lazy initialization of given can wait forever in macro

[scf37]

Compiler version

3.0.0

Minimized code

checkout https://github.com/scf37/macro3
sbt compile
Compilation will hang

Output

   java.lang.Thread.State: WAITING (on object monitor)
        at java.lang.Object.wait(Native Method)
        - waiting on <0x00000000fe4e9388> (a java.lang.Object)
        at java.lang.Object.wait(Object.java:502)
        at scala.runtime.LazyVals$.wait4Notification(LazyVals.scala:89)
        - locked <0x00000000fe4e9388> (a java.lang.Object)
        at MacroVis.symbolInstance(MacroVis.scala:53)
        at MacroVis.symbolInstance(MacroVis.scala:12)
        at MacroVis.<init>(MacroVis.scala:63)
        at Macro$.doImpl(Macro.scala:8)
        at Macro$.inline$doImpl(Macro.scala:6)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:498)
        at dotty.tools.dotc.transform.Splicer$Interpreter.interpretedStaticMethodCall$$anonfun$2$$anonfun$1(Splicer.scala:354)
        at dotty.tools.dotc.transform.Splicer$Interpreter$$Lambda$5916/999733346.apply(Unknown Source)
        at dotty.tools.dotc.transform.Splicer$Interpreter.stopIfRuntimeException(Splicer.scala:414)

Expectation

successful compilation

[soronpo]

I suggest you minimize it further.

[ScoreUnder]

Further minimised repro: https://github.com/ScoreUnder/macro3/tree/fixed

The code itself doesn't make much sense but maybe there's an argument to be made that the compiler should show an error here. For some reason, moving the lazy val out of the object and into the macro makes it die with a stack overflow instead.

[nicolasstucki]

It is caused by a bug in the macro implementation. It calls symbolInstance which has an infinite loop.

lazy val symbolInstance: String = symbolInstance

[nicolasstucki]

We might be able to detect simple recursion like this one and warn the user. The same way we do for def f(x: T) = f(x).
See https://github.com/lampepfl/dotty/blob/master/compiler/src/dotty/tools/dotc/transform/TailRec.scala#L202