diff --git a/CHANGELOG.md b/CHANGELOG.md
index 58074e9a8f1..bd76c512b90 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,12 @@
 
 ### Libraries
 
+#### `dart:async`
+
+- Added `Future.pause` as alternative to `Future.delayed` with no callback.
+- Added `List.unmodifiableOf` with better typing than `List.unmodifiable`.
+- Added `Map.unmodifiableOf` with better typing than `Map.unmodifiable`.
+
 #### `dart:io`
 
 - The cookie-date parser now uses the correct algorithm again.
diff --git a/pkg/front_end/testcases/constructor_tearoffs/lowering/issue47462.dart.strong.expect b/pkg/front_end/testcases/constructor_tearoffs/lowering/issue47462.dart.strong.expect
index 3e00f36be5d..889dd2a6cbb 100644
--- a/pkg/front_end/testcases/constructor_tearoffs/lowering/issue47462.dart.strong.expect
+++ b/pkg/front_end/testcases/constructor_tearoffs/lowering/issue47462.dart.strong.expect
@@ -39,6 +39,8 @@ static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/arr
   return core::List::generate<self::_#MyList#generate#tearOff::T>(length, generator, growable: growable);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#MyList#unmodifiable#tearOff<T extends core::num>(core::Iterable<dynamic> elements) → core::List<self::_#MyList#unmodifiable#tearOff::T>
   return core::List::unmodifiable<self::_#MyList#unmodifiable#tearOff::T>(elements);
+static synthetic method /* from org-dartlang-sdk:///sdk/lib/core/list.dart */ _#MyList#unmodifiableOf#tearOff<T extends core::num>(core::Iterable<self::_#MyList#unmodifiableOf#tearOff::T> elements) → core::List<self::_#MyList#unmodifiableOf#tearOff::T>
+  return core::List::unmodifiableOf<self::_#MyList#unmodifiableOf#tearOff::T>(elements);
 
 constants  {
   #C1 = constructor-tearoff core::List::filled
diff --git a/pkg/front_end/testcases/constructor_tearoffs/lowering/issue47462.dart.strong.modular.expect b/pkg/front_end/testcases/constructor_tearoffs/lowering/issue47462.dart.strong.modular.expect
index 3e00f36be5d..889dd2a6cbb 100644
--- a/pkg/front_end/testcases/constructor_tearoffs/lowering/issue47462.dart.strong.modular.expect
+++ b/pkg/front_end/testcases/constructor_tearoffs/lowering/issue47462.dart.strong.modular.expect
@@ -39,6 +39,8 @@ static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/arr
   return core::List::generate<self::_#MyList#generate#tearOff::T>(length, generator, growable: growable);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#MyList#unmodifiable#tearOff<T extends core::num>(core::Iterable<dynamic> elements) → core::List<self::_#MyList#unmodifiable#tearOff::T>
   return core::List::unmodifiable<self::_#MyList#unmodifiable#tearOff::T>(elements);
+static synthetic method /* from org-dartlang-sdk:///sdk/lib/core/list.dart */ _#MyList#unmodifiableOf#tearOff<T extends core::num>(core::Iterable<self::_#MyList#unmodifiableOf#tearOff::T> elements) → core::List<self::_#MyList#unmodifiableOf#tearOff::T>
+  return core::List::unmodifiableOf<self::_#MyList#unmodifiableOf#tearOff::T>(elements);
 
 constants  {
   #C1 = constructor-tearoff core::List::filled
diff --git a/pkg/front_end/testcases/constructor_tearoffs/lowering/issue47462.dart.strong.outline.expect b/pkg/front_end/testcases/constructor_tearoffs/lowering/issue47462.dart.strong.outline.expect
index 082fb013eb4..cd85b0ac20c 100644
--- a/pkg/front_end/testcases/constructor_tearoffs/lowering/issue47462.dart.strong.outline.expect
+++ b/pkg/front_end/testcases/constructor_tearoffs/lowering/issue47462.dart.strong.outline.expect
@@ -19,3 +19,5 @@ static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/arr
   return core::List::generate<self::_#MyList#generate#tearOff::T>(length, generator, growable: growable);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#MyList#unmodifiable#tearOff<T extends core::num>(core::Iterable<dynamic> elements) → core::List<self::_#MyList#unmodifiable#tearOff::T>
   return core::List::unmodifiable<self::_#MyList#unmodifiable#tearOff::T>(elements);
+static synthetic method /* from org-dartlang-sdk:///sdk/lib/core/list.dart */ _#MyList#unmodifiableOf#tearOff<T extends core::num>(core::Iterable<self::_#MyList#unmodifiableOf#tearOff::T> elements) → core::List<self::_#MyList#unmodifiableOf#tearOff::T>
+  return core::List::unmodifiableOf<self::_#MyList#unmodifiableOf#tearOff::T>(elements);
diff --git a/pkg/front_end/testcases/constructor_tearoffs/lowering/issue47462.dart.strong.transformed.expect b/pkg/front_end/testcases/constructor_tearoffs/lowering/issue47462.dart.strong.transformed.expect
index ffc9bb81945..6f2b132187f 100644
--- a/pkg/front_end/testcases/constructor_tearoffs/lowering/issue47462.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/constructor_tearoffs/lowering/issue47462.dart.strong.transformed.expect
@@ -39,6 +39,8 @@ static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/arr
   return core::List::generate<self::_#MyList#generate#tearOff::T>(length, generator, growable: growable);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#MyList#unmodifiable#tearOff<T extends core::num>(core::Iterable<dynamic> elements) → core::List<self::_#MyList#unmodifiable#tearOff::T>
   return core::List::unmodifiable<self::_#MyList#unmodifiable#tearOff::T>(elements);
+static synthetic method /* from org-dartlang-sdk:///sdk/lib/core/list.dart */ _#MyList#unmodifiableOf#tearOff<T extends core::num>(core::Iterable<self::_#MyList#unmodifiableOf#tearOff::T> elements) → core::List<self::_#MyList#unmodifiableOf#tearOff::T>
+  return core::List::unmodifiableOf<self::_#MyList#unmodifiableOf#tearOff::T>(elements);
 
