[release-branch.go1.12] go/analysis/passes/printf: fix big.Int false positive

It's possible to use a type which implements fmt.Formatter without
importing fmt directly, if the type is imported from another package
such as math/big.

On top of that, it's possible to use printf-like functions without
importing fmt directly, such as using testing.T.Logf.

These two scenarios combined can lead to the printf check not finding
the fmt.Formatter type, since it's not a direct dependency of the root
package.

fmt must still be in the import graph somewhere, so we could search for
it via types.Package.Imports. However, at that point it's simpler to
just look for the Format method manually via go/types.

Fixes #30399.

Change-Id: Id78454bb6a51b3c5e1bcb1984a7fbfb4a29a5be0
Reviewed-on: https://go-review.googlesource.com/c/163817
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Alan Donovan <adonovan@google.com>
(cherry picked from commit 589c23e65e65055d47b9ad4a99723bc389136265)
Reviewed-on: https://go-review.googlesource.com/c/tools/+/164657
Run-TryBot: Alan Donovan <adonovan@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
4 files changed
tree: db089312378b7ef25c58f6417884df09eca762a9
  1. .gitattributes
  2. .gitignore
  3. AUTHORS
  4. CONTRIBUTING.md
  5. CONTRIBUTORS
  6. LICENSE
  7. PATENTS
  8. README.md
  9. benchmark/
  10. blog/
  11. cmd/
  12. codereview.cfg
  13. container/
  14. cover/
  15. go/
  16. godoc/
  17. imports/
  18. internal/
  19. playground/
  20. present/
  21. refactor/
  22. third_party/
README.md

Go Tools

This subrepository holds the source for various packages and tools that support the Go programming language.

Some of the tools, godoc and vet for example, are included in binary Go distributions.

Others, including the Go guru and the test coverage tool, can be fetched with go get.

Packages include a type-checker for Go and an implementation of the Static Single Assignment form (SSA) representation for Go programs.

Download/Install

The easiest way to install is to run go get -u golang.org/x/tools/.... You can also manually git clone the repository to $GOPATH/src/golang.org/x/tools.

Report Issues / Send Patches

This repository uses Gerrit for code changes. To learn how to submit changes to this repository, see https://golang.org/doc/contribute.html.

The main issue tracker for the tools repository is located at https://github.com/golang/go/issues. Prefix your issue with “x/tools/(your subdir):” in the subject line, so it is easy to find.