diff --git a/pkg/front_end/lib/src/fragment/declaration.dart b/pkg/front_end/lib/src/fragment/declaration.dart
index ed803adc9fa..b61b5ec06a2 100644
--- a/pkg/front_end/lib/src/fragment/declaration.dart
+++ b/pkg/front_end/lib/src/fragment/declaration.dart
@@ -22,7 +22,10 @@ abstract class DeclarationFragmentImpl implements DeclarationFragment {
   final LookupScope enclosingScope;
 
   final LookupScope typeParameterScope;
+
+  @override
   final DeclarationBuilderScope bodyScope;
+
   final List<Fragment> _fragments = [];
 
   @override
diff --git a/pkg/front_end/lib/src/fragment/fragment.dart b/pkg/front_end/lib/src/fragment/fragment.dart
index 147a0e29be9..7a32896e76c 100644
--- a/pkg/front_end/lib/src/fragment/fragment.dart
+++ b/pkg/front_end/lib/src/fragment/fragment.dart
@@ -146,4 +146,7 @@ abstract interface class DeclarationFragment {
 
   /// Type parameters declared on this declaration.
   List<TypeParameterFragment>? get typeParameters;
+
+  /// Returns the body scope for this declaration.
+  LookupScope get bodyScope;
 }
diff --git a/pkg/front_end/lib/src/source/fragment_factory_impl.dart b/pkg/front_end/lib/src/source/fragment_factory_impl.dart
index f145bf8af7f..72ec67f8160 100644
--- a/pkg/front_end/lib/src/source/fragment_factory_impl.dart
+++ b/pkg/front_end/lib/src/source/fragment_factory_impl.dart
@@ -1405,6 +1405,10 @@ class FragmentFactoryImpl implements FragmentFactory {
     DeclarationFragmentImpl enclosingDeclaration =
         _declarationFragments.current;
 
+    // The name space is, while initially empty, created to support the lowering
+    // of extension (type) constructors which clone the extension (type) type
+    // parameters into the nominal parameter name space of the primary
+    // constructor.
     NominalParameterNameSpace nominalParameterNameSpace =
         new NominalParameterNameSpace();
     _nominalParameterNameSpaces.push(nominalParameterNameSpace);
@@ -1412,7 +1416,15 @@ class FragmentFactoryImpl implements FragmentFactory {
       new TypeScope(
         TypeScopeKind.memberTypeParameters,
         new NominalParameterScope(
-          _typeScopes.current.lookupScope,
+          libraryFeatures.primaryConstructors.isEnabled
+              // Contrary to most other declarations, the type parameter scope
+              // of a primary constructor is _not_ the current type scope, which
+              // is the type parameter scope of the enclosing declaration, but
+              // instead the body scope of the enclosing declaration.
+              ? enclosingDeclaration.bodyScope
+              // Prior to the primary constructors feature, the enclosing scope
+              // was the current type scope.
+              : _typeScopes.current.lookupScope,
           nominalParameterNameSpace,
         ),
         _typeScopes.current,
diff --git a/pkg/front_end/test/spell_checking_list_code.txt b/pkg/front_end/test/spell_checking_list_code.txt
index a90c5242732..010ccbfcdf5 100644
--- a/pkg/front_end/test/spell_checking_list_code.txt
+++ b/pkg/front_end/test/spell_checking_list_code.txt
@@ -364,6 +364,7 @@ containment
 contextually
 continuations
 contra
+contrary
 contribute
 conveniently
 convention
diff --git a/pkg/front_end/testcases/primary_constructors/generic_primary_constructor.dart b/pkg/front_end/testcases/primary_constructors/generic_primary_constructor.dart
new file mode 100644
index 00000000000..47049666c98
--- /dev/null
+++ b/pkg/front_end/testcases/primary_constructors/generic_primary_constructor.dart
@@ -0,0 +1,57 @@
+// Copyright (c) 2026, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+class C1<T> {
+  T b;
+  final T c;
+  T d;
+  T e;
+  T f;
+  Type g = T;
+
+  C1(T a, this.b, this.c) : d = a, e = b, f = c, g = T {
+    print(T);
+  }
+}
+
+class C2<T>(T a, var T b, final T c) {
+  T d = a;
+  T e = b;
+  T f = c;
+  Type g = T;
+
+  this {
+    print(T);
+  }
+}
+
+enum E1<T> {
+  a<int>(0, 1);
+
+  final T b;
+  final T c;
+  final T d;
+  final Type f;
+
+  const E1(T a, this.b) : c = a, d = b, f = T;
+}
+
+enum E2<T>(T a, final T b) {
+  a<int>(0, 1);
+  final T d = a;
+  final T e = b;
+  final Type f = T;
+}
+
+extension type ET1<T>(T a) {
+  ET1.other(this.a) {
+    print(T);
+  }
+}
+
+extension type ET2<T>(T a) {
+  this {
+    print(T);
+  }
+}
diff --git a/pkg/front_end/testcases/primary_constructors/generic_primary_constructor.dart.strong.expect b/pkg/front_end/testcases/primary_constructors/generic_primary_constructor.dart.strong.expect
new file mode 100644
index 00000000000..e8a97b41759
--- /dev/null
+++ b/pkg/front_end/testcases/primary_constructors/generic_primary_constructor.dart.strong.expect
@@ -0,0 +1,109 @@
+library;
+import self as self;
+import "dart:core" as core;
+
+class C1<T extends core::Object? = dynamic> extends core::Object {
+  covariant-by-class field self::C1::T% b;
+  final field self::C1::T% c;
+  covariant-by-class field self::C1::T% d;
+  covariant-by-class field self::C1::T% e;
+  covariant-by-class field self::C1::T% f;
+  field core::Type g = self::C1::T%;
+  constructor •(self::C1::T% a, self::C1::T% b, self::C1::T% c) → self::C1<self::C1::T%>
+    : self::C1::b = b, self::C1::c = c, self::C1::d = a, self::C1::e = b, self::C1::f = c, self::C1::g = self::C1::T%, super core::Object::•() {
+    core::print(self::C1::T%);
+  }
+}
+class C2<T extends core::Object? = dynamic> extends core::Object {
+  covariant-by-class field self::C2::T% b;
+  final field self::C2::T% c;
+  covariant-by-class field self::C2::T% d;
+  covariant-by-class field self::C2::T% e;
+  covariant-by-class field self::C2::T% f;
+  field core::Type g;
+  constructor •(self::C2::T% a, self::C2::T% b, final self::C2::T% c) → self::C2<self::C2::T%>
+    : self::C2::d = a, self::C2::e = b, self::C2::f = c, self::C2::g = self::C2::T%, self::C2::b = b, self::C2::c = c, super core::Object::•() {
+    core::print(self::C2::T%);
+  }
+}
+class E1<T extends core::Object? = dynamic> extends core::_Enum /*isEnum*/  {
+  enum-element static const field self::E1<core::int> a = #C5;
+  final field self::E1::T% b;
+  final field self::E1::T% c;
+  final field self::E1::T% d;
+  final field core::Type f;
+  static const field core::List<self::E1<dynamic>> values = #C6;
+  const constructor •(core::int #index, core::String #name, self::E1::T% a, self::E1::T% b) → self::E1<self::E1::T%>
+    : self::E1::b = b, self::E1::c = a, self::E1::d = b, self::E1::f = self::E1::T%, super core::_Enum::•(#index, #name)
+    ;
+  method core::_enumToString() → core::String
+    return "E1.${this.{core::_Enum::_name}{core::String}}";
+}
+class E2<T extends core::Object? = dynamic> extends core::_Enum /*isEnum*/  {
+  final field self::E2::T% b;
+  enum-element static const field self::E2<core::int> a = #C7;
+  final field self::E2::T% d;
+  final field self::E2::T% e;
+  final field core::Type f;
+  static const field core::List<self::E2<dynamic>> values = #C8;
+  const constructor •(core::int #index, core::String #name, self::E2::T% a, final self::E2::T% b) → self::E2<self::E2::T%>
+    : self::E2::d = a, self::E2::e = b, self::E2::f = self::E2::T%, self::E2::b = b, super core::_Enum::•(#index, #name)
+    ;
+  method core::_enumToString() → core::String
+    return "E2.${this.{core::_Enum::_name}{core::String}}";
+}
+extension type ET1<T extends core::Object? = dynamic>(T% a) {
+  abstract extension-type-member representation-field get a() → T%;
+  constructor • = self::ET1|constructor#;
+  constructor tearoff • = self::ET1|constructor#_#new#tearOff;
