Compiling the following program causes a crash in javac.

The input is invalid, but it shouldn't crash.

The crash bisects to a range between 16-ea+15-631 and 16-ea+16-712. Earlier versions report an error.

```
import java.util.function.Function;

abstract class T {

  interface I {}
  interface F {}

  abstract F g(I i);
  abstract F w(F f);
  abstract F t(F i, Function<?, ?> f, String e);

  F f(F f) {
    return t(g(w(f)), v -> f);
  }
}
```

$ javac -fullversion T.java
javac full version "20-ea+25-1926"
An exception has occurred in the compiler (20-ea). Please file a bug against the Java compiler via the Java bug reporting page (https://bugreport.java.com) after checking the Bug Database (https://bugs.java.com) for duplicates. Include your program, the following diagnostic, and the parameters passed to the Java compiler in your report. Thank you.
java.lang.ClassCastException: class com.sun.tools.javac.tree.JCTree$JCIdent cannot be cast to class com.sun.tools.javac.tree.JCTree$JCBlock (com.sun.tools.javac.tree.JCTree$JCIdent and com.sun.tools.javac.tree.JCTree$JCBlock are in module jdk.compiler of loader 'app')
at jdk.compiler/com.sun.tools.javac.comp.AttrRecover.doRecovery(AttrRecover.java:161)
at jdk.compiler/com.sun.tools.javac.comp.Attr.attribStat(Attr.java:738)
at jdk.compiler/com.sun.tools.javac.comp.Attr.attribStats(Attr.java:755)
at jdk.compiler/com.sun.tools.javac.comp.Attr.visitBlock(Attr.java:1439)
at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCBlock.accept(JCTree.java:1082)
at jdk.compiler/com.sun.tools.javac.comp.Attr.attribTree(Attr.java:662)
at jdk.compiler/com.sun.tools.javac.comp.Attr.attribStat(Attr.java:736)
at jdk.compiler/com.sun.tools.javac.comp.Attr.visitMethodDef(Attr.java:1229)
at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCMethodDecl.accept(JCTree.java:912)
at jdk.compiler/com.sun.tools.javac.comp.Attr.attribTree(Attr.java:662)
at jdk.compiler/com.sun.tools.javac.comp.Attr.attribStat(Attr.java:736)
at jdk.compiler/com.sun.tools.javac.comp.Attr.attribClassBody(Attr.java:5573)
at jdk.compiler/com.sun.tools.javac.comp.Attr.attribClass(Attr.java:5466)
at jdk.compiler/com.sun.tools.javac.comp.Attr.attribClass(Attr.java:5290)
at jdk.compiler/com.sun.tools.javac.comp.Attr.attrib(Attr.java:5229)
at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.attribute(JavaCompiler.java:1318)
at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.compile(JavaCompiler.java:947)
at jdk.compiler/com.sun.tools.javac.main.Main.compile(Main.java:317)
at jdk.compiler/com.sun.tools.javac.main.Main.compile(Main.java:176)
at jdk.compiler/com.sun.tools.javac.Main.compile(Main.java:64)
at jdk.compiler/com.sun.tools.javac.Main.main(Main.java:50)

$ javac -fullversion T.java
javac full version "16-ea+15-631"
T.java:13: error: incompatible types: F cannot be converted to I
    return t(g(w(f)), v -> f);
                ^
Note: Some messages have been simplified; recompile with -Xdiags:verbose to get full output
1 error