Ensure generic constraints are emitted in correct order

src/Compiler/Microsoft.AspNetCore.Razor.Language/test/IntegrationTests/ComponentCodeGenerationTestBase.cs

@@ -6804,6 +6804,68 @@ @using System.Collections.Generic
         CompileToAssembly(generated);
     }
 
+    [Theory] // https://github.com/dotnet/razor/issues/7074
+    [InlineData("struct", null, "1")]
+    [InlineData("class", null, "string.Empty")]
+    [InlineData("notnull", null, "1")]
+    [InlineData("unmanaged", null, "1")]
+    [InlineData(null, "new()", "1")]
+    public void GenericComponent_ConstraintOrdering(string first, string last, string arg)
+    {
+        // Arrange
+        if (first != null)
+        {
+            first = $"{first}, ";
+        }
+        if (last != null)
+        {
+            last = $", {last}";
+        }
+        AdditionalSyntaxTrees.Add(Parse($$"""
+            using Microsoft.AspNetCore.Components;
+            using System;
+            namespace Test;
+            public class MyComponent<T> : ComponentBase where T : {{first}}IComparable{{last}}
+            {
+                [Parameter] public T Parameter { get; set; }
+            }
+            """));
+
+        // Act
+        var generated = CompileToCSharp($"""
+            @using Test
+            <MyComponent Parameter="{arg}" />
+            """);
+
+        // Assert
+        CompileToAssembly(generated);
+    }
+
+    [Fact]
+    public void GenericComponent_UnmanagedConstraint()
+    {
+        // Arrange
+        AdditionalSyntaxTrees.Add(Parse("""
+            using Microsoft.AspNetCore.Components;
+            namespace Test;
+            public class MyComponent<T> : ComponentBase where T : unmanaged
+            {
+                [Parameter] public T Parameter { get; set; }
+            }
+            """));
+
+        // Act
+        var generated = CompileToCSharp("""
+            @using Test
+            <MyComponent Parameter="1" />
+            """);
+
+        // Assert
+        AssertDocumentNodeMatchesBaseline(generated.CodeDocument);
+        AssertCSharpDocumentMatchesBaseline(generated.CodeDocument);
+        CompileToAssembly(generated);
+    }
+
     #endregion
 
     #region Key

src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/GenericComponent_UnmanagedConstraint/TestComponent.codegen.cs

@@ -0,0 +1,64 @@
+// <auto-generated/>
+#pragma warning disable 1591
+namespace Test
+{
+    #line hidden
+    using System;
+    using System.Collections.Generic;
+    using System.Linq;
+    using System.Threading.Tasks;
+    using Microsoft.AspNetCore.Components;
+#nullable restore
+#line 1 "x:\dir\subdir\Test\TestComponent.cshtml"
+using Test;
+
+#line default
+#line hidden
+#nullable disable
+    public partial class TestComponent : global::Microsoft.AspNetCore.Components.ComponentBase
+    {
+        #pragma warning disable 219
+        private void __RazorDirectiveTokenHelpers__() {
+        }
+        #pragma warning restore 219
+        #pragma warning disable 0414
+        private static System.Object __o = null;
+        #pragma warning restore 0414
+        #pragma warning disable 1998
+        protected override void BuildRenderTree(global::Microsoft.AspNetCore.Components.Rendering.RenderTreeBuilder __builder)
+        {
+            global::__Blazor.Test.TestComponent.TypeInference.CreateMyComponent_0(__builder, -1, -1, 
+#nullable restore
+#line 2 "x:\dir\subdir\Test\TestComponent.cshtml"
+                        1
+
+#line default
+#line hidden
+#nullable disable
+            );
+#nullable restore
+#line 2 "x:\dir\subdir\Test\TestComponent.cshtml"
+__o = typeof(global::Test.MyComponent<>);
+
+#line default
+#line hidden
+#nullable disable
+        }
+        #pragma warning restore 1998
+    }
+}
+namespace __Blazor.Test.TestComponent
+{
+    #line hidden
+    internal static class TypeInference
+    {
+        public static void CreateMyComponent_0<T>(global::Microsoft.AspNetCore.Components.Rendering.RenderTreeBuilder __builder, int seq, int __seq0, T __arg0)
+            where T : unmanaged
+        {
+        __builder.OpenComponent<global::Test.MyComponent<T>>(seq);
+        __builder.AddAttribute(__seq0, "Parameter", __arg0);
+        __builder.CloseComponent();
+        }
+    }
+}
+#pragma warning restore 1591

src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/GenericComponent_UnmanagedConstraint/TestComponent.ir.txt

