The test described below causes an internal compiler
error: "sun.tools.java.CompilerError: codeConversion: 10, 13"

The test is performed in two steps.

Step 1. Compile the source containing definitions
of an interface and a class. It produces two .class
files: "Intrf1.class" and "stmt135.class"

> cat stmt135.java
interface Intrf1
{
  int a = 0;
}
class stmt135
{
  Intrf1 t = null;
  void f()
  {
     synchronized (t)
     {
       t = null;
     }
  }
}

> /usr/local/java/1.0/bin/javac stmt135.java
>

Step 2.
Delete (or comment) the definition of the interface
in the test source and recompile it. The compiler
produces internal compiler error along with regular errors.
It seems like it's the old "Intrf1.class" that
causes the problem.

> cat stmt135.java
/*interface Intrf1
{
  int a = 0;
}*/
class stmt135
{
  Intrf1 t = null;
  void f()
  {
     synchronized (t)
     {
       t = null;
     }
  }
}

> /usr/local/java/1.0/bin/javac stmt135.java
sun.tools.java.CompilerError: codeConversion: 10, 13
at sun.tools.tree.Expression.codeConversion(Expression.java:450)
at sun.tools.tree.ConvertExpression.codeValue(ConvertExpression.java:119)
at sun.tools.tree.SynchronizedStatement.code(SynchronizedStatement.java:81)
at sun.tools.javac.SourceField.code(SourceField.java:406)
at sun.tools.javac.SourceField.code(SourceField.java:368)
at sun.tools.javac.SourceClass.compileClass(SourceClass.java:564)
at sun.tools.javac.SourceClass.compile(SourceClass.java:527)
at sun.tools.javac.Main.compile(Main.java:193)
at sun.tools.javac.Main.main(Main.java:289)
.//stmt135.java:0: class stmt135:void f()@sun.tools.java.CompilerError: codeConversion: 10, 13
/*interface Intrf1
^
.//stmt135.java:5: Class stmt135 already defined in stmt135.java.
class stmt135
      ^
.//stmt135.java:7: Class Intrf1 not found in type declaration.
  Intrf1 t = null;
           ^
.//stmt135.java:10: Class Intrf1 not found in synchronized.
     synchronized (t)
     ^
.//stmt135.java:10: Incompatible type for synchronized. Can't convert Intrf1 to java.lang.Object.
     synchronized (t)
     ^
5 errors



One more example.
Step 1. Try compile first the following text:
-------------arr039.java------------------
class T extends Object {int z;}
class arr039
{
  public static void main(String argv[])
  {
     T[] a = new T[4];
     Object[] a1 = a;
  }
}
------------------------------------------
Step 2. Then change "T" to "A" in it and recompile:
-------------arr039.java------------------
class A extends Object {int z;}
class arr039
{
  public static void main(String argv[])
  {
     A[] a = new T[4];
     Object[] a1 = a;
  }
}
------------------------------------------
> /usr/local/java/1.0/bin/javac arr039.java
sun.tools.java.CompilerError: codeConversion: 9, 13
at sun.tools.tree.Expression.codeConversion(Expression.java:450)
at sun.tools.tree.ConvertExpression.codeValue(ConvertExpression.java:119)
at sun.tools.tree.VarDeclarationStatement.code(VarDeclarationStatement.java:156)
at sun.tools.tree.DeclarationStatement.code(DeclarationStatement.java:81)
at sun.tools.javac.SourceField.code(SourceField.java:406)
at sun.tools.javac.SourceField.code(SourceField.java:368)
at sun.tools.javac.SourceClass.compileClass(SourceClass.java:564)
at sun.tools.javac.SourceClass.compile(SourceClass.java:527)
at sun.tools.javac.Main.compile(Main.java:193)
at sun.tools.javac.Main.main(Main.java:289)
.//arr039.java:0: class arr039:void main(java.lang.String[])@sun.tools.java.CompilerError: codeConversion: 9, 13
class A extends Object {int z;}
^
.//arr039.java:1: Class A already defined in arr039.java.
class A extends Object {int z;}
      ^
.//arr039.java:2: Class arr039 already defined in arr039.java.
class arr039
      ^
.//arr039.java:6: Class T not found in declaration.
     A[] a = new T[4];
         ^
.//arr039.java:6: Incompatible type for declaration. Can't convert T[] to A[].
     A[] a = new T[4];
         ^
5 errors