cmd/go: replace reflect.DeepEqual with slices.Equal and maps.Equal

All of these maps and slices are made up of comparable types,
so we can avoid the overhead of reflection entirely.

Change-Id: If77dbe648a336ba729c171e84c9ff3f7e160297d
Reviewed-on: https://go-review.googlesource.com/c/go/+/574597
Reviewed-by: Than McIntosh <thanm@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>

src/cmd/go/internal/modload/buildlist.go

@@ -8,8 +8,8 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"maps"
 	"os"
-	"reflect"
 	"runtime"
 	"runtime/debug"
 	"slices"
@@ -1228,7 +1228,7 @@ func updatePrunedRoots(ctx context.Context, direct map[string]bool, rs *Requirem
 		}
 	}
 
-	if rs.pruning == pruned && reflect.DeepEqual(roots, rs.rootModules) && reflect.DeepEqual(direct, rs.direct) {
+	if rs.pruning == pruned && slices.Equal(roots, rs.rootModules) && maps.Equal(direct, rs.direct) {
 		// The root set is unchanged and rs was already pruned, so keep rs to
 		// preserve its cached ModuleGraph (if any).
 		return rs, nil
@@ -1469,7 +1469,7 @@ func updateUnprunedRoots(ctx context.Context, direct map[string]bool, rs *Requir
 	if MainModules.Len() > 1 {
 		gover.ModSort(roots)
 	}
-	if rs.pruning == unpruned && reflect.DeepEqual(roots, rs.rootModules) && reflect.DeepEqual(direct, rs.direct) {
+	if rs.pruning == unpruned && slices.Equal(roots, rs.rootModules) && maps.Equal(direct, rs.direct) {
 		// The root set is unchanged and rs was already unpruned, so keep rs to
 		// preserve its cached ModuleGraph (if any).
 		return rs, nil

src/cmd/go/internal/modload/load.go

@@ -99,12 +99,13 @@ import (
 	"fmt"
 	"go/build"
 	"io/fs"
+	"maps"
 	"os"
 	"path"
 	pathpkg "path"
 	"path/filepath"
-	"reflect"
 	"runtime"
+	"slices"
 	"sort"
 	"strings"
 	"sync"
@@ -1181,7 +1182,7 @@ func loadFromRoots(ctx context.Context, params loaderParams) *loader {
 			ld.error(err)
 			break
 		}
-		if reflect.DeepEqual(rs.rootModules, ld.requirements.rootModules) {
+		if slices.Equal(rs.rootModules, ld.requirements.rootModules) {
 			// Something is deeply wrong. resolveMissingImports gave us a non-empty
 			// set of modules to add to the graph, but adding those modules had no
 			// effect — either they were already in the graph, or updateRoots did not
@@ -1319,7 +1320,7 @@ func (ld *loader) updateRequirements(ctx context.Context) (changed bool, err err
 	// imports.AnyTags, then we didn't necessarily load every package that
 	// contributes “direct” imports — so we can't safely mark existing direct
 	// dependencies in ld.requirements as indirect-only. Propagate them as direct.
-	loadedDirect := ld.allPatternIsRoot && reflect.DeepEqual(ld.Tags, imports.AnyTags())
+	loadedDirect := ld.allPatternIsRoot && maps.Equal(ld.Tags, imports.AnyTags())
 	if loadedDirect {
 		direct = make(map[string]bool)
 	} else {
@@ -1465,7 +1466,7 @@ func (ld *loader) updateRequirements(ctx context.Context) (changed bool, err err
 		// packages present in the standard library. If it has changed, it's best to
 		// reload packages once more to be sure everything is stable.
 		changed = true
-	} else if rs != ld.requirements && !reflect.DeepEqual(rs.rootModules, ld.requirements.rootModules) {
+	} else if rs != ld.requirements && !slices.Equal(rs.rootModules, ld.requirements.rootModules) {
 		// The roots of the module graph have changed in some way (not just the
 		// "direct" markings). Check whether the changes affected any of the loaded
 		// packages.
@@ -1779,7 +1780,7 @@ func (ld *loader) preloadRootModules(ctx context.Context, rootPkgs []string) (ch
 		ld.exitIfErrors(ctx)
 		return false
 	}
-	if reflect.DeepEqual(rs.rootModules, ld.requirements.rootModules) {
+	if slices.Equal(rs.rootModules, ld.requirements.rootModules) {
 		// Something is deeply wrong. resolveMissingImports gave us a non-empty
 		// set of modules to add to the graph, but adding those modules had no
 		// effect — either they were already in the graph, or updateRoots did not

src/cmd/go/internal/mvs/mvs.go

@@ -8,7 +8,7 @@ package mvs
 
 import (
 	"fmt"
-	"reflect"
+	"slices"
 	"sort"
 	"sync"
 
@@ -171,7 +171,7 @@ func buildList(targets []module.Version, reqs Reqs, upgrade func(module.Version)
 
 	// The final list is the minimum version of each module found in the graph.
 	list := g.BuildList()
-	if vs := list[:len(targets)]; !reflect.DeepEqual(vs, targets) {
+	if vs := list[:len(targets)]; !slices.Equal(vs, targets) {
 		// target.Version will be "" for modload, the main client of MVS.
 		// "" denotes the main module, which has no version. However, MVS treats
 		// version strings as opaque, so "" is not a special value here.