 constants  {
   #C1 = constructor-tearoff core::List::filled
@@ -52,4 +54,4 @@ constants  {
 Extra constant evaluation status:
 Evaluated: StaticInvocation @ org-dartlang-testcase:///issue47462.dart:18:16 -> BoolConstant(true)
 Evaluated: StaticInvocation @ org-dartlang-testcase:///issue47462.dart:19:17 -> BoolConstant(false)
-Extra constant evaluation: evaluated: 50, effectively constant: 2
+Extra constant evaluation: evaluated: 52, effectively constant: 2
diff --git a/pkg/front_end/testcases/extension_types/cyclic_representation_type.dart.strong.expect b/pkg/front_end/testcases/extension_types/cyclic_representation_type.dart.strong.expect
index 48710e44ff7..d94f898c872 100644
--- a/pkg/front_end/testcases/extension_types/cyclic_representation_type.dart.strong.expect
+++ b/pkg/front_end/testcases/extension_types/cyclic_representation_type.dart.strong.expect
@@ -555,6 +555,8 @@ static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/arr
   return core::List::generate<self::E16b% /* erasure=invalid-type, declared=! */>(length, generator, growable: growable);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#Alias16a#unmodifiable#tearOff<unrelated T extends core::Object? = dynamic>(core::Iterable<dynamic> elements) → core::List<self::E16b% /* erasure=invalid-type, declared=! */>
   return core::List::unmodifiable<self::E16b% /* erasure=invalid-type, declared=! */>(elements);
+static synthetic method /* from org-dartlang-sdk:///sdk/lib/core/list.dart */ _#Alias16a#unmodifiableOf#tearOff<unrelated T extends core::Object? = dynamic>(core::Iterable<self::E16b% /* erasure=invalid-type, declared=! */> elements) → core::List<self::E16b% /* erasure=invalid-type, declared=! */>
+  return core::List::unmodifiableOf<self::E16b% /* erasure=invalid-type, declared=! */>(elements);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#Alias16b#empty#tearOff<unrelated T extends core::Object? = dynamic>({core::bool growable = #C2}) → core::List<self::E16a% /* erasure=invalid-type, declared=! */>
   return core::List::empty<self::E16a% /* erasure=invalid-type, declared=! */>(growable: growable);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#Alias16b#filled#tearOff<unrelated T extends core::Object? = dynamic>(core::int length, self::E16a% /* erasure=invalid-type, declared=! */ fill, {core::bool growable = #C2}) → core::List<self::E16a% /* erasure=invalid-type, declared=! */>
@@ -567,6 +569,8 @@ static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/arr
   return core::List::generate<self::E16a% /* erasure=invalid-type, declared=! */>(length, generator, growable: growable);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#Alias16b#unmodifiable#tearOff<unrelated T extends core::Object? = dynamic>(core::Iterable<dynamic> elements) → core::List<self::E16a% /* erasure=invalid-type, declared=! */>
   return core::List::unmodifiable<self::E16a% /* erasure=invalid-type, declared=! */>(elements);
+static synthetic method /* from org-dartlang-sdk:///sdk/lib/core/list.dart */ _#Alias16b#unmodifiableOf#tearOff<unrelated T extends core::Object? = dynamic>(core::Iterable<self::E16a% /* erasure=invalid-type, declared=! */> elements) → core::List<self::E16a% /* erasure=invalid-type, declared=! */>
+  return core::List::unmodifiableOf<self::E16a% /* erasure=invalid-type, declared=! */>(elements);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#Alias23#empty#tearOff<T extends self::E23% /* erasure=invalid-type, declared=! */>({core::bool growable = #C2}) → core::List<self::_#Alias23#empty#tearOff::T%>
   return core::List::empty<self::_#Alias23#empty#tearOff::T%>(growable: growable);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#Alias23#filled#tearOff<T extends self::E23% /* erasure=invalid-type, declared=! */>(core::int length, self::_#Alias23#filled#tearOff::T% fill, {core::bool growable = #C2}) → core::List<self::_#Alias23#filled#tearOff::T%>
@@ -579,6 +583,8 @@ static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/arr
   return core::List::generate<self::_#Alias23#generate#tearOff::T%>(length, generator, growable: growable);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#Alias23#unmodifiable#tearOff<T extends self::E23% /* erasure=invalid-type, declared=! */>(core::Iterable<dynamic> elements) → core::List<self::_#Alias23#unmodifiable#tearOff::T%>
   return core::List::unmodifiable<self::_#Alias23#unmodifiable#tearOff::T%>(elements);
+static synthetic method /* from org-dartlang-sdk:///sdk/lib/core/list.dart */ _#Alias23#unmodifiableOf#tearOff<T extends self::E23% /* erasure=invalid-type, declared=! */>(core::Iterable<self::_#Alias23#unmodifiableOf#tearOff::T%> elements) → core::List<self::_#Alias23#unmodifiableOf#tearOff::T%>
+  return core::List::unmodifiableOf<self::_#Alias23#unmodifiableOf#tearOff::T%>(elements);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#Alias24#empty#tearOff<T extends self::E24<self::_#Alias24#empty#tearOff::T%>% /* erasure=invalid-type, declared=! */ = self::E24<dynamic>% /* erasure=invalid-type, declared=! */>({core::bool growable = #C2}) → core::List<self::_#Alias24#empty#tearOff::T%>
   return core::List::empty<self::_#Alias24#empty#tearOff::T%>(growable: growable);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#Alias24#filled#tearOff<T extends self::E24<self::_#Alias24#filled#tearOff::T%>% /* erasure=invalid-type, declared=! */ = self::E24<dynamic>% /* erasure=invalid-type, declared=! */>(core::int length, self::_#Alias24#filled#tearOff::T% fill, {core::bool growable = #C2}) → core::List<self::_#Alias24#filled#tearOff::T%>
@@ -591,6 +597,8 @@ static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/arr
   return core::List::generate<self::_#Alias24#generate#tearOff::T%>(length, generator, growable: growable);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#Alias24#unmodifiable#tearOff<T extends self::E24<self::_#Alias24#unmodifiable#tearOff::T%>% /* erasure=invalid-type, declared=! */ = self::E24<dynamic>% /* erasure=invalid-type, declared=! */>(core::Iterable<dynamic> elements) → core::List<self::_#Alias24#unmodifiable#tearOff::T%>
   return core::List::unmodifiable<self::_#Alias24#unmodifiable#tearOff::T%>(elements);
+static synthetic method /* from org-dartlang-sdk:///sdk/lib/core/list.dart */ _#Alias24#unmodifiableOf#tearOff<T extends self::E24<self::_#Alias24#unmodifiableOf#tearOff::T%>% /* erasure=invalid-type, declared=! */ = self::E24<dynamic>% /* erasure=invalid-type, declared=! */>(core::Iterable<self::_#Alias24#unmodifiableOf#tearOff::T%> elements) → core::List<self::_#Alias24#unmodifiableOf#tearOff::T%>
+  return core::List::unmodifiableOf<self::_#Alias24#unmodifiableOf#tearOff::T%>(elements);
 