+  constructor other = self::ET1|constructor#other;
+  constructor tearoff other = self::ET1|constructor#_#other#tearOff;
+}
+extension type ET2<T extends core::Object? = dynamic>(T% a) {
+  abstract extension-type-member representation-field get a() → T%;
+  constructor • = self::ET2|constructor#;
+  constructor tearoff • = self::ET2|constructor#_#new#tearOff;
+}
+static extension-type-member method ET1|constructor#<T extends core::Object? = dynamic>(self::ET1|constructor#::T% a) → self::ET1<self::ET1|constructor#::T%>% /* erasure=self::ET1|constructor#::T%, declared=! */ {
+  lowered final self::ET1<self::ET1|constructor#::T%>% /* erasure=self::ET1|constructor#::T%, declared=! */ #this = a;
+  return #this;
+}
+static extension-type-member synthetic method ET1|constructor#_#new#tearOff<T extends core::Object? = dynamic>(self::ET1|constructor#_#new#tearOff::T% a) → self::ET1<self::ET1|constructor#_#new#tearOff::T%>% /* erasure=self::ET1|constructor#_#new#tearOff::T%, declared=! */
+  return self::ET1|constructor#<self::ET1|constructor#_#new#tearOff::T%>(a);
+static extension-type-member method ET1|constructor#other<T extends core::Object? = dynamic>(self::ET1|constructor#other::T% a) → self::ET1<self::ET1|constructor#other::T%>% /* erasure=self::ET1|constructor#other::T%, declared=! */ {
+  lowered final self::ET1<self::ET1|constructor#other::T%>% /* erasure=self::ET1|constructor#other::T%, declared=! */ #this = a;
+  {
+    core::print(self::ET1|constructor#other::T%);
+  }
+  return #this;
+}
+static extension-type-member synthetic method ET1|constructor#_#other#tearOff<T extends core::Object? = dynamic>(self::ET1|constructor#_#other#tearOff::T% a) → self::ET1<self::ET1|constructor#_#other#tearOff::T%>% /* erasure=self::ET1|constructor#_#other#tearOff::T%, declared=! */
+  return self::ET1|constructor#other<self::ET1|constructor#_#other#tearOff::T%>(a);
+static extension-type-member method ET2|constructor#<T extends core::Object? = dynamic>(self::ET2|constructor#::T% a) → self::ET2<self::ET2|constructor#::T%>% /* erasure=self::ET2|constructor#::T%, declared=! */ {
+  lowered final self::ET2<self::ET2|constructor#::T%>% /* erasure=self::ET2|constructor#::T%, declared=! */ #this = a;
+  {
+    core::print(self::ET2|constructor#::T%);
+  }
+  return #this;
+}
+static extension-type-member synthetic method ET2|constructor#_#new#tearOff<T extends core::Object? = dynamic>(self::ET2|constructor#_#new#tearOff::T% a) → self::ET2<self::ET2|constructor#_#new#tearOff::T%>% /* erasure=self::ET2|constructor#_#new#tearOff::T%, declared=! */
+  return self::ET2|constructor#<self::ET2|constructor#_#new#tearOff::T%>(a);
+
+constants  {
+  #C1 = 1
+  #C2 = 0
+  #C3 = TypeLiteralConstant(core::int)
+  #C4 = "a"
+  #C5 = self::E1<core::int> {b:#C1, c:#C2, d:#C1, f:#C3, index:#C2, _name:#C4}
+  #C6 = <self::E1<dynamic>>[#C5]
+  #C7 = self::E2<core::int> {b:#C1, d:#C2, e:#C1, f:#C3, index:#C2, _name:#C4}
+  #C8 = <self::E2<dynamic>>[#C7]
+}
+
+
+Constructor coverage from constants:
+org-dartlang-testcase:///generic_primary_constructor.dart:
+- E1. (from org-dartlang-testcase:///generic_primary_constructor.dart:37:9)
+- _Enum. (from org-dartlang-sdk:///sdk/lib/core/enum.dart)
+- Object. (from org-dartlang-sdk:///sdk/lib/core/object.dart)
+- E2. (from org-dartlang-testcase:///generic_primary_constructor.dart:40:11)
diff --git a/pkg/front_end/testcases/primary_constructors/generic_primary_constructor.dart.strong.modular.expect b/pkg/front_end/testcases/primary_constructors/generic_primary_constructor.dart.strong.modular.expect
new file mode 100644
index 00000000000..e8a97b41759
--- /dev/null
+++ b/pkg/front_end/testcases/primary_constructors/generic_primary_constructor.dart.strong.modular.expect
@@ -0,0 +1,109 @@
+library;
+import self as self;
+import "dart:core" as core;
+
+class C1<T extends core::Object? = dynamic> extends core::Object {
+  covariant-by-class field self::C1::T% b;
+  final field self::C1::T% c;
+  covariant-by-class field self::C1::T% d;
+  covariant-by-class field self::C1::T% e;
+  covariant-by-class field self::C1::T% f;
+  field core::Type g = self::C1::T%;
+  constructor •(self::C1::T% a, self::C1::T% b, self::C1::T% c) → self::C1<self::C1::T%>
+    : self::C1::b = b, self::C1::c = c, self::C1::d = a, self::C1::e = b, self::C1::f = c, self::C1::g = self::C1::T%, super core::Object::•() {
+    core::print(self::C1::T%);
+  }
+}
+class C2<T extends core::Object? = dynamic> extends core::Object {
+  covariant-by-class field self::C2::T% b;
+  final field self::C2::T% c;
+  covariant-by-class field self::C2::T% d;
+  covariant-by-class field self::C2::T% e;
+  covariant-by-class field self::C2::T% f;
+  field core::Type g;
+  constructor •(self::C2::T% a, self::C2::T% b, final self::C2::T% c) → self::C2<self::C2::T%>
+    : self::C2::d = a, self::C2::e = b, self::C2::f = c, self::C2::g = self::C2::T%, self::C2::b = b, self::C2::c = c, super core::Object::•() {
+    core::print(self::C2::T%);
+  }
+}
+class E1<T extends core::Object? = dynamic> extends core::_Enum /*isEnum*/  {
+  enum-element static const field self::E1<core::int> a = #C5;
+  final field self::E1::T% b;
+  final field self::E1::T% c;
+  final field self::E1::T% d;
+  final field core::Type f;
+  static const field core::List<self::E1<dynamic>> values = #C6;
+  const constructor •(core::int #index, core::String #name, self::E1::T% a, self::E1::T% b) → self::E1<self::E1::T%>
+    : self::E1::b = b, self::E1::c = a, self::E1::d = b, self::E1::f = self::E1::T%, super core::_Enum::•(#index, #name)
+    ;
+  method core::_enumToString() → core::String
+    return "E1.${this.{core::_Enum::_name}{core::String}}";
+}
+class E2<T extends core::Object? = dynamic> extends core::_Enum /*isEnum*/  {
+  final field self::E2::T% b;
+  enum-element static const field self::E2<core::int> a = #C7;
+  final field self::E2::T% d;
+  final field self::E2::T% e;
+  final field core::Type f;
+  static const field core::List<self::E2<dynamic>> values = #C8;
+  const constructor •(core::int #index, core::String #name, self::E2::T% a, final self::E2::T% b) → self::E2<self::E2::T%>
+    : self::E2::d = a, self::E2::e = b, self::E2::f = self::E2::T%, self::E2::b = b, super core::_Enum::•(#index, #name)
+    ;
+  method core::_enumToString() → core::String
+    return "E2.${this.{core::_Enum::_name}{core::String}}";
+}
+extension type ET1<T extends core::Object? = dynamic>(T% a) {
+  abstract extension-type-member representation-field get a() → T%;
+  constructor • = self::ET1|constructor#;
+  constructor tearoff • = self::ET1|constructor#_#new#tearOff;
+  constructor other = self::ET1|constructor#other;
+  constructor tearoff other = self::ET1|constructor#_#other#tearOff;
+}
+extension type ET2<T extends core::Object? = dynamic>(T% a) {
+  abstract extension-type-member representation-field get a() → T%;
+  constructor • = self::ET2|constructor#;
+  constructor tearoff • = self::ET2|constructor#_#new#tearOff;
+}
+static extension-type-member method ET1|constructor#<T extends core::Object? = dynamic>(self::ET1|constructor#::T% a) → self::ET1<self::ET1|constructor#::T%>% /* erasure=self::ET1|constructor#::T%, declared=! */ {
+  lowered final self::ET1<self::ET1|constructor#::T%>% /* erasure=self::ET1|constructor#::T%, declared=! */ #this = a;
+  return #this;
+}
+static extension-type-member synthetic method ET1|constructor#_#new#tearOff<T extends core::Object? = dynamic>(self::ET1|constructor#_#new#tearOff::T% a) → self::ET1<self::ET1|constructor#_#new#tearOff::T%>% /* erasure=self::ET1|constructor#_#new#tearOff::T%, declared=! */
