func (err *error_) addf(at positioner, format string, args ...interface{}) {
	err.desc = append(err.desc, errorDesc{at, err.check.sprintf(format, args...)})
}

// addAltDecl is a specialized form of addf reporting another declaration of obj.
func (err *error_) addAltDecl(obj Object) {
	if pos := obj.Pos(); pos.IsValid() {
		// We use "other" rather than "previous" here because
		// the first declaration seen may not be textually

func (err *error_) addf(at poser, format string, args ...interface{}) {
	err.desc = append(err.desc, errorDesc{atPos(at), err.check.sprintf(format, args...)})
}

// addAltDecl is a specialized form of addf reporting another declaration of obj.
func (err *error_) addAltDecl(obj Object) {
	if pos := obj.Pos(); pos.IsKnown() {
		// We use "other" rather than "previous" here because
		// the first declaration seen may not be textually

					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
					err.addAltDecl(obj)
				}
				err.report()
			}
		}
	}

					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
					err.addAltDecl(obj)
				}
				err.report()
			}
		}
	}

func (check *Checker) declareInSet(oset *objset, pos token.Pos, obj Object) bool {
	if alt := oset.insert(obj); alt != nil {
		err := check.newError(DuplicateDecl)
		err.addf(atPos(pos), "%s redeclared", obj.Name())
		err.addAltDecl(alt)
		err.report()
		return false
	}
	return true
}

func (check *Checker) tag(t *ast.BasicLit) string {
	if t != nil {
		if t.Kind == token.STRING {

func (check *Checker) declareInSet(oset *objset, pos syntax.Pos, obj Object) bool {
	if alt := oset.insert(obj); alt != nil {
		err := check.newError(DuplicateDecl)
		err.addf(pos, "%s redeclared", obj.Name())
		err.addAltDecl(alt)
		err.report()
		return false
	}
	return true
}

func (check *Checker) tag(t *syntax.BasicLit) string {
	// If t.Bad, an error was reported during parsing.
	if t != nil && !t.Bad {

				if alt := all.Insert(lbl); alt != nil {
					err := check.newError(DuplicateLabel)
					err.soft = true
					err.addf(lbl, "label %s already declared", name)
					err.addAltDecl(alt)
					err.report()
					// ok to continue
				} else {
					b.insert(s)
					check.recordDef(s.Label, lbl)
				}
				// resolve matching forward jumps and remove them from fwdJumps
				i := 0

				if alt := all.Insert(lbl); alt != nil {
					err := check.newError(DuplicateLabel)
					err.soft = true
					err.addf(lbl.pos, "label %s already declared", name)
					err.addAltDecl(alt)
					err.report()
					// ok to continue
				} else {
					b.insert(s)
					check.recordDef(s.Label, lbl)
				}
				// resolve matching forward jumps and remove them from fwdJumps
				i := 0

	// binding."
	if obj.Name() != "_" {
		if alt := scope.Insert(obj); alt != nil {
			err := check.newError(DuplicateDecl)
			err.addf(obj, "%s redeclared in this block", obj.Name())
			err.addAltDecl(alt)
			err.report()
			return
		}
		obj.setScopePos(pos)
	}
	if id != nil {
		check.recordDef(id, obj)
	}
}

// pathString returns a string of the form a->b-> ... ->g for a path [a, b, ... g].

	results, _ := check.collectParams(scope, ftyp.ResultList, false, scopePos)
	scope.Squash(func(obj, alt Object) {
		err := check.newError(DuplicateDecl)
		err.addf(obj, "%s redeclared in this block", obj.Name())
		err.addAltDecl(alt)
		err.report()
	})

	if recvPar != nil {
		// recv parameter list present (may be empty)
		// spec: "The receiver is specified via an extra parameter section preceding the