 constants  {
   #C1 = 0
diff --git a/pkg/front_end/testcases/extension_types/cyclic_representation_type.dart.strong.modular.expect b/pkg/front_end/testcases/extension_types/cyclic_representation_type.dart.strong.modular.expect
index 48710e44ff7..d94f898c872 100644
--- a/pkg/front_end/testcases/extension_types/cyclic_representation_type.dart.strong.modular.expect
+++ b/pkg/front_end/testcases/extension_types/cyclic_representation_type.dart.strong.modular.expect
@@ -555,6 +555,8 @@ static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/arr
   return core::List::generate<self::E16b% /* erasure=invalid-type, declared=! */>(length, generator, growable: growable);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#Alias16a#unmodifiable#tearOff<unrelated T extends core::Object? = dynamic>(core::Iterable<dynamic> elements) → core::List<self::E16b% /* erasure=invalid-type, declared=! */>
   return core::List::unmodifiable<self::E16b% /* erasure=invalid-type, declared=! */>(elements);
+static synthetic method /* from org-dartlang-sdk:///sdk/lib/core/list.dart */ _#Alias16a#unmodifiableOf#tearOff<unrelated T extends core::Object? = dynamic>(core::Iterable<self::E16b% /* erasure=invalid-type, declared=! */> elements) → core::List<self::E16b% /* erasure=invalid-type, declared=! */>
+  return core::List::unmodifiableOf<self::E16b% /* erasure=invalid-type, declared=! */>(elements);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#Alias16b#empty#tearOff<unrelated T extends core::Object? = dynamic>({core::bool growable = #C2}) → core::List<self::E16a% /* erasure=invalid-type, declared=! */>
   return core::List::empty<self::E16a% /* erasure=invalid-type, declared=! */>(growable: growable);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#Alias16b#filled#tearOff<unrelated T extends core::Object? = dynamic>(core::int length, self::E16a% /* erasure=invalid-type, declared=! */ fill, {core::bool growable = #C2}) → core::List<self::E16a% /* erasure=invalid-type, declared=! */>
@@ -567,6 +569,8 @@ static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/arr
   return core::List::generate<self::E16a% /* erasure=invalid-type, declared=! */>(length, generator, growable: growable);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#Alias16b#unmodifiable#tearOff<unrelated T extends core::Object? = dynamic>(core::Iterable<dynamic> elements) → core::List<self::E16a% /* erasure=invalid-type, declared=! */>
   return core::List::unmodifiable<self::E16a% /* erasure=invalid-type, declared=! */>(elements);
+static synthetic method /* from org-dartlang-sdk:///sdk/lib/core/list.dart */ _#Alias16b#unmodifiableOf#tearOff<unrelated T extends core::Object? = dynamic>(core::Iterable<self::E16a% /* erasure=invalid-type, declared=! */> elements) → core::List<self::E16a% /* erasure=invalid-type, declared=! */>
+  return core::List::unmodifiableOf<self::E16a% /* erasure=invalid-type, declared=! */>(elements);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#Alias23#empty#tearOff<T extends self::E23% /* erasure=invalid-type, declared=! */>({core::bool growable = #C2}) → core::List<self::_#Alias23#empty#tearOff::T%>
   return core::List::empty<self::_#Alias23#empty#tearOff::T%>(growable: growable);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#Alias23#filled#tearOff<T extends self::E23% /* erasure=invalid-type, declared=! */>(core::int length, self::_#Alias23#filled#tearOff::T% fill, {core::bool growable = #C2}) → core::List<self::_#Alias23#filled#tearOff::T%>
@@ -579,6 +583,8 @@ static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/arr
   return core::List::generate<self::_#Alias23#generate#tearOff::T%>(length, generator, growable: growable);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#Alias23#unmodifiable#tearOff<T extends self::E23% /* erasure=invalid-type, declared=! */>(core::Iterable<dynamic> elements) → core::List<self::_#Alias23#unmodifiable#tearOff::T%>
   return core::List::unmodifiable<self::_#Alias23#unmodifiable#tearOff::T%>(elements);
+static synthetic method /* from org-dartlang-sdk:///sdk/lib/core/list.dart */ _#Alias23#unmodifiableOf#tearOff<T extends self::E23% /* erasure=invalid-type, declared=! */>(core::Iterable<self::_#Alias23#unmodifiableOf#tearOff::T%> elements) → core::List<self::_#Alias23#unmodifiableOf#tearOff::T%>
+  return core::List::unmodifiableOf<self::_#Alias23#unmodifiableOf#tearOff::T%>(elements);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#Alias24#empty#tearOff<T extends self::E24<self::_#Alias24#empty#tearOff::T%>% /* erasure=invalid-type, declared=! */ = self::E24<dynamic>% /* erasure=invalid-type, declared=! */>({core::bool growable = #C2}) → core::List<self::_#Alias24#empty#tearOff::T%>
   return core::List::empty<self::_#Alias24#empty#tearOff::T%>(growable: growable);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#Alias24#filled#tearOff<T extends self::E24<self::_#Alias24#filled#tearOff::T%>% /* erasure=invalid-type, declared=! */ = self::E24<dynamic>% /* erasure=invalid-type, declared=! */>(core::int length, self::_#Alias24#filled#tearOff::T% fill, {core::bool growable = #C2}) → core::List<self::_#Alias24#filled#tearOff::T%>
@@ -591,6 +597,8 @@ static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/arr
   return core::List::generate<self::_#Alias24#generate#tearOff::T%>(length, generator, growable: growable);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#Alias24#unmodifiable#tearOff<T extends self::E24<self::_#Alias24#unmodifiable#tearOff::T%>% /* erasure=invalid-type, declared=! */ = self::E24<dynamic>% /* erasure=invalid-type, declared=! */>(core::Iterable<dynamic> elements) → core::List<self::_#Alias24#unmodifiable#tearOff::T%>
   return core::List::unmodifiable<self::_#Alias24#unmodifiable#tearOff::T%>(elements);
+static synthetic method /* from org-dartlang-sdk:///sdk/lib/core/list.dart */ _#Alias24#unmodifiableOf#tearOff<T extends self::E24<self::_#Alias24#unmodifiableOf#tearOff::T%>% /* erasure=invalid-type, declared=! */ = self::E24<dynamic>% /* erasure=invalid-type, declared=! */>(core::Iterable<self::_#Alias24#unmodifiableOf#tearOff::T%> elements) → core::List<self::_#Alias24#unmodifiableOf#tearOff::T%>
+  return core::List::unmodifiableOf<self::_#Alias24#unmodifiableOf#tearOff::T%>(elements);
 