+  return self::ET1|constructor#<self::ET1|constructor#_#new#tearOff::T%>(a);
+static extension-type-member method ET1|constructor#other<T extends core::Object? = dynamic>(self::ET1|constructor#other::T% a) → self::ET1<self::ET1|constructor#other::T%>% /* erasure=self::ET1|constructor#other::T%, declared=! */ {
+  lowered final self::ET1<self::ET1|constructor#other::T%>% /* erasure=self::ET1|constructor#other::T%, declared=! */ #this = a;
+  {
+    core::print(self::ET1|constructor#other::T%);
+  }
+  return #this;
+}
+static extension-type-member synthetic method ET1|constructor#_#other#tearOff<T extends core::Object? = dynamic>(self::ET1|constructor#_#other#tearOff::T% a) → self::ET1<self::ET1|constructor#_#other#tearOff::T%>% /* erasure=self::ET1|constructor#_#other#tearOff::T%, declared=! */
+  return self::ET1|constructor#other<self::ET1|constructor#_#other#tearOff::T%>(a);
+static extension-type-member method ET2|constructor#<T extends core::Object? = dynamic>(self::ET2|constructor#::T% a) → self::ET2<self::ET2|constructor#::T%>% /* erasure=self::ET2|constructor#::T%, declared=! */ {
+  lowered final self::ET2<self::ET2|constructor#::T%>% /* erasure=self::ET2|constructor#::T%, declared=! */ #this = a;
+  {
+    core::print(self::ET2|constructor#::T%);
+  }
+  return #this;
+}
+static extension-type-member synthetic method ET2|constructor#_#new#tearOff<T extends core::Object? = dynamic>(self::ET2|constructor#_#new#tearOff::T% a) → self::ET2<self::ET2|constructor#_#new#tearOff::T%>% /* erasure=self::ET2|constructor#_#new#tearOff::T%, declared=! */
+  return self::ET2|constructor#<self::ET2|constructor#_#new#tearOff::T%>(a);
+
+constants  {
+  #C1 = 1
+  #C2 = 0
+  #C3 = TypeLiteralConstant(core::int)
+  #C4 = "a"
+  #C5 = self::E1<core::int> {b:#C1, c:#C2, d:#C1, f:#C3, index:#C2, _name:#C4}
+  #C6 = <self::E1<dynamic>>[#C5]
+  #C7 = self::E2<core::int> {b:#C1, d:#C2, e:#C1, f:#C3, index:#C2, _name:#C4}
+  #C8 = <self::E2<dynamic>>[#C7]
+}
+
+
+Constructor coverage from constants:
+org-dartlang-testcase:///generic_primary_constructor.dart:
+- E1. (from org-dartlang-testcase:///generic_primary_constructor.dart:37:9)
+- _Enum. (from org-dartlang-sdk:///sdk/lib/core/enum.dart)
+- Object. (from org-dartlang-sdk:///sdk/lib/core/object.dart)
+- E2. (from org-dartlang-testcase:///generic_primary_constructor.dart:40:11)
diff --git a/pkg/front_end/testcases/primary_constructors/generic_primary_constructor.dart.strong.outline.expect b/pkg/front_end/testcases/primary_constructors/generic_primary_constructor.dart.strong.outline.expect
new file mode 100644
index 00000000000..33e1d22abd6
--- /dev/null
+++ b/pkg/front_end/testcases/primary_constructors/generic_primary_constructor.dart.strong.outline.expect
@@ -0,0 +1,82 @@
+library;
+import self as self;
+import "dart:core" as core;
+
+class C1<T extends core::Object? = dynamic> extends core::Object {
+  covariant-by-class field self::C1::T% b;
+  final field self::C1::T% c;
+  covariant-by-class field self::C1::T% d;
+  covariant-by-class field self::C1::T% e;
+  covariant-by-class field self::C1::T% f;
+  field core::Type g;
+  constructor •(self::C1::T% a, self::C1::T% b, self::C1::T% c) → self::C1<self::C1::T%>
+    ;
+}
+class C2<T extends core::Object? = dynamic> extends core::Object {
+  covariant-by-class field self::C2::T% b;
+  final field self::C2::T% c;
+  covariant-by-class field self::C2::T% d;
+  covariant-by-class field self::C2::T% e;
+  covariant-by-class field self::C2::T% f;
+  field core::Type g;
+  constructor •(self::C2::T% a, self::C2::T% b, final self::C2::T% c) → self::C2<self::C2::T%>
+    ;
+}
+class E1<T extends core::Object? = dynamic> extends core::_Enum /*isEnum*/  {
+  enum-element static const field self::E1<core::int> a = const self::E1::•<core::int>(0, "a", 0, 1);
+  final field self::E1::T% b;
+  final field self::E1::T% c;
+  final field self::E1::T% d;
+  final field core::Type f;
+  static const field core::List<self::E1<dynamic>> values = const <self::E1<dynamic>>[self::E1::a];
+  const constructor •(core::int #index, core::String #name, self::E1::T% a, self::E1::T% b) → self::E1<self::E1::T%>
+    : self::E1::b = b, self::E1::c = a, self::E1::d = b, self::E1::f = self::E1::T%, super core::_Enum::•(#index, #name)
+    ;
+  method core::_enumToString() → core::String
+    return "E1.${this.{core::_Enum::_name}{core::String}}";
+}
+class E2<T extends core::Object? = dynamic> extends core::_Enum /*isEnum*/  {
+  final field self::E2::T% b;
+  enum-element static const field self::E2<core::int> a = const self::E2::•<core::int>(0, "a", 0, 1);
+  final field self::E2::T% d;
+  final field self::E2::T% e;
+  final field core::Type f;
+  static const field core::List<self::E2<dynamic>> values = const <self::E2<dynamic>>[self::E2::a];
+  const constructor •(core::int #index, core::String #name, self::E2::T% a, final self::E2::T% b) → self::E2<self::E2::T%>
+    : self::E2::b = b, super core::_Enum::•(#index, #name)
+    ;
+  method core::_enumToString() → core::String
+    return "E2.${this.{core::_Enum::_name}{core::String}}";
+}
+extension type ET1<T extends core::Object? = dynamic>(T% a) {
+  abstract extension-type-member representation-field get a() → T%;
+  constructor • = self::ET1|constructor#;
+  constructor tearoff • = self::ET1|constructor#_#new#tearOff;
+  constructor other = self::ET1|constructor#other;
+  constructor tearoff other = self::ET1|constructor#_#other#tearOff;
+}
+extension type ET2<T extends core::Object? = dynamic>(T% a) {
+  abstract extension-type-member representation-field get a() → T%;
+  constructor • = self::ET2|constructor#;
+  constructor tearoff • = self::ET2|constructor#_#new#tearOff;
+}
+static extension-type-member method ET1|constructor#<T extends core::Object? = dynamic>(self::ET1|constructor#::T% a) → self::ET1<self::ET1|constructor#::T%>% /* erasure=self::ET1|constructor#::T%, declared=! */
+  ;
+static extension-type-member synthetic method ET1|constructor#_#new#tearOff<T extends core::Object? = dynamic>(self::ET1|constructor#_#new#tearOff::T% a) → self::ET1<self::ET1|constructor#_#new#tearOff::T%>% /* erasure=self::ET1|constructor#_#new#tearOff::T%, declared=! */
+  return self::ET1|constructor#<self::ET1|constructor#_#new#tearOff::T%>(a);
+static extension-type-member method ET1|constructor#other<T extends core::Object? = dynamic>(self::ET1|constructor#other::T% a) → self::ET1<self::ET1|constructor#other::T%>% /* erasure=self::ET1|constructor#other::T%, declared=! */
+  ;
+static extension-type-member synthetic method ET1|constructor#_#other#tearOff<T extends core::Object? = dynamic>(self::ET1|constructor#_#other#tearOff::T% a) → self::ET1<self::ET1|constructor#_#other#tearOff::T%>% /* erasure=self::ET1|constructor#_#other#tearOff::T%, declared=! */
+  return self::ET1|constructor#other<self::ET1|constructor#_#other#tearOff::T%>(a);
+static extension-type-member method ET2|constructor#<T extends core::Object? = dynamic>(self::ET2|constructor#::T% a) → self::ET2<self::ET2|constructor#::T%>% /* erasure=self::ET2|constructor#::T%, declared=! */
+  ;
+static extension-type-member synthetic method ET2|constructor#_#new#tearOff<T extends core::Object? = dynamic>(self::ET2|constructor#_#new#tearOff::T% a) → self::ET2<self::ET2|constructor#_#new#tearOff::T%>% /* erasure=self::ET2|constructor#_#new#tearOff::T%, declared=! */
