Apply some new go collection features (#36818)

internal/backend/local/backend_local.go

@@ -13,6 +13,8 @@ import (
 	"github.com/hashicorp/hcl/v2"
 	"github.com/zclconf/go-cty/cty"
 
+	"maps"
+
 	"github.com/hashicorp/terraform/internal/backend/backendrun"
 	"github.com/hashicorp/terraform/internal/configs"
 	"github.com/hashicorp/terraform/internal/configs/configload"
@@ -400,9 +402,8 @@ func (b *Local) interactiveCollectVariables(ctx context.Context, existing map[st
 	// variable's value.
 	sort.Strings(needed) // prompt in lexical order
 	ret := make(map[string]backendrun.UnparsedVariableValue, len(vcs))
-	for k, v := range existing {
-		ret[k] = v
-	}
+	maps.Copy(ret, existing) // don't use clone here, so we can have a non-nil map
+
 	for _, name := range needed {
 		vc := vcs[name]
 		query := fmt.Sprintf("var.%s", name)
@@ -467,9 +468,8 @@ func (b *Local) stubUnsetRequiredVariables(existing map[string]backendrun.Unpars
 
 	// If we get down here then there's at least one variable value to add.
 	ret := make(map[string]backendrun.UnparsedVariableValue, len(vcs))
-	for k, v := range existing {
-		ret[k] = v
-	}
+	maps.Copy(ret, existing) // don't use clone here, so we can return a non-nil map
+
 	for name, vc := range vcs {
 		if !vc.Required() {
 			continue

internal/backend/local/test.go

@@ -8,10 +8,12 @@ import (
 	"fmt"
 	"log"
 	"path/filepath"
-	"sort"
+	"slices"
 
 	"github.com/zclconf/go-cty/cty"
 
+	"maps"
+
 	"github.com/hashicorp/terraform/internal/backend/backendrun"
 	"github.com/hashicorp/terraform/internal/command/junit"
 	"github.com/hashicorp/terraform/internal/command/views"
@@ -94,28 +96,18 @@ func (runner *TestSuiteRunner) Test() (moduletest.Status, tfdiags.Diagnostics) {
 
 	runner.View.Abstract(suite)
 
-	var files []string
-	for name := range suite.Files {
-		files = append(files, name)
-	}
-	sort.Strings(files) // execute the files in alphabetical order
-
 	// We have two sets of variables that are available to different test files.
 	// Test files in the root directory have access to the GlobalVariables only,
 	// while test files in the test directory have access to the union of
 	// GlobalVariables and GlobalTestVariables.
 	testDirectoryGlobalVariables := make(map[string]backendrun.UnparsedVariableValue)
-	for name, value := range runner.GlobalVariables {
-		testDirectoryGlobalVariables[name] = value
-	}
-	for name, value := range runner.GlobalTestVariables {
-		// We're okay to overwrite the global variables in case of name
-		// collisions, as the test directory variables should take precedence.
-		testDirectoryGlobalVariables[name] = value
-	}
+	maps.Copy(testDirectoryGlobalVariables, runner.GlobalVariables)
+	// We're okay to overwrite the global variables in case of name
+	// collisions, as the test directory variables should take precedence.
+	maps.Copy(testDirectoryGlobalVariables, runner.GlobalTestVariables)
 
 	suite.Status = moduletest.Pass
-	for _, name := range files {
+	for _, name := range slices.Sorted(maps.Keys(suite.Files)) {
 		if runner.Cancelled {
 			return suite.Status, diags
 		}
@@ -144,9 +136,7 @@ func (runner *TestSuiteRunner) Test() (moduletest.Status, tfdiags.Diagnostics) {
 		}
 
 		evalCtx.VariableCaches = hcltest.NewVariableCaches(func(vc *hcltest.VariableCaches) {
-			for name, value := range currentGlobalVariables {
-				vc.GlobalVariables[name] = value
-			}
+			maps.Copy(vc.GlobalVariables, currentGlobalVariables)
 			vc.FileVariables = file.Config.Variables
 		})
 		fileRunner := &TestFileRunner{

internal/backend/remote-state/kubernetes/client.go

@@ -26,6 +26,8 @@ import (
 	"github.com/hashicorp/terraform/internal/states/remote"
 	"github.com/hashicorp/terraform/internal/states/statemgr"
 
