1 files changed, 134 insertions, 0 deletions
diff --git a/misc/cgo/errors/argposition_test.go b/misc/cgo/errors/argposition_test.go
new file mode 100644
index 0000000000..331095f747
--- /dev/null
+++ b/misc/cgo/errors/argposition_test.go
@@ -0,0 +1,134 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Issue 42580: cmd/cgo: shifting identifier position in ast
+
+package errorstest
+
+import (
+	"bytes"
+	"fmt"
+	"go/ast"
+	"go/parser"
+	"go/token"
+	"io/ioutil"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+type ShortPosition struct {
+	Line    int
+	Column  int
+	Visited bool
+}
+
+type IdentPositionInfo map[string][]ShortPosition
+
+type Visitor struct {
+	identPosInfo IdentPositionInfo
+	fset         *token.FileSet
+	t            *testing.T
+}
+
+func (v *Visitor) Visit(node ast.Node) ast.Visitor {
+	if ident, ok := node.(*ast.Ident); ok {
+		if expectedPositions, ok := v.identPosInfo[ident.Name]; ok {
+			gotMatch := false
+			var errorMessage strings.Builder
+			for caseIndex, expectedPos := range expectedPositions {
+				actualPosition := v.fset.PositionFor(ident.Pos(), true)
+				errorOccured := false
+				if expectedPos.Line != actualPosition.Line {
+					fmt.Fprintf(&errorMessage, "wrong line number for ident %s: expected: %d got: %d\n", ident.Name, expectedPos.Line, actualPosition.Line)
+					errorOccured = true
+				}
+				if expectedPos.Column != actualPosition.Column {
+					fmt.Fprintf(&errorMessage, "wrong column number for ident %s: expected: %d got: %d\n", ident.Name, expectedPos.Column, actualPosition.Column)
+					errorOccured = true
+				}
+				if errorOccured {
+					continue
+				}
+				gotMatch = true
+				expectedPositions[caseIndex].Visited = true
+			}
+
+			if !gotMatch {
+				v.t.Errorf(errorMessage.String())
+			}
+		}
+	}
+	return v
+}
+
+func TestArgumentsPositions(t *testing.T) {
+	testdata, err := filepath.Abs("testdata")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	tmpPath := t.TempDir()
+
+	dir := filepath.Join(tmpPath, "src", "testpositions")
+	if err := os.MkdirAll(dir, 0755); err != nil {
+		t.Fatal(err)
+	}
+
+	cmd := exec.Command("go", "tool", "cgo",
+		"-srcdir", testdata,
+		"-objdir", dir,
+		"issue42580.go")
+	cmd.Stderr = new(bytes.Buffer)
+
+	err = cmd.Run()
+	if err != nil {
+		t.Fatalf("%s: %v\n%s", cmd, err, cmd.Stderr)
+	}
+	mainProcessed, err := ioutil.ReadFile(filepath.Join(dir, "issue42580.cgo1.go"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	fset := token.NewFileSet()
+	f, err := parser.ParseFile(fset, "", mainProcessed, parser.AllErrors)
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+
+	expectation := IdentPositionInfo{
+		"checkedPointer": []ShortPosition{
+			ShortPosition{
+				Line:   32,
+				Column: 56,
+			},
+		},
+		"singleInnerPointerChecked": []ShortPosition{
+			ShortPosition{
+				Line:   37,
+				Column: 91,
+			},
+		},
+		"doublePointerChecked": []ShortPosition{
+			ShortPosition{
+				Line:   42,
+				Column: 91,
+			},
+		},
+	}
+	for _, decl := range f.Decls {
+		if fdecl, ok := decl.(*ast.FuncDecl); ok {
+			ast.Walk(&Visitor{expectation, fset, t}, fdecl.Body)
+		}
+	}
+	for ident, positions := range expectation {
+		for _, position := range positions {
+			if !position.Visited {
+				t.Errorf("Position %d:%d missed for %s ident", position.Line, position.Column, ident)
+			}
+		}
+	}
+}