+  return self::ET2|constructor#<self::ET2|constructor#_#new#tearOff::T%>(a);
+
+
+Extra constant evaluation status:
+Evaluated: ConstructorInvocation @ org-dartlang-testcase:///generic_primary_constructor.dart:30:3 -> InstanceConstant(const E1<int>{E1.b: 1, E1.c: 0, E1.d: 1, E1.f: int, _Enum.index: 0, _Enum._name: "a"})
+Evaluated: ListLiteral @ org-dartlang-testcase:///generic_primary_constructor.dart:29:6 -> ListConstant(const <E1<dynamic>>[const E1<int>{E1.b: 1, E1.c: 0, E1.d: 1, E1.f: int, _Enum.index: 0, _Enum._name: "a"}])
+Evaluated: ConstructorInvocation @ org-dartlang-testcase:///generic_primary_constructor.dart:41:3 -> InstanceConstant(const E2<int>{E2.b: 1, E2.d: null, E2.e: null, E2.f: null, _Enum.index: 0, _Enum._name: "a"})
+Evaluated: ListLiteral @ org-dartlang-testcase:///generic_primary_constructor.dart:40:6 -> ListConstant(const <E2<dynamic>>[const E2<int>{E2.b: 1, E2.d: null, E2.e: null, E2.f: null, _Enum.index: 0, _Enum._name: "a"}])
+Extra constant evaluation: evaluated: 25, effectively constant: 4
diff --git a/pkg/front_end/testcases/primary_constructors/generic_primary_constructor.dart.strong.transformed.expect b/pkg/front_end/testcases/primary_constructors/generic_primary_constructor.dart.strong.transformed.expect
new file mode 100644
index 00000000000..e8a97b41759
--- /dev/null
+++ b/pkg/front_end/testcases/primary_constructors/generic_primary_constructor.dart.strong.transformed.expect
@@ -0,0 +1,109 @@
+library;
+import self as self;
+import "dart:core" as core;
+
+class C1<T extends core::Object? = dynamic> extends core::Object {
+  covariant-by-class field self::C1::T% b;
+  final field self::C1::T% c;
+  covariant-by-class field self::C1::T% d;
+  covariant-by-class field self::C1::T% e;
+  covariant-by-class field self::C1::T% f;
+  field core::Type g = self::C1::T%;
+  constructor •(self::C1::T% a, self::C1::T% b, self::C1::T% c) → self::C1<self::C1::T%>
+    : self::C1::b = b, self::C1::c = c, self::C1::d = a, self::C1::e = b, self::C1::f = c, self::C1::g = self::C1::T%, super core::Object::•() {
+    core::print(self::C1::T%);
+  }
+}
+class C2<T extends core::Object? = dynamic> extends core::Object {
+  covariant-by-class field self::C2::T% b;
+  final field self::C2::T% c;
+  covariant-by-class field self::C2::T% d;
+  covariant-by-class field self::C2::T% e;
+  covariant-by-class field self::C2::T% f;
+  field core::Type g;
+  constructor •(self::C2::T% a, self::C2::T% b, final self::C2::T% c) → self::C2<self::C2::T%>
+    : self::C2::d = a, self::C2::e = b, self::C2::f = c, self::C2::g = self::C2::T%, self::C2::b = b, self::C2::c = c, super core::Object::•() {
+    core::print(self::C2::T%);
+  }
+}
+class E1<T extends core::Object? = dynamic> extends core::_Enum /*isEnum*/  {
+  enum-element static const field self::E1<core::int> a = #C5;
+  final field self::E1::T% b;
+  final field self::E1::T% c;
+  final field self::E1::T% d;
+  final field core::Type f;
+  static const field core::List<self::E1<dynamic>> values = #C6;
+  const constructor •(core::int #index, core::String #name, self::E1::T% a, self::E1::T% b) → self::E1<self::E1::T%>
+    : self::E1::b = b, self::E1::c = a, self::E1::d = b, self::E1::f = self::E1::T%, super core::_Enum::•(#index, #name)
+    ;
+  method core::_enumToString() → core::String
+    return "E1.${this.{core::_Enum::_name}{core::String}}";
+}
+class E2<T extends core::Object? = dynamic> extends core::_Enum /*isEnum*/  {
+  final field self::E2::T% b;
+  enum-element static const field self::E2<core::int> a = #C7;
+  final field self::E2::T% d;
+  final field self::E2::T% e;
+  final field core::Type f;
+  static const field core::List<self::E2<dynamic>> values = #C8;
+  const constructor •(core::int #index, core::String #name, self::E2::T% a, final self::E2::T% b) → self::E2<self::E2::T%>
+    : self::E2::d = a, self::E2::e = b, self::E2::f = self::E2::T%, self::E2::b = b, super core::_Enum::•(#index, #name)
+    ;
+  method core::_enumToString() → core::String
+    return "E2.${this.{core::_Enum::_name}{core::String}}";
+}
+extension type ET1<T extends core::Object? = dynamic>(T% a) {
+  abstract extension-type-member representation-field get a() → T%;
+  constructor • = self::ET1|constructor#;
+  constructor tearoff • = self::ET1|constructor#_#new#tearOff;
+  constructor other = self::ET1|constructor#other;
+  constructor tearoff other = self::ET1|constructor#_#other#tearOff;
+}
+extension type ET2<T extends core::Object? = dynamic>(T% a) {
+  abstract extension-type-member representation-field get a() → T%;
+  constructor • = self::ET2|constructor#;
+  constructor tearoff • = self::ET2|constructor#_#new#tearOff;
+}
+static extension-type-member method ET1|constructor#<T extends core::Object? = dynamic>(self::ET1|constructor#::T% a) → self::ET1<self::ET1|constructor#::T%>% /* erasure=self::ET1|constructor#::T%, declared=! */ {
+  lowered final self::ET1<self::ET1|constructor#::T%>% /* erasure=self::ET1|constructor#::T%, declared=! */ #this = a;
+  return #this;
+}
+static extension-type-member synthetic method ET1|constructor#_#new#tearOff<T extends core::Object? = dynamic>(self::ET1|constructor#_#new#tearOff::T% a) → self::ET1<self::ET1|constructor#_#new#tearOff::T%>% /* erasure=self::ET1|constructor#_#new#tearOff::T%, declared=! */
+  return self::ET1|constructor#<self::ET1|constructor#_#new#tearOff::T%>(a);
+static extension-type-member method ET1|constructor#other<T extends core::Object? = dynamic>(self::ET1|constructor#other::T% a) → self::ET1<self::ET1|constructor#other::T%>% /* erasure=self::ET1|constructor#other::T%, declared=! */ {
+  lowered final self::ET1<self::ET1|constructor#other::T%>% /* erasure=self::ET1|constructor#other::T%, declared=! */ #this = a;
+  {
+    core::print(self::ET1|constructor#other::T%);
+  }
+  return #this;
+}
+static extension-type-member synthetic method ET1|constructor#_#other#tearOff<T extends core::Object? = dynamic>(self::ET1|constructor#_#other#tearOff::T% a) → self::ET1<self::ET1|constructor#_#other#tearOff::T%>% /* erasure=self::ET1|constructor#_#other#tearOff::T%, declared=! */
+  return self::ET1|constructor#other<self::ET1|constructor#_#other#tearOff::T%>(a);
+static extension-type-member method ET2|constructor#<T extends core::Object? = dynamic>(self::ET2|constructor#::T% a) → self::ET2<self::ET2|constructor#::T%>% /* erasure=self::ET2|constructor#::T%, declared=! */ {
+  lowered final self::ET2<self::ET2|constructor#::T%>% /* erasure=self::ET2|constructor#::T%, declared=! */ #this = a;
+  {
+    core::print(self::ET2|constructor#::T%);
+  }
+  return #this;
+}
+static extension-type-member synthetic method ET2|constructor#_#new#tearOff<T extends core::Object? = dynamic>(self::ET2|constructor#_#new#tearOff::T% a) → self::ET2<self::ET2|constructor#_#new#tearOff::T%>% /* erasure=self::ET2|constructor#_#new#tearOff::T%, declared=! */
+  return self::ET2|constructor#<self::ET2|constructor#_#new#tearOff::T%>(a);
+
+constants  {
+  #C1 = 1
+  #C2 = 0
+  #C3 = TypeLiteralConstant(core::int)
+  #C4 = "a"
+  #C5 = self::E1<core::int> {b:#C1, c:#C2, d:#C1, f:#C3, index:#C2, _name:#C4}
+  #C6 = <self::E1<dynamic>>[#C5]
+  #C7 = self::E2<core::int> {b:#C1, d:#C2, e:#C1, f:#C3, index:#C2, _name:#C4}
+  #C8 = <self::E2<dynamic>>[#C7]
+}
+
+
+Constructor coverage from constants:
+org-dartlang-testcase:///generic_primary_constructor.dart:
+- E1. (from org-dartlang-testcase:///generic_primary_constructor.dart:37:9)
+- _Enum. (from org-dartlang-sdk:///sdk/lib/core/enum.dart)