+	"maps"
+
 	coordinationv1 "k8s.io/api/coordination/v1"
 	coordinationclientv1 "k8s.io/client-go/kubernetes/typed/coordination/v1"
 )
@@ -351,12 +353,7 @@ func (c *RemoteClient) getLabels() map[string]string {
 		tfstateWorkspaceKey:    c.workspace,
 		managedByKey:           "terraform",
 	}
-
-	if len(c.labels) != 0 {
-		for k, v := range c.labels {
-			l[k] = v
-		}
-	}
+	maps.Copy(l, c.labels)
 
 	return l
 }

internal/command/cliconfig/cliconfig.go

@@ -17,6 +17,7 @@ import (
 	"io/fs"
 	"io/ioutil"
 	"log"
+	"maps"
 	"os"
 	"path/filepath"
 	"strings"
@@ -341,18 +342,14 @@ func (c *Config) Merge(c2 *Config) *Config {
 	var result Config
 	result.Providers = make(map[string]string)
 	result.Provisioners = make(map[string]string)
-	for k, v := range c.Providers {
-		result.Providers[k] = v
-	}
+	maps.Copy(result.Providers, c.Providers)
+	maps.Copy(result.Provisioners, c.Provisioners)
 	for k, v := range c2.Providers {
 		if v1, ok := c.Providers[k]; ok {
 			log.Printf("[INFO] Local %s provider configuration '%s' overrides '%s'", k, v, v1)
 		}
 		result.Providers[k] = v
 	}
-	for k, v := range c.Provisioners {
-		result.Provisioners[k] = v
-	}
 	for k, v := range c2.Provisioners {
 		if v1, ok := c.Provisioners[k]; ok {
 			log.Printf("[INFO] Local %s provisioner configuration '%s' overrides '%s'", k, v, v1)
@@ -375,35 +372,23 @@ func (c *Config) Merge(c2 *Config) *Config {
 
 	if (len(c.Hosts) + len(c2.Hosts)) > 0 {
 		result.Hosts = make(map[string]*ConfigHost)
-		for name, host := range c.Hosts {
-			result.Hosts[name] = host
-		}
-		for name, host := range c2.Hosts {
-			result.Hosts[name] = host
-		}
+		maps.Copy(result.Hosts, c.Hosts)
+		maps.Copy(result.Hosts, c2.Hosts)
 	}
 
 	if (len(c.Credentials) + len(c2.Credentials)) > 0 {
 		result.Credentials = make(map[string]map[string]interface{})
-		for host, creds := range c.Credentials {
-			result.Credentials[host] = creds
-		}
-		for host, creds := range c2.Credentials {
-			// We just clobber an entry from the other file right now. Will
-			// improve on this later using the more-robust merging behavior
-			// built in to HCL2.
-			result.Credentials[host] = creds
-		}
+		maps.Copy(result.Credentials, c.Credentials)
+		// We just clobber an entry from the other file right now. Will
+		// improve on this later using the more-robust merging behavior
+		// built in to HCL2.
+		maps.Copy(result.Credentials, c2.Credentials)
 	}
 
 	if (len(c.CredentialsHelpers) + len(c2.CredentialsHelpers)) > 0 {
 		result.CredentialsHelpers = make(map[string]*ConfigCredentialsHelper)
-		for name, helper := range c.CredentialsHelpers {
-			result.CredentialsHelpers[name] = helper
-		}
-		for name, helper := range c2.CredentialsHelpers {
-			result.CredentialsHelpers[name] = helper
-		}
+		maps.Copy(result.CredentialsHelpers, c.CredentialsHelpers)
+		maps.Copy(result.CredentialsHelpers, c2.CredentialsHelpers)
 	}
 
 	if (len(c.ProviderInstallation) + len(c2.ProviderInstallation)) > 0 {

internal/command/format/diagnostic.go

@@ -8,6 +8,7 @@ import (
 	"bytes"
 	"fmt"
 	"iter"
+	"slices"
 	"sort"
 	"strings"
 
@@ -300,8 +301,7 @@ func (f *snippetFormatter) write() {
 			// This is particularly useful for expressions that get evaluated
 			// multiple times with different values, such as blocks using
 			// "count" and "for_each", or within "for" expressions.
-			values := make([]viewsjson.DiagnosticExpressionValue, len(snippet.Values))
-			copy(values, snippet.Values)
+			values := slices.Clone(snippet.Values)
 			sort.Slice(values, func(i, j int) bool {
 				return values[i].Traversal < values[j].Traversal
 			})

internal/command/jsonformat/state.go

@@ -4,7 +4,8 @@
 package jsonformat
 
 import (
-	"sort"
+	"maps"
+	"slices"
 
 	ctyjson "github.com/zclconf/go-cty/cty/json"
 
@@ -88,13 +89,7 @@ func (state State) renderHumanStateOutputs(renderer Renderer, opts computed.Rend
 	if len(state.RootModuleOutputs) > 0 {
 		renderer.Streams.Printf("\n\nOutputs:\n\n")
 
-		var keys []string
-		for key := range state.RootModuleOutputs {
-			keys = append(keys, key)
-		}
-		sort.Strings(keys)
-
-		for _, key := range keys {
+		for _, key := range slices.Sorted(maps.Keys(state.RootModuleOutputs)) {
 			output := state.RootModuleOutputs[key]
 			change := structured.FromJsonOutput(output)
 			ctype, err := ctyjson.UnmarshalType(output.Type)

internal/command/jsonstate/state.go

@@ -6,6 +6,8 @@ package jsonstate
 import (
 	"encoding/json"
 	"fmt"
+	"maps"
+	"slices"
 	"sort"
 