 constants  {
   #C1 = 0
diff --git a/pkg/front_end/testcases/extension_types/cyclic_representation_type.dart.strong.outline.expect b/pkg/front_end/testcases/extension_types/cyclic_representation_type.dart.strong.outline.expect
index 78b01499c34..0bfba13c806 100644
--- a/pkg/front_end/testcases/extension_types/cyclic_representation_type.dart.strong.outline.expect
+++ b/pkg/front_end/testcases/extension_types/cyclic_representation_type.dart.strong.outline.expect
@@ -495,6 +495,8 @@ static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/arr
   return core::List::generate<self::E16b% /* erasure=invalid-type, declared=! */>(length, generator, growable: growable);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#Alias16a#unmodifiable#tearOff<unrelated T extends core::Object? = dynamic>(core::Iterable<dynamic> elements) → core::List<self::E16b% /* erasure=invalid-type, declared=! */>
   return core::List::unmodifiable<self::E16b% /* erasure=invalid-type, declared=! */>(elements);
+static synthetic method /* from org-dartlang-sdk:///sdk/lib/core/list.dart */ _#Alias16a#unmodifiableOf#tearOff<unrelated T extends core::Object? = dynamic>(core::Iterable<self::E16b% /* erasure=invalid-type, declared=! */> elements) → core::List<self::E16b% /* erasure=invalid-type, declared=! */>
+  return core::List::unmodifiableOf<self::E16b% /* erasure=invalid-type, declared=! */>(elements);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#Alias16b#empty#tearOff<unrelated T extends core::Object? = dynamic>({has-declared-initializer core::bool growable}) → core::List<self::E16a% /* erasure=invalid-type, declared=! */>
   return core::List::empty<self::E16a% /* erasure=invalid-type, declared=! */>(growable: growable);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#Alias16b#filled#tearOff<unrelated T extends core::Object? = dynamic>(core::int length, self::E16a% /* erasure=invalid-type, declared=! */ fill, {has-declared-initializer core::bool growable}) → core::List<self::E16a% /* erasure=invalid-type, declared=! */>
@@ -507,6 +509,8 @@ static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/arr
   return core::List::generate<self::E16a% /* erasure=invalid-type, declared=! */>(length, generator, growable: growable);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#Alias16b#unmodifiable#tearOff<unrelated T extends core::Object? = dynamic>(core::Iterable<dynamic> elements) → core::List<self::E16a% /* erasure=invalid-type, declared=! */>
   return core::List::unmodifiable<self::E16a% /* erasure=invalid-type, declared=! */>(elements);
+static synthetic method /* from org-dartlang-sdk:///sdk/lib/core/list.dart */ _#Alias16b#unmodifiableOf#tearOff<unrelated T extends core::Object? = dynamic>(core::Iterable<self::E16a% /* erasure=invalid-type, declared=! */> elements) → core::List<self::E16a% /* erasure=invalid-type, declared=! */>
+  return core::List::unmodifiableOf<self::E16a% /* erasure=invalid-type, declared=! */>(elements);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#Alias23#empty#tearOff<T extends self::E23% /* erasure=invalid-type, declared=! */>({has-declared-initializer core::bool growable}) → core::List<self::_#Alias23#empty#tearOff::T%>
   return core::List::empty<self::_#Alias23#empty#tearOff::T%>(growable: growable);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#Alias23#filled#tearOff<T extends self::E23% /* erasure=invalid-type, declared=! */>(core::int length, self::_#Alias23#filled#tearOff::T% fill, {has-declared-initializer core::bool growable}) → core::List<self::_#Alias23#filled#tearOff::T%>
@@ -519,6 +523,8 @@ static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/arr
   return core::List::generate<self::_#Alias23#generate#tearOff::T%>(length, generator, growable: growable);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#Alias23#unmodifiable#tearOff<T extends self::E23% /* erasure=invalid-type, declared=! */>(core::Iterable<dynamic> elements) → core::List<self::_#Alias23#unmodifiable#tearOff::T%>
   return core::List::unmodifiable<self::_#Alias23#unmodifiable#tearOff::T%>(elements);
+static synthetic method /* from org-dartlang-sdk:///sdk/lib/core/list.dart */ _#Alias23#unmodifiableOf#tearOff<T extends self::E23% /* erasure=invalid-type, declared=! */>(core::Iterable<self::_#Alias23#unmodifiableOf#tearOff::T%> elements) → core::List<self::_#Alias23#unmodifiableOf#tearOff::T%>
+  return core::List::unmodifiableOf<self::_#Alias23#unmodifiableOf#tearOff::T%>(elements);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#Alias24#empty#tearOff<T extends self::E24<self::_#Alias24#empty#tearOff::T%>% /* erasure=invalid-type, declared=! */ = self::E24<dynamic>% /* erasure=invalid-type, declared=! */>({has-declared-initializer core::bool growable}) → core::List<self::_#Alias24#empty#tearOff::T%>
   return core::List::empty<self::_#Alias24#empty#tearOff::T%>(growable: growable);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#Alias24#filled#tearOff<T extends self::E24<self::_#Alias24#filled#tearOff::T%>% /* erasure=invalid-type, declared=! */ = self::E24<dynamic>% /* erasure=invalid-type, declared=! */>(core::int length, self::_#Alias24#filled#tearOff::T% fill, {has-declared-initializer core::bool growable}) → core::List<self::_#Alias24#filled#tearOff::T%>
@@ -531,3 +537,5 @@ static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/arr
   return core::List::generate<self::_#Alias24#generate#tearOff::T%>(length, generator, growable: growable);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#Alias24#unmodifiable#tearOff<T extends self::E24<self::_#Alias24#unmodifiable#tearOff::T%>% /* erasure=invalid-type, declared=! */ = self::E24<dynamic>% /* erasure=invalid-type, declared=! */>(core::Iterable<dynamic> elements) → core::List<self::_#Alias24#unmodifiable#tearOff::T%>
   return core::List::unmodifiable<self::_#Alias24#unmodifiable#tearOff::T%>(elements);
+static synthetic method /* from org-dartlang-sdk:///sdk/lib/core/list.dart */ _#Alias24#unmodifiableOf#tearOff<T extends self::E24<self::_#Alias24#unmodifiableOf#tearOff::T%>% /* erasure=invalid-type, declared=! */ = self::E24<dynamic>% /* erasure=invalid-type, declared=! */>(core::Iterable<self::_#Alias24#unmodifiableOf#tearOff::T%> elements) → core::List<self::_#Alias24#unmodifiableOf#tearOff::T%>
+  return core::List::unmodifiableOf<self::_#Alias24#unmodifiableOf#tearOff::T%>(elements);
diff --git a/pkg/front_end/testcases/extension_types/cyclic_representation_type.dart.strong.transformed.expect b/pkg/front_end/testcases/extension_types/cyclic_representation_type.dart.strong.transformed.expect
index 48710e44ff7..d94f898c872 100644
--- a/pkg/front_end/testcases/extension_types/cyclic_representation_type.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/extension_types/cyclic_representation_type.dart.strong.transformed.expect
@@ -555,6 +555,8 @@ static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/arr
   return core::List::generate<self::E16b% /* erasure=invalid-type, declared=! */>(length, generator, growable: growable);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#Alias16a#unmodifiable#tearOff<unrelated T extends core::Object? = dynamic>(core::Iterable<dynamic> elements) → core::List<self::E16b% /* erasure=invalid-type, declared=! */>
   return core::List::unmodifiable<self::E16b% /* erasure=invalid-type, declared=! */>(elements);
+static synthetic method /* from org-dartlang-sdk:///sdk/lib/core/list.dart */ _#Alias16a#unmodifiableOf#tearOff<unrelated T extends core::Object? = dynamic>(core::Iterable<self::E16b% /* erasure=invalid-type, declared=! */> elements) → core::List<self::E16b% /* erasure=invalid-type, declared=! */>
+  return core::List::unmodifiableOf<self::E16b% /* erasure=invalid-type, declared=! */>(elements);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#Alias16b#empty#tearOff<unrelated T extends core::Object? = dynamic>({core::bool growable = #C2}) → core::List<self::E16a% /* erasure=invalid-type, declared=! */>
   return core::List::empty<self::E16a% /* erasure=invalid-type, declared=! */>(growable: growable);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#Alias16b#filled#tearOff<unrelated T extends core::Object? = dynamic>(core::int length, self::E16a% /* erasure=invalid-type, declared=! */ fill, {core::bool growable = #C2}) → core::List<self::E16a% /* erasure=invalid-type, declared=! */>
@@ -567,6 +569,8 @@ static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/arr
   return core::List::generate<self::E16a% /* erasure=invalid-type, declared=! */>(length, generator, growable: growable);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#Alias16b#unmodifiable#tearOff<unrelated T extends core::Object? = dynamic>(core::Iterable<dynamic> elements) → core::List<self::E16a% /* erasure=invalid-type, declared=! */>
   return core::List::unmodifiable<self::E16a% /* erasure=invalid-type, declared=! */>(elements);
+static synthetic method /* from org-dartlang-sdk:///sdk/lib/core/list.dart */ _#Alias16b#unmodifiableOf#tearOff<unrelated T extends core::Object? = dynamic>(core::Iterable<self::E16a% /* erasure=invalid-type, declared=! */> elements) → core::List<self::E16a% /* erasure=invalid-type, declared=! */>
+  return core::List::unmodifiableOf<self::E16a% /* erasure=invalid-type, declared=! */>(elements);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#Alias23#empty#tearOff<T extends self::E23% /* erasure=invalid-type, declared=! */>({core::bool growable = #C2}) → core::List<self::_#Alias23#empty#tearOff::T%>
   return core::List::empty<self::_#Alias23#empty#tearOff::T%>(growable: growable);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#Alias23#filled#tearOff<T extends self::E23% /* erasure=invalid-type, declared=! */>(core::int length, self::_#Alias23#filled#tearOff::T% fill, {core::bool growable = #C2}) → core::List<self::_#Alias23#filled#tearOff::T%>
@@ -579,6 +583,8 @@ static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/arr
   return core::List::generate<self::_#Alias23#generate#tearOff::T%>(length, generator, growable: growable);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#Alias23#unmodifiable#tearOff<T extends self::E23% /* erasure=invalid-type, declared=! */>(core::Iterable<dynamic> elements) → core::List<self::_#Alias23#unmodifiable#tearOff::T%>
   return core::List::unmodifiable<self::_#Alias23#unmodifiable#tearOff::T%>(elements);
+static synthetic method /* from org-dartlang-sdk:///sdk/lib/core/list.dart */ _#Alias23#unmodifiableOf#tearOff<T extends self::E23% /* erasure=invalid-type, declared=! */>(core::Iterable<self::_#Alias23#unmodifiableOf#tearOff::T%> elements) → core::List<self::_#Alias23#unmodifiableOf#tearOff::T%>
+  return core::List::unmodifiableOf<self::_#Alias23#unmodifiableOf#tearOff::T%>(elements);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#Alias24#empty#tearOff<T extends self::E24<self::_#Alias24#empty#tearOff::T%>% /* erasure=invalid-type, declared=! */ = self::E24<dynamic>% /* erasure=invalid-type, declared=! */>({core::bool growable = #C2}) → core::List<self::_#Alias24#empty#tearOff::T%>
   return core::List::empty<self::_#Alias24#empty#tearOff::T%>(growable: growable);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#Alias24#filled#tearOff<T extends self::E24<self::_#Alias24#filled#tearOff::T%>% /* erasure=invalid-type, declared=! */ = self::E24<dynamic>% /* erasure=invalid-type, declared=! */>(core::int length, self::_#Alias24#filled#tearOff::T% fill, {core::bool growable = #C2}) → core::List<self::_#Alias24#filled#tearOff::T%>
@@ -591,6 +597,8 @@ static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/arr
   return core::List::generate<self::_#Alias24#generate#tearOff::T%>(length, generator, growable: growable);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#Alias24#unmodifiable#tearOff<T extends self::E24<self::_#Alias24#unmodifiable#tearOff::T%>% /* erasure=invalid-type, declared=! */ = self::E24<dynamic>% /* erasure=invalid-type, declared=! */>(core::Iterable<dynamic> elements) → core::List<self::_#Alias24#unmodifiable#tearOff::T%>
   return core::List::unmodifiable<self::_#Alias24#unmodifiable#tearOff::T%>(elements);
+static synthetic method /* from org-dartlang-sdk:///sdk/lib/core/list.dart */ _#Alias24#unmodifiableOf#tearOff<T extends self::E24<self::_#Alias24#unmodifiableOf#tearOff::T%>% /* erasure=invalid-type, declared=! */ = self::E24<dynamic>% /* erasure=invalid-type, declared=! */>(core::Iterable<self::_#Alias24#unmodifiableOf#tearOff::T%> elements) → core::List<self::_#Alias24#unmodifiableOf#tearOff::T%>
+  return core::List::unmodifiableOf<self::_#Alias24#unmodifiableOf#tearOff::T%>(elements);
 
