internal/typesinternal: add ReceiverNamed helper

...and factor numerous places to use it.

(This pattern kept recurring during my types.Alias audit,
golang/go#65294.)

Change-Id: I93228b735f7a8ff70df5c998017437d43742d9f3
Reviewed-on: https://go-review.googlesource.com/c/tools/+/565075
Auto-Submit: Alan Donovan <[email protected]>
Reviewed-by: Jonathan Amsterdam <[email protected]>
Reviewed-by: Tim King <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Robert Findley <[email protected]>

Author: adonovan

cmd/deadcode/deadcode.go

@@ -33,7 +33,7 @@ import (
 	"golang.org/x/tools/go/packages"
 	"golang.org/x/tools/go/ssa"
 	"golang.org/x/tools/go/ssa/ssautil"
-	"golang.org/x/tools/internal/aliases"
+	"golang.org/x/tools/internal/typesinternal"
 )
 
 //go:embed doc.go
@@ -385,11 +385,8 @@ func prettyName(fn *ssa.Function, qualified bool) string {
 
 		// method receiver?
 		if recv := fn.Signature.Recv(); recv != nil {
-			t := recv.Type()
-			if ptr, ok := aliases.Unalias(t).(*types.Pointer); ok {
-				t = ptr.Elem()
-			}
-			buf.WriteString(aliases.Unalias(t).(*types.Named).Obj().Name())
+			_, named := typesinternal.ReceiverNamed(recv)
+			buf.WriteString(named.Obj().Name())
 			buf.WriteByte('.')
 		}
 

cmd/guru/describe.go

@@ -19,6 +19,7 @@ import (
 	"golang.org/x/tools/go/ast/astutil"
 	"golang.org/x/tools/go/loader"
 	"golang.org/x/tools/go/types/typeutil"
+	"golang.org/x/tools/internal/typesinternal"
 )
 
 // describe describes the syntax node denoted by the query position,
@@ -911,11 +912,7 @@ func accessibleFields(recv types.Type, from *types.Package) []describeField {
 
 			// Handle recursion through anonymous fields.
 			if f.Anonymous() {
-				tf := f.Type()
-				if ptr, ok := tf.(*types.Pointer); ok {
-					tf = ptr.Elem()
-				}
-				if named, ok := tf.(*types.Named); ok { // (be defensive)
+				if _, named := typesinternal.ReceiverNamed(f); named != nil {
 					// If we've already visited this named type
 					// on this path, break the cycle.
 					for _, x := range stack {

go/analysis/passes/httpmux/httpmux.go

@@ -17,6 +17,7 @@ import (
 	"golang.org/x/tools/go/analysis/passes/internal/analysisutil"
 	"golang.org/x/tools/go/ast/inspector"
 	"golang.org/x/tools/go/types/typeutil"
+	"golang.org/x/tools/internal/typesinternal"
 )
 
 const Doc = `report using Go 1.22 enhanced ServeMux patterns in older Go versions
@@ -83,11 +84,8 @@ func isServeMuxRegisterCall(pass *analysis.Pass, call *ast.CallExpr) bool {
 	if !isMethodNamed(fn, "net/http", "Handle", "HandleFunc") {
 		return false
 	}
-	t, ok := fn.Type().(*types.Signature).Recv().Type().(*types.Pointer)
-	if !ok {
-		return false
-	}
-	return analysisutil.IsNamedType(t.Elem(), "net/http", "ServeMux")
+	isPtr, named := typesinternal.ReceiverNamed(fn.Type().(*types.Signature).Recv())
+	return isPtr && analysisutil.IsNamedType(named, "net/http", "ServeMux")
 }
 
 func isMethodNamed(f *types.Func, pkgPath string, names ...string) bool {

go/analysis/passes/httpresponse/httpresponse.go

@@ -14,6 +14,7 @@ import (
 	"golang.org/x/tools/go/analysis/passes/inspect"
 	"golang.org/x/tools/go/analysis/passes/internal/analysisutil"
 	"golang.org/x/tools/go/ast/inspector"
+	"golang.org/x/tools/internal/typesinternal"
 )
 
