"illegal start of expression" compile error with malformed @GuardedBy

[jhonnen]

The following malformed @GuardedBy expression results in an compile error on the package statement:

package example;

import javax.annotation.concurrent.GuardedBy;

public class IllegalStartOfExpression {
    @GuardedBy("itself (synchronized blocks)")
    int field;
}

Compile output with options.errorprone.warn("GuardedBy"):

...\src\main\java\example\IllegalStartOfExpression.java:1: error: illegal start of expression
package example;
        ^
...\src\main\java\example\IllegalStartOfExpression.java:7: warning: [GuardedBy] Invalid @GuardedBy expression: could not resolve guard
    int field;
        ^
    (see https://errorprone.info/bugpattern/GuardedBy)
1 error
1 warning

The first error is very misleading due to the unrelated source location.

ErrorProne version: 2.42.0

[cushon]

A fix for this is out for review, but hasn't been merged yet: #5456

[graememorgan]

Oops, I thought that had already gone in.