 constants  {
   #C1 = 0
diff --git a/pkg/front_end/testcases/general/issue47462.dart.strong.expect b/pkg/front_end/testcases/general/issue47462.dart.strong.expect
index 3e00f36be5d..889dd2a6cbb 100644
--- a/pkg/front_end/testcases/general/issue47462.dart.strong.expect
+++ b/pkg/front_end/testcases/general/issue47462.dart.strong.expect
@@ -39,6 +39,8 @@ static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/arr
   return core::List::generate<self::_#MyList#generate#tearOff::T>(length, generator, growable: growable);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#MyList#unmodifiable#tearOff<T extends core::num>(core::Iterable<dynamic> elements) → core::List<self::_#MyList#unmodifiable#tearOff::T>
   return core::List::unmodifiable<self::_#MyList#unmodifiable#tearOff::T>(elements);
+static synthetic method /* from org-dartlang-sdk:///sdk/lib/core/list.dart */ _#MyList#unmodifiableOf#tearOff<T extends core::num>(core::Iterable<self::_#MyList#unmodifiableOf#tearOff::T> elements) → core::List<self::_#MyList#unmodifiableOf#tearOff::T>
+  return core::List::unmodifiableOf<self::_#MyList#unmodifiableOf#tearOff::T>(elements);
 
 constants  {
   #C1 = constructor-tearoff core::List::filled
diff --git a/pkg/front_end/testcases/general/issue47462.dart.strong.modular.expect b/pkg/front_end/testcases/general/issue47462.dart.strong.modular.expect
index 3e00f36be5d..889dd2a6cbb 100644
--- a/pkg/front_end/testcases/general/issue47462.dart.strong.modular.expect
+++ b/pkg/front_end/testcases/general/issue47462.dart.strong.modular.expect
@@ -39,6 +39,8 @@ static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/arr
   return core::List::generate<self::_#MyList#generate#tearOff::T>(length, generator, growable: growable);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#MyList#unmodifiable#tearOff<T extends core::num>(core::Iterable<dynamic> elements) → core::List<self::_#MyList#unmodifiable#tearOff::T>
   return core::List::unmodifiable<self::_#MyList#unmodifiable#tearOff::T>(elements);
+static synthetic method /* from org-dartlang-sdk:///sdk/lib/core/list.dart */ _#MyList#unmodifiableOf#tearOff<T extends core::num>(core::Iterable<self::_#MyList#unmodifiableOf#tearOff::T> elements) → core::List<self::_#MyList#unmodifiableOf#tearOff::T>
+  return core::List::unmodifiableOf<self::_#MyList#unmodifiableOf#tearOff::T>(elements);
 
 constants  {
   #C1 = constructor-tearoff core::List::filled
diff --git a/pkg/front_end/testcases/general/issue47462.dart.strong.outline.expect b/pkg/front_end/testcases/general/issue47462.dart.strong.outline.expect
index 082fb013eb4..cd85b0ac20c 100644
--- a/pkg/front_end/testcases/general/issue47462.dart.strong.outline.expect
+++ b/pkg/front_end/testcases/general/issue47462.dart.strong.outline.expect
@@ -19,3 +19,5 @@ static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/arr
   return core::List::generate<self::_#MyList#generate#tearOff::T>(length, generator, growable: growable);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#MyList#unmodifiable#tearOff<T extends core::num>(core::Iterable<dynamic> elements) → core::List<self::_#MyList#unmodifiable#tearOff::T>
   return core::List::unmodifiable<self::_#MyList#unmodifiable#tearOff::T>(elements);
+static synthetic method /* from org-dartlang-sdk:///sdk/lib/core/list.dart */ _#MyList#unmodifiableOf#tearOff<T extends core::num>(core::Iterable<self::_#MyList#unmodifiableOf#tearOff::T> elements) → core::List<self::_#MyList#unmodifiableOf#tearOff::T>
+  return core::List::unmodifiableOf<self::_#MyList#unmodifiableOf#tearOff::T>(elements);
diff --git a/pkg/front_end/testcases/general/issue47462.dart.strong.transformed.expect b/pkg/front_end/testcases/general/issue47462.dart.strong.transformed.expect
index ffc9bb81945..6f2b132187f 100644
--- a/pkg/front_end/testcases/general/issue47462.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general/issue47462.dart.strong.transformed.expect
@@ -39,6 +39,8 @@ static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/arr
   return core::List::generate<self::_#MyList#generate#tearOff::T>(length, generator, growable: growable);
 static synthetic method /* from org-dartlang-sdk:///sdk/lib/_internal/vm/lib/array_patch.dart */ _#MyList#unmodifiable#tearOff<T extends core::num>(core::Iterable<dynamic> elements) → core::List<self::_#MyList#unmodifiable#tearOff::T>
   return core::List::unmodifiable<self::_#MyList#unmodifiable#tearOff::T>(elements);
+static synthetic method /* from org-dartlang-sdk:///sdk/lib/core/list.dart */ _#MyList#unmodifiableOf#tearOff<T extends core::num>(core::Iterable<self::_#MyList#unmodifiableOf#tearOff::T> elements) → core::List<self::_#MyList#unmodifiableOf#tearOff::T>
+  return core::List::unmodifiableOf<self::_#MyList#unmodifiableOf#tearOff::T>(elements);
 
 constants  {
   #C1 = constructor-tearoff core::List::filled
@@ -52,4 +54,4 @@ constants  {
 Extra constant evaluation status:
 Evaluated: StaticInvocation @ org-dartlang-testcase:///issue47462.dart:18:16 -> BoolConstant(true)
 Evaluated: StaticInvocation @ org-dartlang-testcase:///issue47462.dart:19:17 -> BoolConstant(false)
-Extra constant evaluation: evaluated: 50, effectively constant: 2
+Extra constant evaluation: evaluated: 52, effectively constant: 2
diff --git a/sdk/lib/async/future.dart b/sdk/lib/async/future.dart
index 98f8447caf7..490b12d0064 100644
--- a/sdk/lib/async/future.dart
+++ b/sdk/lib/async/future.dart
@@ -399,16 +399,19 @@ abstract interface class Future<T> {
   ///
   /// If [computation] returns a future,
   /// the future returned by this constructor will complete with the value or
-  /// error of that future.
+  /// error of that future, which may not be available until even later.
   ///
   /// If the duration is 0 or less,
   /// it completes no sooner than in the next event-loop iteration,
   /// after all microtasks have run.
+  /// (The waiting for the delay uses a [Timer] created in the current zone.)
   ///
-  /// If [computation] is omitted,
-  /// it will be treated as if [computation] was `() => null`,
+  /// The computation must not be omitted, and must not be null.
+  /// Use [Future.pause] instead if you just want to wait for duration.
+  /// Until that is reflected in the signature, if [computation] is omitted,
+  /// then [T] must be nullable.
+  /// Then the computation will be treated as if it was `() => null`,
   /// and the future will eventually complete with the `null` value.
-  /// In that case, [T] must be nullable.
   ///
   /// If calling [computation] throws, the created future will complete with the
   /// error.
@@ -418,11 +421,16 @@ abstract interface class Future<T> {
   ///
   /// Example:
   /// ```dart
-  /// Future.delayed(const Duration(seconds: 1), () {
-  ///   print('One second has passed.'); // Prints after 1 second.
+  /// var now = DateTime.now();
+  /// var later = await Future.delayed(const Duration(seconds: 1), () {
+  ///   return DateTime.timestamp();
   /// });
+  /// print(now.difference(later)); // At least a second.
   /// ```
-  factory Future.delayed(Duration duration, [FutureOr<T> computation()?]) {
+  factory Future.delayed(
+    Duration duration, [
+    FutureOr<T> Function()? computation,
+  ]) {
     if (computation == null && !typeAcceptsNull<T>()) {
       throw ArgumentError.value(
         null,
@@ -448,6 +456,19 @@ abstract interface class Future<T> {
     return result;
   }
 
