5 files changed, 163 insertions, 11 deletions
diff --git a/src/cmd/vendor/golang.org/x/mod/modfile/read.go b/src/cmd/vendor/golang.org/x/mod/modfile/read.go
index 5b5bb5e115..2205682591 100644
--- a/src/cmd/vendor/golang.org/x/mod/modfile/read.go
+++ b/src/cmd/vendor/golang.org/x/mod/modfile/read.go
@@ -225,7 +225,7 @@ func (x *FileSyntax) Cleanup() {
 			if ww == 0 {
 				continue
 			}
-			if ww == 1 {
+			if ww == 1 && len(stmt.RParen.Comments.Before) == 0 {
 				// Collapse block into single line.
 				line := &Line{
 					Comments: Comments{
diff --git a/src/cmd/vendor/golang.org/x/mod/modfile/rule.go b/src/cmd/vendor/golang.org/x/mod/modfile/rule.go
index 26acaa5f7c..66dcaf9803 100644
--- a/src/cmd/vendor/golang.org/x/mod/modfile/rule.go
+++ b/src/cmd/vendor/golang.org/x/mod/modfile/rule.go
@@ -38,6 +38,7 @@ type File struct {
 	Module    *Module
 	Go        *Go
 	Toolchain *Toolchain
+	Godebug   []*Godebug
 	Require   []*Require
 	Exclude   []*Exclude
 	Replace   []*Replace
@@ -65,6 +66,13 @@ type Toolchain struct {
 	Syntax *Line
 }
 
+// A Godebug is a single godebug key=value statement.
+type Godebug struct {
+	Key    string
+	Value  string
+	Syntax *Line
+}
+
 // An Exclude is a single exclude statement.
 type Exclude struct {
 	Mod    module.Version
@@ -289,7 +297,7 @@ func parseToFile(file string, data []byte, fix VersionFixer, strict bool) (parse
 					})
 				}
 				continue
-			case "module", "require", "exclude", "replace", "retract":
+			case "module", "godebug", "require", "exclude", "replace", "retract":
 				for _, l := range x.Line {
 					f.add(&errs, x, l, x.Token[0], l.Token, fix, strict)
 				}
@@ -308,7 +316,9 @@ var laxGoVersionRE = lazyregexp.New(`^v?(([1-9][0-9]*)\.(0|[1-9][0-9]*))([^0-9].
 
 // Toolchains must be named beginning with `go1`,
 // like "go1.20.3" or "go1.20.3-gccgo". As a special case, "default" is also permitted.
-// TODO(samthanawalla): Replace regex with https://pkg.go.dev/go/version#IsValid in 1.23+
+// Note that this regexp is a much looser condition than go/version.IsValid,
+// for forward compatibility.
+// (This code has to be work to identify new toolchains even if we tweak the syntax in the future.)
 var ToolchainRE = lazyregexp.New(`^default$|^go1($|\.)`)
 
 func (f *File) add(errs *ErrorList, block *LineBlock, line *Line, verb string, args []string, fix VersionFixer, strict bool) {
@@ -384,7 +394,7 @@ func (f *File) add(errs *ErrorList, block *LineBlock, line *Line, verb string, a
 		if len(args) != 1 {
 			errorf("toolchain directive expects exactly one argument")
 			return
-		} else if strict && !ToolchainRE.MatchString(args[0]) {
+		} else if !ToolchainRE.MatchString(args[0]) {
 			errorf("invalid toolchain version '%s': must match format go1.23.0 or default", args[0])
 			return
 		}
@@ -412,6 +422,22 @@ func (f *File) add(errs *ErrorList, block *LineBlock, line *Line, verb string, a
 		}
 		f.Module.Mod = module.Version{Path: s}
 
+	case "godebug":
+		if len(args) != 1 || strings.ContainsAny(args[0], "\"`',") {
+			errorf("usage: godebug key=value")
+			return
+		}
+		key, value, ok := strings.Cut(args[0], "=")
+		if !ok {
+			errorf("usage: godebug key=value")
+			return
+		}
+		f.Godebug = append(f.Godebug, &Godebug{
+			Key:    key,
+			Value:  value,
+			Syntax: line,
+		})
+
 	case "require", "exclude":
 		if len(args) != 2 {
 			errorf("usage: %s module/path v1.2.3", verb)
@@ -654,6 +680,22 @@ func (f *WorkFile) add(errs *ErrorList, line *Line, verb string, args []string,
 		f.Toolchain = &Toolchain{Syntax: line}
 		f.Toolchain.Name = args[0]
 
