A DESCRIPTION OF THE PROBLEM :
javac crashes at "jdk.compiler/com.sun.tools.javac.jvm.Code.emitop0" with NPE when trying to compile a correct program. The program compiles successfully with 16.0.1 compiler, but crashes with 17.ea.22.

Pasting the error messages below. Also attached the source code with the bug report.

java.lang.NullPointerException: Cannot read field "sym" because "this.lvar[2]" is null
        at jdk.compiler/com.sun.tools.javac.jvm.Code.emitop0(Code.java:574)
        at jdk.compiler/com.sun.tools.javac.jvm.Items$LocalItem.load(Items.java:399)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.visitTypeTest(Gen.java:2233)
        at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCInstanceOf.accept(JCTree.java:2172)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genExpr(Gen.java:877)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genCond(Gen.java:783)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genCond(Gen.java:696)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.visitBinary(Gen.java:2136)
        at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCBinary.accept(JCTree.java:2114)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genExpr(Gen.java:877)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.visitParens(Gen.java:2005)
        at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCParens.accept(JCTree.java:1972)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genExpr(Gen.java:877)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genCond(Gen.java:783)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genCond(Gen.java:696)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.visitConditional(Gen.java:1878)
        at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCConditional.accept(JCTree.java:1475)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genExpr(Gen.java:877)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.visitLetExpr(Gen.java:2368)
        at jdk.compiler/com.sun.tools.javac.tree.JCTree$LetExpr.accept(JCTree.java:3120)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genExpr(Gen.java:877)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.visitParens(Gen.java:2005)
        at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCParens.accept(JCTree.java:1972)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genExpr(Gen.java:877)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.visitReturn(Gen.java:1830)
        at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCReturn.accept(JCTree.java:1667)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genDef(Gen.java:610)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genStat(Gen.java:645)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genStat(Gen.java:631)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genStats(Gen.java:682)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.visitBlock(Gen.java:1097)
        at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCBlock.accept(JCTree.java:1055)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genDef(Gen.java:610)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genStat(Gen.java:645)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genMethod(Gen.java:967)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.visitMethodDef(Gen.java:930)
        at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCMethodDecl.accept(JCTree.java:901)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genDef(Gen.java:610)
        at jdk.compiler/com.sun.tools.javac.jvm.Gen.genClass(Gen.java:2407)
        at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.genCode(JavaCompiler.java:756)
        at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.generate(JavaCompiler.java:1644)
        at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.generate(JavaCompiler.java:1612)
        at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.compile(JavaCompiler.java:973)
        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)

REGRESSION : Last worked in version 16.0.1

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
javac Main.java

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
compile successfully
ACTUAL -
javac crashes

---------- BEGIN SOURCE ----------
import java.util.function.Supplier;

class Main {
  public Integer foo(Object x) {
    Integer bar = 1;
    return ((x instanceof Number y) ?
        ((Supplier<Integer>) (() -> {
          return ((y instanceof Integer z) ? z : bar);
        })).get() : bar);
  }
}

---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
Remove the bar variable and use an integer value directly.

FREQUENCY : always