+  /// Creates a [Future] that completes with no result after [duration].
+  ///
+  /// Like [Future.delayed], but does not perform any action,
+  /// and cannot complete with an error.
+  @Since("3.13")
+  static Future<void> pause([Duration duration = Duration.zero]) {
+    var result = _Future<void>();
+    Zone._current.createTimer(duration, () {
+      result._completeWithValue(null);
+    });
+    return result;
+  }
+
   /// Waits for multiple futures to complete and collects their results.
   ///
   /// Returns a future which will complete once all the provided futures
diff --git a/sdk/lib/core/list.dart b/sdk/lib/core/list.dart
index 429209e9daa..c898dfeb125 100644
--- a/sdk/lib/core/list.dart
+++ b/sdk/lib/core/list.dart
@@ -191,7 +191,10 @@ abstract interface class List<E> implements Iterable<E>, _ListIterable<E> {
   ///
   /// This constructor creates a growable list when [growable] is true;
   /// otherwise, it returns a fixed-length list.
-  external factory List.from(Iterable elements, {bool growable = true});
+  external factory List.from(
+    Iterable<Object?> elements, {
+    bool growable = true,
+  });
 
   /// Creates a list from [elements].
   ///
@@ -241,8 +244,24 @@ abstract interface class List<E> implements Iterable<E>, _ListIterable<E> {
   /// final unmodifiableList = List.unmodifiable(numbers); // [1, 2, 3]
   /// unmodifiableList[1] = 87; // Throws.
   /// ```
+  // @Deprecated("Use List.unmodifiableOf instead")
   external factory List.unmodifiable(Iterable elements);
 
+  /// Creates an unmodifiable list containing all [elements].
+  ///
+  /// The [Iterator] of [elements] provides the order of the elements.
+  ///
+  /// An unmodifiable list cannot have its length or elements changed.
+  /// If the elements are themselves immutable, then the resulting list
+  /// is also immutable.
+  /// ```dart
+  /// final numbers = <int>[1, 2, 3];
+  /// final unmodifiableList = List.unmodifiable(numbers); // [1, 2, 3]
+  /// unmodifiableList[1] = 87; // Throws.
+  /// ```
+  @Since("3.13")
+  factory List.unmodifiableOf(Iterable<E> elements) = List<E>.unmodifiable;
+
   /// Adapts [source] to be a `List<T>`.
   ///
   /// Any time the list would produce an element that is not a [T],
diff --git a/sdk/lib/core/map.dart b/sdk/lib/core/map.dart
index 12c0cca11a3..42bc4f5529b 100644
--- a/sdk/lib/core/map.dart
+++ b/sdk/lib/core/map.dart
@@ -92,8 +92,26 @@ abstract interface class Map<K, V> {
   /// final unmodifiableMap = Map.unmodifiable(planets);
   /// unmodifiableMap[4] = 'Mars'; // Throws
   /// ```
+  // @Deprecated("Use Map.unmodifiableOf instead")
   external factory Map.unmodifiable(Map<dynamic, dynamic> other);
 
+  /// Creates an unmodifiable hash-based map containing the entries of [other].
+  ///
+  /// The map requires the keys to implement compatible
+  /// `operator==` and `hashCode`.
+  /// The created map iterates keys in a fixed order,
+  /// preserving the order provided by [other].
+  ///
+  /// The resulting map behaves like the result of [Map.of],
+  /// except that the map returned by this constructor is not modifiable.
+  /// ```dart
+  /// final planets = <int, String>{1: 'Mercury', 2: 'Venus', 3: 'Earth'};
+  /// final unmodifiableMap = Map.unmodifiableOf(planets);
+  /// unmodifiableMap[4] = 'Mars'; // Throws
+  /// ```
+  @Since("3.13")
+  factory Map.unmodifiableOf(Map<K, V> other) = Map<K, V>.unmodifiable;
+
   /// Creates an identity map with the default implementation, [LinkedHashMap].
   ///
   /// An identity map uses [identical] for equality and [identityHashCode]
diff --git a/tests/corelib/list_unmodifiable_test.dart b/tests/corelib/list_unmodifiable_test.dart
index deb16effccc..a1a15e31c42 100644
--- a/tests/corelib/list_unmodifiable_test.dart
+++ b/tests/corelib/list_unmodifiable_test.dart
@@ -36,13 +36,13 @@ class Test<E> {
 
   Test(this.element);
 
-  run(name, Iterable create(int size)) {
+  void run(String name, Iterable<Object?> create(int size)) {
     test(name, create(0));
     test(name, create(1));
     test(name, create(3));
   }
 
-  test(name, iterable) {
+  void test(String name, Iterable<Object?> iterable) {
     testSingle(name, iterable);
     testSingle("$name-where", iterable.where((x) => true));
     testSingle("$name-map", iterable.map((x) => x));
@@ -53,180 +53,188 @@ class Test<E> {
     testSingle("$name-takeWhile", iterable.takeWhile((x) => true));
   }
 
-  testSingle(name, iterable) {
+  void testSingle(String name, Iterable<Object?> iterable) {
     var elements = iterable.toList();
     int length = elements.length;
 
-    var list = new List<E>.unmodifiable(iterable);
+    for (var list in [
+      new List<E>.unmodifiable(iterable),
+      // Not the case for "subclass" test.
+      if (iterable is Iterable<E>) new List<E>.unmodifiableOf(iterable),
+    ]) {
+      Expect.isTrue(list is List<E>, "$name-type-$E");
+      Expect.isTrue(list is! List<Test>, "$name-!type-!$E");
 
-    Expect.isTrue(list is List<E>, "$name-type-$E");
-    Expect.isTrue(list is! List<Test>, "$name-!type-!$E");
-
-    checkElements() {
-      Expect.equals(length, list.length);
-      for (int i = 0; i < length; i++) {
-        Expect.identical(elements[i], list[i], "$name-identical-$i");
+      checkElements() {
+        Expect.equals(length, list.length);
+        for (int i = 0; i < length; i++) {
+          Expect.identical(elements[i], list[i], "$name-identical-$i");
+        }
       }
-    }
 
-    checkElements();
-
-    throws(funcName, func) {
-      try {
-        func();
-      } catch (e, s) {
-        Expect.isTrue(e is UnsupportedError, "$name: $funcName threw $e");
-        return;
-      }
       checkElements();
-      Expect.fail("$name: $funcName didn't throw");
-    }
 
-    throws("[]=", () {
-      list[0] = element;
-    });
-    throws("length=", () {
-      list.length = length + 1;
-    });
-    throws("length=", () {
-      list.length = length - 1;
-    });
-    throws("setAll", () {
-      list.setAll(0, []);
-    });
-    throws("add", () {
-      list.add(element);
-    });
-    throws("insert", () {
-      list.insert(0, element);
-    });
-    throws("insertAll", () {
-      list.insertAll(0, []);
-    });
-    throws("addAll", () {
-      list.addAll([]);
-    });
-    throws("remove", () {
-      list.remove(element);
-    });
-    throws("removeWhere", () {
-      list.removeWhere((x) => true);
-    });
-    throws("retainWhere", () {
-      list.retainWhere((x) => false);
-    });
-    throws("sort", () {
-      list.sort();
-    });
-    throws("shuffle", () {
-      list.shuffle();
-    });
-    throws("clear", () {
-      list.clear();
-    });
-    throws("removeAt", () {
-      list.removeAt(0);
-    });
-    throws("removeLast", () {
-      list.removeLast();
-    });
-    throws("setRange", () {
-      list.setRange(0, 1, []);
-    });
-    throws("removeRange", () {
-      list.removeRange(0, 1);
-    });
-    throws("replaceRange", () {
-      list.replaceRange(0, 1, []);
-    });
-    throws("fillRange", () {
-      list.fillRange(0, 1, element);
-    });
+      throws(funcName, func) {
+        try {
+          func();
+        } catch (e, s) {
+          Expect.isTrue(e is UnsupportedError, "$name: $funcName threw $e");
+          return;
+        }
+        checkElements();
+        Expect.fail("$name: $funcName didn't throw");
+      }
 