 const Doc = `check for mistakes using HTTP responses
@@ -116,7 +117,8 @@ func isHTTPFuncOrMethodOnClient(info *types.Info, expr *ast.CallExpr) bool {
 	if res.Len() != 2 {
 		return false // the function called does not return two values.
 	}
-	if ptr, ok := res.At(0).Type().(*types.Pointer); !ok || !analysisutil.IsNamedType(ptr.Elem(), "net/http", "Response") {
+	isPtr, named := typesinternal.ReceiverNamed(res.At(0))
+	if !isPtr || !analysisutil.IsNamedType(named, "net/http", "Response") {
 		return false // the first return type is not *http.Response.
 	}
 

go/analysis/passes/loopclosure/loopclosure.go

@@ -14,6 +14,7 @@ import (
 	"golang.org/x/tools/go/analysis/passes/internal/analysisutil"
 	"golang.org/x/tools/go/ast/inspector"
 	"golang.org/x/tools/go/types/typeutil"
+	"golang.org/x/tools/internal/typesinternal"
 	"golang.org/x/tools/internal/versions"
 )
 
@@ -367,9 +368,6 @@ func isMethodCall(info *types.Info, expr ast.Expr, pkgPath, typeName, method str
 
 	// Check that the receiver is a <pkgPath>.<typeName> or
 	// *<pkgPath>.<typeName>.
-	rtype := recv.Type()
-	if ptr, ok := recv.Type().(*types.Pointer); ok {
-		rtype = ptr.Elem()
-	}
-	return analysisutil.IsNamedType(rtype, pkgPath, typeName)
+	_, named := typesinternal.ReceiverNamed(recv)
+	return analysisutil.IsNamedType(named, pkgPath, typeName)
 }

go/analysis/passes/slog/slog.go

@@ -20,6 +20,7 @@ import (
 	"golang.org/x/tools/go/analysis/passes/internal/analysisutil"
 	"golang.org/x/tools/go/ast/inspector"
 	"golang.org/x/tools/go/types/typeutil"
+	"golang.org/x/tools/internal/typesinternal"
 )
 
 //go:embed doc.go
@@ -150,14 +151,10 @@ func isAttr(t types.Type) bool {
 func shortName(fn *types.Func) string {
 	var r string
 	if recv := fn.Type().(*types.Signature).Recv(); recv != nil {
-		t := recv.Type()
-		if pt, ok := t.(*types.Pointer); ok {
-			t = pt.Elem()
-		}
-		if nt, ok := t.(*types.Named); ok {
-			r = nt.Obj().Name()
+		if _, named := typesinternal.ReceiverNamed(recv); named != nil {
+			r = named.Obj().Name()
 		} else {
-			r = recv.Type().String()
+			r = recv.Type().String() // anon struct/interface
 		}
 		r += "."
 	}
@@ -173,17 +170,12 @@ func kvFuncSkipArgs(fn *types.Func) (int, bool) {
 		return 0, false
 	}
 	var recvName string // by default a slog package function
-	recv := fn.Type().(*types.Signature).Recv()
-	if recv != nil {
-		t := recv.Type()
-		if pt, ok := t.(*types.Pointer); ok {
-			t = pt.Elem()
-		}
-		if nt, ok := t.(*types.Named); !ok {
-			return 0, false
-		} else {
-			recvName = nt.Obj().Name()
+	if recv := fn.Type().(*types.Signature).Recv(); recv != nil {
+		_, named := typesinternal.ReceiverNamed(recv)
+		if named == nil {
+			return 0, false // anon struct/interface
 		}
+		recvName = named.Obj().Name()
 	}
 	skip, ok := kvFuncs[recvName][fn.Name()]
 	return skip, ok

go/analysis/passes/unmarshal/unmarshal.go

@@ -14,6 +14,7 @@ import (
 	"golang.org/x/tools/go/analysis/passes/internal/analysisutil"
 	"golang.org/x/tools/go/ast/inspector"
 	"golang.org/x/tools/go/types/typeutil"
+	"golang.org/x/tools/internal/typesinternal"
 )
 
