Use types.Func.Origin instead of typeparams.OriginMethod

The Origin method was added in Go 1.19.

Using it also avoids a bug in typeparams.OriginMethod, where methods
named "_" lead to panics.

go/ir/methods.go

@@ -11,8 +11,6 @@ import (
 	"go/types"
 
 	"honnef.co/go/tools/analysis/lint"
-
-	"golang.org/x/exp/typeparams"
 )
 
 // MethodValue returns the Function implementing method sel, building
@@ -118,7 +116,7 @@ func (prog *Program) RuntimeTypes() []types.Type {
 // declaredFunc returns the concrete function/method denoted by obj.
 // Panic ensues if there is none.
 func (prog *Program) declaredFunc(obj *types.Func) *Function {
-	if origin := typeparams.OriginMethod(obj); origin != obj {
+	if origin := obj.Origin(); origin != obj {
 		// Calling method on instantiated type, create a wrapper that calls the generic type's method
 		base := prog.packageLevelValue(origin)
 		return makeInstance(prog, base.(*Function), obj.Type().(*types.Signature), nil)

go/ir/source.go

@@ -14,8 +14,6 @@ import (
 	"go/ast"
 	"go/token"
 	"go/types"
-
-	"golang.org/x/exp/typeparams"
 )
 
 // EnclosingFunction returns the function that contains the syntax
@@ -170,7 +168,7 @@ func (prog *Program) packageLevelValue(obj types.Object) Value {
 // TODO(adonovan): check the invariant that obj.Type() matches the
 // result's Signature, both in the params/results and in the receiver.
 func (prog *Program) FuncValue(obj *types.Func) *Function {
-	obj = typeparams.OriginMethod(obj)
+	obj = obj.Origin()
 	fn, _ := prog.packageLevelValue(obj).(*Function)
 	return fn
 }

staticcheck/lint.go

@@ -3182,7 +3182,7 @@ func CheckDeprecated(pass *analysis.Pass) (interface{}, error) {
 
 		obj := pass.TypesInfo.ObjectOf(sel.Sel)
 		if obj_, ok := obj.(*types.Func); ok {
-			obj = typeparams.OriginMethod(obj_)
+			obj = obj_.Origin()
 		}
 		if obj.Pkg() == nil {
 			return true

unused/unused.go

@@ -17,7 +17,6 @@ import (
 	"honnef.co/go/tools/go/ast/astutil"
 	"honnef.co/go/tools/go/types/typeutil"
 
-	"golang.org/x/exp/typeparams"
 	"golang.org/x/tools/go/analysis"
 	"golang.org/x/tools/go/types/objectpath"
 )
@@ -1151,8 +1150,7 @@ func (g *graph) decl(decl ast.Decl, by types.Object) {
 		}
 
 	case *ast.FuncDecl:
-		// XXX calling OriginMethod is unnecessary if we use types.Func.Origin
-		obj := typeparams.OriginMethod(g.info.ObjectOf(decl.Name).(*types.Func))
+		obj := g.info.ObjectOf(decl.Name).(*types.Func).Origin()
 		g.see(obj, nil)
 
 		if token.IsExported(decl.Name.Name) && g.opts.ExportedIsUsed {