+	case "godebug":
+		if len(args) != 1 || strings.ContainsAny(args[0], "\"`',") {
+			errorf("usage: godebug key=value")
+			return
+		}
+		key, value, ok := strings.Cut(args[0], "=")
+		if !ok {
+			errorf("usage: godebug key=value")
+			return
+		}
+		f.Godebug = append(f.Godebug, &Godebug{
+			Key:    key,
+			Value:  value,
+			Syntax: line,
+		})
+
 	case "use":
 		if len(args) != 1 {
 			errorf("usage: %s local/dir", verb)
@@ -929,6 +971,15 @@ func (f *File) Format() ([]byte, error) {
 // Cleanup cleans out all the cleared entries.
 func (f *File) Cleanup() {
 	w := 0
+	for _, g := range f.Godebug {
+		if g.Key != "" {
+			f.Godebug[w] = g
+			w++
+		}
+	}
+	f.Godebug = f.Godebug[:w]
+
+	w = 0
 	for _, r := range f.Require {
 		if r.Mod.Path != "" {
 			f.Require[w] = r
@@ -975,6 +1026,8 @@ func (f *File) AddGoStmt(version string) error {
 		var hint Expr
 		if f.Module != nil && f.Module.Syntax != nil {
 			hint = f.Module.Syntax
+		} else if f.Syntax == nil {
+			f.Syntax = new(FileSyntax)
 		}
 		f.Go = &Go{
 			Version: version,
@@ -1025,6 +1078,45 @@ func (f *File) AddToolchainStmt(name string) error {
 	return nil
 }
 
+// AddGodebug sets the first godebug line for key to value,
+// preserving any existing comments for that line and removing all
+// other godebug lines for key.
+//
+// If no line currently exists for key, AddGodebug adds a new line
+// at the end of the last godebug block.
+func (f *File) AddGodebug(key, value string) error {
+	need := true
+	for _, g := range f.Godebug {
+		if g.Key == key {
+			if need {
+				g.Value = value
+				f.Syntax.updateLine(g.Syntax, "godebug", key+"="+value)
+				need = false
+			} else {
+				g.Syntax.markRemoved()
+				*g = Godebug{}
+			}
+		}
+	}
+
+	if need {
+		f.addNewGodebug(key, value)
+	}
+	return nil
+}
+
+// addNewGodebug adds a new godebug key=value line at the end
+// of the last godebug block, regardless of any existing godebug lines for key.
+func (f *File) addNewGodebug(key, value string) {
+	line := f.Syntax.addLine(nil, "godebug", key+"="+value)
+	g := &Godebug{
+		Key:    key,
+		Value:  value,
+		Syntax: line,
+	}
+	f.Godebug = append(f.Godebug, g)
+}
+
 // AddRequire sets the first require line for path to version vers,
 // preserving any existing comments for that line and removing all
 // other lines for path.
@@ -1332,6 +1424,16 @@ func (f *File) SetRequireSeparateIndirect(req []*Require) {
 	f.SortBlocks()
 }
 
+func (f *File) DropGodebug(key string) error {
+	for _, g := range f.Godebug {
+		if g.Key == key {
+			g.Syntax.markRemoved()
+			*g = Godebug{}
+		}
+	}
+	return nil
+}
+
 func (f *File) DropRequire(path string) error {
 	for _, r := range f.Require {
 		if r.Mod.Path == path {
diff --git a/src/cmd/vendor/golang.org/x/mod/modfile/work.go b/src/cmd/vendor/golang.org/x/mod/modfile/work.go
index d7b99376eb..8f54897cf7 100644
--- a/src/cmd/vendor/golang.org/x/mod/modfile/work.go
+++ b/src/cmd/vendor/golang.org/x/mod/modfile/work.go
@@ -14,6 +14,7 @@ import (
 type WorkFile struct {
 	Go        *Go
 	Toolchain *Toolchain
+	Godebug   []*Godebug
 	Use       []*Use
 	Replace   []*Replace
 
