Merge branch 'main' into copilot/fix-9141961-29048891-8f02666a-f3c0-4c69-bf82-fde45e879f9c

Author: abonie

docs/release-notes/.FSharp.Compiler.Service/11.0.100.md

@@ -3,6 +3,7 @@
 * Fix DU case names matching IWSAM member names no longer cause duplicate property entries. (Issue [#14321](https://github.com/dotnet/fsharp/issues/14321), [PR #19341](https://github.com/dotnet/fsharp/pull/19341))
 * Fix DefaultAugmentation(false) duplicate entry in method table. (Issue [#16565](https://github.com/dotnet/fsharp/issues/16565), [PR #19341](https://github.com/dotnet/fsharp/pull/19341))
 * Fix abstract event accessors now have SpecialName flag. (Issue [#5834](https://github.com/dotnet/fsharp/issues/5834), [PR #19341](https://github.com/dotnet/fsharp/pull/19341))
+* Fix warning 20 ("expression is implicitly ignored") pointing at the wrong range when the last expression in a sequential block (e.g. inside `for`, `while` loops) is non-unit. The squiggle now correctly highlights only the offending expression. ([Issue #5735](https://github.com/dotnet/fsharp/issues/5735), [PR #19504](https://github.com/dotnet/fsharp/pull/19504))
 * Fix CLIEvent properties to be correctly recognized as events: `IsEvent` returns `true` and `XmlDocSig` uses `E:` prefix instead of `P:`. ([Issue #10273](https://github.com/dotnet/fsharp/issues/10273), [PR #18584](https://github.com/dotnet/fsharp/pull/18584))
 * Fix extra sequence point at the end of match expressions. ([Issue #12052](https://github.com/dotnet/fsharp/issues/12052), [PR #19278](https://github.com/dotnet/fsharp/pull/19278))
 * Fix wrong sequence point range for `return`/`yield`/`return!`/`yield!` inside computation expressions. ([Issue #19248](https://github.com/dotnet/fsharp/issues/19248), [PR #19278](https://github.com/dotnet/fsharp/pull/19278))

src/Compiler/Checking/Expressions/CheckExpressions.fs

@@ -5522,7 +5522,16 @@ and TcStmtThatCantBeCtorBody (cenv: cenv) env tpenv synExpr =
 and TcStmt (cenv: cenv) env tpenv synExpr =
     let g = cenv.g
     let expr, ty, tpenv = TcExprOfUnknownType cenv env tpenv synExpr
-    let m = synExpr.Range
+
+    // Use the range of the last expression in a sequential chain for warnings,
+    // so that "expression is ignored" diagnostics point at the offending expression
+    // rather than the entire sequential body. See https://github.com/dotnet/fsharp/issues/5735
+    let rec lastExprRange (e: SynExpr) =
+        match e with
+        | SynExpr.Sequential(expr2 = expr2) -> lastExprRange expr2
+        | _ -> e.Range
+
+    let m = lastExprRange synExpr
     let wasUnit = UnifyUnitType cenv env m ty expr
     if wasUnit then
         expr, tpenv

tests/FSharp.Compiler.ComponentTests/ErrorMessages/DiagnosticRegressionTests.fs

@@ -50,6 +50,43 @@ type Vehicle() = class end
         [ (Error 39, Line 3, Col 14, Line 3, Col 28, "The type 'OutOfScopeType' is not defined.")
           (Error 267, Line 3, Col 7, Line 3, Col 29, "This is not a valid constant expression or custom attribute value") ]
 
