Program: 130678
Project: 130678
Buggy source:
public boolean generate(World par1World,Random par2Random,int par3,int par4,int par5){
  int l=par2Random.nextInt(3) + this.minTreeHeight;
  boolean flag=true;
  if (par4 >= 1 && par4 + l + 1 <= 256) {
    byte b0;
    int k1;
    Block block;
    for (int i1=par4; i1 <= par4 + 1 + l; ++i1) {
      b0=1;
      if (i1 == par4) {
        b0=0;
      }
      if (i1 >= par4 + 1 + l - 2) {
        b0=2;
      }
      for (int j1=par3 - b0; j1 <= par3 + b0 && flag; ++j1) {
        for (k1=par5 - b0; k1 <= par5 + b0 && flag; ++k1) {
          if (i1 >= 0 && i1 < 256) {
            block=par1World.getBlock(j1,i1,k1);
            if (!this.isReplaceable(par1World,j1,i1,k1))             flag=false;
          }
 else {
            flag=false;
          }
        }
      }
    }
    if (!flag) {
      return false;
    }
 else {
      Block block2=par1World.getBlock(par3,par4 - 1,par5);
      boolean isSoil=block2.canSustainPlant(par1World,par3,par4 - 1,par5,ForgeDirection.UP,(BlockSapling)Blocks.sapling);
      if (isSoil && par4 < 256 - l - 1) {
        block2.onPlantGrow(par1World,par3,par4 - 1,par5,par3,par4,par5);
        b0=3;
        byte b1=0;
        int l1;
        int i2;
        int j2;
        int i3;
        for (k1=par4 - b0 + l; k1 <= par4 + l; ++k1) {
          i3=k1 - (par4 + l);
          l1=b1 + 1 - i3 / 2;
          for (i2=par3 - l1; i2 <= par3 + l1; ++i2) {
            j2=i2 - par3;
            for (int k2=par5 - l1; k2 <= par5 + l1; ++k2) {
              int l2=k2 - par5;
              if (Math.abs(j2) != l1 || Math.abs(l2) != l1 || par2Random.nextInt(2) != 0 && i3 != 0) {
                Block block1=par1World.getBlock(i2,k1,k2);
                if (block1.isAir(par1World,i2,k1,k2) || block1.isLeaves(par1World,i2,k1,k2)) {
                  this.setBlockAndNotifyAdequately(par1World,i2,k1,k2,TwilightBlocks.skythernLeaves,this.metaLeaves);
                }
              }
            }
          }
        }
        for (k1=0; k1 < l; ++k1) {
          block=par1World.getBlock(par3,par4 + k1,par5);
          if (block.isAir(par1World,par3,par4 + k1,par5) || block.isLeaves(par1World,par3,par4 + k1,par5)) {
            this.setBlockAndNotifyAdequately(par1World,par3,par4 + k1,par5,TwilightBlocks.edenLogs,this.metaWood);
          }
        }
        return true;
      }
 else {
        return false;
      }
    }
  }
 else {
    return false;
  }
}

Fixed version (ground truth):
@Override public boolean generate(World par1World,Random par2Random,int par3,int par4,int par5){
  int l=par2Random.nextInt(3) + this.minTreeHeight;
  boolean flag=true;
  if (par4 >= 1 && par4 + l + 1 <= 256) {
    byte b0;
    int k1;
    Block block;
    for (int i1=par4; i1 <= par4 + 1 + l; ++i1) {
      b0=1;
      if (i1 == par4) {
        b0=0;
      }
      if (i1 >= par4 + 1 + l - 2) {
        b0=2;
      }
      for (int j1=par3 - b0; j1 <= par3 + b0 && flag; ++j1) {
        for (k1=par5 - b0; k1 <= par5 + b0 && flag; ++k1) {
          if (i1 >= 0 && i1 < 256) {
            block=par1World.getBlock(j1,i1,k1);
            if (!this.isReplaceable(par1World,j1,i1,k1))             flag=false;
          }
 else {
            flag=false;
          }
        }
      }
    }
    if (!flag) {
      return false;
    }
 else {
      Block block2=par1World.getBlock(par3,par4 - 1,par5);
      boolean isSoil=block2 == TwilightBlocks.skythernGrass;
      if (isSoil && par4 < 256 - l - 1) {
        block2.onPlantGrow(par1World,par3,par4 - 1,par5,par3,par4,par5);
        b0=3;
        byte b1=0;
        int l1;
        int i2;
        int j2;
        int i3;
        for (k1=par4 - b0 + l; k1 <= par4 + l; ++k1) {
          i3=k1 - (par4 + l);
          l1=b1 + 1 - i3 / 2;
          for (i2=par3 - l1; i2 <= par3 + l1; ++i2) {
            j2=i2 - par3;
            for (int k2=par5 - l1; k2 <= par5 + l1; ++k2) {
              int l2=k2 - par5;
              if (Math.abs(j2) != l1 || Math.abs(l2) != l1 || par2Random.nextInt(2) != 0 && i3 != 0) {
                Block block1=par1World.getBlock(i2,k1,k2);
                if (block1.isAir(par1World,i2,k1,k2) || block1.isLeaves(par1World,i2,k1,k2)) {
                  this.setBlockAndNotifyAdequately(par1World,i2,k1,k2,TwilightBlocks.skythernLeaves,this.metaLeaves);
                }
              }
            }
          }
        }
        for (k1=0; k1 < l; ++k1) {
          block=par1World.getBlock(par3,par4 + k1,par5);
          if (block.isAir(par1World,par3,par4 + k1,par5) || block.isLeaves(par1World,par3,par4 + k1,par5)) {
            this.setBlockAndNotifyAdequately(par1World,par3,par4 + k1,par5,TwilightBlocks.skythernLogs,this.metaWood);
          }
        }
        return true;
      }
 else {
        return false;
      }
    }
  }
 else {
    return false;
  }
}