 	"github.com/zclconf/go-cty/cty"
@@ -477,13 +479,7 @@ func marshalResources(resources map[string]*states.Resource, module addrs.Module
 				ret = append(ret, current)
 			}
 
-			var sortedDeposedKeys []string
-			for k := range ri.Deposed {
-				sortedDeposedKeys = append(sortedDeposedKeys, string(k))
-			}
-			sort.Strings(sortedDeposedKeys)
-
-			for _, deposedKey := range sortedDeposedKeys {
+			for _, deposedKey := range slices.Sorted(maps.Keys(ri.Deposed)) {
 				rios := ri.Deposed[states.DeposedKey(deposedKey)]
 
 				// copy the base fields from the current instance
@@ -531,7 +527,7 @@ func marshalResources(resources map[string]*states.Resource, module addrs.Module
 				if riObj.Status == states.ObjectTainted {
 					deposed.Tainted = true
 				}
-				deposed.DeposedKey = deposedKey
+				deposed.DeposedKey = string(deposedKey)
 				ret = append(ret, deposed)
 			}
 		}

internal/command/junit/junit.go

@@ -6,6 +6,7 @@ import (
 	"bytes"
 	"encoding/xml"
 	"fmt"
+	"maps"
 	"os"
 	"slices"
 	"strconv"
@@ -155,8 +156,9 @@ func junitXMLTestReport(suite *moduletest.Suite, suiteRunnerStopped bool, source
 
 	enc.EncodeToken(xml.StartElement{Name: suitesName})
 
-	sortedFiles := suiteFilesAsSortedList(suite.Files) // to ensure consistent ordering in XML
-	for _, file := range sortedFiles {
+	// Sort the file names to ensure consistent ordering in XML
+	for _, name := range slices.Sorted(maps.Keys(suite.Files)) {
+		file := suite.Files[name]
 		// Each test file is modelled as a "test suite".
 
 		// First we'll count the number of tests and number of failures/errors
@@ -327,22 +329,6 @@ func skipDetails(runIndex int, file *moduletest.File, suiteStopped bool) *withMe
 	return &withMessage{}
 }
 
-func suiteFilesAsSortedList(files map[string]*moduletest.File) []*moduletest.File {
-	fileNames := make([]string, len(files))
-	i := 0
-	for k := range files {
-		fileNames[i] = k
-		i++
-	}
-	slices.Sort(fileNames)
-
-	sortedFiles := make([]*moduletest.File, len(files))
-	for i, name := range fileNames {
-		sortedFiles[i] = files[name]
-	}
-	return sortedFiles
-}
-
 func getDiagString(diags tfdiags.Diagnostics, sources map[string][]byte) string {
 	var diagsStr strings.Builder
 	for _, d := range diags {

internal/command/junit/junit_internal_test.go

@@ -7,8 +7,6 @@ import (
 	"fmt"
 	"os"
 	"testing"
-
-	"github.com/hashicorp/terraform/internal/moduletest"
 )
 
 func Test_TestJUnitXMLFile_save(t *testing.T) {
@@ -66,88 +64,3 @@ func Test_TestJUnitXMLFile_save(t *testing.T) {
 		})
 	}
 }
-
-func Test_suiteFilesAsSortedList(t *testing.T) {
-	cases := map[string]struct {
-		Suite         *moduletest.Suite
-		ExpectedNames map[int]string
-	}{
-		"no test files": {
-			Suite: &moduletest.Suite{},
-		},
-		"3 test files ordered in map": {
-			Suite: &moduletest.Suite{
-				Status: moduletest.Skip,
-				Files: map[string]*moduletest.File{
-					"test_file_1.tftest.hcl": {
-						Name:   "test_file_1.tftest.hcl",
-						Status: moduletest.Skip,
-						Runs:   []*moduletest.Run{},
-					},
-					"test_file_2.tftest.hcl": {
-						Name:   "test_file_2.tftest.hcl",
-						Status: moduletest.Skip,
-						Runs:   []*moduletest.Run{},
-					},
-					"test_file_3.tftest.hcl": {
-						Name:   "test_file_3.tftest.hcl",
-						Status: moduletest.Skip,
-						Runs:   []*moduletest.Run{},
-					},
-				},
-			},
-			ExpectedNames: map[int]string{
-				0: "test_file_1.tftest.hcl",
-				1: "test_file_2.tftest.hcl",
-				2: "test_file_3.tftest.hcl",
-			},
-		},
-		"3 test files unordered in map": {
-			Suite: &moduletest.Suite{
-				Status: moduletest.Skip,
-				Files: map[string]*moduletest.File{
-					"test_file_3.tftest.hcl": {
-						Name:   "test_file_3.tftest.hcl",
-						Status: moduletest.Skip,
-						Runs:   []*moduletest.Run{},
-					},
-					"test_file_1.tftest.hcl": {
-						Name:   "test_file_1.tftest.hcl",
-						Status: moduletest.Skip,
-						Runs:   []*moduletest.Run{},
-					},
-					"test_file_2.tftest.hcl": {
-						Name:   "test_file_2.tftest.hcl",
-						Status: moduletest.Skip,
-						Runs:   []*moduletest.Run{},
-					},
-				},
-			},
-			ExpectedNames: map[int]string{
-				0: "test_file_1.tftest.hcl",
-				1: "test_file_2.tftest.hcl",
-				2: "test_file_3.tftest.hcl",
-			},
-		},
-	}
-
-	for tn, tc := range cases {
-		t.Run(tn, func(t *testing.T) {
-			list := suiteFilesAsSortedList(tc.Suite.Files)
-
-			if len(tc.ExpectedNames) != len(tc.Suite.Files) {
-				t.Fatalf("expected there to be %d items, got %d", len(tc.ExpectedNames), len(tc.Suite.Files))
-			}
-
-			if len(tc.ExpectedNames) == 0 {
-				return
-			}
-
-			for k, v := range tc.ExpectedNames {
-				if list[k].Name != v {
-					t.Fatalf("expected element %d in sorted list to be named %s, got %s", k, v, list[k].Name)
-				}
-			}
-		})
-	}
-}

