Adding a custom record constructor prevents successful compilation

[andreaskornstaedt]

**GWT version: 2.12.1
**Browser (with version): any
**Operating System: any

---

Description

A custom record constructor prevents successful compilation even if never invoked

         Compiling 1 permutation
            Compiling permutation 0...
            [ERROR] An internal compiler exception occurred
com.google.gwt.dev.jjs.InternalCompilerException: Unexpected error during visit.
	at com.google.gwt.dev.jjs.ast.JVisitor.translateException(JVisitor.java:111)
	at com.google.gwt.dev.jjs.ast.JVisitor.accept(JVisitor.java:130)
	at com.google.gwt.dev.jjs.ast.JVisitor.accept(JVisitor.java:122)
	at com.google.gwt.dev.jjs.ast.JTransformer.transform(JTransformer.java:1100)
	at com.google.gwt.dev.jjs.impl.GenerateJavaScriptAST$GenerateJavaScriptTransformer.transform(GenerateJavaScriptAST.java:2659)
	at com.google.gwt.dev.jjs.impl.GenerateJavaScriptAST$GenerateJavaScriptTransformer.transformDeclarationStatement(GenerateJavaScriptAST.java:686)
	at com.google.gwt.dev.jjs.impl.GenerateJavaScriptAST$GenerateJavaScriptTransformer.transformDeclarationStatement(GenerateJavaScriptAST.java:520)
	at com.google.gwt.dev.jjs.ast.JTransformer$JRewriterVisitor.visit(JTransformer.java:725)
	at com.google.gwt.dev.jjs.ast.JDeclarationStatement.traverse(JDeclarationStatement.java:46)
	at com.google.gwt.dev.jjs.ast.JVisitor.accept(JVisitor.java:127)
	at com.google.gwt.dev.jjs.ast.JVisitor.accept(JVisitor.java:122)
	at com.google.gwt.dev.jjs.ast.JTransformer.transform(JTransformer.java:1100)
	at com.google.gwt.dev.jjs.ast.JTransformer.transformIntoExcludingNulls(JTransformer.java:1120)
	at com.google.gwt.dev.jjs.impl.GenerateJavaScriptAST$GenerateJavaScriptTransformer.transformBlock(GenerateJavaScriptAST.java:583)
	at com.google.gwt.dev.jjs.impl.GenerateJavaScriptAST$GenerateJavaScriptTransformer.transformBlock(GenerateJavaScriptAST.java:520)
	at com.google.gwt.dev.jjs.ast.JTransformer$JRewriterVisitor.visit(JTransformer.java:647)
	at com.google.gwt.dev.jjs.ast.JBlock.traverse(JBlock.java:93)
	at com.google.gwt.dev.jjs.ast.JVisitor.accept(JVisitor.java:127)
	at com.google.gwt.dev.jjs.ast.JVisitor.accept(JVisitor.java:122)
	at com.google.gwt.dev.jjs.ast.JTransformer.transform(JTransformer.java:1100)
	at com.google.gwt.dev.jjs.impl.GenerateJavaScriptAST$GenerateJavaScriptTransformer.transform(GenerateJavaScriptAST.java:2672)
	at com.google.gwt.dev.jjs.impl.GenerateJavaScriptAST$GenerateJavaScriptTransformer.transformMethodBody(GenerateJavaScriptAST.java:833)
	at com.google.gwt.dev.jjs.impl.GenerateJavaScriptAST$GenerateJavaScriptTransformer.transformMethodBody(GenerateJavaScriptAST.java:520)
	at com.google.gwt.dev.jjs.ast.JTransformer$JRewriterVisitor.visit(JTransformer.java:854)
	at com.google.gwt.dev.jjs.ast.JMethodBody.traverse(JMethodBody.java:81)
	at com.google.gwt.dev.jjs.ast.JVisitor.accept(JVisitor.java:127)
	at com.google.gwt.dev.jjs.ast.JVisitor.accept(JVisitor.java:122)
	at com.google.gwt.dev.jjs.ast.JTransformer.transform(JTransformer.java:1100)
	at com.google.gwt.dev.jjs.impl.GenerateJavaScriptAST$GenerateJavaScriptTransformer.transformMethod(GenerateJavaScriptAST.java:804)
	at com.google.gwt.dev.jjs.impl.GenerateJavaScriptAST$GenerateJavaScriptTransformer.generatePrototypeDefinitions(GenerateJavaScriptAST.java:2474)
	at com.google.gwt.dev.jjs.impl.GenerateJavaScriptAST$GenerateJavaScriptTransformer.generateTypeSetup(GenerateJavaScriptAST.java:1951)
	at com.google.gwt.dev.jjs.impl.GenerateJavaScriptAST$GenerateJavaScriptTransformer.transformDeclaredType(GenerateJavaScriptAST.java:649)
	at com.google.gwt.dev.jjs.impl.GenerateJavaScriptAST$GenerateJavaScriptTransformer.transformDeclaredType(GenerateJavaScriptAST.java:520)
	at com.google.gwt.dev.jjs.ast.JTransformer.transformClassType(JTransformer.java:95)
	at com.google.gwt.dev.jjs.ast.JTransformer$JRewriterVisitor.visit(JTransformer.java:695)
	at com.google.gwt.dev.jjs.ast.JClassType.traverse(JClassType.java:145)
	at com.google.gwt.dev.jjs.ast.JVisitor.accept(JVisitor.java:127)
