bpf2go: import package structs when all structs are typedefs

cmd/bpf2go/gen/output.go

@@ -169,7 +169,7 @@ func Generate(args GenerateArgs) error {
 		if err != nil {
 			return fmt.Errorf("generating %s: %w", name, err)
 		}
-		_, ok := typ.(*btf.Struct)
+		_, ok := btf.As[*btf.Struct](typ)
 		needsStructsPkg = needsStructsPkg || ok
 		typeDecls = append(typeDecls, decl)
 	}

cmd/bpf2go/gen/output_test.go

@@ -118,3 +118,56 @@ func TestObjects(t *testing.T) {
 	qt.Assert(t, qt.StringContains(str, "Var1 *ebpf.Variable `ebpf:\"var_1\"`"))
 	qt.Assert(t, qt.StringContains(str, "ProgFoo1 *ebpf.Program `ebpf:\"prog_foo_1\"`"))
 }
+
+func TestGenerateStructTypes(t *testing.T) {
+	ts := &btf.Struct{
+		Name: "test_struct",
+		Size: 8,
+		Members: []btf.Member{
+			{
+				Name:   "field1",
+				Type:   &btf.Int{Size: 8, Encoding: btf.Unsigned},
+				Offset: 0,
+			},
+		},
+	}
+	td := &btf.Typedef{
+		Name: "test_typedef",
+		Type: ts,
+	}
+
+	tests := []struct {
+		name     string
+		types    []btf.Type
+		expected string
+	}{
+		{
+			name:     "simple struct",
+			types:    []btf.Type{ts},
+			expected: "type stemTestStruct struct {\n\t_      structs.HostLayout\n\tField1 uint64\n}",
+		},
+		{
+			name:     "typedef struct",
+			types:    []btf.Type{td},
+			expected: "type stemTestTypedef struct {\n\t_      structs.HostLayout\n\tField1 uint64\n}",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			var buf bytes.Buffer
+			err := Generate(GenerateArgs{
+				Package:     "test",
+				Stem:        "stem",
+				Types:       tt.types,
+				Output:      &buf,
+				Constraints: nil,
+			})
+			qt.Assert(t, qt.IsNil(err))
+
+			str := buf.String()
+			qt.Assert(t, qt.StringContains(str, tt.expected))
+			qt.Assert(t, qt.StringContains(str, "\"structs\""))
+		})
+	}
+}