internal/command/meta.go

@@ -11,6 +11,7 @@ import (
 	"fmt"
 	"io/ioutil"
 	"log"
+	"maps"
 	"os"
 	"path/filepath"
 	"strconv"
@@ -293,9 +294,7 @@ func (m *Meta) StateOutPath() string {
 // Colorize returns the colorization structure for a command.
 func (m *Meta) Colorize() *colorstring.Colorize {
 	colors := make(map[string]string)
-	for k, v := range colorstring.DefaultColors {
-		colors[k] = v
-	}
+	maps.Copy(colors, colorstring.DefaultColors)
 	colors["purple"] = "38;5;57"
 
 	return &colorstring.Colorize{

internal/configs/config.go

@@ -6,7 +6,10 @@ package configs
 import (
 	"fmt"
 	"log"
+	"maps"
+	"slices"
 	"sort"
+	"strings"
 
 	version "github.com/hashicorp/go-version"
 	"github.com/hashicorp/hcl/v2"
@@ -135,13 +138,8 @@ func (c *Config) Depth() int {
 func (c *Config) DeepEach(cb func(c *Config)) {
 	cb(c)
 
-	names := make([]string, 0, len(c.Children))
-	for name := range c.Children {
-		names = append(names, name)
-	}
-
-	for _, name := range names {
-		c.Children[name].DeepEach(cb)
+	for _, ch := range c.Children {
+		ch.DeepEach(cb)
 	}
 }
 
@@ -826,12 +824,8 @@ func (c *Config) ProviderTypes() []addrs.Provider {
 	// Ignore diagnostics here because they relate to version constraints
 	reqs, _ := c.ProviderRequirements()
 
-	ret := make([]addrs.Provider, 0, len(reqs))
-	for k := range reqs {
-		ret = append(ret, k)
-	}
-	sort.Slice(ret, func(i, j int) bool {
-		return ret[i].String() < ret[j].String()
+	ret := slices.SortedFunc(maps.Keys(reqs), func(i, j addrs.Provider) int {
+		return strings.Compare(i.String(), j.String())
 	})
 	return ret
 }

internal/configs/config_build.go

@@ -5,8 +5,9 @@ package configs
 
 import (
 	"fmt"
+	"maps"
 	"path"
-	"sort"
+	"slices"
 	"strings"
 
 	version "github.com/hashicorp/go-version"
@@ -150,17 +151,10 @@ func buildChildModules(parent *Config, walker ModuleWalker) (map[string]*Config,
 
 	// We'll sort the calls by their local names so that they'll appear in a
 	// predictable order in any logging that's produced during the walk.
-	callNames := make([]string, 0, len(calls))
-	for k := range calls {
-		callNames = append(callNames, k)
-	}
-	sort.Strings(callNames)
-
-	for _, callName := range callNames {
+	for _, callName := range slices.Sorted(maps.Keys(calls)) {
 		call := calls[callName]
-		path := make([]string, len(parent.Path)+1)
-		copy(path, parent.Path)
-		path[len(path)-1] = call.Name
+		path := slices.Clone(parent.Path)
+		path = append(path, call.Name)
 
 		req := ModuleRequest{
 			Name:              call.Name,

internal/configs/configload/loader_snapshot.go

@@ -6,9 +6,10 @@ package configload
 import (
 	"fmt"
 	"io"
+	"maps"
 	"os"
 	"path/filepath"
-	"sort"
+	"slices"
 	"time"
 