 //go:embed doc.go
@@ -69,12 +70,8 @@ func run(pass *analysis.Pass) (interface{}, error) {
 			// (*"encoding/json".Decoder).Decode
 			// (* "encoding/gob".Decoder).Decode
 			// (* "encoding/xml".Decoder).Decode
-			t := recv.Type()
-			if ptr, ok := t.(*types.Pointer); ok {
-				t = ptr.Elem()
-			}
-			tname := t.(*types.Named).Obj()
-			if tname.Name() == "Decoder" {
+			_, named := typesinternal.ReceiverNamed(recv)
+			if tname := named.Obj(); tname.Name() == "Decoder" {
 				switch tname.Pkg().Path() {
 				case "encoding/json", "encoding/xml", "encoding/gob":
 					argidx = 0 // func(interface{})

go/analysis/passes/unusedwrite/unusedwrite.go

@@ -13,6 +13,7 @@ import (
 	"golang.org/x/tools/go/analysis/passes/buildssa"
 	"golang.org/x/tools/go/analysis/passes/internal/analysisutil"
 	"golang.org/x/tools/go/ssa"
+	"golang.org/x/tools/internal/aliases"
 )
 
 //go:embed doc.go
@@ -159,10 +160,13 @@ func hasStructOrArrayType(v ssa.Value) bool {
 //
 // For example, for struct T {x int, y int), getFieldName(*T, 1) returns "y".
 func getFieldName(tp types.Type, index int) string {
-	if pt, ok := tp.(*types.Pointer); ok {
+	// TODO(adonovan): use
+	//   stp, ok := typeparams.Deref(tp).Underlying().(*types.Struct); ok {
+	// when Deref is defined.
+	if pt, ok := aliases.Unalias(tp).(*types.Pointer); ok {
 		tp = pt.Elem()
 	}
-	if named, ok := tp.(*types.Named); ok {
+	if named, ok := aliases.Unalias(tp).(*types.Named); ok {
 		tp = named.Underlying()
 	}
 	if stp, ok := tp.(*types.Struct); ok {

go/ssa/util.go

@@ -18,6 +18,7 @@ import (
 	"golang.org/x/tools/go/ast/astutil"
 	"golang.org/x/tools/go/types/typeutil"
 	"golang.org/x/tools/internal/typeparams"
+	"golang.org/x/tools/internal/typesinternal"
 )
 
 //// Sanity checking utilities
@@ -180,17 +181,13 @@ func makeLen(T types.Type) *Builtin {
 	}
 }
 
-// receiverTypeArgs returns the type arguments to a function's receiver.
-// Returns an empty list if obj does not have a receiver or its receiver does not have type arguments.
-func receiverTypeArgs(obj *types.Func) []types.Type {
-	rtype := recvType(obj)
-	if rtype == nil {
-		return nil
-	}
-	rtype, _ = deptr(rtype)
-	named, ok := rtype.(*types.Named)
-	if !ok {
-		return nil
+// receiverTypeArgs returns the type arguments to a method's receiver.
+// Returns an empty list if the receiver does not have type arguments.
+func receiverTypeArgs(method *types.Func) []types.Type {
+	recv := method.Type().(*types.Signature).Recv()
+	_, named := typesinternal.ReceiverNamed(recv)
+	if named == nil {
+		return nil // recv is anonymous struct/interface
 	}
 	ts := named.TypeArgs()
 	if ts.Len() == 0 {

go/types/objectpath/objectpath.go

@@ -30,6 +30,7 @@ import (
 	"strings"
 
 	"golang.org/x/tools/internal/typeparams"
+	"golang.org/x/tools/internal/typesinternal"
 )
 
 // A Path is an opaque name that identifies a types.Object
@@ -395,13 +396,8 @@ func (enc *Encoder) concreteMethod(meth *types.Func) (Path, bool) {
 		return "", false
 	}
 
-	recvT := meth.Type().(*types.Signature).Recv().Type()
-	if ptr, ok := recvT.(*types.Pointer); ok {
-		recvT = ptr.Elem()
-	}
-
-	named, ok := recvT.(*types.Named)
-	if !ok {
+	_, named := typesinternal.ReceiverNamed(meth.Type().(*types.Signature).Recv())
+	if named == nil {
 		return "", false
 	}