+- Object. (from org-dartlang-sdk:///sdk/lib/core/object.dart)
+- E2. (from org-dartlang-testcase:///generic_primary_constructor.dart:40:11)
diff --git a/pkg/front_end/testcases/primary_constructors/generic_primary_constructor.dart.textual_outline.expect b/pkg/front_end/testcases/primary_constructors/generic_primary_constructor.dart.textual_outline.expect
new file mode 100644
index 00000000000..95636f37a40
--- /dev/null
+++ b/pkg/front_end/testcases/primary_constructors/generic_primary_constructor.dart.textual_outline.expect
@@ -0,0 +1,29 @@
+class C1<T> {
+  T b;
+  final T c;
+  T d;
+  T e;
+  T f;
+  Type g = T;
+  C1(T a, this.b, this.c) : d = a, e = b, f = c, g = T {}
+}
+
+class C2<T>(T a, var T b, final T c) {
+  T d = a;
+  T e = b;
+  T f = c;
+  Type g = T;
+  this {}
+}
+
+enum E1<T> { a<int>(0, 1); final T b; final T c; final T d; final Type f; const E1(T a, this.b) : c = a, d = b, f = T; }
+
+enum E2<T>(T a, final T b) { a<int>(0, 1); final T d = a; final T e = b; final Type f = T; }
+
+extension type ET1<T>(T a) {
+  ET1.other(this.a) {}
+}
+
+extension type ET2<T>(T a) {
+  this {}
+}
diff --git a/pkg/front_end/testcases/primary_constructors/generic_primary_constructor.dart.textual_outline_modelled.expect b/pkg/front_end/testcases/primary_constructors/generic_primary_constructor.dart.textual_outline_modelled.expect
new file mode 100644
index 00000000000..a345b78699b
--- /dev/null
+++ b/pkg/front_end/testcases/primary_constructors/generic_primary_constructor.dart.textual_outline_modelled.expect
@@ -0,0 +1,29 @@
+class C1<T> {
+  C1(T a, this.b, this.c) : d = a, e = b, f = c, g = T {}
+  T b;
+  T d;
+  T e;
+  T f;
+  Type g = T;
+  final T c;
+}
+
+class C2<T>(T a, var T b, final T c) {
+  T d = a;
+  T e = b;
+  T f = c;
+  Type g = T;
+  this {}
+}
+
+enum E1<T> { a<int>(0, 1); final T b; final T c; final T d; final Type f; const E1(T a, this.b) : c = a, d = b, f = T; }
+
+enum E2<T>(T a, final T b) { a<int>(0, 1); final T d = a; final T e = b; final Type f = T; }
+
+extension type ET1<T>(T a) {
+  ET1.other(this.a) {}
+}
+
+extension type ET2<T>(T a) {
+  this {}
+}
diff --git a/pkg/front_end/testcases/primary_constructors/parameter_scope.dart b/pkg/front_end/testcases/primary_constructors/parameter_scope.dart
new file mode 100644
index 00000000000..2a6c7ee1704
--- /dev/null
+++ b/pkg/front_end/testcases/primary_constructors/parameter_scope.dart
@@ -0,0 +1,29 @@
+// Copyright (c) 2026, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+class C1([@m int x = m]) {
+  static const int m = 42;
+}
+
+class C2(int x) { // Error
+  static const String int = 'not a type';
+}
+
+enum E1([@a int x = m]) {
+  a(0);
+  static const int m = 42;
+}
+
+enum E2(int x) { // Error
+  a(0);
+  static const String int = 'not a type';
+}
+
+extension type ET1([@m int x = m]) {
+  static const int m = 42;
+}
+
+extension type ET2(int x) { // Error
+  static const String int = 'not a type';
+}
diff --git a/pkg/front_end/testcases/primary_constructors/parameter_scope.dart.strong.expect b/pkg/front_end/testcases/primary_constructors/parameter_scope.dart.strong.expect
new file mode 100644
index 00000000000..aec5ec2e32a
--- /dev/null
+++ b/pkg/front_end/testcases/primary_constructors/parameter_scope.dart.strong.expect
@@ -0,0 +1,96 @@
+library;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/primary_constructors/parameter_scope.dart:9:10: Error: 'int' isn't a type.
+// class C2(int x) { // Error
+//          ^^^
+//
+// pkg/front_end/testcases/primary_constructors/parameter_scope.dart:18:9: Error: 'int' isn't a type.
+// enum E2(int x) { // Error
+//         ^^^
+//
+// pkg/front_end/testcases/primary_constructors/parameter_scope.dart:27:20: Error: 'int' isn't a type.
+// extension type ET2(int x) { // Error
+//                    ^^^
+//
+import self as self;
+import "dart:core" as core;
+
+class C1 extends core::Object {
+  static const field core::int m = #C1;
+  constructor •([@#C1 core::int x = #C1]) → self::C1
+    : super core::Object::•()
+    ;
+}
+class C2 extends core::Object {
+  static const field core::String int = #C2;
+  constructor •(core::int x) → self::C2
+    : super core::Object::•()
+    ;
+}
+class E1 extends core::_Enum /*isEnum*/  {
+  enum-element static const field self::E1 a = #C5;
+  static const field core::int m = #C1;
+  static const field core::List<self::E1> values = #C6;
+  const constructor •(core::int #index, core::String #name, [@#C5 core::int x = #C1]) → self::E1
+    : super core::_Enum::•(#index, #name)
+    ;
+  method core::_enumToString() → core::String
+    return "E1.${this.{core::_Enum::_name}{core::String}}";
+}
+class E2 extends core::_Enum /*isEnum*/  {
+  enum-element static const field self::E2 a = #C7;
+  static const field core::String int = #C2;
+  static const field core::List<self::E2> values = #C8;
+  const constructor •(core::int #index, core::String #name, core::int x) → self::E2
+    : super core::_Enum::•(#index, #name)
+    ;
+  method core::_enumToString() → core::String
+    return "E2.${this.{core::_Enum::_name}{core::String}}";
+}
+extension type ET1(core::int x) {
+  abstract extension-type-member representation-field get x() → core::int;
+  static field m = self::ET1|m;
+  constructor • = self::ET1|constructor#;
+  constructor tearoff • = self::ET1|constructor#_#new#tearOff;
+}
+extension type ET2(core::int x) {
+  abstract extension-type-member representation-field get x() → core::int;
+  static field int = self::ET2|int;
+  constructor • = self::ET2|constructor#;
+  constructor tearoff • = self::ET2|constructor#_#new#tearOff;
+}
+static const field core::int ET1|m = #C1;
+static const field core::String ET2|int = #C2;
+static extension-type-member method ET1|constructor#([@#C1 core::int x = #C1]) → self::ET1% /* erasure=core::int, declared=! */ {
+  lowered final self::ET1% /* erasure=core::int, declared=! */ #this = x;
+  return #this;
+}
+static extension-type-member synthetic method ET1|constructor#_#new#tearOff([core::int x = #C1]) → self::ET1% /* erasure=core::int, declared=! */
+  return self::ET1|constructor#(x);
+static extension-type-member method ET2|constructor#(core::int x) → self::ET2% /* erasure=core::int, declared=! */ {
+  lowered final self::ET2% /* erasure=core::int, declared=! */ #this = x;
+  return #this;
+}
+static extension-type-member synthetic method ET2|constructor#_#new#tearOff(core::int x) → self::ET2% /* erasure=core::int, declared=! */
+  return self::ET2|constructor#(x);
+
+constants  {
+  #C1 = 42
+  #C2 = "not a type"
+  #C3 = 0
+  #C4 = "a"
+  #C5 = self::E1 {index:#C3, _name:#C4}
+  #C6 = <self::E1>[#C5]
+  #C7 = self::E2 {index:#C3, _name:#C4}
+  #C8 = <self::E2>[#C7]
+}
+
+
+Constructor coverage from constants:
+org-dartlang-testcase:///parameter_scope.dart:
+- E1. (from org-dartlang-testcase:///parameter_scope.dart:13:8)
+- _Enum. (from org-dartlang-sdk:///sdk/lib/core/enum.dart)
+- Object. (from org-dartlang-sdk:///sdk/lib/core/object.dart)
+- E2. (from org-dartlang-testcase:///parameter_scope.dart:18:8)
diff --git a/pkg/front_end/testcases/primary_constructors/parameter_scope.dart.strong.modular.expect b/pkg/front_end/testcases/primary_constructors/parameter_scope.dart.strong.modular.expect
new file mode 100644
index 00000000000..aec5ec2e32a
--- /dev/null
+++ b/pkg/front_end/testcases/primary_constructors/parameter_scope.dart.strong.modular.expect
@@ -0,0 +1,96 @@
+library;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/primary_constructors/parameter_scope.dart:9:10: Error: 'int' isn't a type.
