// Walk the input and output dependencies of the Ops in `operations` to form
  // the closer of Ops needed to evaluate 'operations'. Input dependencies are
  // walked if 'predecessors' is true and output dependencies are walked if
  // 'successors' is true. In either case, if a discoverd Op is in the
  // 'ops_to_avoid' set, then the dependency walking is terminated.

	truth, ok := isTrue(indirectInterface(val))
	if !ok {
		s.errorf("if/with can't use %v", val)
	}
	if truth {
		if typ == parse.NodeWith {
			s.walk(val, list)
		} else {
			s.walk(dot, list)
		}
	} else if elseList != nil {
		s.walk(dot, elseList)
	}
}

// IsTrue reports whether the value is 'true', in the sense of not the zero of its type,

		}

		// Walk backwards looking for dead stores. Keep track of shadowed addresses.
		// A "shadowed address" is a pointer, offset, and size describing a memory region that
		// is known to be written. We keep track of shadowed addresses in the shadowed map,
		// mapping the ID of the address to a shadowRange where future writes will happen.
		// Since we're walking backwards, writes to a shadowed region are useless,

	if as.X != nil && as.Y != nil {
		return convas(as, init)
	}
	return as
}

// walkAssignDotType walks an OAS2DOTTYPE node.
func walkAssignDotType(n *ir.AssignListStmt, init *ir.Nodes) ir.Node {
	walkExprListSafe(n.Lhs, init)
	n.Rhs[0] = walkExpr(n.Rhs[0], init)
	return n
}

// walkAssignFunc walks an OAS2FUNC node.
func walkAssignFunc(init *ir.Nodes, n *ir.AssignListStmt) ir.Node {
	init.Append(ir.TakeInit(n)...)

// resolveFwdRefs links all FwdRef uses up to their nearest dominating definition.
func (s *phiState) resolveFwdRefs() {
	// Do a depth-first walk of the dominator tree, keeping track
	// of the most-recently-seen value for each variable.

	// Map from variable ID to SSA value at the current point of the walk.
	values := make([]*ssa.Value, len(s.varnum))
	for i := range values {
		values[i] = s.placeholder
	}

	// Stack of work to do.

	r := ir.NewBlockStmt(base.Pos, nil)
	r.List = calls
	return walkStmt(typecheck.Stmt(r))
}

// walkRecoverFP walks an ORECOVERFP node.
func walkRecoverFP(nn *ir.CallExpr, init *ir.Nodes) ir.Node {
	return mkcall("gorecover", nn.Type(), init, walkExpr(nn.Args[0], init))
}

// walkUnsafeData walks an OUNSAFESLICEDATA or OUNSAFESTRINGDATA expression.
func walkUnsafeData(n *ir.UnaryExpr, init *ir.Nodes) ir.Node {

  // for such regions to a new unique-id. This is required because walk() walks
  // the attached regions first before visiting the op, so there is no
  // opportunity during the walk to seed region arguments. Also note that walk
  // eventually also visits the Op on which the walk() is called, so make sure
  // we do not overwrite the function argument mapping here.
  func_op.walk([&](Operation* op) {
    if (op == func_op) return;

		op    walkState
	}

	work := make([]bp, 0, 256)
	work = append(work, bp{block: f.Entry})

	// map from value ID to known non-nil version of that value ID
	// (in the current dominator path being walked). This slice is updated by
	// walkStates to maintain the known non-nil values.
	// If there is extrinsic information about non-nil-ness, this map
	// points a value to itself. If a value is known non-nil because we

				}
				return f
			}
		}
		f.addCounters(n.Lbrace, n.Lbrace+1, n.Rbrace+1, n.List, true) // +1 to step past closing brace.
	case *ast.IfStmt:
		if n.Init != nil {
			ast.Walk(f, n.Init)
		}
		ast.Walk(f, n.Cond)
		ast.Walk(f, n.Body)
		if n.Else == nil {
			return nil
		}
		// The elses are special, because if we have
		//	if x {
		//	} else if y {
		//	}

//  1. The payload is validated; if the payload is invalid, the function returns
//
//  2. The current timestamped directory is detected by reading the data directory
//     symlink
//
//  3. The old version of the volume is walked to determine whether any
//     portion of the payload was deleted and is still present on disk.
//
//  4. The data in the current timestamped directory is compared to the projected