groovy-eclipse-compiler compiles but javac compilation fails

My project builds successfully with groovy-eclipse-compiler, but fails without groovy-eclipse-compiler (using just javac). The build fails with an error message as given below (reported in a test class, while mocking an invocation)

java: reference to getFileResource is ambiguous

In order to debug the issue, I created a project with minimal files (given below). Though in project we have groovy source also, but I have not included them here to keep the code minimal.
The code is also pushed to git and is available at https://github.com/kaushalkumar/project-debug

My Doubt: The reported issue looks to be legitimate and I feel that groovy-eclipse-compiler must also fail, but it seems that the error is ignored. I am trying to understand what make groovy compiler to ignore it. Is it an issue in groovy compiler?

src/main/java/pkg1/IStrategy.java
package pkg1;

import java.util.Map;

public interface IStrategy {
	Map<String, Object> getEnvMap();
}

src/main/java/pkg1/SharedResourceHelper.java
package pkg1;

import java.io.File;
import java.io.IOException;
import java.util.Map;

public class SharedResourceHelper {
	public static File getFileResource(final String resourceName, final IStrategy strategy) throws IOException {
      return getFileResource(resourceName, strategy.getEnvMap());
	}
	public static File getFileResource(final String resourceName, final Map<String, Object> envConfig) throws IOException {
      return null;
	}
}

src/test/java/pkg1/StrategyTest.java
package pkg1;

import pkg1.SharedResourceHelper;
import org.easymock.EasyMock;
import org.powermock.api.easymock.PowerMock;
import org.powermock.core.classloader.annotations.PrepareForTest;
import org.junit.Test;
import org.powermock.modules.junit4.PowerMockRunner;
import org.junit.runner.RunWith;
import java.io.File;

@PrepareForTest({SharedResourceHelper.class})
@RunWith(PowerMockRunner.class)
public class StrategyTest {
	@Test
	@PrepareForTest({SharedResourceHelper.class})
	public void testGetFileResource() throws Exception {
      PowerMock.mockStatic(SharedResourceHelper.class);
      EasyMock.expect(SharedResourceHelper.getFileResource(EasyMock.anyString(), EasyMock.anyObject())).andReturn(File.createTempFile("tmp", "s"));
//      EasyMock.expect(SharedResourceHelper.getFileResource("test", null)).andReturn(File.createTempFile("tmp", "s"));
      
	}
}

/pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>project.debug</groupId>
  <artifactId>project</artifactId>
  <packaging>jar</packaging>
  <version>1.0-SNAPSHOT</version>
  <dependencies>
    <dependency>
      <groupId>org.powermock</groupId>
      <artifactId>powermock-api-easymock</artifactId>
      <version>2.0.7</version>
      <scope>test</scope>
    </dependency>
    <dependency>
      <groupId>org.powermock</groupId>
      <artifactId>powermock-module-junit4</artifactId>
      <version>2.0.7</version>
      <scope>test</scope>
    </dependency>
  </dependencies>
  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-compiler-plugin</artifactId>
        <version>3.3</version>
        <configuration>
          <compilerId>groovy-eclipse-compiler</compilerId>
          <source>1.8</source>
          <target>1.8</target>
        </configuration>
        <dependencies>
          <dependency>
            <groupId>org.codehaus.groovy</groupId>
            <artifactId>groovy-eclipse-compiler</artifactId>
            <version>2.9.2-01</version>
          </dependency>
          <dependency>
            <groupId>org.codehaus.groovy</groupId>
            <artifactId>groovy-eclipse-batch</artifactId>
            <version>2.4.3-01</version>
          </dependency>
        </dependencies>
      </plugin>
    </plugins>
  </build>
</project>

• Java version - 1.8.0_231
• Maven - 3.6.2
• OS - Mac 10.15.6
• groovy-eclipse-compiler - 2.9.2-01
• groovy-eclipse-batch - 2.4.3-01

You reference "SharedResourceHelper.getFileResource(EasyMock.anyString(), EasyMock.anyObject())" is indeed ambiguous. If you add a typecast before "EasyMock.anyObject()" you could disambiguate. And EasyMock probably provides an "any" method that you can pass a type into as well.

groovy-eclipse-compiler is based upon ecj (eclipse compiler for java) and not javac, so there are bound to be differences. It may also be that ecj has a different default error/warning level for this particular case. If you feel this should be an error, you can file a JDT bug at bugs.eclipse.org.

eric-milles gave some direction to further explore this. His input is available at https://github.com/groovy/groovy-eclipse/issues/1157.

Based on his comment, we explored the history of https://github.com/groovy/groovy-eclipse/blob/master/extras/groovy-eclipse-batch-builder/build.properties and found that the compilation issue was between 2.4.12-01 (compilation works) and 2.4.12-02 (compilation breaks- as expected), which was part of release 2.9.2.

The change happened on Aug 10, 2017 (13c1c2a#diff-c8c111c3afb6080ae6b32148caaf6a0a), with comment as "Remove codehaus references". The jdt.patch.target was targeted for e44 which is Luna. This was same for both the files.

I invested some time in exploring https://github.com/eclipse/eclipse.jdt.core, to figure out how compiler behaviour could have altered, but could not get much. Though I am not very sure, but I feel that change in groovy-eclipse-batch (between 2.4.12-01 and 2.4.12-02) might be the cause of this.

Having invested this much time, I feel that it is not worth to further debug on this to figure out the root cause as the issue is already fixed in next version(s) [2.4.12-02 and beyond].