cmd/compile: switch to final unified IR export format

Now that there's a native go/types importer for unified IR, the
compiler no longer needs to stay backwards compatible with old iexport
importers.

This CL also updates the go/types and go/internal/gcimporter tests to
expect that the unified IR importer sets the receiver parameter type
to the underlying Interface type, rather than the Named type. This is
a temporary workaround until we make a decision on #49906.

Notably, this makes `GOEXPERIMENT=unified go test` work on generics
code without requiring `-vet=off` (because previously cmd/vet was
relying on unified IR's backwards-compatible iexport data, which
omitted generic types).

Change-Id: Iac7a2346bb7a91e6690fb2978fb702fadae5559d
Reviewed-on: https://go-review.googlesource.com/c/go/+/386004
Trust: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Robert Griesemer <gri@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

7 files changed, 89 insertions, 133 deletions

diff --git a/src/cmd/compile/internal/importer/gcimporter_test.go b/src/cmd/compile/internal/importer/gcimporter_test.go
index 9fecf742fb..3b6d77747b 100644
--- a/src/cmd/compile/internal/importer/gcimporter_test.go
+++ b/src/cmd/compile/internal/importer/gcimporter_test.go
@@ -115,10 +115,14 @@ func TestImportTestdata(t *testing.T) {
 	}
 
 	testfiles := map[string][]string{
-		"exports.go": {"go/ast", "go/token"},
+		"exports.go":  {"go/ast", "go/token"},
+		"generics.go": nil,
 	}
-	if !goexperiment.Unified {
-		testfiles["generics.go"] = nil
+	if goexperiment.Unified {
+		// TODO(mdempsky): Fix test below to flatten the transitive
+		// Package.Imports graph. Unified IR is more precise about
+		// recreating the package import graph.
+		testfiles["exports.go"] = []string{"go/ast"}
 	}
 
 	for testfile, wantImports := range testfiles {
@@ -326,6 +330,14 @@ func verifyInterfaceMethodRecvs(t *testing.T, named *types2.Named, level int) {
 		return // not an interface
 	}
 
+	// The unified IR importer always sets interface method receiver
+	// parameters to point to the Interface type, rather than the Named.
+	// See #49906.
+	var want types2.Type = named
+	if goexperiment.Unified {
+		want = iface
+	}
+
 	// check explicitly declared methods
 	for i := 0; i < iface.NumExplicitMethods(); i++ {
 		m := iface.ExplicitMethod(i)
@@ -334,7 +346,7 @@ func verifyInterfaceMethodRecvs(t *testing.T, named *types2.Named, level int) {
 			t.Errorf("%s: missing receiver type", m)
 			continue
 		}
-		if recv.Type() != named {
+		if recv.Type() != want {
 			t.Errorf("%s: got recv type %s; want %s", m, recv.Type(), named)
 		}
 	}
diff --git a/src/cmd/compile/internal/noder/export.go b/src/cmd/compile/internal/noder/export.go
index 1a296e22c8..263cdc262b 100644
--- a/src/cmd/compile/internal/noder/export.go
+++ b/src/cmd/compile/internal/noder/export.go
@@ -14,52 +14,22 @@ import (
 	"cmd/internal/bio"
 )
 
-// writeNewExportFunc is a hook that can be added to append extra
-// export data after the normal export data section. It allows
-// experimenting with new export data format designs without requiring
-// immediate support in the go/internal or x/tools importers.
-var writeNewExportFunc func(out io.Writer)
-
 func WriteExports(out *bio.Writer) {
-	// When unified IR exports are enable, we simply append it to the
-	// end of the normal export data (with compiler extensions
-	// disabled), and write an extra header giving its size.
-	//
-	// If the compiler sees this header, it knows to read the new data
-	// instead; meanwhile the go/types importers will silently ignore it
-	// and continue processing the old export instead.
-	//
-	// This allows us to experiment with changes to the new export data
-	// format without needing to update the go/internal/gcimporter or
-	// (worse) x/tools/go/gcexportdata.
-
-	useNewExport := writeNewExportFunc != nil
-
-	var old, new bytes.Buffer
-
-	typecheck.WriteExports(&old, !useNewExport)
-
-	if useNewExport {
-		writeNewExportFunc(&new)
-	}
-
-	oldLen := old.Len()
-	newLen := new.Len()
+	var data bytes.Buffer
 
-	if useNewExport {
-		fmt.Fprintf(out, "\nnewexportsize %v\n", newLen)
+	if base.Debug.Unified != 0 {
+		data.WriteByte('u')
+		writeUnifiedExport(&data)
+	} else {
+		typecheck.WriteExports(&data, true)
 	}
 
