Gradle+Lombok compile error on @Builder, works in Eclipse with Lombok

[bvkatwijk]

I'm running into a compilation error when compiling with Gradle using @Builder. Eclipse with Lombok installed does not raise a compilation error. The following is a minimal reproduction of the issue:

A.java:

import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.IntStream;

import lombok.Builder;
import lombok.RequiredArgsConstructor;

@Builder
@RequiredArgsConstructor
public class A {

	private final List<Object> list;

	public static class ABuilder {

		private List<Object> list = IntStream.range(0, getInt())
				.mapToObj(i -> new Object())
				.collect(Collectors.toList()); 

		private int getInt() {
			return 10;
		}

	}

}

Running ./gradlew jar gives the following error:

A.java:10: error: incompatible types: no instance(s) of type variable(s) T exist so that Collector<T,?,List<T>> conforms to int
@Builder
^
  where T is a type-variable:
    T extends Object declared in method <T>toList()

Some remarks about this example:

• Inlining the getInt method removes the compilation error
• Replacing Collectors.toList() with Collectors.<Object>toList() removes the compilation error
• Removing @Builder removes the compilation error

build.gradle:

plugins {
    id 'net.ltgt.apt' version '0.10'
}

apply plugin: 'java'
apply plugin: 'eclipse'

sourceCompatibility = 1.9

repositories {
    mavenCentral()
}

dependencies {
    compileOnly group: 'org.projectlombok', name: 'lombok', version: '1.16.20'
    apt "org.projectlombok:lombok:1.16.20"
}

Gradle Wrapper Version:

------------------------------------------------------------
Gradle 4.5.1
------------------------------------------------------------

Build time:   2018-02-05 13:22:49 UTC
Revision:     37007e1c012001ff09973e0bd095139239ecd3b3

Groovy:       2.4.12
Ant:          Apache Ant(TM) version 1.9.9 compiled on February 2 2017
JVM:          9.0.4 (Oracle Corporation 9.0.4+11)
OS:           Mac OS X 10.13.3 x86_64

[wrprice]

Maybe a javac bug in the improved type inference code? Compiling on Java 8 works for me, but 9 and 10 fail. Passing -Xdiags:verbose to javac provides additional details, note that the required/found actually match in spite of what the error says:

error: method range in interface IntStream cannot be applied to given types;
@Builder
^
  required: int,int
  found: int,int
  reason: argument mismatch; no instance(s) of type variable(s) T exist so that Collector<T,?,List<T>> conforms to int
  where T is a type-variable:
    T extends Object declared in method <T>toList()

Possibly related:

• JDK-8178150: Regression in logic for handling inference stuck constraints
• JDK-8189683: Non-deterministic solving order of inference variables

On that second one, note these comments:

The dependencies of an inference node are currently stored in a 'HashSet' that doesn't preserve insertion order . . . In addition to that, 'hashCode()' is inherited from 'Object' giving no guarantee of consistency between two compilations of the same code sample . . .

Tarjan's algorithm iterates on these dependencies to compute the acyclic graph determining the solving order which is then non-deterministic . . .

Picking a node to be solved from a stuck expression also iterates on those dependencies leading to a non-deterministic solving order too . . .