-    success(opName, op(List list), [bool throws = false]) {
-      if (throws) {
-        var e1, e2;
-        Expect.throws(() => op(elements), (e) {
-          e1 = e;
-          return true;
-        }, '$name :: $opName should throw for $elements');
-        Expect.throws(() => op(list), (e) {
-          e2 = e;
-          return true;
-        }, '$name :: $opName should throw for $list');
-        Expect.equals(
-          e1.runtimeType,
-          e2.runtimeType,
-          "$name :: $opName threw different errors for $elements and $list: "
-          "${e1.runtimeType} vs ${e2.runtimeType}",
+      throws("[]=", () {
+        list[0] = element;
+      });
+      throws("length=", () {
+        list.length = length + 1;
+      });
+      throws("length=", () {
+        list.length = length - 1;
+      });
+      throws("setAll", () {
+        list.setAll(0, []);
+      });
+      throws("add", () {
+        list.add(element);
+      });
+      throws("insert", () {
+        list.insert(0, element);
+      });
+      throws("insertAll", () {
+        list.insertAll(0, []);
+      });
+      throws("addAll", () {
+        list.addAll([]);
+      });
+      throws("remove", () {
+        list.remove(element);
+      });
+      throws("removeWhere", () {
+        list.removeWhere((x) => true);
+      });
+      throws("retainWhere", () {
+        list.retainWhere((x) => false);
+      });
+      throws("sort", () {
+        list.sort();
+      });
+      throws("shuffle", () {
+        list.shuffle();
+      });
+      throws("clear", () {
+        list.clear();
+      });
+      throws("removeAt", () {
+        list.removeAt(0);
+      });
+      throws("removeLast", () {
+        list.removeLast();
+      });
+      throws("setRange", () {
+        list.setRange(0, 1, []);
+      });
+      throws("removeRange", () {
+        list.removeRange(0, 1);
+      });
+      throws("replaceRange", () {
+        list.replaceRange(0, 1, []);
+      });
+      throws("fillRange", () {
+        list.fillRange(0, 1, element);
+      });
+
+      success(opName, op(List list), [bool throws = false]) {
+        if (throws) {
+          var e1, e2;
+          Expect.throws(() => op(elements), (e) {
+            e1 = e;
+            return true;
+          }, '$name :: $opName should throw for $elements');
+          Expect.throws(() => op(list), (e) {
+            e2 = e;
+            return true;
+          }, '$name :: $opName should throw for $list');
+          Expect.equals(
+            e1.runtimeType,
+            e2.runtimeType,
+            "$name :: $opName threw different errors for $elements and $list: "
+            "${e1.runtimeType} vs ${e2.runtimeType}",
+          );
+          return;
+        }
+        var expect = op(elements);
+        var actual = op(list);
+        checkElements();
+        if (expect is List) {
+          Expect.listEquals(expect, actual, "$name-$opName");
+        } else if (expect is Iterable) {
+          Expect.isTrue(actual is Iterable);
+          Expect.listEquals(expect.toList(), actual.toList(), "$name-$opName");
+        } else {
+          Expect.equals(expect, actual, "$name-$opName");
+        }
+      }
+
+      success("indexOf", (l) => l.indexOf(element));
+      success("lastIndexOf", (l) => l.lastIndexOf(element));
+      success("contains", (l) => l.contains(2));
+      success("elementAt", (l) => l.elementAt(1), list.length < 2);
+      success("reversed", (l) => l.reversed);
+      success("sublist0-1", (l) => l.sublist(0, 1), list.isEmpty);
+      success("getRange0-1", (l) => l.getRange(0, 1), list.isEmpty);
+      success("asMap-keys", (l) => l.asMap().keys);
+      success("asMap-values", (l) => l.asMap().values);
+      success("where", (l) => l.where((x) => true));
+      success("map", (l) => l.map((x) => x));
+      success("expand", (l) => l.expand((x) => [x, x]));
+      success("skip", (l) => l.skip(1));
+      success("take", (l) => l.take(1));
+      success("skipWhile", (l) => l.skipWhile((x) => false));
+      success("takeWhile", (l) => l.takeWhile((x) => true));
+      success("first", (l) => l.first, list.isEmpty);
+      success("last", (l) => l.last, list.isEmpty);
+      success("single", (l) => l.single, list.length != 1);
+      success("firstWhere", (l) => l.firstWhere((x) => true), list.isEmpty);
+      success("lastWhere", (l) => l.lastWhere((x) => true), list.isEmpty);
+      success(
+        "singleWhere",
+        (l) => l.singleWhere((x) => true),
+        list.length != 1,
+      );
+      success("isEmpty", (l) => l.isEmpty);
+      success("isNotEmpty", (l) => l.isNotEmpty);
+      success("join", (l) => l.join("/"));
+      success("fold", (l) => l.fold("--", (a, b) => "$a/$b"));
+      if (elements is List<num> && list is List<num>) {
+        success(
+          "reduce",
+          (l) => (l as List<num>).reduce((a, b) => (a + b).floor()),
+          list.isEmpty,
         );
-        return;
       }
-      var expect = op(elements);
-      var actual = op(list);
-      checkElements();
-      if (expect is List) {
-        Expect.listEquals(expect, actual, "$name-$opName");
-      } else if (expect is Iterable) {
-        Expect.isTrue(actual is Iterable);
-        Expect.listEquals(expect.toList(), actual.toList(), "$name-$opName");
-      } else {
-        Expect.equals(expect, actual, "$name-$opName");
+      success("every", (l) => l.every((x) => x == 0));
+      success("any", (l) => l.any((x) => x == 2));
+      success("toList", (l) => l.toList());
+      success("toSet", (l) => l.toSet());
+      success("toString", (l) => l.toString());
+
+      var it = elements.iterator;
+      list.forEach((v) {
+        Expect.isTrue(it.moveNext());
+        Expect.equals(it.current, v);
+      });
+      Expect.isFalse(it.moveNext());
+
+      if (elements is List<int> && list is List<int>) {
+        success(
+          "String.fromCharCodes",
+          (l) => new String.fromCharCodes(l as List<int>),
+        );
       }
     }
-
-    success("indexOf", (l) => l.indexOf(element));
-    success("lastIndexOf", (l) => l.lastIndexOf(element));
-    success("contains", (l) => l.contains(2));
-    success("elementAt", (l) => l.elementAt(1), list.length < 2);
-    success("reversed", (l) => l.reversed);
-    success("sublist0-1", (l) => l.sublist(0, 1), list.isEmpty);
-    success("getRange0-1", (l) => l.getRange(0, 1), list.isEmpty);
-    success("asMap-keys", (l) => l.asMap().keys);
-    success("asMap-values", (l) => l.asMap().values);
-    success("where", (l) => l.where((x) => true));
-    success("map", (l) => l.map((x) => x));
-    success("expand", (l) => l.expand((x) => [x, x]));
-    success("skip", (l) => l.skip(1));
-    success("take", (l) => l.take(1));
-    success("skipWhile", (l) => l.skipWhile((x) => false));
-    success("takeWhile", (l) => l.takeWhile((x) => true));
-    success("first", (l) => l.first, list.isEmpty);
-    success("last", (l) => l.last, list.isEmpty);
-    success("single", (l) => l.single, list.length != 1);
-    success("firstWhere", (l) => l.firstWhere((x) => true), list.isEmpty);
-    success("lastWhere", (l) => l.lastWhere((x) => true), list.isEmpty);
-    success("singleWhere", (l) => l.singleWhere((x) => true), list.length != 1);
-    success("isEmpty", (l) => l.isEmpty);
-    success("isNotEmpty", (l) => l.isNotEmpty);
-    success("join", (l) => l.join("/"));
-    success("fold", (l) => l.fold("--", (a, b) => "$a/$b"));
-    if (elements is List<num> && list is List<num>) {
-      success(
-        "reduce",
-        (l) => (l as List<num>).reduce((a, b) => (a + b).floor()),
-        list.isEmpty,
-      );
-    }
-    success("every", (l) => l.every((x) => x == 0));
-    success("any", (l) => l.any((x) => x == 2));
-    success("toList", (l) => l.toList());
-    success("toSet", (l) => l.toSet());
-    success("toString", (l) => l.toString());
-
-    var it = elements.iterator;
-    list.forEach((v) {
-      Expect.isTrue(it.moveNext());
-      Expect.equals(it.current, v);
-    });
-    Expect.isFalse(it.moveNext());
-
-    if (elements is List<int> && list is List<int>) {
-      success(
-        "String.fromCharCodes",
-        (l) => new String.fromCharCodes(l as List<int>),
-      );
-    }
   }
 }
 