@@ -0,0 +1,25 @@
+Document - 
+    NamespaceDeclaration -  - Test
+        UsingDirective - (3:1,1 [12] ) - System
+        UsingDirective - (18:2,1 [32] ) - System.Collections.Generic
+        UsingDirective - (53:3,1 [17] ) - System.Linq
+        UsingDirective - (73:4,1 [28] ) - System.Threading.Tasks
+        UsingDirective - (104:5,1 [37] ) - Microsoft.AspNetCore.Components
+        UsingDirective - (1:0,1 [10] x:\dir\subdir\Test\TestComponent.cshtml) - Test
+        ClassDeclaration -  - public partial - TestComponent - global::Microsoft.AspNetCore.Components.ComponentBase - 
+            DesignTimeDirective - 
+            CSharpCode - 
+                IntermediateToken -  - CSharp - #pragma warning disable 0414
+            CSharpCode - 
+                IntermediateToken -  - CSharp - private static System.Object __o = null;
+            CSharpCode - 
+                IntermediateToken -  - CSharp - #pragma warning restore 0414
+            MethodDeclaration -  - protected override - void - BuildRenderTree
+                HtmlContent - (11:0,11 [2] x:\dir\subdir\Test\TestComponent.cshtml)
+                    LazyIntermediateToken - (11:0,11 [2] x:\dir\subdir\Test\TestComponent.cshtml) - Html - \n
+                Component - (13:1,0 [29] x:\dir\subdir\Test\TestComponent.cshtml) - MyComponent
+                    ComponentAttribute - (37:1,24 [1] x:\dir\subdir\Test\TestComponent.cshtml) - Parameter - Parameter - AttributeStructure.DoubleQuotes
+                        LazyIntermediateToken - (37:1,24 [1] x:\dir\subdir\Test\TestComponent.cshtml) - CSharp - 1
+    NamespaceDeclaration -  - __Blazor.Test.TestComponent
+        ClassDeclaration -  - internal static - TypeInference -  - 
+            ComponentTypeInferenceMethod -  - __Blazor.Test.TestComponent.TypeInference - CreateMyComponent_0

src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/GenericComponent_UnmanagedConstraint/TestComponent.mappings.txt

@@ -0,0 +1,10 @@
+Source Location: (1:0,1 [10] x:\dir\subdir\Test\TestComponent.cshtml)
+|using Test|
+Generated Location: (320:12,0 [10] )
+|using Test|
+
+Source Location: (37:1,24 [1] x:\dir\subdir\Test\TestComponent.cshtml)
+|1|
+Generated Location: (1128:32,24 [1] )
+|1|
+

src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/GenericComponent_UnmanagedConstraint/TestComponent.codegen.cs

@@ -0,0 +1,50 @@
+// <auto-generated/>
+#pragma warning disable 1591
+namespace Test
+{
+    #line hidden
+    using System;
+    using System.Collections.Generic;
+    using System.Linq;
+    using System.Threading.Tasks;
+    using Microsoft.AspNetCore.Components;
+#nullable restore
+#line 1 "x:\dir\subdir\Test\TestComponent.cshtml"
+using Test;
+
+#line default
+#line hidden
+#nullable disable
+    public partial class TestComponent : global::Microsoft.AspNetCore.Components.ComponentBase
+    {
+        #pragma warning disable 1998
+        protected override void BuildRenderTree(global::Microsoft.AspNetCore.Components.Rendering.RenderTreeBuilder __builder)
+        {
+            global::__Blazor.Test.TestComponent.TypeInference.CreateMyComponent_0(__builder, 0, 1, 
+#nullable restore
+#line 2 "x:\dir\subdir\Test\TestComponent.cshtml"
+                        1
+
+#line default
+#line hidden
+#nullable disable
+            );
+        }
+        #pragma warning restore 1998
+    }
+}
+namespace __Blazor.Test.TestComponent
+{
+    #line hidden
+    internal static class TypeInference
+    {
+        public static void CreateMyComponent_0<T>(global::Microsoft.AspNetCore.Components.Rendering.RenderTreeBuilder __builder, int seq, int __seq0, T __arg0)
+            where T : unmanaged
+        {
+        __builder.OpenComponent<global::Test.MyComponent<T>>(seq);
+        __builder.AddAttribute(__seq0, "Parameter", __arg0);
+        __builder.CloseComponent();
+        }
+    }
+}
+#pragma warning restore 1591

