Support GODEBUG=gotypesalias=1

errcheck/analyzer_test.go

@@ -8,22 +8,33 @@ import (
 )
 
 func TestAnalyzer(t *testing.T) {
-	t.Run("default flags", func(t *testing.T) {
-		packageDir := filepath.Join(analysistest.TestData(), "src/a/")
-		_ = analysistest.Run(t, packageDir, Analyzer)
-	})
+	// Test with and without the gotypesalias flag,
+	// which will be set to 1 by default in Go 1.23.
+	for _, tt := range []string{
+		"gotypesalias=0",
+		"gotypesalias=1",
+	} {
+		t.Run(tt, func(t *testing.T) {
+			t.Setenv("GODEBUG", tt)
 
-	t.Run("check blanks", func(t *testing.T) {
-		packageDir := filepath.Join(analysistest.TestData(), "src/blank/")
-		_ = Analyzer.Flags.Set("blank", "true")
-		_ = analysistest.Run(t, packageDir, Analyzer)
-		_ = Analyzer.Flags.Set("blank", "false") // reset it
-	})
+			t.Run("default flags", func(t *testing.T) {
+				packageDir := filepath.Join(analysistest.TestData(), "src/a/")
+				_ = analysistest.Run(t, packageDir, Analyzer)
+			})
 
-	t.Run("check asserts", func(t *testing.T) {
-		packageDir := filepath.Join(analysistest.TestData(), "src/assert/")
-		_ = Analyzer.Flags.Set("assert", "true")
-		_ = analysistest.Run(t, packageDir, Analyzer)
-		_ = Analyzer.Flags.Set("assert", "false") // reset it
-	})
+			t.Run("check blanks", func(t *testing.T) {
+				packageDir := filepath.Join(analysistest.TestData(), "src/blank/")
+				_ = Analyzer.Flags.Set("blank", "true")
+				_ = analysistest.Run(t, packageDir, Analyzer)
+				_ = Analyzer.Flags.Set("blank", "false") // reset it
+			})
+
+			t.Run("check asserts", func(t *testing.T) {
+				packageDir := filepath.Join(analysistest.TestData(), "src/assert/")
+				_ = Analyzer.Flags.Set("assert", "true")
+				_ = analysistest.Run(t, packageDir, Analyzer)
+				_ = Analyzer.Flags.Set("assert", "false") // reset it
+			})
+		})
+	}
 }

errcheck/embedded_walker.go

@@ -84,7 +84,8 @@ func walkThroughEmbeddedInterfaces(sel *types.Selection) ([]types.Type, bool) {
 }
 
 func getTypeAtFieldIndex(startingAt types.Type, fieldIndex int) types.Type {
-	t := maybeUnname(maybeDereference(startingAt))
+	t := maybeDereference(maybeUnalias(startingAt))
+	t = maybeUnname(maybeUnalias(t))
 	s, ok := t.(*types.Struct)
 	if !ok {
 		panic(fmt.Sprintf("cannot get Field of a type that is not a struct, got a %T", t))

errcheck/embedded_walker_121.go

@@ -0,0 +1,10 @@
+//go:build !go1.22
+// +build !go1.22
+
+package errcheck
+
+import "go/types"
+
+func maybeUnalias(t types.Type) types.Type {
+	return t
+}

errcheck/embedded_walker_122.go

@@ -0,0 +1,10 @@
+//go:build go1.22
+// +build go1.22
+
+package errcheck
+
+import "go/types"
+
+func maybeUnalias(t types.Type) types.Type {
+	return types.Unalias(t)
+}

errcheck/testdata/src/a/main.go

@@ -105,6 +105,19 @@ func main() {
 	_ = x.a() // ok, assigned to blank
 	x.a()     // want "unchecked error"
 
+	// Methods on alias types and pointers to alias types
+	x2 := embedtalias{}
+	_ = x2.a() // ok, assigned to blank
+	x2.a()     // want "unchecked error"
+
+	x3 := &embedtalias{}
+	_ = x3.a() // ok, assigned to blank
+	x3.a()     // want "unchecked error"
+
+	var x4 embedtptralias
+	_ = x4.a() // ok, assigned to blank
+	x4.a()     // want "unchecked error"
+
 	// Method call on a struct member
 	y := u{x}
 	_ = y.t.a() // ok, assigned to blank

errcheck/testdata/src/a/t.go

@@ -15,3 +15,11 @@ func (x t) a() error {
 type u struct {
 	t t
 }
+
+type embedt struct {
+	t
+}
+
+type embedtalias = embedt
+
+type embedtptralias = *embedt