[core][D8] Multi-variable type inference failed for types: [boolean, int]

[nitram84]

A multi-variable type inference can be observed when this class is decompiled with lastest git (compiled with openjdk8, decompiled with "use dx/d8" and option "d8"). This class is a minimized extract. The original class didn't have any useless variables or dead stores.

import java.util.List;

public class MultiVariableTypeInferenceFailed {

  public void doSomething() {
    Object o1 = null;
    List<String> stringList = this.getStrings();
    int num = 0;
    Object o2 = null;
    boolean cond = false;
    for (String curString : stringList) {
      String s0 = curString;
      Object o3 = getObject(0);
      for (int i = 1; i < 42; i++) {
   	    String s1 = "jadx";
        String s2 = "is great!";
        getObject(0);
        setFlag(false);
        String s3 = s0;
        for (String s : getStrings()) {
          write(s);
        }
      }
    }
  }

  private List<String> getStrings() {
    return null;
  }

  private void write(String s) {
  }

  private void setFlag(boolean b) {
  }

  private Object getObject(int i) {
    return null;
  }
}

Decompiled result is:

import java.util.List;

/* loaded from: classes.dex */
public class MultiVariableTypeInferenceFailed {
    /* JADX WARN: Multi-variable type inference failed */
    /* JADX WARN: Type inference failed for: r9v0 */
    /* JADX WARN: Type inference failed for: r9v1, types: [boolean, int] */
    /* JADX WARN: Type inference failed for: r9v2 */
    public void doSomething() {
        List<String> stringList = getStrings();
        for (String str : stringList) {
            ?? r9 = 0;
            getObject(0);
            int i = 1;
            while (i < 42) {
                getObject(r9);
                setFlag(r9);
                for (String s : getStrings()) {
                    write(s);
                }
                i++;
                r9 = 0;
            }
        }
    }

    private List<String> getStrings() {
        return null;
    }

    private void write(String s) {
    }

    private void setFlag(boolean b2) {
    }

    private Object getObject(int i) {
        return null;
    }
}

[skylot]

@nitram84 thanks, this case is weird 🤣
There are 2 ways for fix:

1. Check if variable value not changes in loop and inline it (correct types will be used)
2. Apply in place int to boolean conversion, similar to this case: [core] Miss of casts among primitive types #921 (comment)

Actually, second should be implemented anyway, and first can be a little tricky.