go/ssa/ssautil: isolate deprecated CreateProgram

Isolate CreateProgram and its test into their own files
to further emphasize that these are deprecated.

Change-Id: I441a456752cc3d1728ab86c98e785c59696980f2
Reviewed-on: https://go-review.googlesource.com/c/tools/+/616976
Reviewed-by: Alan Donovan <adonovan@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Tim King <taking@google.com>

Author: timothy-king

go/ssa/ssautil/deprecated.go

@@ -0,0 +1,36 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssautil
+
+// This file contains deprecated public APIs.
+// We discourage their use.
+
+import (
+	"golang.org/x/tools/go/loader"
+	"golang.org/x/tools/go/ssa"
+)
+
+// CreateProgram returns a new program in SSA form, given a program
+// loaded from source.  An SSA package is created for each transitively
+// error-free package of lprog.
+//
+// Code for bodies of functions is not built until Build is called
+// on the result.
+//
+// The mode parameter controls diagnostics and checking during SSA construction.
+//
+// Deprecated: Use [golang.org/x/tools/go/packages] and the [Packages]
+// function instead; see ssa.Example_loadPackages.
+func CreateProgram(lprog *loader.Program, mode ssa.BuilderMode) *ssa.Program {
+	prog := ssa.NewProgram(lprog.Fset, mode)
+
+	for _, info := range lprog.AllPackages {
+		if info.TransitivelyErrorFree {
+			prog.CreatePackage(info.Pkg, info.Files, &info.Info, info.Importable)
+		}
+	}
+
+	return prog
+}

go/ssa/ssautil/deprecated_test.go

@@ -0,0 +1,49 @@
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssautil_test
+
+// Tests of deprecated public APIs.
+// We are keeping some tests around to have some test of the public API.
+
+import (
+	"go/parser"
+	"os"
+	"testing"
+
+	"golang.org/x/tools/go/loader"
+	"golang.org/x/tools/go/ssa"
+	"golang.org/x/tools/go/ssa/ssautil"
+)
+
+// TestCreateProgram tests CreateProgram which has an x/tools/go/loader.Program.
+func TestCreateProgram(t *testing.T) {
+	conf := loader.Config{ParserMode: parser.ParseComments}
+	f, err := conf.ParseFile("hello.go", hello)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	conf.CreateFromFiles("main", f)
+	iprog, err := conf.Load()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(iprog.Created) != 1 {
+		t.Fatalf("Expected 1 Created package. got %d", len(iprog.Created))
+	}
+	pkg := iprog.Created[0].Pkg
+
+	prog := ssautil.CreateProgram(iprog, ssa.BuilderMode(0))
+	ssapkg := prog.Package(pkg)
+	ssapkg.Build()
+
+	if pkg.Name() != "main" {
+		t.Errorf("pkg.Name() = %s, want main", pkg.Name())
+	}
+	if ssapkg.Func("main") == nil {
+		ssapkg.WriteTo(os.Stderr)
+		t.Errorf("ssapkg has no main function")
+	}
+}

go/ssa/ssautil/load.go

@@ -11,7 +11,6 @@ import (
 	"go/token"
 	"go/types"
 
-	"golang.org/x/tools/go/loader"
 	"golang.org/x/tools/go/packages"
 	"golang.org/x/tools/go/ssa"
 	"golang.org/x/tools/internal/versions"
@@ -111,29 +110,6 @@ func doPackages(initial []*packages.Package, mode ssa.BuilderMode, deps bool) (*
 	return prog, ssapkgs
 }
 
-// CreateProgram returns a new program in SSA form, given a program
-// loaded from source.  An SSA package is created for each transitively
-// error-free package of lprog.
-//
-// Code for bodies of functions is not built until Build is called
-// on the result.
-//
-// The mode parameter controls diagnostics and checking during SSA construction.
-//
-// Deprecated: Use [golang.org/x/tools/go/packages] and the [Packages]
-// function instead; see ssa.Example_loadPackages.
-func CreateProgram(lprog *loader.Program, mode ssa.BuilderMode) *ssa.Program {
-	prog := ssa.NewProgram(lprog.Fset, mode)
-
-	for _, info := range lprog.AllPackages {
-		if info.TransitivelyErrorFree {
-			prog.CreatePackage(info.Pkg, info.Files, &info.Info, info.Importable)
-		}
-	}
-
-	return prog
-}
-
 // BuildPackage builds an SSA program with SSA intermediate
 // representation (IR) for all functions of a single package.
 //

go/ssa/ssautil/switch_test.go

@@ -10,13 +10,9 @@
 package ssautil_test
 
 import (
-	"go/ast"
-	"go/parser"
-	"path/filepath"
 	"strings"
 	"testing"
 
-	"golang.org/x/tools/go/loader"
 	"golang.org/x/tools/go/ssa"
 	"golang.org/x/tools/go/ssa/ssautil"
 	"golang.org/x/tools/internal/testfiles"
@@ -32,39 +28,12 @@ func TestSwitches(t *testing.T) {
 	if len(ppkgs) != 1 {
 		t.Fatalf("Expected to load one package but got %d", len(ppkgs))
 	}
+	f := ppkgs[0].Syntax[0]
 
 	prog, _ := ssautil.Packages(ppkgs, ssa.BuilderMode(0))
 	mainPkg := prog.Package(ppkgs[0].Types)
 	mainPkg.Build()
-	testSwitches(t, ppkgs[0].Syntax[0], mainPkg)
-}
-
-// TestCreateProgram uses loader and ssautil.CreateProgram to create an *ssa.Program.
-// It has the same testing logic with TestSwitches.
-// CreateProgram is deprecated, but it is a part of the public API.
-// For now keep a test that exercises it.
-func TestCreateProgram(t *testing.T) {
-	dir := testfiles.ExtractTxtarFileToTmp(t, "testdata/switches.txtar")
-	conf := loader.Config{ParserMode: parser.ParseComments}
-	f, err := conf.ParseFile(filepath.Join(dir, "switches.go"), nil)
-	if err != nil {
-		t.Error(err)
-		return
-	}
-
-	conf.CreateFromFiles("main", f)
-	iprog, err := conf.Load()
-	if err != nil {
-		t.Error(err)
-		return
-	}
-	prog := ssautil.CreateProgram(iprog, ssa.BuilderMode(0))
-	mainPkg := prog.Package(iprog.Created[0].Pkg)
-	mainPkg.Build()
-	testSwitches(t, f, mainPkg)
-}
 
-func testSwitches(t *testing.T, f *ast.File, mainPkg *ssa.Package) {
 	for _, mem := range mainPkg.Members {
 		if fn, ok := mem.(*ssa.Function); ok {
 			if fn.Synthetic != "" {