 	version "github.com/hashicorp/go-version"
@@ -257,11 +258,7 @@ func (fs snapshotFS) Open(name string) (afero.File, error) {
 		modDir := filepath.Clean(candidate.Dir)
 		if modDir == directDir {
 			// We've matched the module directory itself
-			filenames := make([]string, 0, len(candidate.Files))
-			for n := range candidate.Files {
-				filenames = append(filenames, n)
-			}
-			sort.Strings(filenames)
+			filenames := slices.Sorted(maps.Keys(candidate.Files))
 			return &snapshotDir{
 				filenames: filenames,
 			}, nil

internal/dag/dot.go

@@ -6,6 +6,8 @@ package dag
 import (
 	"bytes"
 	"fmt"
+	"maps"
+	"slices"
 	"sort"
 	"strings"
 )
@@ -97,13 +99,8 @@ func (v *marshalVertex) dot(g *marshalGraph, opts *DotOpts) []byte {
 			return []byte{}
 		}
 
-		newAttrs := make(map[string]string)
-		for k, v := range attrs {
-			newAttrs[k] = v
-		}
-		for k, v := range node.Attrs {
-			newAttrs[k] = v
-		}
+		newAttrs := maps.Clone(attrs)
+		maps.Copy(newAttrs, node.Attrs)
 
 		name = node.Name
 		attrs = newAttrs
@@ -218,13 +215,7 @@ func (g *marshalGraph) writeBody(opts *DotOpts, w *indentWriter) {
 	}
 
 	// sort these again to match the old output
-	dotEdgesList := make([]string, 0, len(dotEdges))
-	for _, v := range dotEdges {
-		dotEdgesList = append(dotEdgesList, v)
-	}
-	sort.Strings(dotEdgesList)
-
-	for _, e := range dotEdgesList {
+	for _, e := range slices.Sorted(maps.Values(dotEdges)) {
 		w.WriteString(e + "\n")
 	}
 

internal/dag/set.go

@@ -3,6 +3,11 @@
 
 package dag
 
+import (
+	"iter"
+	"maps"
+)
+
 // Set is a set data structure.
 type Set map[interface{}]interface{}
 
@@ -92,25 +97,18 @@ func (s Set) Len() int {
 	return len(s)
 }
 
-// List returns the list of set elements.
-func (s Set) List() []interface{} {
-	if s == nil {
-		return nil
-	}
-
-	r := make([]interface{}, 0, len(s))
-	for _, v := range s {
-		r = append(r, v)
+// List returns the sequence of set elements.
+func (s Set) List() iter.Seq[any] {
+	return func(yield func(any) bool) {
+		for _, v := range s {
+			if !yield(v) {
+				return
+			}
+		}
 	}
-
-	return r
 }
 
 // Copy returns a shallow copy of the set.
 func (s Set) Copy() Set {
-	c := make(Set, len(s))
-	for k, v := range s {
-		c[k] = v
-	}
-	return c
+	return maps.Clone(s)
 }

internal/depsfile/locks.go

@@ -5,8 +5,11 @@ package depsfile
 
 import (
 	"fmt"
+	"slices"
 	"sort"
 
+	"maps"
+
 	"github.com/hashicorp/terraform/internal/addrs"
 	"github.com/hashicorp/terraform/internal/getproviders/providerreqs"
 )
@@ -69,11 +72,7 @@ func (l *Locks) Provider(addr addrs.Provider) *ProviderLock {
 func (l *Locks) AllProviders() map[addrs.Provider]*ProviderLock {
 	// We return a copy of our internal map so that future calls to
 	// SetProvider won't modify the map we're returning, or vice-versa.
-	ret := make(map[addrs.Provider]*ProviderLock, len(l.providers))
-	for k, v := range l.providers {
-		ret[k] = v
-	}
-	return ret
+	return maps.Clone(l.providers)
 }
 
 // SetProvider creates a new lock or replaces the existing lock for the given
@@ -315,11 +314,7 @@ func (l *Locks) Empty() bool {
 func (l *Locks) DeepCopy() *Locks {
 	ret := NewLocks()
 	for addr, lock := range l.providers {
-		var hashes []providerreqs.Hash
-		if len(lock.hashes) > 0 {
-			hashes = make([]providerreqs.Hash, len(lock.hashes))
-			copy(hashes, lock.hashes)
-		}
+		hashes := slices.Clone(lock.hashes)
 		ret.SetProvider(addr, lock.version, lock.versionConstraints, hashes)
 	}
 	return ret

internal/depsfile/locks_file.go

@@ -5,6 +5,8 @@ package depsfile
 
 import (
 	"fmt"
+	"maps"
+	"slices"
 	"sort"
 