 	// The linker also looks for the $$ marker - use char after $$ to distinguish format.
 	out.WriteString("\n$$B\n") // indicate binary export format
-	io.Copy(out, &old)
+	io.Copy(out, &data)
 	out.WriteString("\n$$\n")
-	io.Copy(out, &new)
 
 	if base.Debug.Export != 0 {
-		fmt.Printf("BenchmarkExportSize:%s 1 %d bytes\n", base.Ctxt.Pkgpath, oldLen)
-		if useNewExport {
-			fmt.Printf("BenchmarkNewExportSize:%s 1 %d bytes\n", base.Ctxt.Pkgpath, newLen)
-		}
+		fmt.Printf("BenchmarkExportSize:%s 1 %d bytes\n", base.Ctxt.Pkgpath, data.Len())
 	}
 }
diff --git a/src/cmd/compile/internal/noder/import.go b/src/cmd/compile/internal/noder/import.go
index 7ba1b23d12..2cef9f75e8 100644
--- a/src/cmd/compile/internal/noder/import.go
+++ b/src/cmd/compile/internal/noder/import.go
@@ -8,10 +8,10 @@ import (
 	"errors"
 	"fmt"
 	"internal/buildcfg"
+	"internal/pkgbits"
 	"os"
 	pathpkg "path"
 	"runtime"
-	"strconv"
 	"strings"
 	"unicode"
 	"unicode/utf8"
@@ -28,22 +28,6 @@ import (
 	"cmd/internal/objabi"
 )
 
-// haveLegacyImports records whether we've imported any packages
-// without a new export data section. This is useful for experimenting
-// with new export data format designs, when you need to support
-// existing tests that manually compile files with inconsistent
-// compiler flags.
-var haveLegacyImports = false
-
-// newReadImportFunc is an extension hook for experimenting with new
-// export data formats. If a new export data payload was written out
-// for an imported package by overloading writeNewExportFunc, then
-// that payload will be mapped into memory and passed to
-// newReadImportFunc.
-var newReadImportFunc = func(data string, pkg1 *types.Pkg, env *types2.Context, packages map[string]*types2.Package) (pkg2 *types2.Package, err error) {
-	panic("unexpected new export data payload")
-}
-
 type gcimports struct {
 	ctxt     *types2.Context
 	packages map[string]*types2.Package
@@ -220,7 +204,7 @@ func readImportFile(path string, target *ir.Package, env *types2.Context, packag
 	}
 	defer f.Close()
 
-	r, end, newsize, err := findExportData(f)
+	r, end, err := findExportData(f)
 	if err != nil {
 		return
 	}
@@ -229,41 +213,40 @@ func readImportFile(path string, target *ir.Package, env *types2.Context, packag
 		fmt.Printf("importing %s (%s)\n", path, f.Name())
 	}
 
-	if newsize != 0 {
-		// We have unified IR data. Map it, and feed to the importers.
-		end -= newsize
-		var data string
-		data, err = base.MapFile(r.File(), end, newsize)
-		if err != nil {
-			return
-		}
+	c, err := r.ReadByte()
+	if err != nil {
+		return
+	}
 
-		pkg2, err = newReadImportFunc(data, pkg1, env, packages)
-	} else {
-		// We only have old data. Oh well, fall back to the legacy importers.
-		haveLegacyImports = true
+	pos := r.Offset()
 
-		var c byte
-		switch c, err = r.ReadByte(); {
-		case err != nil:
-			return
+	// Map export data section into memory as a single large
+	// string. This reduces heap fragmentation and allows returning
+	// individual substrings very efficiently.
+	var data string
+	data, err = base.MapFile(r.File(), pos, end-pos)
+	if err != nil {
+		return
+	}
 
-		case c != 'i':
-			// Indexed format is distinguished by an 'i' byte,
-			// whereas previous export formats started with 'c', 'd', or 'v'.
-			err = fmt.Errorf("unexpected package format byte: %v", c)
-			return
+	switch c {
+	case 'u':
+		if !buildcfg.Experiment.Unified {
+			base.Fatalf("unexpected export data format")
 		}
 
-		pos := r.Offset()
+		// TODO(mdempsky): This seems a bit clunky.
+		data = strings.TrimSuffix(data, "\n$$\n")
 