@@ -68,7 +69,7 @@ func ParseWork(file string, data []byte, fix VersionFixer) (*WorkFile, error) {
 					Err:      fmt.Errorf("unknown block type: %s", strings.Join(x.Token, " ")),
 				})
 				continue
-			case "use", "replace":
+			case "godebug", "use", "replace":
 				for _, l := range x.Line {
 					f.add(&errs, l, x.Token[0], l.Token, fix)
 				}
@@ -184,6 +185,55 @@ func (f *WorkFile) DropToolchainStmt() {
 	}
 }
 
+// AddGodebug sets the first godebug line for key to value,
+// preserving any existing comments for that line and removing all
+// other godebug lines for key.
+//
+// If no line currently exists for key, AddGodebug adds a new line
+// at the end of the last godebug block.
+func (f *WorkFile) AddGodebug(key, value string) error {
+	need := true
+	for _, g := range f.Godebug {
+		if g.Key == key {
+			if need {
+				g.Value = value
+				f.Syntax.updateLine(g.Syntax, "godebug", key+"="+value)
+				need = false
+			} else {
+				g.Syntax.markRemoved()
+				*g = Godebug{}
+			}
+		}
+	}
+
+	if need {
+		f.addNewGodebug(key, value)
+	}
+	return nil
+}
+
+// addNewGodebug adds a new godebug key=value line at the end
+// of the last godebug block, regardless of any existing godebug lines for key.
+func (f *WorkFile) addNewGodebug(key, value string) {
+	line := f.Syntax.addLine(nil, "godebug", key+"="+value)
+	g := &Godebug{
+		Key:    key,
+		Value:  value,
+		Syntax: line,
+	}
+	f.Godebug = append(f.Godebug, g)
+}
+
+func (f *WorkFile) DropGodebug(key string) error {
+	for _, g := range f.Godebug {
+		if g.Key == key {
+			g.Syntax.markRemoved()
+			*g = Godebug{}
+		}
+	}
+	return nil
+}
+
 func (f *WorkFile) AddUse(diskPath, modulePath string) error {
 	need := true
 	for _, d := range f.Use {
diff --git a/src/cmd/vendor/golang.org/x/mod/module/module.go b/src/cmd/vendor/golang.org/x/mod/module/module.go
index 2a364b229b..cac1a899e9 100644
--- a/src/cmd/vendor/golang.org/x/mod/module/module.go
+++ b/src/cmd/vendor/golang.org/x/mod/module/module.go
@@ -506,6 +506,7 @@ var badWindowsNames = []string{
 	"PRN",
 	"AUX",
 	"NUL",
+	"COM0",
 	"COM1",
 	"COM2",
 	"COM3",
@@ -515,6 +516,7 @@ var badWindowsNames = []string{
 	"COM7",
 	"COM8",
 	"COM9",
+	"LPT0",
 	"LPT1",
 	"LPT2",
 	"LPT3",
diff --git a/src/cmd/vendor/golang.org/x/mod/sumdb/tlog/tile.go b/src/cmd/vendor/golang.org/x/mod/sumdb/tlog/tile.go
index 857d487551..37771c5310 100644
--- a/src/cmd/vendor/golang.org/x/mod/sumdb/tlog/tile.go
+++ b/src/cmd/vendor/golang.org/x/mod/sumdb/tlog/tile.go
@@ -115,16 +115,14 @@ func NewTiles(h int, oldTreeSize, newTreeSize int64) []Tile {
 	for level := uint(0); newTreeSize>>(H*level) > 0; level++ {
 		oldN := oldTreeSize >> (H * level)
 		newN := newTreeSize >> (H * level)
+		if oldN == newN {
+			continue
+		}
 		for n := oldN >> H; n < newN>>H; n++ {
 			tiles = append(tiles, Tile{H: h, L: int(level), N: n, W: 1 << H})
 		}
 		n := newN >> H
-		maxW := int(newN - n<<H)
-		minW := 1
-		if oldN > n<<H {
-			minW = int(oldN - n<<H)
-		}
-		for w := minW; w <= maxW; w++ {
+		if w := int(newN - n<<H); w > 0 {
 			tiles = append(tiles, Tile{H: h, L: int(level), N: n, W: w})
 		}
 	}