 	"github.com/hashicorp/hcl/v2"
@@ -138,10 +140,7 @@ func SaveLocksToBytes(locks *Locks) ([]byte, tfdiags.Diagnostics) {
 		},
 	})
 
-	providers := make([]addrs.Provider, 0, len(locks.providers))
-	for provider := range locks.providers {
-		providers = append(providers, provider)
-	}
+	providers := slices.Collect(maps.Keys(locks.providers))
 	sort.Slice(providers, func(i, j int) bool {
 		return providers[i].LessThan(providers[j])
 	})

internal/genconfig/generate_config.go

@@ -6,7 +6,8 @@ package genconfig
 import (
 	"encoding/json"
 	"fmt"
-	"sort"
+	"maps"
+	"slices"
 	"strings"
 
 	"github.com/hashicorp/hcl/v2"
@@ -72,14 +73,7 @@ func writeConfigAttributes(addr addrs.AbsResourceInstance, buf *strings.Builder,
 	}
 
 	// Get a list of sorted attribute names so the output will be consistent between runs.
-	keys := make([]string, 0, len(attrs))
-	for k := range attrs {
-		keys = append(keys, k)
-	}
-	sort.Strings(keys)
-
-	for i := range keys {
-		name := keys[i]
+	for _, name := range slices.Sorted(maps.Keys(attrs)) {
 		attrS := attrs[name]
 		if attrS.NestedType != nil {
 			diags = diags.Append(writeConfigNestedTypeAttribute(addr, buf, name, attrS, indent))
@@ -124,15 +118,8 @@ func writeConfigAttributesFromExisting(addr addrs.AbsResourceInstance, buf *stri
 		return diags
 	}
 
-	// Get a list of sorted attribute names so the output will be consistent between runs.
-	keys := make([]string, 0, len(attrs))
-	for k := range attrs {
-		keys = append(keys, k)
-	}
-	sort.Strings(keys)
-
-	for i := range keys {
-		name := keys[i]
+	// Sort attribute names so the output will be consistent between runs.
+	for _, name := range slices.Sorted(maps.Keys(attrs)) {
 		attrS := attrs[name]
 		if attrS.NestedType != nil {
 			writeConfigNestedTypeAttributeFromExisting(addr, buf, name, attrS, stateVal, indent)
@@ -233,14 +220,7 @@ func writeConfigBlocks(addr addrs.AbsResourceInstance, buf *strings.Builder, blo
 	}
 
 	// Get a list of sorted block names so the output will be consistent between runs.
-	names := make([]string, 0, len(blocks))
-	for k := range blocks {
-		names = append(names, k)
-	}
-	sort.Strings(names)
-
-	for i := range names {
-		name := names[i]
+	for _, name := range slices.Sorted(maps.Keys(blocks)) {
 		blockS := blocks[name]
 		diags = diags.Append(writeConfigNestedBlock(addr, buf, name, blockS, indent))
 	}
@@ -329,14 +309,8 @@ func writeConfigBlocksFromExisting(addr addrs.AbsResourceInstance, buf *strings.
 		return diags
 	}
 
-	// Get a list of sorted block names so the output will be consistent between runs.
-	names := make([]string, 0, len(blocks))
-	for k := range blocks {
-		names = append(names, k)
-	}
-	sort.Strings(names)
-
-	for _, name := range names {
+	// Sort block names so the output will be consistent between runs.
+	for _, name := range slices.Sorted(maps.Keys(blocks)) {
 		blockS := blocks[name]
 		// This shouldn't happen in real usage; state always has all values (set
 		// to null as needed), but it protects against panics in tests (and any
@@ -436,15 +410,10 @@ func writeConfigNestedTypeAttributeFromExisting(addr addrs.AbsResourceInstance,
 		}
 
 		vals := attr.AsValueMap()
-		keys := make([]string, 0, len(vals))
-		for key := range vals {
-			keys = append(keys, key)
-		}
-		sort.Strings(keys)
 
 		buf.WriteString(strings.Repeat(" ", indent))
 		buf.WriteString(fmt.Sprintf("%s = {\n", name))
-		for _, key := range keys {
+		for _, key := range slices.Sorted(maps.Keys(vals)) {
 			buf.WriteString(strings.Repeat(" ", indent+2))
 			buf.WriteString(fmt.Sprintf("%s = {", hclEscapeString(key)))
 
@@ -513,12 +482,7 @@ func writeConfigNestedBlockFromExisting(addr addrs.AbsResourceInstance, buf *str
 		}
 
 		vals := stateVal.AsValueMap()
-		keys := make([]string, 0, len(vals))
-		for key := range vals {
-			keys = append(keys, key)
-		}
-		sort.Strings(keys)
-		for _, key := range keys {
+		for _, key := range slices.Sorted(maps.Keys(vals)) {
 			buf.WriteString(strings.Repeat(" ", indent))
 			buf.WriteString(fmt.Sprintf("%s %q {", name, key))
 			// This entire map element is marked

internal/lang/eval.go

@@ -15,6 +15,8 @@ import (
 	"github.com/zclconf/go-cty/cty"
 	"github.com/zclconf/go-cty/cty/convert"
 
