// fixErrErrorfCall updates calls of the form err.addf(obj, ...) to err.addf(obj.Pos(), ...).
func fixErrErrorfCall(f *ast.File) {
	ast.Inspect(f, func(n ast.Node) bool {
		switch n := n.(type) {
		case *ast.CallExpr:
			if selx, _ := n.Fun.(*ast.SelectorExpr); selx != nil {
				if isIdent(selx.X, "err") {
					switch selx.Sel.Name {
					case "errorf":
						// rewrite err.addf(obj, ... ) to err.addf(obj.Pos(), ... )

		// the more general CannotInferTypeArgs.
		if inferred != tpar {
			if reverse {
				err.addf(arg, "inferred type %s for %s does not match type %s of %s", inferred, tpar, targ, arg.expr)
			} else {
				err.addf(arg, "type %s of %s does not match inferred type %s for %s", targ, arg.expr, inferred, tpar)
			}
		} else {
			err.addf(arg, "type %s of %s does not match %s", targ, arg.expr, tpar)
		}
	}

			// (quadratic algorithm, but these lists tend to be very short)
			for _, vt := range seen[val] {
				if Identical(v.typ, vt.typ) {
					err := check.newError(DuplicateCase)
					err.addf(&v, "duplicate case %s in expression switch", &v)
					err.addf(vt.pos, "previous case")
					err.report()
					continue L
				}
			}
			seen[val] = append(seen[val], valueType{v.Pos(), v.typ})
		}
	}
}

		case other == nil:
			allMethods = append(allMethods, m)
			mpos[m] = pos
		case explicit:
			if check != nil {
				err := check.newError(DuplicateDecl)
				err.addf(atPos(pos), "duplicate method %s", m.name)
				err.addf(atPos(mpos[other.(*Func)]), "other declaration of method %s", m.name)
				err.report()
			}
		default:
			// We have a duplicate method name in an embedded (not explicitly declared) method.

		// the more general CannotInferTypeArgs.
		if inferred != tpar {
			if reverse {
				err.addf(arg, "inferred type %s for %s does not match type %s of %s", inferred, tpar, targ, arg.expr)
			} else {
				err.addf(arg, "type %s of %s does not match inferred type %s for %s", targ, arg.expr, inferred, tpar)
			}
		} else {
			err.addf(arg, "type %s of %s does not match %s", targ, arg.expr, tpar)
		}
	}

			// (quadratic algorithm, but these lists tend to be very short)
			for _, vt := range seen[val] {
				if Identical(v.typ, vt.typ) {
					err := check.newError(DuplicateCase)
					err.addf(&v, "duplicate case %s in expression switch", &v)
					err.addf(atPos(vt.pos), "previous case")
					err.report()
					continue L
				}
			}
			seen[val] = append(seen[val], valueType{v.Pos(), v.typ})
		}
	}
}

		case other == nil:
			allMethods = append(allMethods, m)
			mpos[m] = pos
		case explicit:
			if check != nil {
				err := check.newError(DuplicateDecl)
				err.addf(atPos(pos), "duplicate method %s", m.name)
				err.addf(atPos(mpos[other.(*Func)]), "other declaration of method %s", m.name)
				err.report()
			}
		default:
			// We have a duplicate method name in an embedded (not explicitly declared) method.

	if tname != nil {
		err.addf(obj, "invalid recursive type %s", objName)
	} else {
		err.addf(obj, "invalid cycle in declaration of %s", objName)
	}
	i := start
	for range cycle {
		err.addf(obj, "%s refers to", objName)
		i++
		if i >= len(cycle) {
			i = 0
		}
		obj = cycle[i]
		objName = name(obj)
	}
	err.addf(obj, "%s", objName)
	err.report()
}

	if tname != nil {
		err.addf(obj, "invalid recursive type %s", objName)
	} else {
		err.addf(obj, "invalid cycle in declaration of %s", objName)
	}
	i := start
	for range cycle {
		err.addf(obj, "%s refers to", objName)
		i++
		if i >= len(cycle) {
			i = 0
		}
		obj = cycle[i]
		objName = name(obj)
	}
	err.addf(obj, "%s", objName)
	err.report()
}

				obj = resolve(name, obj)
				err := check.newError(DuplicateDecl)
				if pkg, ok := obj.(*PkgName); ok {
					err.addf(alt, "%s already declared through import of %s", alt.Name(), pkg.Imported())
					err.addAltDecl(pkg)
				} else {
					err.addf(alt, "%s already declared through dot-import of %s", alt.Name(), obj.Pkg())
					// TODO(gri) dot-imported objects don't have a position; addAltDecl won't print anything