	at com.google.gwt.dev.jjs.ast.JVisitor.accept(JVisitor.java:122)
	at com.google.gwt.dev.jjs.ast.JTransformer.transform(JTransformer.java:1100)
	at com.google.gwt.dev.jjs.impl.GenerateJavaScriptAST$GenerateJavaScriptTransformer.transformProgram(GenerateJavaScriptAST.java:1242)
	at com.google.gwt.dev.jjs.impl.GenerateJavaScriptAST$GenerateJavaScriptTransformer.transformProgram(GenerateJavaScriptAST.java:520)
	at com.google.gwt.dev.jjs.ast.JTransformer$JRewriterVisitor.visit(JTransformer.java:943)
	at com.google.gwt.dev.jjs.ast.JProgram.traverse(JProgram.java:1248)
	at com.google.gwt.dev.jjs.ast.JVisitor.accept(JVisitor.java:127)
	at com.google.gwt.dev.jjs.ast.JVisitor.accept(JVisitor.java:122)
	at com.google.gwt.dev.jjs.ast.JTransformer.transform(JTransformer.java:1100)
	at com.google.gwt.dev.jjs.impl.GenerateJavaScriptAST.execImpl(GenerateJavaScriptAST.java:3171)
	at com.google.gwt.dev.jjs.impl.GenerateJavaScriptAST.exec(GenerateJavaScriptAST.java:2944)
	at com.google.gwt.dev.jjs.JavaToJavaScriptCompiler.compilePermutation(JavaToJavaScriptCompiler.java:380)
	at com.google.gwt.dev.jjs.JavaToJavaScriptCompiler.compilePermutation(JavaToJavaScriptCompiler.java:274)
	at com.google.gwt.dev.CompilePerms.compile(CompilePerms.java:198)
	at com.google.gwt.dev.ThreadedPermutationWorkerFactory$ThreadedPermutationWorker.compile(ThreadedPermutationWorkerFactory.java:50)
	at com.google.gwt.dev.PermutationWorkerFactory$Manager$WorkerThread.run(PermutationWorkerFactory.java:74)
	at java.base/java.lang.Thread.run(Thread.java:1583)
Caused by: java.lang.NullPointerException: Cannot invoke "String.isEmpty()" because "actualJsName" is null
	at com.google.gwt.dev.jjs.ast.JMethod.getQualifiedJsName(JMethod.java:172)
	at com.google.gwt.dev.jjs.impl.GenerateJavaScriptAST$GenerateJavaScriptTransformer.transformNewInstance(GenerateJavaScriptAST.java:1002)
	at com.google.gwt.dev.jjs.impl.GenerateJavaScriptAST$GenerateJavaScriptTransformer.transformNewInstance(GenerateJavaScriptAST.java:520)
	at com.google.gwt.dev.jjs.ast.JTransformer$JRewriterVisitor.visit(JTransformer.java:884)
	at com.google.gwt.dev.jjs.ast.JNewInstance.traverse(JNewInstance.java:73)
	at com.google.gwt.dev.jjs.ast.JVisitor.accept(JVisitor.java:127)
	... 52 more
               [ERROR] at Intro.java(36): new Rec("1")
                  com.google.gwt.dev.jjs.ast.JNewInstance
               [ERROR] at Intro.java(36): Rec r = new Rec("1")
                  com.google.gwt.dev.jjs.ast.JDeclarationStatement
               [ERROR] at Intro.java(33): {
  Rec r = new Rec("1");
  Window.alert(r.toString());
}
                  com.google.gwt.dev.jjs.ast.JBlock
               [ERROR] at Intro.java(33): {
  Rec r = new Rec("1");
  Window.alert(r.toString());
}
                  com.google.gwt.dev.jjs.ast.JMethodBody
               [ERROR] at Intro.java(22): co.intro.client.Intro (extends Object implements EntryPoint)
                  com.google.gwt.dev.jjs.ast.JClassType
               [ERROR] at Unknown(0): <JProgram>
                  com.google.gwt.dev.jjs.ast.JProgram
            [ERROR] Unrecoverable exception, shutting down
com.google.gwt.core.ext.UnableToCompleteException: (see previous log entries)
	at com.google.gwt.dev.javac.CompilationProblemReporter.logAndTranslateException(CompilationProblemReporter.java:106)
	at com.google.gwt.dev.jjs.JavaToJavaScriptCompiler.compilePermutation(JavaToJavaScriptCompiler.java:461)
	at com.google.gwt.dev.jjs.JavaToJavaScriptCompiler.compilePermutation(JavaToJavaScriptCompiler.java:274)
	at com.google.gwt.dev.CompilePerms.compile(CompilePerms.java:198)
	at com.google.gwt.dev.ThreadedPermutationWorkerFactory$ThreadedPermutationWorker.compile(ThreadedPermutationWorkerFactory.java:50)
	at com.google.gwt.dev.PermutationWorkerFactory$Manager$WorkerThread.run(PermutationWorkerFactory.java:74)
	at java.base/java.lang.Thread.run(Thread.java:1583)
            [ERROR] Not all permutation were compiled , completed (0/1)
      [WARN] recompile failed
      [WARN] continuing to serve previous version