+	"maps"
+
 	"github.com/hashicorp/terraform/internal/addrs"
 	"github.com/hashicorp/terraform/internal/configs/configschema"
 	"github.com/hashicorp/terraform/internal/instances"
@@ -442,10 +444,10 @@ func (s *Scope) evalContext(refs []*addrs.Reference, selfAddr addrs.Referenceabl
 	// traversal, but we also expose them under "resource" as an escaping
 	// technique if we add a reserved name in a future language edition which
 	// conflicts with someone's existing provider.
-	for k, v := range buildResourceObjects(managedResources) {
-		vals[k] = v
-	}
-	vals["resource"] = cty.ObjectVal(buildResourceObjects(managedResources))
+	builtManagedResources := buildResourceObjects(managedResources)
+	maps.Copy(vals, builtManagedResources)
+
+	vals["resource"] = cty.ObjectVal(builtManagedResources)
 	vals["ephemeral"] = cty.ObjectVal(buildResourceObjects(ephemeralResources))
 	vals["data"] = cty.ObjectVal(buildResourceObjects(dataResources))
 	vals["module"] = cty.ObjectVal(wholeModules)

internal/moduleref/resolver.go

@@ -4,6 +4,7 @@
 package moduleref
 
 import (
+	"maps"
 	"strings"
 
 	"github.com/hashicorp/go-version"
@@ -23,10 +24,7 @@ type Resolver struct {
 func NewResolver(internalManifest modsdir.Manifest) *Resolver {
 	// Since maps are pointers, create a copy of the internal manifest to
 	// prevent introducing side effects to the original
-	internalManifestCopy := make(modsdir.Manifest, len(internalManifest))
-	for k, v := range internalManifest {
-		internalManifestCopy[k] = v
-	}
+	internalManifestCopy := maps.Clone(internalManifest)
 
 	// Remove the root module entry from the internal manifest as it is
 	// never directly referenced.

internal/moduletest/graph/eval_context.go

@@ -14,6 +14,8 @@ import (
 	"github.com/zclconf/go-cty/cty"
 	"github.com/zclconf/go-cty/cty/convert"
 
+	"maps"
+
 	"github.com/hashicorp/terraform/internal/addrs"
 	"github.com/hashicorp/terraform/internal/command/views"
 	"github.com/hashicorp/terraform/internal/configs"
@@ -313,9 +315,7 @@ func (ec *EvalContext) GetOutputs() map[addrs.Run]cty.Value {
 	ec.outputsLock.Lock()
 	defer ec.outputsLock.Unlock()
 	outputCopy := make(map[addrs.Run]cty.Value, len(ec.runOutputs))
-	for k, v := range ec.runOutputs {
-		outputCopy[k] = v
-	}
+	maps.Copy(outputCopy, ec.runOutputs) // don't use clone here, so we can return a non-nil map
 	return outputCopy
 }
 

internal/plans/planfile/config_snapshot.go

@@ -8,8 +8,9 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
+	"maps"
 	"path"
-	"sort"
+	"slices"
 	"strings"
 	"time"
 
@@ -158,15 +159,10 @@ func writeConfigSnapshot(snap *configload.Snapshot, z *zip.Writer) error {
 	// need to be user-actionable.
 
 	var manifest configSnapshotModuleManifest
-	keys := make([]string, 0, len(snap.Modules))
-	for k := range snap.Modules {
-		keys = append(keys, k)
-	}
-	sort.Strings(keys)
 
 	// We'll re-use this fileheader for each Create we do below.
 
-	for _, k := range keys {
+	for _, k := range slices.Sorted(maps.Keys(snap.Modules)) {
 		snapMod := snap.Modules[k]
 		record := configSnapshotModuleRecord{
 			Dir:        snapMod.Dir,

internal/plans/planfile/tfplan.go

@@ -6,6 +6,7 @@ package planfile
 import (
 	"fmt"
 	"io"
+	"slices"
 	"time"
 
 	"github.com/zclconf/go-cty/cty"
@@ -598,10 +599,7 @@ func writeTfplan(plan *plans.Plan, w io.Writer) error {
 		rawPlan.Variables[name] = valueToTfplan(val)
 	}
 	if plan.ApplyTimeVariables.Len() != 0 {
-		rawPlan.ApplyTimeVariables = make([]string, 0, plan.ApplyTimeVariables.Len())
-		for name := range plan.ApplyTimeVariables.All() {
-			rawPlan.ApplyTimeVariables = append(rawPlan.ApplyTimeVariables, name)
-		}
+		rawPlan.ApplyTimeVariables = slices.Collect(plan.ApplyTimeVariables.All())
 	}
 
 	for _, hash := range plan.ProviderFunctionResults {

internal/states/state_deepcopy.go

@@ -4,8 +4,10 @@
 package states
 
 import (
+	"maps"
+	"slices"
+
 	"github.com/hashicorp/terraform/internal/addrs"
-	"github.com/zclconf/go-cty/cty"
 )
 
