Raise diagnostics when not exposing expression bodies members

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

@@ -340,6 +340,49 @@ namespace Foo {
             return Verifier.Verify(result.GeneratedTrees[0].ToString());
         }
 
+        [Fact]
+        public void BlockBodiedMember_RaisesDiagnostics()
+        {
+            var compilation = CreateCompilation(@"
+using System;
+using EntityFrameworkCore.Projections;
+namespace Foo {
+    class C {
+        [Projectable]
+        public int Foo 
+        {
+            get => 1;
+        }
+    }
+}
+");
+
+            var result = RunGenerator(compilation);
+
+            Assert.Single(result.Diagnostics);
+        }
+
+        [Fact]
+        public void BlockBodiedMethod_RaisesDiagnostics()
+        {
+            var compilation = CreateCompilation(@"
+using System;
+using EntityFrameworkCore.Projections;
+namespace Foo {
+    class C {
+        [Projectable]
+        public int Foo() 
+        {
+            return 1;
+        }
+    }
+}
+");
+
+            var result = RunGenerator(compilation);
+
+            Assert.Single(result.Diagnostics);
+        }
 
         #region Helpers