Steps to reproduce

public record Rec(String s) {
	public Rec(int i) {
		this("" + i);
	}
}

invoked like this

public void onModuleLoad() {
	Rec r = new Rec("1");
	Window.alert(r.toString());
}

Known workarounds

Don't use custom constructors

Links to further discussions

[niloc132]

Workaround:
Declare the default constructor. In this example, that would look like:

public record Rec(String s) {
        public Rec { }
	public Rec(int i) {
		this("" + i);
	}
}

Two stack traces I've identified that can come from this bug - this looks like the one reported:

Caused by: java.lang.NullPointerException: Cannot invoke "String.isEmpty()" because "actualJsName" is null
	at com.google.gwt.dev.jjs.ast.JMethod.getQualifiedJsName(JMethod.java:172)
	at com.google.gwt.dev.jjs.impl.GenerateJavaScriptAST$GenerateJavaScriptTransformer.transformNewInstance(GenerateJavaScriptAST.java:1002)
	at com.google.gwt.dev.jjs.impl.GenerateJavaScriptAST$GenerateJavaScriptTransformer.transformNewInstance(GenerateJavaScriptAST.java:520)
	at com.google.gwt.dev.jjs.ast.JTransformer$JRewriterVisitor.visit(JTransformer.java:884)
	at com.google.gwt.dev.jjs.ast.JNewInstance.traverse(JNewInstance.java:73)
	at com.google.gwt.dev.jjs.ast.JVisitor.accept(JVisitor.java:127)
	... 52 more

And another that is similar, but not quite the same:

Caused by: java.lang.NullPointerException: Cannot invoke "String.isEmpty()" because "actualJsName" is null
	at com.google.gwt.dev.jjs.ast.JMethod.getQualifiedJsName(JMethod.java:172)
	at com.google.gwt.dev.jjs.impl.GenerateJavaScriptAST$GenerateJavaScriptTransformer.dispatchToSuper(GenerateJavaScriptAST.java:920)
	at com.google.gwt.dev.jjs.impl.GenerateJavaScriptAST$GenerateJavaScriptTransformer.transformMethodCall(GenerateJavaScriptAST.java:898)
	at com.google.gwt.dev.jjs.impl.GenerateJavaScriptAST$GenerateJavaScriptTransformer.transformMethodCall(GenerateJavaScriptAST.java:520)
	at com.google.gwt.dev.jjs.ast.JTransformer$JRewriterVisitor.visit(JTransformer.java:860)
	at com.google.gwt.dev.jjs.ast.JMethodCall.traverse(JMethodCall.java:265)
	at com.google.gwt.dev.jjs.ast.JVisitor.accept(JVisitor.java:127)
	... 58 more

The bug is that when being called in this way, the "super" constructor is incorrectly identified as being a native method as it has no body. I'm still working out why it has no body - it appears that either JDT doesn't emit a body for the canonical record constructor if there is a non-default constructor declared, or GWT just doesn't read it properly - but if the canonical constructor is declared or no constructors are declared at all, it will correctly have the field assignments as expected.

[niloc132]

This is an upstream JDT bug, already fixed there: eclipse-jdt/eclipse.jdt.core#365. It appears that updating to 3.33 may resolve this. That version is also compiled to work with Java 11 so we should be safe to update, but it might be risky to do so on a point release like 2.12.2.

We should be able to work around it in a way that still works when JDT is later updated, by detecting if the body is missing from the canonical constructor, and if so, generate the field assignments. There is a caveat here that this must end up in the GwtAstBuilder rather than in ImplementRecordComponents - since the field assignments never were generated, the first pruneDeadFieldsAndMethods pass that runs as part of UnifyAst.exec ends up removing those fields outright, so we can't generate the correct constructor later.

[andreaskornstaedt]

Workaround: Declare the default constructor. In this example, that would look like:

public record Rec(String s) {
        public Rec { }
	public Rec(int i) {
		this("" + i);
	}
}

Very helpful 👍