+// class C2(int x) { // Error
+//          ^^^
+//
+// pkg/front_end/testcases/primary_constructors/parameter_scope.dart:18:9: Error: 'int' isn't a type.
+// enum E2(int x) { // Error
+//         ^^^
+//
+// pkg/front_end/testcases/primary_constructors/parameter_scope.dart:27:20: Error: 'int' isn't a type.
+// extension type ET2(int x) { // Error
+//                    ^^^
+//
+import self as self;
+import "dart:core" as core;
+
+class C1 extends core::Object {
+  static const field core::int m = #C1;
+  constructor •([@#C1 core::int x = #C1]) → self::C1
+    : super core::Object::•()
+    ;
+}
+class C2 extends core::Object {
+  static const field core::String int = #C2;
+  constructor •(core::int x) → self::C2
+    : super core::Object::•()
+    ;
+}
+class E1 extends core::_Enum /*isEnum*/  {
+  enum-element static const field self::E1 a = #C5;
+  static const field core::int m = #C1;
+  static const field core::List<self::E1> values = #C6;
+  const constructor •(core::int #index, core::String #name, [@#C5 core::int x = #C1]) → self::E1
+    : super core::_Enum::•(#index, #name)
+    ;
+  method core::_enumToString() → core::String
+    return "E1.${this.{core::_Enum::_name}{core::String}}";
+}
+class E2 extends core::_Enum /*isEnum*/  {
+  enum-element static const field self::E2 a = #C7;
+  static const field core::String int = #C2;
+  static const field core::List<self::E2> values = #C8;
+  const constructor •(core::int #index, core::String #name, core::int x) → self::E2
+    : super core::_Enum::•(#index, #name)
+    ;
+  method core::_enumToString() → core::String
+    return "E2.${this.{core::_Enum::_name}{core::String}}";
+}
+extension type ET1(core::int x) {
+  abstract extension-type-member representation-field get x() → core::int;
+  static field m = self::ET1|m;
+  constructor • = self::ET1|constructor#;
+  constructor tearoff • = self::ET1|constructor#_#new#tearOff;
+}
+extension type ET2(core::int x) {
+  abstract extension-type-member representation-field get x() → core::int;
+  static field int = self::ET2|int;
+  constructor • = self::ET2|constructor#;
+  constructor tearoff • = self::ET2|constructor#_#new#tearOff;
+}
+static const field core::int ET1|m = #C1;
+static const field core::String ET2|int = #C2;
+static extension-type-member method ET1|constructor#([@#C1 core::int x = #C1]) → self::ET1% /* erasure=core::int, declared=! */ {
+  lowered final self::ET1% /* erasure=core::int, declared=! */ #this = x;
+  return #this;
+}
+static extension-type-member synthetic method ET1|constructor#_#new#tearOff([core::int x = #C1]) → self::ET1% /* erasure=core::int, declared=! */
+  return self::ET1|constructor#(x);
+static extension-type-member method ET2|constructor#(core::int x) → self::ET2% /* erasure=core::int, declared=! */ {
+  lowered final self::ET2% /* erasure=core::int, declared=! */ #this = x;
+  return #this;
+}
+static extension-type-member synthetic method ET2|constructor#_#new#tearOff(core::int x) → self::ET2% /* erasure=core::int, declared=! */
+  return self::ET2|constructor#(x);
+
+constants  {
+  #C1 = 42
+  #C2 = "not a type"
+  #C3 = 0
+  #C4 = "a"
+  #C5 = self::E1 {index:#C3, _name:#C4}
+  #C6 = <self::E1>[#C5]
+  #C7 = self::E2 {index:#C3, _name:#C4}
+  #C8 = <self::E2>[#C7]
+}
+
+
+Constructor coverage from constants:
+org-dartlang-testcase:///parameter_scope.dart:
+- E1. (from org-dartlang-testcase:///parameter_scope.dart:13:8)
+- _Enum. (from org-dartlang-sdk:///sdk/lib/core/enum.dart)
+- Object. (from org-dartlang-sdk:///sdk/lib/core/object.dart)
+- E2. (from org-dartlang-testcase:///parameter_scope.dart:18:8)
diff --git a/pkg/front_end/testcases/primary_constructors/parameter_scope.dart.strong.outline.expect b/pkg/front_end/testcases/primary_constructors/parameter_scope.dart.strong.outline.expect
new file mode 100644
index 00000000000..88ab7046ab8
--- /dev/null
+++ b/pkg/front_end/testcases/primary_constructors/parameter_scope.dart.strong.outline.expect
@@ -0,0 +1,67 @@
+library;
+import self as self;
+import "dart:core" as core;
+
+class C1 extends core::Object {
+  static const field core::int m = 42;
+  constructor •([core::int x = self::C1::m]) → self::C1
+    ;
+}
+class C2 extends core::Object {
+  static const field core::String int = "not a type";
+  constructor •(core::int x) → self::C2
+    ;
+}
+class E1 extends core::_Enum /*isEnum*/  {
+  enum-element static const field self::E1 a = const self::E1::•(0, "a", 0);
+  static const field core::int m = 42;
+  static const field core::List<self::E1> values = const <self::E1>[self::E1::a];
+  const constructor •(core::int #index, core::String #name, [core::int x = self::E1::m]) → self::E1
+    : super core::_Enum::•(#index, #name)
+    ;
+  method core::_enumToString() → core::String
+    return "E1.${this.{core::_Enum::_name}{core::String}}";
+}
+class E2 extends core::_Enum /*isEnum*/  {
+  enum-element static const field self::E2 a = const self::E2::•(0, "a", 0);
+  static const field core::String int = "not a type";
+  static const field core::List<self::E2> values = const <self::E2>[self::E2::a];
+  const constructor •(core::int #index, core::String #name, core::int x) → self::E2
+    : super core::_Enum::•(#index, #name)
+    ;
+  method core::_enumToString() → core::String
+    return "E2.${this.{core::_Enum::_name}{core::String}}";
+}
+extension type ET1(core::int x) {
+  abstract extension-type-member representation-field get x() → core::int;
+  static field m = self::ET1|m;
+  constructor • = self::ET1|constructor#;
+  constructor tearoff • = self::ET1|constructor#_#new#tearOff;
+}
+extension type ET2(core::int x) {
+  abstract extension-type-member representation-field get x() → core::int;
+  static field int = self::ET2|int;
+  constructor • = self::ET2|constructor#;
+  constructor tearoff • = self::ET2|constructor#_#new#tearOff;
+}
+static const field core::int ET1|m = 42;
+static const field core::String ET2|int = "not a type";
+static extension-type-member method ET1|constructor#([core::int x = self::ET1|m]) → self::ET1% /* erasure=core::int, declared=! */
+  ;
+static extension-type-member synthetic method ET1|constructor#_#new#tearOff([has-declared-initializer core::int x]) → self::ET1% /* erasure=core::int, declared=! */
+  return self::ET1|constructor#(x);
+static extension-type-member method ET2|constructor#(core::int x) → self::ET2% /* erasure=core::int, declared=! */
+  ;
+static extension-type-member synthetic method ET2|constructor#_#new#tearOff(core::int x) → self::ET2% /* erasure=core::int, declared=! */
+  return self::ET2|constructor#(x);
+
+
+Extra constant evaluation status:
+Evaluated: StaticGet @ org-dartlang-testcase:///parameter_scope.dart:5:22 -> IntConstant(42)
+Evaluated: StaticGet @ org-dartlang-testcase:///parameter_scope.dart:13:21 -> IntConstant(42)
+Evaluated: ConstructorInvocation @ org-dartlang-testcase:///parameter_scope.dart:14:3 -> InstanceConstant(const E1{_Enum.index: 0, _Enum._name: "a"})
+Evaluated: ListLiteral @ org-dartlang-testcase:///parameter_scope.dart:13:6 -> ListConstant(const <E1>[const E1{_Enum.index: 0, _Enum._name: "a"}])
+Evaluated: ConstructorInvocation @ org-dartlang-testcase:///parameter_scope.dart:19:3 -> InstanceConstant(const E2{_Enum.index: 0, _Enum._name: "a"})
+Evaluated: ListLiteral @ org-dartlang-testcase:///parameter_scope.dart:18:6 -> ListConstant(const <E2>[const E2{_Enum.index: 0, _Enum._name: "a"}])
+Evaluated: StaticGet @ org-dartlang-testcase:///parameter_scope.dart:23:32 -> IntConstant(42)
+Extra constant evaluation: evaluated: 21, effectively constant: 7
diff --git a/pkg/front_end/testcases/primary_constructors/parameter_scope.dart.strong.transformed.expect b/pkg/front_end/testcases/primary_constructors/parameter_scope.dart.strong.transformed.expect
new file mode 100644
index 00000000000..aec5ec2e32a
--- /dev/null
+++ b/pkg/front_end/testcases/primary_constructors/parameter_scope.dart.strong.transformed.expect
@@ -0,0 +1,96 @@
+library;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/primary_constructors/parameter_scope.dart:9:10: Error: 'int' isn't a type.