-		// Map string (and data) section into memory as a single large
-		// string. This reduces heap fragmentation and allows
-		// returning individual substrings very efficiently.
-		var data string
-		data, err = base.MapFile(r.File(), pos, end-pos)
-		if err != nil {
-			return
+		pr := pkgbits.NewPkgDecoder(pkg1.Path, data)
+
+		// Read package descriptors for both types2 and compiler backend.
+		readPackage(newPkgReader(pr), pkg1)
+		pkg2 = importer.ReadPackage(env, packages, pr)
+
+	case 'i':
+		if buildcfg.Experiment.Unified {
+			base.Fatalf("unexpected export data format")
 		}
 
 		typecheck.ReadImports(pkg1, data)
@@ -274,6 +257,12 @@ func readImportFile(path string, target *ir.Package, env *types2.Context, packag
 				return
 			}
 		}
+
+	default:
+		// Indexed format is distinguished by an 'i' byte,
+		// whereas previous export formats started with 'c', 'd', or 'v'.
+		err = fmt.Errorf("unexpected package format byte: %v", c)
+		return
 	}
 
 	err = addFingerprint(path, f, end)
@@ -283,7 +272,7 @@ func readImportFile(path string, target *ir.Package, env *types2.Context, packag
 // findExportData returns a *bio.Reader positioned at the start of the
 // binary export data section, and a file offset for where to stop
 // reading.
-func findExportData(f *os.File) (r *bio.Reader, end, newsize int64, err error) {
+func findExportData(f *os.File) (r *bio.Reader, end int64, err error) {
 	r = bio.NewReader(f)
 
 	// check object header
@@ -326,14 +315,6 @@ func findExportData(f *os.File) (r *bio.Reader, end, newsize int64, err error) {
 
 	// process header lines
 	for !strings.HasPrefix(line, "$$") {
-		if strings.HasPrefix(line, "newexportsize ") {
-			fields := strings.Fields(line)
-			newsize, err = strconv.ParseInt(fields[1], 10, 64)
-			if err != nil {
-				return
-			}
-		}
-
 		line, err = r.ReadString('\n')
 		if err != nil {
 			return
diff --git a/src/cmd/compile/internal/noder/reader.go b/src/cmd/compile/internal/noder/reader.go
index 71efac80aa..1350c22467 100644
--- a/src/cmd/compile/internal/noder/reader.go
+++ b/src/cmd/compile/internal/noder/reader.go
@@ -589,10 +589,6 @@ func (pr *pkgReader) objIdx(idx int, implicits, explicits []*types.Type) ir.Node
 		if pri, ok := objReader[sym]; ok {
 			return pri.pr.objIdx(pri.idx, nil, explicits)
 		}
-		if haveLegacyImports {
-			assert(len(explicits) == 0)
-			return typecheck.Resolve(ir.NewIdent(src.NoXPos, sym))
-		}
 		base.Fatalf("unresolved stub: %v", sym)
 	}
 
@@ -1972,12 +1968,6 @@ func InlineCall(call *ir.CallExpr, fn *ir.Func, inlIndex int) *ir.InlinedCallExp
 
 	pri, ok := bodyReader[fn]
 	if !ok {
-		// Assume it's an imported function or something that we don't
-		// have access to in quirks mode.
-		if haveLegacyImports {
-			return nil
-		}
-
 		base.FatalfAt(call.Pos(), "missing function body for call to %v", fn)
 	}
 
diff --git a/src/cmd/compile/internal/noder/unified.go b/src/cmd/compile/internal/noder/unified.go
index f45c4a7ea8..2c1f2362ad 100644
--- a/src/cmd/compile/internal/noder/unified.go
+++ b/src/cmd/compile/internal/noder/unified.go
@@ -16,7 +16,6 @@ import (
 	"sort"
 
 	"cmd/compile/internal/base"
-	"cmd/compile/internal/importer"
 	"cmd/compile/internal/inline"
 	"cmd/compile/internal/ir"
 	"cmd/compile/internal/typecheck"
@@ -74,17 +73,6 @@ var localPkgReader *pkgReader
 func unified(noders []*noder) {
 	inline.NewInline = InlineCall
 
-	writeNewExportFunc = writeNewExport
-
-	newReadImportFunc = func(data string, pkg1 *types.Pkg, ctxt *types2.Context, packages map[string]*types2.Package) (pkg2 *types2.Package, err error) {
-		pr := pkgbits.NewPkgDecoder(pkg1.Path, data)
-
-		// Read package descriptors for both types2 and compiler backend.
-		readPackage(newPkgReader(pr), pkg1)
-		pkg2 = importer.ReadPackage(ctxt, packages, pr)
-		return
-	}
-
 	data := writePkgStub(noders)
 