+// https://github.com/dotnet/fsharp/issues/10043
+[<Fact>]
+let ``Issue 10043 - backtick in type annotation should not report unexpected keyword`` () =
+    FSharp
+        """
+let i:float`1 = 3.0
+        """
+    |> typecheck
+    |> shouldFail
+    |> withDiagnostics
+        [ (Error 3563, Line 2, Col 12, Line 2, Col 13, "This is not a valid identifier")
+          (Error 10, Line 2, Col 13, Line 2, Col 14, "Unexpected integer literal in binding. Expected '=' or other token.") ]
+
+// https://github.com/dotnet/fsharp/issues/10043
+[<Fact>]
+let ``Issue 10043 - at sign in type annotation should report infix operator`` () =
+    FSharp
+        """
+let i:float@1 = 3.0
+        """
+    |> typecheck
+    |> shouldFail
+    |> withDiagnostics
+        [ (Error 615, Line 2, Col 12, Line 2, Col 13, "Unexpected infix operator in type expression") ]
+
+// https://github.com/dotnet/fsharp/issues/10043
+[<Fact>]
+let ``Issue 10043 - bang in type annotation should report reserved identifier`` () =
+    FSharp
+        """
+let i:float!1 = 3.0
+        """
+    |> typecheck
+    |> shouldFail
+    |> withDiagnostics
+        [ (Error 1141, Line 2, Col 7, Line 2, Col 13, "Identifiers followed by '!' are reserved for future use")
+          (Error 10, Line 2, Col 13, Line 2, Col 14, "Unexpected integer literal in binding. Expected '=' or other token.") ]
 
 // https://github.com/dotnet/fsharp/issues/7177
 [<Fact>]

tests/FSharp.Compiler.ComponentTests/ErrorMessages/WarnExpressionTests.fs

@@ -176,6 +176,63 @@ while x < 1 do
         |> withSingleDiagnostic (Warning 20, Line 6, Col 5, Line 6, Col 9,
                                  "The result of this expression has type 'bool' and is implicitly ignored. Consider using 'ignore' to discard this value explicitly, e.g. 'expr |> ignore', or 'let' to bind the result to a name, e.g. 'let result = expr'.")
 
+    // https://github.com/dotnet/fsharp/issues/5735
+    [<Fact>]
+    let ``Warn On Last Expression In For Loop - int``() =
+        FSharp """
+module ClassLibrary17
+
+for i in 1 .. 10 do
+    printfn ""
+    printfn "" |> ignore
+    123
+        """
+        |> typecheck
+        |> shouldFail
+        |> withSingleDiagnostic (Warning 20, Line 7, Col 5, Line 7, Col 8,
+                                 "The result of this expression has type 'int' and is implicitly ignored. Consider using 'ignore' to discard this value explicitly, e.g. 'expr |> ignore', or 'let' to bind the result to a name, e.g. 'let result = expr'.")
+
+    // https://github.com/dotnet/fsharp/issues/5735
+    [<Fact>]
+    let ``Warn On Last Expression In For Loop - string``() =
+        FSharp """
+for i in 1 .. 10 do
+    printfn ""
+    "hello"
+        """
+        |> typecheck
+        |> shouldFail
+        |> withSingleDiagnostic (Warning 20, Line 4, Col 5, Line 4, Col 12,
+                                 "The result of this expression has type 'string' and is implicitly ignored. Consider using 'ignore' to discard this value explicitly, e.g. 'expr |> ignore', or 'let' to bind the result to a name, e.g. 'let result = expr'.")
+
+    // https://github.com/dotnet/fsharp/issues/5735
+    [<Fact>]
+    let ``Warn On Last Expression In Integer For Loop``() =
+        FSharp """
+for i = 1 to 10 do
+    printfn ""
+    42
+        """
+        |> typecheck
+        |> shouldFail
+        |> withSingleDiagnostic (Warning 20, Line 4, Col 5, Line 4, Col 7,
+                                 "The result of this expression has type 'int' and is implicitly ignored. Consider using 'ignore' to discard this value explicitly, e.g. 'expr |> ignore', or 'let' to bind the result to a name, e.g. 'let result = expr'.")
+
+    // https://github.com/dotnet/fsharp/issues/5735
+    [<Fact>]
+    let ``Warn On Last Expression In While Loop - non-bool``() =
+        FSharp """
+let mutable x = 0
+while x < 1 do
+    printfn "unneeded"
+    x <- x + 1
+    123
+        """
+        |> typecheck
+        |> shouldFail
+        |> withSingleDiagnostic (Warning 20, Line 6, Col 5, Line 6, Col 8,
+                                 "The result of this expression has type 'int' and is implicitly ignored. Consider using 'ignore' to discard this value explicitly, e.g. 'expr |> ignore', or 'let' to bind the result to a name, e.g. 'let result = expr'.")
+
     [<Fact>]
     let ``Warn If Possible Property Setter``() =
         FSharp """