From d96f0d16f1abeb828d47005db18cb52cc88c95a5 Mon Sep 17 00:00:00 2001
From: Chris Bandy <bandy.chris@gmail.com>
Date: Thu, 14 Nov 2024 16:59:46 -0600
Subject: [PATCH 1/2] Use the Go toolchain installed by actions/setup-go

Since version 1.21, Go may automatically download a different version of Go.
Disable this behavior so that pipeline jobs use only one version.

See: https://go.dev/doc/toolchain
---
 .github/workflows/ci.yml | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 889f3f4..c335c91 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -18,6 +18,11 @@ on:
 permissions:
   contents: read
 
+env:
+  # Use the Go toolchain installed by setup-go
+  # https://github.com/actions/setup-go/issues/457
+  GOTOOLCHAIN: local
+
 jobs:
 
   test:
@@ -86,7 +91,7 @@ jobs:
     - uses: actions/setup-go@v5
       name: Set up Go
       with:
-        # Use the Go version specified in the go.mod for linting.
+        # Use the Go language version in go.mod for linting.
         go-version-file: go.mod
         cache: false  # managed by golangci-lint
 

From 8fad5b37c8941430bea43c94b4bda21b2eb4a863 Mon Sep 17 00:00:00 2001
From: Chris Bandy <bandy.chris@gmail.com>
Date: Thu, 14 Nov 2024 17:02:29 -0600
Subject: [PATCH 2/2] Remove Go 1.21 polyfills

We can drop these now that the main module requires Go 1.21.

Co-authored-by: Prashant V <github@prashantv.com>
---
 CHANGELOG.md                              |  2 +-
 cmd/errtrace/slices_contains_go121.go     |  9 ---------
 cmd/errtrace/slices_contains_pre_go121.go | 12 ------------
 cmd/errtrace/toolexec.go                  |  2 +-
 tree.go                                   |  3 ++-
 tree_go121.go                             |  9 ---------
 tree_pre_go121.go                         |  9 ---------
 7 files changed, 4 insertions(+), 42 deletions(-)
 delete mode 100644 cmd/errtrace/slices_contains_go121.go
 delete mode 100644 cmd/errtrace/slices_contains_pre_go121.go
 delete mode 100644 tree_go121.go
 delete mode 100644 tree_pre_go121.go

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0036a2f..9fdf6a9 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -37,7 +37,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   Example: `go build -toolexec="errtrace -required-packages pkg/..." pkg/to/build`
 
 ### Changed
-- Update `go` directive in go.mod to 1.21.
+- Update `go` directive in go.mod to 1.21, and drop compatibility with Go 1.20 and earlier.
 
 ### Fixed
 - cmd/errtrace: Don't exit with a non-zero status when `-h` is used.
diff --git a/cmd/errtrace/slices_contains_go121.go b/cmd/errtrace/slices_contains_go121.go
deleted file mode 100644
index c6188ca..0000000
--- a/cmd/errtrace/slices_contains_go121.go
+++ /dev/null
@@ -1,9 +0,0 @@
-//go:build go1.21
-
-package main
-
-import "slices"
-
-func slicesContains[T comparable](s []T, find T) bool {
-	return slices.Contains[[]T](s, find)
-}
diff --git a/cmd/errtrace/slices_contains_pre_go121.go b/cmd/errtrace/slices_contains_pre_go121.go
deleted file mode 100644
index ec19412..0000000
--- a/cmd/errtrace/slices_contains_pre_go121.go
+++ /dev/null
@@ -1,12 +0,0 @@
-//go:build !go1.21
-
-package main
-
-func slicesContains[T comparable](s []T, find T) bool {
-	for _, v := range s {
-		if v == find {
-			return true
-		}
-	}
-	return false
-}
diff --git a/cmd/errtrace/toolexec.go b/cmd/errtrace/toolexec.go
index 911899e..76be1c3 100644
--- a/cmd/errtrace/toolexec.go
+++ b/cmd/errtrace/toolexec.go
@@ -309,7 +309,7 @@ func readBuildSHA() (_ string, ok bool) {
 
 // isStdLib checks if the current execution is for stdlib.
 func isStdLib(args []string) bool {
-	return slicesContains(args, "-std")
+	return slices.Contains(args, "-std")
 }
 
 func packageSelectorMatch(selector, importPath string) bool {
diff --git a/tree.go b/tree.go
index 1d06efa..1565833 100644
--- a/tree.go
+++ b/tree.go
@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"io"
 	"runtime"
+	"slices"
 	"strings"
 )
 
@@ -72,7 +73,7 @@ loop:
 		}
 	}
 
-	sliceReverse(current.Trace)
+	slices.Reverse(current.Trace)
 	return current
 }
 
diff --git a/tree_go121.go b/tree_go121.go
deleted file mode 100644
index 73d9c26..0000000
--- a/tree_go121.go
+++ /dev/null
@@ -1,9 +0,0 @@
-//go:build go1.21
-
-package errtrace
-
-import "slices"
-
-func sliceReverse[T any](s []T) {
-	slices.Reverse(s)
-}
diff --git a/tree_pre_go121.go b/tree_pre_go121.go
deleted file mode 100644
index ad7d640..0000000
--- a/tree_pre_go121.go
+++ /dev/null
@@ -1,9 +0,0 @@
-//go:build !go1.21
-
-package errtrace
-
-func sliceReverse[T any](s []T) {
-	for i, j := 0, len(s)-1; i < j; i, j = i+1, j-1 {
-		s[j], s[i] = s[i], s[j]
-	}
-}