RFR: JDK-8191981: javac crash when detecting lambda candidates

[Jan Lahoda]

Hi,

Consider this code:
---
public class LambdaWithMethod {
     public static void run(Runnable r) {
         run(new Runnable() {
             public void run() {
                 put(get());
             }
         });
     }
     private static String get() { return null; }
     private static void put(String i) {}
}
---

When detecting lambda candidates, this crashes javac (please see the bug 
for full exception):
---
$ javac -XDfind=lambda /tmp/LambdaWithMethod.java
[snip]
java.lang.AssertionError: Analyzer error when processing: [snip]
at jdk.compiler/com.sun.tools.javac.util.Assert.error(Assert.java:162)
at 
jdk.compiler/com.sun.tools.javac.comp.Analyzer.doAnalysis(Analyzer.java:562)
[snip]
---

The underlying exception is:
---
java.lang.ClassCastException: 
jdk.compiler/com.sun.tools.javac.tree.JCTree$JCMethodInvocation cannot 
be cast to jdk.compiler/com.sun.tools.javac.tree.JCTree$JCLambda
         at 
jdk.compiler/com.sun.tools.javac.comp.ArgumentAttr$ExplicitLambdaType.dup(ArgumentAttr.java:456)
         at 
jdk.compiler/com.sun.tools.javac.comp.ArgumentAttr.processArg(ArgumentAttr.java:237)
[snip]
---

(Full exception in the bug.)

The problem appears to be that when the trial lambda node (that replaces 
the anonymous class) is created, there is no explicit position set, and 
so the last position set is used. And the ArgumentAttr.argumentTypeCache 
uses the position as key, and so the value for "get()" is (appears to 
be) used for the lambda, which leads to the crash.

Bug; https://bugs.openjdk.java.net/browse/JDK-8191981
Proposed patch: http://cr.openjdk.java.net/~jlahoda/8191981/webrev.00

How does this look?

Thanks,
    Jan