 // Taking deep copies of states is an important operation because state is
@@ -128,45 +130,15 @@ func (os *ResourceInstanceObjectSrc) DeepCopy() *ResourceInstanceObjectSrc {
 		return nil
 	}
 
-	var attrsFlat map[string]string
-	if os.AttrsFlat != nil {
-		attrsFlat = make(map[string]string, len(os.AttrsFlat))
-		for k, v := range os.AttrsFlat {
-			attrsFlat[k] = v
-		}
-	}
-
-	var attrsJSON []byte
-	if os.AttrsJSON != nil {
-		attrsJSON = make([]byte, len(os.AttrsJSON))
-		copy(attrsJSON, os.AttrsJSON)
-	}
-
-	var identityJSON []byte
-	if os.IdentityJSON != nil {
-		identityJSON = make([]byte, len(os.IdentityJSON))
-		copy(identityJSON, os.IdentityJSON)
-	}
-
-	var sensitiveAttrPaths []cty.Path
-	if os.AttrSensitivePaths != nil {
-		sensitiveAttrPaths = make([]cty.Path, len(os.AttrSensitivePaths))
-		copy(sensitiveAttrPaths, os.AttrSensitivePaths)
-	}
-
-	var private []byte
-	if os.Private != nil {
-		private = make([]byte, len(os.Private))
-		copy(private, os.Private)
-	}
+	attrsFlat := maps.Clone(os.AttrsFlat)
+	attrsJSON := slices.Clone(os.AttrsJSON)
+	identityJSON := slices.Clone(os.IdentityJSON)
+	sensitiveAttrPaths := slices.Clone(os.AttrSensitivePaths)
+	private := slices.Clone(os.Private)
 
 	// Some addrs.Referencable implementations are technically mutable, but
 	// we treat them as immutable by convention and so we don't deep-copy here.
-	var dependencies []addrs.ConfigResource
-	if os.Dependencies != nil {
-		dependencies = make([]addrs.ConfigResource, len(os.Dependencies))
-		copy(dependencies, os.Dependencies)
-	}
+	dependencies := slices.Clone(os.Dependencies)
 
 	return &ResourceInstanceObjectSrc{
 		Status:                os.Status,
@@ -197,19 +169,11 @@ func (o *ResourceInstanceObject) DeepCopy() *ResourceInstanceObject {
 		return nil
 	}
 
-	var private []byte
-	if o.Private != nil {
-		private = make([]byte, len(o.Private))
-		copy(private, o.Private)
-	}
+	private := slices.Clone(o.Private)
 
 	// Some addrs.Referenceable implementations are technically mutable, but
 	// we treat them as immutable by convention and so we don't deep-copy here.
-	var dependencies []addrs.ConfigResource
-	if o.Dependencies != nil {
-		dependencies = make([]addrs.ConfigResource, len(o.Dependencies))
-		copy(dependencies, o.Dependencies)
-	}
+	dependencies := slices.Clone(o.Dependencies)
 
 	return &ResourceInstanceObject{
 		Value:               o.Value,

internal/states/statefile/version3_upgrade.go

@@ -13,6 +13,8 @@ import (
 	"github.com/zclconf/go-cty/cty"
 	ctyjson "github.com/zclconf/go-cty/cty/json"
 
+	"maps"
+
 	"github.com/hashicorp/terraform/internal/addrs"
 	"github.com/hashicorp/terraform/internal/configs"
 	"github.com/hashicorp/terraform/internal/states"
@@ -315,13 +317,7 @@ func upgradeInstanceObjectV3ToV4(rsOld *resourceStateV2, isOld *instanceStateV2,
 		}
 	}
 
-	var attributes map[string]string
-	if isOld.Attributes != nil {
-		attributes = make(map[string]string, len(isOld.Attributes))
-		for k, v := range isOld.Attributes {
-			attributes[k] = v
-		}
-	}
+	attributes := maps.Clone(isOld.Attributes)
 	if isOld.ID != "" {
 		// As a special case, if we don't already have an "id" attribute and
 		// yet there's a non-empty first-class ID on the old object then we'll

internal/terraform/transform_ephemeral_resource_close.go

@@ -76,7 +76,7 @@ func (t *ephemeralResourceCloseTransformer) Transform(g *Graph) error {
 			return len(up) == 0
 		})
 
-		for _, last := range lastReferences.List() {
+		for last := range lastReferences.List() {
 			g.Connect(dag.BasicEdge(closeNode, last))
 		}
 	}