+// class C2(int x) { // Error
+//          ^^^
+//
+// pkg/front_end/testcases/primary_constructors/parameter_scope.dart:18:9: Error: 'int' isn't a type.
+// enum E2(int x) { // Error
+//         ^^^
+//
+// pkg/front_end/testcases/primary_constructors/parameter_scope.dart:27:20: Error: 'int' isn't a type.
+// extension type ET2(int x) { // Error
+//                    ^^^
+//
+import self as self;
+import "dart:core" as core;
+
+class C1 extends core::Object {
+  static const field core::int m = #C1;
+  constructor •([@#C1 core::int x = #C1]) → self::C1
+    : super core::Object::•()
+    ;
+}
+class C2 extends core::Object {
+  static const field core::String int = #C2;
+  constructor •(core::int x) → self::C2
+    : super core::Object::•()
+    ;
+}
+class E1 extends core::_Enum /*isEnum*/  {
+  enum-element static const field self::E1 a = #C5;
+  static const field core::int m = #C1;
+  static const field core::List<self::E1> values = #C6;
+  const constructor •(core::int #index, core::String #name, [@#C5 core::int x = #C1]) → self::E1
+    : super core::_Enum::•(#index, #name)
+    ;
+  method core::_enumToString() → core::String
+    return "E1.${this.{core::_Enum::_name}{core::String}}";
+}
+class E2 extends core::_Enum /*isEnum*/  {
+  enum-element static const field self::E2 a = #C7;
+  static const field core::String int = #C2;
+  static const field core::List<self::E2> values = #C8;
+  const constructor •(core::int #index, core::String #name, core::int x) → self::E2
+    : super core::_Enum::•(#index, #name)
+    ;
+  method core::_enumToString() → core::String
+    return "E2.${this.{core::_Enum::_name}{core::String}}";
+}
+extension type ET1(core::int x) {
+  abstract extension-type-member representation-field get x() → core::int;
+  static field m = self::ET1|m;
+  constructor • = self::ET1|constructor#;
+  constructor tearoff • = self::ET1|constructor#_#new#tearOff;
+}
+extension type ET2(core::int x) {
+  abstract extension-type-member representation-field get x() → core::int;
+  static field int = self::ET2|int;
+  constructor • = self::ET2|constructor#;
+  constructor tearoff • = self::ET2|constructor#_#new#tearOff;
+}
+static const field core::int ET1|m = #C1;
+static const field core::String ET2|int = #C2;
+static extension-type-member method ET1|constructor#([@#C1 core::int x = #C1]) → self::ET1% /* erasure=core::int, declared=! */ {
+  lowered final self::ET1% /* erasure=core::int, declared=! */ #this = x;
+  return #this;
+}
+static extension-type-member synthetic method ET1|constructor#_#new#tearOff([core::int x = #C1]) → self::ET1% /* erasure=core::int, declared=! */
+  return self::ET1|constructor#(x);
+static extension-type-member method ET2|constructor#(core::int x) → self::ET2% /* erasure=core::int, declared=! */ {
+  lowered final self::ET2% /* erasure=core::int, declared=! */ #this = x;
+  return #this;
+}
+static extension-type-member synthetic method ET2|constructor#_#new#tearOff(core::int x) → self::ET2% /* erasure=core::int, declared=! */
+  return self::ET2|constructor#(x);
+
+constants  {
+  #C1 = 42
+  #C2 = "not a type"
+  #C3 = 0
+  #C4 = "a"
+  #C5 = self::E1 {index:#C3, _name:#C4}
+  #C6 = <self::E1>[#C5]
+  #C7 = self::E2 {index:#C3, _name:#C4}
+  #C8 = <self::E2>[#C7]
+}
+
+
+Constructor coverage from constants:
+org-dartlang-testcase:///parameter_scope.dart:
+- E1. (from org-dartlang-testcase:///parameter_scope.dart:13:8)
+- _Enum. (from org-dartlang-sdk:///sdk/lib/core/enum.dart)
+- Object. (from org-dartlang-sdk:///sdk/lib/core/object.dart)
+- E2. (from org-dartlang-testcase:///parameter_scope.dart:18:8)
diff --git a/pkg/front_end/testcases/primary_constructors/parameter_scope.dart.textual_outline.expect b/pkg/front_end/testcases/primary_constructors/parameter_scope.dart.textual_outline.expect
new file mode 100644
index 00000000000..44728357dae
--- /dev/null
+++ b/pkg/front_end/testcases/primary_constructors/parameter_scope.dart.textual_outline.expect
@@ -0,0 +1,19 @@
+class C1([@m int x = m]) {
+  static const int m = 42;
+}
+
+class C2(int x) {
+  static const String int = 'not a type';
+}
+
+enum E1([@a int x = m]) { a(0); static const int m = 42; }
+
+enum E2(int x) { a(0); static const String int = 'not a type'; }
+
+extension type ET1([@m int x = m]) {
+  static const int m = 42;
+}
+
+extension type ET2(int x) {
+  static const String int = 'not a type';
+}
diff --git a/pkg/front_end/testcases/primary_constructors/parameter_scope.dart.textual_outline_modelled.expect b/pkg/front_end/testcases/primary_constructors/parameter_scope.dart.textual_outline_modelled.expect
new file mode 100644
index 00000000000..44728357dae
--- /dev/null
+++ b/pkg/front_end/testcases/primary_constructors/parameter_scope.dart.textual_outline_modelled.expect
@@ -0,0 +1,19 @@
+class C1([@m int x = m]) {
+  static const int m = 42;
+}
+
+class C2(int x) {
+  static const String int = 'not a type';
+}
+
+enum E1([@a int x = m]) { a(0); static const int m = 42; }
+
+enum E2(int x) { a(0); static const String int = 'not a type'; }
+
+extension type ET1([@m int x = m]) {
+  static const int m = 42;
+}
+
+extension type ET2(int x) {
+  static const String int = 'not a type';
+}
diff --git a/pkg/front_end/testcases/primary_constructors/parameter_scope_pre_feature.dart b/pkg/front_end/testcases/primary_constructors/parameter_scope_pre_feature.dart
new file mode 100644
index 00000000000..830bd56c3b8
--- /dev/null
+++ b/pkg/front_end/testcases/primary_constructors/parameter_scope_pre_feature.dart
@@ -0,0 +1,9 @@
+// Copyright (c) 2026, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// @dart=3.10
+
+extension type ET2(int x) /* Ok */ {
+  static const String int = 'not a type';
+}
diff --git a/pkg/front_end/testcases/primary_constructors/parameter_scope_pre_feature.dart.strong.expect b/pkg/front_end/testcases/primary_constructors/parameter_scope_pre_feature.dart.strong.expect
new file mode 100644
index 00000000000..01c326b1d55
--- /dev/null
+++ b/pkg/front_end/testcases/primary_constructors/parameter_scope_pre_feature.dart.strong.expect
@@ -0,0 +1,21 @@
+library;
+import self as self;
+import "dart:core" as core;
+
+extension type ET2(core::int x) {
+  abstract extension-type-member representation-field get x() → core::int;
+  static field int = self::ET2|int;
+  constructor • = self::ET2|constructor#;
+  constructor tearoff • = self::ET2|constructor#_#new#tearOff;
+}
+static const field core::String ET2|int = #C1;
+static extension-type-member method ET2|constructor#(core::int x) → self::ET2% /* erasure=core::int, declared=! */ {
+  lowered final self::ET2% /* erasure=core::int, declared=! */ #this = x;
