Psi/extensions: fix resolve for F# 8 types without attribute

Author: auduchinok

ReSharper.FSharp/src/FSharp/FSharp.Psi/src/Impl/Cache2/Parts/FSharpTypePart.cs

@@ -3,6 +3,7 @@
 using JetBrains.Annotations;
 using JetBrains.Metadata.Reader.API;
 using JetBrains.Metadata.Reader.Impl;
+using JetBrains.ReSharper.Plugins.FSharp.ProjectModel;
 using JetBrains.ReSharper.Plugins.FSharp.Psi.Tree;
 using JetBrains.ReSharper.Plugins.FSharp.Util;
 using JetBrains.ReSharper.Psi;
@@ -81,13 +82,19 @@ public TypePart GetFirstPart()
 
     public override HybridCollection<IMethod> FindExtensionMethod(ExtensionMethodInfo info)
     {
-      if (!TypeElement.HasAttributeInstance(PredefinedType.EXTENSION_ATTRIBUTE_CLASS, false))
+      var typeElement = TypeElement;
+      if (typeElement == null)
         return HybridCollection<IMethod>.Empty;
 
       var declaration = GetDeclaration();
       if (declaration == null)
         return HybridCollection<IMethod>.Empty;
 
+      var languageLevel = declaration.GetFSharpLanguageLevel();
+      if (languageLevel < FSharpLanguageLevel.FSharp80 && 
+          !typeElement.HasAttributeInstance(PredefinedType.EXTENSION_ATTRIBUTE_CLASS, false))
+        return HybridCollection<IMethod>.Empty;
+
       var result = HybridCollection<IMethod>.Empty;
       foreach (var memberDeclaration in declaration.MemberDeclarations)
         if (info.ShortName == memberDeclaration.DeclaredName &&

ReSharper.FSharp/test/data/cache/csharpResolve/Module bindings - Extension 01 - F# 7.cs

@@ -0,0 +1,10 @@
+using Ns;
+
+public class Class1
+{
+  public Class1()
+  {
+    string s1 = 1.Ext();
+    string s2 = 1.ExtNoTypeAttr();
+  }
+}

ReSharper.FSharp/test/data/cache/csharpResolve/Module bindings - Extension 01 - F# 7.fs

@@ -0,0 +1,12 @@
+namespace Ns
+
+open System.Runtime.CompilerServices
+
+[<Extension>]
+module Module1 =
+    [<Extension; CompiledName("Ext")>]
+    let ext (i: int) = i.ToString()
+
+module Module2 =
+    [<Extension; CompiledName("ExtNoTypeAttr")>]
+    let ext (i: int) = i.ToString()

ReSharper.FSharp/test/data/cache/csharpResolve/Module bindings - Extension 01 - F# 7.gold

@@ -0,0 +1,15 @@
+using Ns;
+
+public class Class1
+{
+  public Class1()
+  {
+    string s1 = 1.Ext();
+    string s2 = 1.|ExtNoTypeAttr|(0)();
+  }
+}
+
+---------------------------------------------------------
+(0): ReSharper Error Highlighting: Cannot resolve symbol 'ExtNoTypeAttr'
+M:Ns.Module1.Ext(System.Int32)
+M:Ns.Module1.Ext(System.Int32)

ReSharper.FSharp/test/data/cache/csharpResolve/Module bindings - Extension 02 - F# 8.cs

@@ -0,0 +1,10 @@
+using Ns;
+
+public class Class1
+{
+  public Class1()
+  {
+    string s1 = 1.Ext();
+    string s2 = 1.ExtNoTypeAttr();
+  }
+}

ReSharper.FSharp/test/data/cache/csharpResolve/Module bindings - Extension 02 - F# 8.fs

@@ -0,0 +1,12 @@
+namespace Ns
+
+open System.Runtime.CompilerServices
+
+[<Extension>]
+module Module1 =
+    [<Extension; CompiledName("Ext")>]
+    let ext (i: int) = i.ToString()
+
+module Module2 =
+    [<Extension; CompiledName("ExtNoTypeAttr")>]
+    let ext (i: int) = i.ToString()

ReSharper.FSharp/test/data/cache/csharpResolve/Module bindings - Extension 02 - F# 8.gold

@@ -0,0 +1,16 @@
+using Ns;
+
+public class Class1
+{
+  public Class1()
+  {
+    string s1 = 1.Ext();
+    string s2 = 1.ExtNoTypeAttr();
+  }
+}
+
+---------------------------------------------------------
+M:Ns.Module1.Ext(System.Int32)
+M:Ns.Module1.Ext(System.Int32)
+M:Ns.Module2.ExtNoTypeAttr(System.Int32)
+M:Ns.Module2.ExtNoTypeAttr(System.Int32)

ReSharper.FSharp/test/src/FSharp.Tests/Cache/CSharpResolveTest.fs

@@ -3,6 +3,7 @@ namespace JetBrains.ReSharper.Plugins.FSharp.Tests.Features
 open JetBrains.ProjectModel
 open JetBrains.ReSharper.FeaturesTestFramework.Daemon
 open JetBrains.ReSharper.Plugins.FSharp
+open JetBrains.ReSharper.Plugins.FSharp.ProjectModel
 open JetBrains.ReSharper.Plugins.FSharp.Tests
 open JetBrains.ReSharper.TestFramework
 open NUnit.Framework
@@ -105,6 +106,11 @@ type CSharpResolveTest() =
     [<Test>] member x.``Properties 20 - Simple property with accessors``() = x.DoNamedTest()
     [<Test>] member x.``Properties 21 - static val``() = x.DoNamedTest()
 
+    [<FSharpLanguageLevel(FSharpLanguageLevel.FSharp70)>]
+    [<Test>] member x.``Module bindings - Extension 01 - F# 7``() = x.DoNamedTest()
+    [<FSharpLanguageLevel(FSharpLanguageLevel.FSharp80)>]
+    [<Test>] member x.``Module bindings - Extension 02 - F# 8``() = x.DoNamedTest()
+
     [<Test>] member x.``Module bindings 01 - Simple``() = x.DoNamedTest()
     [<Test>] member x.``Module bindings 02 - Records``() = x.DoNamedTest()
     [<Test>] member x.``Module bindings 03 - extension methods 01``() = x.DoNamedTest()