src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/GenericComponent_UnmanagedConstraint/TestComponent.ir.txt

@@ -0,0 +1,16 @@
+Document - 
+    NamespaceDeclaration -  - Test
+        UsingDirective - (3:1,1 [14] ) - System
+        UsingDirective - (18:2,1 [34] ) - System.Collections.Generic
+        UsingDirective - (53:3,1 [19] ) - System.Linq
+        UsingDirective - (73:4,1 [30] ) - System.Threading.Tasks
+        UsingDirective - (104:5,1 [39] ) - Microsoft.AspNetCore.Components
+        UsingDirective - (1:0,1 [12] x:\dir\subdir\Test\TestComponent.cshtml) - Test
+        ClassDeclaration -  - public partial - TestComponent - global::Microsoft.AspNetCore.Components.ComponentBase - 
+            MethodDeclaration -  - protected override - void - BuildRenderTree
+                Component - (13:1,0 [29] x:\dir\subdir\Test\TestComponent.cshtml) - MyComponent
+                    ComponentAttribute - (37:1,24 [1] x:\dir\subdir\Test\TestComponent.cshtml) - Parameter - Parameter - AttributeStructure.DoubleQuotes
+                        LazyIntermediateToken - (37:1,24 [1] x:\dir\subdir\Test\TestComponent.cshtml) - CSharp - 1
+    NamespaceDeclaration -  - __Blazor.Test.TestComponent
+        ClassDeclaration -  - internal static - TypeInference -  - 
+            ComponentTypeInferenceMethod -  - __Blazor.Test.TestComponent.TypeInference - CreateMyComponent_0

src/Compiler/Microsoft.CodeAnalysis.Razor/src/ComponentTagHelperDescriptorProvider.cs

@@ -333,27 +333,36 @@ private void CreateTypeParameterProperty(TagHelperDescriptorBuilder builder, ITy
             // type parameter so we create a single string representation of all the constraints
             // here.
             var list = new List<string>();
-            for (var i = 0; i < typeParameter.ConstraintTypes.Length; i++)
-            {
-                var constraintType = typeParameter.ConstraintTypes[i];
-                list.Add(constraintType.ToDisplayString(GloballyQualifiedFullNameTypeDisplayFormat));
-            }
+
+            // CS0449: The 'class', 'struct', 'unmanaged', 'notnull', and 'default' constraints
+            // cannot be combined or duplicated, and must be specified first in the constraints list.
             if (typeParameter.HasReferenceTypeConstraint)
             {
                 list.Add("class");
             }
-            if (typeParameter.HasValueTypeConstraint)
-            {
-                list.Add("struct");
-            }
+
             if (typeParameter.HasNotNullConstraint)
             {
                 list.Add("notnull");
             }
+
             if (typeParameter.HasUnmanagedTypeConstraint)
             {
                 list.Add("unmanaged");
             }
+            else if (typeParameter.HasValueTypeConstraint)
+            {
+                // `HasValueTypeConstraint` is also true when `unmanaged` constraint is present.
+                list.Add("struct");
+            }
+
+            for (var i = 0; i < typeParameter.ConstraintTypes.Length; i++)
+            {
+                var constraintType = typeParameter.ConstraintTypes[i];
+                list.Add(constraintType.ToDisplayString(GloballyQualifiedFullNameTypeDisplayFormat));
+            }
+
+            // CS0401: The new() constraint must be the last constraint specified.
             if (typeParameter.HasConstructorConstraint)
             {
                 list.Add("new()");