internal/xtypes: handle new Union and TypeParam types (#399)

Fixes #398

.github/workflows/go.yml

@@ -8,9 +8,9 @@
       "runs-on": "ubuntu-latest",
       steps: [
         {
-          name: "Set up Go 1.16",
+          name: "Set up Go 1.18",
           uses: "actions/setup-go@v1",
-          "with": {"go-version": 1.16},
+          "with": {"go-version": 1.18},
           id: "go",
         },
         {name: "Check out code into the Go module directory", uses: "actions/checkout@v1"},

Makefile

@@ -32,7 +32,7 @@ test-release:
 	@echo "everything is OK"
 
 lint:
-	curl -sSfL https://raw.githubusercontent.com/golangci/golangci-lint/master/install.sh | sh -s -- -b $(GOPATH_DIR)/bin v1.43.0
+	curl -sSfL https://raw.githubusercontent.com/golangci/golangci-lint/master/install.sh | sh -s -- -b $(GOPATH_DIR)/bin v1.49.0
 	$(GOPATH_DIR)/bin/golangci-lint run ./...
 	go build -o go-ruleguard ./cmd/ruleguard
 	./go-ruleguard -debug-imports -rules rules.go ./...

analyzer/analyzer_test.go

@@ -48,6 +48,7 @@ var tests = []struct {
 	{name: "localfunc"},
 	{name: "goversion", flags: map[string]string{"go": "1.16"}},
 	{name: "imports"},
+	{name: "generics"},
 
 	{name: "quickfix", quickfixes: true},
 }

analyzer/testdata/src/generics/rules.go

@@ -0,0 +1,12 @@
+//go:build ignore
+// +build ignore
+
+package gorules
+
+import "github.com/quasilyte/go-ruleguard/dsl"
+
+func externalErrorReassign(m dsl.Matcher) {
+	m.Match(`$pkg.$err = $x`).
+		Where(m["err"].Type.Is(`error`) && m["pkg"].Object.Is(`PkgName`)).
+		Report(`suspicious reassigment of error from another package`)
+}

analyzer/testdata/src/generics/target.go

@@ -0,0 +1,9 @@
+package main
+
+type myType[T any] struct {
+	value T
+}
+
+func (m *myType[T]) set(v T) {
+	m.value = v
+}

go.mod

@@ -9,6 +9,7 @@ require (
 	github.com/quasilyte/go-ruleguard/rules v0.0.0-20211022131956-028d6511ab71
 	github.com/quasilyte/gogrep v0.0.0-20220120141003-628d8b3623b5
 	github.com/quasilyte/stdinfo v0.0.0-20220114132959-f7386bf02567
+	golang.org/x/exp/typeparams v0.0.0-20220827204233-334a2380cb91
 	golang.org/x/tools v0.1.12
 )
 

go.sum

@@ -26,6 +26,8 @@ golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACk
 golang.org/x/crypto v0.0.0-20191011191535-87dc89f01550/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
 golang.org/x/crypto v0.0.0-20200622213623-75b288015ac9/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
 golang.org/x/crypto v0.0.0-20210921155107-089bfa567519/go.mod h1:GvvjBRRGRdwPK5ydBHafDWAxML/pGHZbMvKqRZ5+Abc=
+golang.org/x/exp/typeparams v0.0.0-20220827204233-334a2380cb91 h1:Ic/qN6TEifvObMGQy72k0n1LlJr7DjWWEi+MOsDOiSk=
+golang.org/x/exp/typeparams v0.0.0-20220827204233-334a2380cb91/go.mod h1:AbB0pIl9nAr9wVwH+Z2ZpaocVmF5I4GyWCDIsVjR0bk=
 golang.org/x/mod v0.3.0/go.mod h1:s0Qsj1ACt9ePp/hMypM3fl4fZqREWJwdYDEqhRiZZUA=
 golang.org/x/mod v0.6.0-dev.0.20220419223038-86c51ed26bb4 h1:6zppjxzCulZykYSLyVDYbneBfbaBIQPYMevg0bEwv2s=
 golang.org/x/mod v0.6.0-dev.0.20220419223038-86c51ed26bb4/go.mod h1:jJ57K6gSWd91VN4djpZkiMVwK6gcyfeH4XE8wZrZaV4=

internal/xtypes/xtypes.go

@@ -2,6 +2,8 @@ package xtypes
 
 import (
 	"go/types"
+
+	"golang.org/x/exp/typeparams"
 )
 
 // Implements reports whether type v implements iface.
@@ -63,9 +65,6 @@ func typeIdentical(x, y types.Type, p *ifacePair) bool {
 	}
 
 	switch x := x.(type) {
-	case nil:
-		return false
-
 	case *types.Basic:
 		// Basic types are singletons except for the rune and byte
 		// aliases, thus we cannot solely rely on the x == y check
@@ -142,6 +141,11 @@ func typeIdentical(x, y types.Type, p *ifacePair) bool {
 				typeIdentical(x.Results(), y.Results(), p)
 		}
 
+	case *typeparams.Union:
+		// TODO(quasilyte): do we want to match generic union types too?
+		// It would require copying a lot of code from the go/types.
+		return false
+
 	case *types.Interface:
 		// Two interface types are identical if they have the same set of methods with
 		// the same names and identical function types. Lower-case method names from
@@ -214,6 +218,12 @@ func typeIdentical(x, y types.Type, p *ifacePair) bool {
 		}
 		return sameID(x.Obj(), y.Obj().Pkg(), y.Obj().Name())
 
+	case *typeparams.TypeParam:
+		// nothing to do (x and y being equal is caught in the very beginning of this function)
+
+	case nil:
+		// avoid a crash in case of nil type
+
 	default:
 		panic("unreachable")
 	}