Keep leading and traling trivias on identifiers to prevent some syntax errors

src/EntityFrameworkCore.Projectables.Generator/ExpressionSyntaxRewriter.cs

@@ -29,6 +29,14 @@ namespace EntityFrameworkCore.Projectables.Generator
             _context = context;
         }
 
+        private SyntaxNode? VisitThisBaseExpression(CSharpSyntaxNode node)
+        {
+            // Swap out the use of this to @this and base to @base and keep leading and trailing trivias
+            return SyntaxFactory.IdentifierName("@this")
+                .WithLeadingTrivia(node.GetLeadingTrivia())
+                .WithTrailingTrivia(node.GetTrailingTrivia());
+        }
+
         public override SyntaxNode? VisitConditionalAccessExpression(ConditionalAccessExpressionSyntax node)
         {
             var targetExpression = (ExpressionSyntax)Visit(node.Expression);
@@ -100,13 +108,13 @@ namespace EntityFrameworkCore.Projectables.Generator
         public override SyntaxNode? VisitThisExpression(ThisExpressionSyntax node)
         {
             // Swap out the use of this to @this
-            return SyntaxFactory.IdentifierName("@this");
+            return VisitThisBaseExpression(node);
         }
 
         public override SyntaxNode? VisitBaseExpression(BaseExpressionSyntax node)
         {
             // Swap out the use of this to @this
-            return SyntaxFactory.IdentifierName("@this");
+            return VisitThisBaseExpression(node);
         }
 
         public override SyntaxNode? VisitIdentifierName(IdentifierNameSyntax node)

tests/EntityFrameworkCore.Projectables.Generator.Tests/ProjectionExpressionGeneratorTests.InOperator.verified.txt

@@ -0,0 +1,17 @@
+using System;
+using EntityFrameworkCore.Projectables;
+using Foo;
+
+// <auto-generated/>
+namespace EntityFrameworkCore.Projectables.Generated
+#nullable disable
+{
+    public static class Foo_A_IsB
+    {
+        public static System.Linq.Expressions.Expression<System.Func<global::Foo.A, bool>> Expression()
+        {
+            return (global::Foo.A @this) => 
+                @this is global::Foo.B;
+        }
+    }
+}

tests/EntityFrameworkCore.Projectables.Generator.Tests/ProjectionExpressionGeneratorTests.cs

@@ -343,6 +343,32 @@ namespace Foo {
             return Verifier.Verify(result.GeneratedTrees[0].ToString());
         }
 
+        [Fact]
+        public Task InOperator()
+        {
+            var compilation = CreateCompilation(@"
+using System;
+using System.Linq;
+using EntityFrameworkCore.Projectables;
+namespace Foo {
+    class A {
+        [Projectable] 
+        public bool IsB => this is B;
+    }
+    
+    class B : A {
+    }
+}
+");
+
+            var result = RunGenerator(compilation);
+
+            Assert.Empty(result.Diagnostics);
+            Assert.Single(result.GeneratedTrees);
+
+            return Verifier.Verify(result.GeneratedTrees[0].ToString());
+        }
+
         [Fact]
         public Task ProjectableExtensionMethod()
         {