@@ -243,36 +251,36 @@ List<int> createGrowableList(int n) {
   return new List<int>.filled(n, n, growable: true);
 }
 
-Iterable createIterable(int n) => new Iterable.generate(n);
-Iterable createConstMapKeys(int n) {
+Iterable<int> createIterable(int n) => new Iterable.generate(n);
+Iterable<int> createConstMapKeys(int n) {
   if (n == 0) return const <int, int>{}.keys;
   return const <int, int>{0: 0, 1: 1, 2: 2}.keys;
 }
 
-Iterable createConstMapValues(int n) {
+Iterable<int> createConstMapValues(int n) {
   if (n == 0) return const <int, int>{}.values;
   return const <int, int>{0: 0, 1: 1, 2: 2}.values;
 }
 
-Iterable createMapKeys(int n) {
+Iterable<int> createMapKeys(int n) {
   var map = <int, int>{};
   for (int i = 0; i < n; i++) map[i] = i;
   return map.keys;
 }
 
-Iterable createMapValues(int n) {
+Iterable<int> createMapValues(int n) {
   var map = <int, int>{};
   for (int i = 0; i < n; i++) map[i] = i;
   return map.values;
 }
 
-Iterable createSplayMapKeys(int n) {
+Iterable<int> createSplayMapKeys(int n) {
   var map = new SplayTreeMap<int, int>();
   for (int i = 0; i < n; i++) map[i] = i;
   return map.keys;
 }
 
-Iterable createSplayMapValues(int n) {
+Iterable<int> createSplayMapValues(int n) {
   var map = new SplayTreeMap<int, int>();
   for (int i = 0; i < n; i++) map[i] = i;
   return map.values;
@@ -296,11 +304,11 @@ Queue<int> createQueue(int n) {
   return queue;
 }
 
-Iterable createListMapKeys(int n) {
+Iterable<int> createListMapKeys(int n) {
   return createGrowableList(n).asMap().keys;
 }
 
-Iterable createListMapValues(int n) {
+Iterable<int> createListMapValues(int n) {
   return createGrowableList(n).asMap().values;
 }
 
diff --git a/tests/corelib/map_test.dart b/tests/corelib/map_test.dart
index 17940797396..4bba7e80758 100644
--- a/tests/corelib/map_test.dart
+++ b/tests/corelib/map_test.dart
@@ -1115,6 +1115,7 @@ void testUnmodifiableMaps() {
 
   checkUnmodifiable(const {1: 1});
   checkUnmodifiable(Map.unmodifiable({1: 1}));
+  checkUnmodifiable(Map.unmodifiableOf({1: 1}));
   checkUnmodifiable(UnmodifiableMapView({1: 1}));
   checkUnmodifiable(const MapView({1: 1}));
 }
diff --git a/tests/corelib/map_unmodifiable_cast_test.dart b/tests/corelib/map_unmodifiable_cast_test.dart
index d2fb897403d..115200077ff 100644
--- a/tests/corelib/map_unmodifiable_cast_test.dart
+++ b/tests/corelib/map_unmodifiable_cast_test.dart
@@ -30,9 +30,13 @@ void main() {
     "unmodView<Object>(int).cast<num>",
   );
 
-  var m2 = new Map<num, num>.unmodifiable({1: 37});
-  testNum(m2, "Map<num>.unmod");
-  testNum(m2.cast<int, int>(), "Map<num>.unmod.cast<int>");
+  for (var map in [
+    new Map<num, num>.unmodifiable({1: 37}),
+    new Map<num, num>.unmodifiableOf({1: 37}),
+  ]) {
+    testNum(map, "Map<num>.unmod");
+    testNum(map.cast<int, int>(), "Map<num>.unmod.cast<int>");
+  }
 
   Map<Symbol, dynamic> nsm = new NsmMap().foo(a: 0);
   test<Symbol, dynamic>(nsm, #a, 0, "nsm", noSuchMethodMap: true);
diff --git a/tests/lib/async/future_test.dart b/tests/lib/async/future_test.dart
index 9805ed29f80..f1ee7936b50 100644
--- a/tests/lib/async/future_test.dart
+++ b/tests/lib/async/future_test.dart
@@ -1319,6 +1319,109 @@ void testIgnoreWhenCompleteError() {
   Future.delayed(Duration.zero, asyncEnd);
 }
 
+void testFuturePause() {
+  const Duration low = Duration(milliseconds: 10);
+  const Duration mid = Duration(milliseconds: 20);
+  const Duration hi = Duration(milliseconds: 30);
+  // No argument means Duration.zero.
+
+  asyncStart();
+  var timers = 0;
+  void expectTimer(int n) {
+    timers++;
+    Expect.equals(n, timers);
+  }
+
+  Timer(hi, () {
+    expectTimer(10);
+  });
+  Timer(mid, () {
+    expectTimer(7);
+  });
+  Timer(low, () {
+    expectTimer(4);
+  });
+  Timer(Duration.zero, () {
+    expectTimer(1);
+  });
+  Future.pause(hi).then((_) {
+    expectTimer(11);
+  });
+  Future.pause(mid).then((_) {
+    expectTimer(8);
+  });
+  Future.pause(low).then((_) {
+    expectTimer(5);
+  });
+  Future.pause().then((_) {
+    expectTimer(2);
+  });
+  Timer(hi, () {
+    expectTimer(12);
+    asyncEnd();
+  });
+  Timer(mid, () {
+    expectTimer(9);
+  });
+  Timer(low, () {
+    expectTimer(6);
+  });
+  Timer(Duration.zero, () {
+    expectTimer(3);
+  });
+}
+
+void testFuturePauseNoArg() {
+  asyncStart();
+  // No argument means Duration.zero.
+  var microtasks = 0;
+  var timers = 0;
+  void expectMicrotask(int expectedMicrotasks, int expectedTimers) {
+    microtasks++;
+    Expect.equals(expectedMicrotasks, microtasks);
+    Expect.equals(expectedTimers, timers);
+  }
+
+  void expectTimer(int expectedTimers) {
+    timers++;
+    microtasks = 0;
+    Expect.equals(expectedTimers, timers);
+  }
+
+  scheduleMicrotask(() {
+    expectMicrotask(1, 0);
+  });
+  Future.microtask(() {
+    expectMicrotask(2, 0);
+  });
+  Timer(Duration.zero, () {
+    expectTimer(1);
+    scheduleMicrotask(() {
+      expectMicrotask(1, 1);
+    });
+  });
+  Timer(const Duration(milliseconds: 10), () {
+    expectTimer(4);
+    asyncEnd();
+  });
+  // Behaves as timer.zero.
+  Future.pause().then((_) {
+    expectTimer(2);
+    scheduleMicrotask(() {
+      expectMicrotask(1, 2);
+    });
+  });
+  scheduleMicrotask(() {
+    expectMicrotask(3, 0);
+  });
+  Future.microtask(() {
+    expectMicrotask(4, 0);
+  });
+  Timer(Duration.zero, () {
+    expectTimer(3);
+  });
+}
+
 void main() {
   asyncStart();
 
@@ -1373,6 +1476,9 @@ void main() {
   testChainedFutureValueDelay();
   testChainedFutureError();
 
+  testFuturePause();
+  testFuturePauseNoArg();
+
   testSyncFuture_i13368();
 
   testWaitCleanUp();