all: clean up TODO after fixing issue 44505

For #44505

Change-Id: I89220be02372b5340cb987bf2ac870a9346a8c8f
Reviewed-on: https://go-review.googlesource.com/c/go/+/421079
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>

src/cmd/asm/internal/lex/tokenizer.go

@@ -5,6 +5,7 @@
 package lex
 
 import (
+	"go/build/constraint"
 	"io"
 	"os"
 	"strings"
@@ -109,8 +110,7 @@ func (t *Tokenizer) Next() ScanToken {
 		}
 		text := s.TokenText()
 		t.line += strings.Count(text, "\n")
-		// TODO: Use constraint.IsGoBuild once #44505 fixed.
-		if strings.HasPrefix(text, "//go:build") {
+		if constraint.IsGoBuild(text) {
 			t.tok = BuildComment
 			break
 		}

src/cmd/compile/internal/noder/unified.go

@@ -5,13 +5,13 @@
 package noder
 
 import (
-	"bytes"
 	"fmt"
 	"internal/goversion"
 	"internal/pkgbits"
 	"io"
 	"runtime"
 	"sort"
+	"strings"
 
 	"cmd/compile/internal/base"
 	"cmd/compile/internal/inline"
@@ -180,7 +180,7 @@ func writePkgStub(noders []*noder) string {
 		w.Flush()
 	}
 
-	var sb bytes.Buffer // TODO(mdempsky): strings.Builder after #44505 is resolved
+	var sb strings.Builder
 	pw.DumpTo(&sb)
 
 	// At this point, we're done with types2. Make sure the package is

src/cmd/compile/internal/typecheck/iimport.go

@@ -11,6 +11,7 @@ import (
 	"encoding/binary"
 	"fmt"
 	"go/constant"
+	"io"
 	"math/big"
 	"os"
 	"strings"
@@ -148,9 +149,7 @@ func ReadImports(pkg *types.Pkg, data string) {
 	sLen := int64(ird.uint64())
 	dLen := int64(ird.uint64())
 
-	// TODO(mdempsky): Replace os.SEEK_CUR with io.SeekCurrent after
-	// #44505 is fixed.
-	whence, _ := ird.Seek(0, os.SEEK_CUR)
+	whence, _ := ird.Seek(0, io.SeekCurrent)
 	stringData := data[whence : whence+sLen]
 	declData := data[whence+sLen : whence+sLen+dLen]
 	ird.Seek(sLen+dLen, os.SEEK_CUR)

src/internal/pkgbits/decoder.go

@@ -9,6 +9,7 @@ import (
 	"fmt"
 	"go/constant"
 	"go/token"
+	"io"
 	"math/big"
 	"os"
 	"runtime"
@@ -174,9 +175,7 @@ func (pr *PkgDecoder) NewDecoderRaw(k RelocKind, idx Index) Decoder {
 		Idx:    idx,
 	}
 
-	// TODO(mdempsky) r.data.Reset(...) after #44505 is resolved.
-	r.Data = *strings.NewReader(pr.DataIdx(k, idx))
-
+	r.Data.Reset(pr.DataIdx(k, idx))
 	r.Sync(SyncRelocs)
 	r.Relocs = make([]RelocEnt, r.Len())
 	for i := range r.Relocs {
@@ -237,7 +236,7 @@ func (r *Decoder) Sync(mWant SyncMarker) {
 		return
 	}
 
-	pos, _ := r.Data.Seek(0, os.SEEK_CUR) // TODO(mdempsky): io.SeekCurrent after #44505 is resolved
+	pos, _ := r.Data.Seek(0, io.SeekCurrent)
 	mHave := SyncMarker(r.rawUvarint())
 	writerPCs := make([]int, r.rawUvarint())
 	for i := range writerPCs {

src/internal/pkgbits/encoder.go

@@ -12,6 +12,7 @@ import (
 	"io"
 	"math/big"
 	"runtime"
+	"strings"
 )
 
 // currentVersion is the current version number.
@@ -161,7 +162,7 @@ type Encoder struct {
 
 // Flush finalizes the element's bitstream and returns its Index.
 func (w *Encoder) Flush() Index {
-	var sb bytes.Buffer // TODO(mdempsky): strings.Builder after #44505 is resolved
+	var sb strings.Builder
 
 	// Backup the data so we write the relocations at the front.
 	var tmp bytes.Buffer