 	// We already passed base.Flag.Lang to types2 to handle validating
@@ -266,7 +254,7 @@ func readPackage(pr *pkgReader, importpkg *types.Pkg) {
 	}
 }
 
-func writeNewExport(out io.Writer) {
+func writeUnifiedExport(out io.Writer) {
 	l := linker{
 		pw: pkgbits.NewPkgEncoder(base.Debug.SyncFrames),
 
@@ -332,5 +320,5 @@ func writeNewExport(out io.Writer) {
 		w.Flush()
 	}
 
-	l.pw.DumpTo(out)
+	base.Ctxt.Fingerprint = l.pw.DumpTo(out)
 }
diff --git a/src/go/internal/gcimporter/gcimporter_test.go b/src/go/internal/gcimporter/gcimporter_test.go
index 89b7fde836..c10915fdf5 100644
--- a/src/go/internal/gcimporter/gcimporter_test.go
+++ b/src/go/internal/gcimporter/gcimporter_test.go
@@ -125,10 +125,14 @@ func TestImportTestdata(t *testing.T) {
 	}
 
 	testfiles := map[string][]string{
-		"exports.go": {"go/ast", "go/token"},
+		"exports.go":  {"go/ast", "go/token"},
+		"generics.go": nil,
 	}
-	if !goexperiment.Unified {
-		testfiles["generics.go"] = nil
+	if goexperiment.Unified {
+		// TODO(mdempsky): Fix test below to flatten the transitive
+		// Package.Imports graph. Unified IR is more precise about
+		// recreating the package import graph.
+		testfiles["exports.go"] = []string{"go/ast"}
 	}
 
 	for testfile, wantImports := range testfiles {
@@ -153,11 +157,6 @@ func TestImportTestdata(t *testing.T) {
 }
 
 func TestImportTypeparamTests(t *testing.T) {
-	// This test doesn't yet work with the unified export format.
-	if goexperiment.Unified {
-		t.Skip("unified export data format is currently unsupported")
-	}
-
 	// This package only handles gc export data.
 	if runtime.Compiler != "gc" {
 		t.Skipf("gc-built packages not available (compiler = %s)", runtime.Compiler)
@@ -460,6 +459,14 @@ func verifyInterfaceMethodRecvs(t *testing.T, named *types.Named, level int) {
 		return // not an interface
 	}
 
+	// The unified IR importer always sets interface method receiver
+	// parameters to point to the Interface type, rather than the Named.
+	// See #49906.
+	var want types.Type = named
+	if goexperiment.Unified {
+		want = iface
+	}
+
 	// check explicitly declared methods
 	for i := 0; i < iface.NumExplicitMethods(); i++ {
 		m := iface.ExplicitMethod(i)
@@ -468,8 +475,8 @@ func verifyInterfaceMethodRecvs(t *testing.T, named *types.Named, level int) {
 			t.Errorf("%s: missing receiver type", m)
 			continue
 		}
-		if recv.Type() != named {
-			t.Errorf("%s: got recv type %s; want %s", m, recv.Type(), named)
+		if recv.Type() != want {
+			t.Errorf("%s: got recv type %s; want %s", m, recv.Type(), want)
 		}
 	}
 
diff --git a/src/go/types/eval_test.go b/src/go/types/eval_test.go
index b0745c16d9..6f5b548eb2 100644
--- a/src/go/types/eval_test.go
+++ b/src/go/types/eval_test.go
@@ -12,6 +12,7 @@ import (
 	"go/importer"
 	"go/parser"
 	"go/token"
+	"internal/goexperiment"
 	"internal/testenv"
 	"strings"
 	"testing"
@@ -208,7 +209,7 @@ func TestCheckExpr(t *testing.T) {
 	// expr is an identifier or selector expression that is passed
 	// to CheckExpr at the position of the comment, and object is
 	// the string form of the object it denotes.
-	const src = `
+	src := `
 package p
 
 import "fmt"
@@ -235,6 +236,13 @@ func f(a int, s string) S {
 	return S{}
 }`
 
+	// The unified IR importer always sets interface method receiver
+	// parameters to point to the Interface type, rather than the Named.
+	// See #49906.
+	if goexperiment.Unified {
+		src = strings.ReplaceAll(src, "func (fmt.Stringer).", "func (interface).")
+	}
+
 	fset := token.NewFileSet()
 	f, err := parser.ParseFile(fset, "p", src, parser.ParseComments)
 	if err != nil {