+  return #this;
+}
+static extension-type-member synthetic method ET2|constructor#_#new#tearOff(core::int x) → self::ET2% /* erasure=core::int, declared=! */
+  return self::ET2|constructor#(x);
+
+constants  {
+  #C1 = "not a type"
+}
diff --git a/pkg/front_end/testcases/primary_constructors/parameter_scope_pre_feature.dart.strong.modular.expect b/pkg/front_end/testcases/primary_constructors/parameter_scope_pre_feature.dart.strong.modular.expect
new file mode 100644
index 00000000000..01c326b1d55
--- /dev/null
+++ b/pkg/front_end/testcases/primary_constructors/parameter_scope_pre_feature.dart.strong.modular.expect
@@ -0,0 +1,21 @@
+library;
+import self as self;
+import "dart:core" as core;
+
+extension type ET2(core::int x) {
+  abstract extension-type-member representation-field get x() → core::int;
+  static field int = self::ET2|int;
+  constructor • = self::ET2|constructor#;
+  constructor tearoff • = self::ET2|constructor#_#new#tearOff;
+}
+static const field core::String ET2|int = #C1;
+static extension-type-member method ET2|constructor#(core::int x) → self::ET2% /* erasure=core::int, declared=! */ {
+  lowered final self::ET2% /* erasure=core::int, declared=! */ #this = x;
+  return #this;
+}
+static extension-type-member synthetic method ET2|constructor#_#new#tearOff(core::int x) → self::ET2% /* erasure=core::int, declared=! */
+  return self::ET2|constructor#(x);
+
+constants  {
+  #C1 = "not a type"
+}
diff --git a/pkg/front_end/testcases/primary_constructors/parameter_scope_pre_feature.dart.strong.outline.expect b/pkg/front_end/testcases/primary_constructors/parameter_scope_pre_feature.dart.strong.outline.expect
new file mode 100644
index 00000000000..4354604cfc0
--- /dev/null
+++ b/pkg/front_end/testcases/primary_constructors/parameter_scope_pre_feature.dart.strong.outline.expect
@@ -0,0 +1,15 @@
+library;
+import self as self;
+import "dart:core" as core;
+
+extension type ET2(core::int x) {
+  abstract extension-type-member representation-field get x() → core::int;
+  static field int = self::ET2|int;
+  constructor • = self::ET2|constructor#;
+  constructor tearoff • = self::ET2|constructor#_#new#tearOff;
+}
+static const field core::String ET2|int = "not a type";
+static extension-type-member method ET2|constructor#(core::int x) → self::ET2% /* erasure=core::int, declared=! */
+  ;
+static extension-type-member synthetic method ET2|constructor#_#new#tearOff(core::int x) → self::ET2% /* erasure=core::int, declared=! */
+  return self::ET2|constructor#(x);
diff --git a/pkg/front_end/testcases/primary_constructors/parameter_scope_pre_feature.dart.strong.transformed.expect b/pkg/front_end/testcases/primary_constructors/parameter_scope_pre_feature.dart.strong.transformed.expect
new file mode 100644
index 00000000000..01c326b1d55
--- /dev/null
+++ b/pkg/front_end/testcases/primary_constructors/parameter_scope_pre_feature.dart.strong.transformed.expect
@@ -0,0 +1,21 @@
+library;
+import self as self;
+import "dart:core" as core;
+
+extension type ET2(core::int x) {
+  abstract extension-type-member representation-field get x() → core::int;
+  static field int = self::ET2|int;
+  constructor • = self::ET2|constructor#;
+  constructor tearoff • = self::ET2|constructor#_#new#tearOff;
+}
+static const field core::String ET2|int = #C1;
+static extension-type-member method ET2|constructor#(core::int x) → self::ET2% /* erasure=core::int, declared=! */ {
+  lowered final self::ET2% /* erasure=core::int, declared=! */ #this = x;
+  return #this;
+}
+static extension-type-member synthetic method ET2|constructor#_#new#tearOff(core::int x) → self::ET2% /* erasure=core::int, declared=! */
+  return self::ET2|constructor#(x);
+
+constants  {
+  #C1 = "not a type"
+}
diff --git a/pkg/front_end/testcases/primary_constructors/parameter_scope_pre_feature.dart.textual_outline.expect b/pkg/front_end/testcases/primary_constructors/parameter_scope_pre_feature.dart.textual_outline.expect
new file mode 100644
index 00000000000..ec34091cf2e
--- /dev/null
+++ b/pkg/front_end/testcases/primary_constructors/parameter_scope_pre_feature.dart.textual_outline.expect
@@ -0,0 +1,5 @@
+// @dart = 3.10
+
+extension type ET2(int x) {
+  static const String int = 'not a type';
+}
diff --git a/pkg/front_end/testcases/primary_constructors/parameter_scope_pre_feature.dart.textual_outline_modelled.expect b/pkg/front_end/testcases/primary_constructors/parameter_scope_pre_feature.dart.textual_outline_modelled.expect
new file mode 100644
index 00000000000..ec34091cf2e
--- /dev/null
+++ b/pkg/front_end/testcases/primary_constructors/parameter_scope_pre_feature.dart.textual_outline_modelled.expect
@@ -0,0 +1,5 @@
+// @dart = 3.10
+
+extension type ET2(int x) {
+  static const String int = 'not a type';
+}
diff --git a/tests/language/primary_constructors/header/parameter_scope_error_test.dart b/tests/language/primary_constructors/header/parameter_scope_error_test.dart
new file mode 100644
index 00000000000..f72aafc308a
--- /dev/null
+++ b/tests/language/primary_constructors/header/parameter_scope_error_test.dart
@@ -0,0 +1,33 @@
+// Copyright (c) 2026, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// Formal parameter types of primary constructor are resolved within the body
+// scope of the enclosing declaration.
+
+// SharedOptions=--enable-experiment=primary-constructors
+
+class C(int x) {
+//      ^
+// [analyzer] unspecified
+// [cfe] 'int' isn't a type.
+
+  static const String int = 'not a type';
+}
+
+enum E(int x) {
+//     ^
+// [cfe] 'int' isn't a type.
+// [analyzer] unspecified
+  a(0);
+
+  static const String int = 'not a type';
+}
+
+extension type ET(int x) {
+//                ^
+// [analyzer] unspecified
+// [cfe] 'int' isn't a type.
+
+  static const String int = 'not a type';
+}
diff --git a/tests/language/primary_constructors/header/parameter_scope_pre_feature_test.dart b/tests/language/primary_constructors/header/parameter_scope_pre_feature_test.dart
new file mode 100644
index 00000000000..d95f1c8d9b5
--- /dev/null
+++ b/tests/language/primary_constructors/header/parameter_scope_pre_feature_test.dart
@@ -0,0 +1,20 @@
+// Copyright (c) 2026, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// @dart=3.10
+
+// Prior to the primary-constructors feature, formal parameter types of
+// primary constructor were not resolved within the body scope of the
+// enclosing declaration.
+
+// SharedOptions=--enable-experiment=primary-constructors
+
+extension type ET(int x) {
+  static const String int = 'not a type';
+}
+
+main() {
+  print(ET(0));
+  print(ET.int);
+}