From f5d0fbfe7af809b1e4d43a171dbbac98c4a7a8d0 Mon Sep 17 00:00:00 2001
From: Tomas Grosup <tomasgrosup@microsoft.com>
Date: Mon, 25 May 2026 08:04:05 +0200
Subject: [PATCH 1/3] Fix colorization of type name in MyType<Qualified.Name>.S
 (#18009)

Accept ItemOccurrence.InvalidUse in LegitTypeOccurrence so that the
type-name span in expressions like MyType<System.Int32>.S - which name
resolution flags as InvalidUse via isWrongItemInExpr - is still classified
as a ReferenceType, matching the behavior for the unqualified form
MyType<int>.S.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
 .../Service/SemanticClassification.fs         |  1 +
 .../SemanticClassificationRegressions.fs      | 71 +++++++++++++++++++
 2 files changed, 72 insertions(+)

diff --git a/src/Compiler/Service/SemanticClassification.fs b/src/Compiler/Service/SemanticClassification.fs
index 8fe61e20dd..5dbce47dc6 100644
--- a/src/Compiler/Service/SemanticClassification.fs
+++ b/src/Compiler/Service/SemanticClassification.fs
@@ -151,6 +151,7 @@ module TcResolutionsExtensions =
                         | ItemOccurrence.UseInType
                         | ItemOccurrence.UseInAttribute
                         | ItemOccurrence.Use
+                        | ItemOccurrence.InvalidUse
                         | ItemOccurrence.Binding
                         | ItemOccurrence.Pattern
                         | ItemOccurrence.Open -> Some()
diff --git a/tests/FSharp.Compiler.ComponentTests/FSharpChecker/SemanticClassificationRegressions.fs b/tests/FSharp.Compiler.ComponentTests/FSharpChecker/SemanticClassificationRegressions.fs
index 8af90a38e5..84aff53a4f 100644
--- a/tests/FSharp.Compiler.ComponentTests/FSharpChecker/SemanticClassificationRegressions.fs
+++ b/tests/FSharp.Compiler.ComponentTests/FSharpChecker/SemanticClassificationRegressions.fs
@@ -136,3 +136,74 @@ type Animal =
           (7, 2, 8)    // s.IsCircle && s.IsSquare — two on same line
           (12, 1, 7)   // t.IsIdent — RequireQualifiedAccess
           (17, 1, 5) ] // this.IsCat — self-referential member
+
+/// (#18009 regression) Static method on a generic type with a *qualified* type argument
+/// must still classify the type name as a type.
+[<Fact>]
+let ``Static method on generic type should classify type name as type`` () =
+    let source =
+        """
+module Test
+
+type MyType<'T> =
+    static member S = 1
+
+let _ = MyType<int>.S
+let _ = MyType<System.Int32>.S
+"""
+
+    let items = getClassifications source
+
+    let isMyTypeRefOnLine line (item: SemanticClassificationItem) =
+        item.Type = SemanticClassificationType.ReferenceType
+        && item.Range.StartLine = line
+        && item.Range.StartColumn = 8
+        && item.Range.EndColumn = 14
+
+    let unqualified = items |> Array.filter (isMyTypeRefOnLine 7)
+    Assert.True(
+        unqualified.Length = 1,
+        sprintf
+            "Expected exactly one ReferenceType classification for MyType on line 7, got: %A"
+            (items |> Array.filter (fun i -> i.Range.StartLine = 7)
+                   |> Array.map (fun i -> i.Range.StartColumn, i.Range.EndColumn, i.Type))
+    )
+
+    let qualified = items |> Array.filter (isMyTypeRefOnLine 8)
+    Assert.True(
+        qualified.Length = 1,
+        sprintf
+            "Expected exactly one ReferenceType classification for MyType on line 8, got: %A"
+            (items |> Array.filter (fun i -> i.Range.StartLine = 8)
+                   |> Array.map (fun i -> i.Range.StartColumn, i.Range.EndColumn, i.Type))
+    )
+
+/// (#18009 follow-up) Accepting ItemOccurrence.InvalidUse in LegitTypeOccurrence must
+/// not cause unresolved identifiers to be classified as types.
+[<Fact>]
+let ``Undeclared identifier in expression position is not classified as a type`` () =
+    let source =
+        """
+module Test
+
+let _ = NotDeclaredAnywhere.S
+"""
+
+    let items = getClassifications source
+
+    let badSpans =
+        items
+        |> Array.filter (fun item ->
+            item.Range.StartLine = 4
+            && item.Range.StartColumn = 8
+            && item.Range.EndColumn = 27
+            && (item.Type = SemanticClassificationType.ReferenceType
+                || item.Type = SemanticClassificationType.ValueType
+                || item.Type = SemanticClassificationType.Type))
+
+    Assert.True(
+        badSpans.Length = 0,
+        sprintf
+            "Undeclared identifier should not be classified as a type, but found: %A"
+            (badSpans |> Array.map (fun i -> i.Range.StartColumn, i.Range.EndColumn, i.Type))
+    )

From 2e24ca91a819bc91abb71b84c8c7a541d825bd20 Mon Sep 17 00:00:00 2001
From: Tomas Grosup <tomasgrosup@microsoft.com>
Date: Mon, 25 May 2026 08:35:57 +0200
Subject: [PATCH 2/3] Apply remaining changes

---
 .executor-pid | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 .executor-pid

diff --git a/.executor-pid b/.executor-pid
new file mode 100644
index 0000000000..876998c761
--- /dev/null
+++ b/.executor-pid
@@ -0,0 +1 @@
+33492
\ No newline at end of file

From de3dd994f1c81319516fdf4afdb28a768129f104 Mon Sep 17 00:00:00 2001
From: Tomas Grosup <tomasgrosup@microsoft.com>
Date: Tue, 26 May 2026 14:30:44 +0200
Subject: [PATCH 3/3] Remove executor artifact

---
 .executor-pid | 1 -
 1 file changed, 1 deletion(-)
 delete mode 100644 .executor-pid

diff --git a/.executor-pid b/.executor-pid
deleted file mode 100644
index 876998c761..0000000000
--- a/.executor-pid
+++ /dev/null
@@ -1 +0,0 @@
-33492
\ No newline at end of file