgressManager.java:166)
at com.intellij.openapi.progress.impl.CoreProgressManager.registerIndicatorAndRun(CoreProgressManager.java:627)
at com.intellij.openapi.progress.impl.CoreProgressManager.executeProcessUnderProgress(CoreProgressManager.java:572)
at com.intellij.openapi.progress.impl.ProgressManagerImpl.executeProcessUnderProgress(ProgressManagerImpl.java:61)
at com.intellij.openapi.progress.impl.CoreProgressManager.runProcess(CoreProgressManager.java:153)
at org.jetbrains.kotlin.idea.util.LongRunningReadTask.runWithWriteActionPriority(LongRunningReadTask.java:235)
at org.jetbrains.kotlin.idea.util.LongRunningReadTask$1.run(LongRunningReadTask.java:110)
at com.intellij.util.RunnableCallable.call(RunnableCallable.java:20)
at com.intellij.util.RunnableCallable.call(RunnableCallable.java:11)
at com.intellij.openapi.application.impl.ApplicationImpl$1.call(ApplicationImpl.java:255)
at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
at java.base/java.lang.Thread.run(Thread.java:834)
Caused by: java.lang.AssertionError: Couldn't find descriptor for 'length'
at org.jetbrains.kotlin.codegen.ExpressionCodegen.visitSimpleNameExpression(ExpressionCodegen.java:1797)
at org.jetbrains.kotlin.codegen.ExpressionCodegen.visitSimpleNameExpression(ExpressionCodegen.java:112)
at org.jetbrains.kotlin.psi.KtNameReferenceExpression.accept(KtNameReferenceExpression.kt:59)
at org.jetbrains.kotlin.codegen.ExpressionCodegen.genQualified(ExpressionCodegen.java:304)
... 105 more
看起来编译器没有遵循代码的优化。因此，即使它应该或不应该编译，也有两种不同的行为，这意味着其中一种是不正确的。