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Fix wrong [<TailCall>] warning with unit-returning match expression #17637

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merged 4 commits into from
Aug 30, 2024
Merged

Fix wrong [<TailCall>] warning with unit-returning match expression #17637

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edc16d0
add unit test for issue 17604
dawedawe Aug 30, 2024
0be33ab
check if the expr type is unit for match expressions, too.
dawedawe Aug 30, 2024
f86f1a5
add release notes entry
dawedawe Aug 30, 2024
0b88ab8
Merge branch 'main' into fix_17604
psfinaki Aug 30, 2024
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1 change: 1 addition & 0 deletions docs/release-notes/.FSharp.Compiler.Service/9.0.100.md
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Original file line number Diff line number Diff line change
@@ -1,5 +1,6 @@
### Fixed

* Fix wrong TailCall warning ([Issue #17604](https://github.com/dotnet/fsharp/issues/17604), [PR #17637](https://github.com/dotnet/fsharp/pull/17637))
* Compiler hangs when compiling inline recursive invocation ([Issue #17376](https://github.com/dotnet/fsharp/issues/17376), [PR #17394](https://github.com/dotnet/fsharp/pull/17394))
* Fix reporting IsFromComputationExpression only for CE builder type constructors and let bindings. ([PR #17375](https://github.com/dotnet/fsharp/pull/17375))
* Optimize simple mappings in comprehensions when the body of the mapping has `let`-bindings and/or sequential expressions before a single yield. ([PR #17419](https://github.com/dotnet/fsharp/pull/17419))
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8 changes: 8 additions & 0 deletions src/Compiler/Checking/TailCallChecks.fs
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Expand Up @@ -47,8 +47,16 @@ type TailCall =
static member YesFromVal (g: TcGlobals) (v: Val) = TailCall.Yes(TailCall.IsVoidRet g v)

static member YesFromExpr (g: TcGlobals) (expr: Expr) =
let yesFromTType (t: TType) =
if isUnitTy g t then
TailCall.Yes TailCallReturnType.MustReturnVoid
else
TailCall.Yes TailCallReturnType.NonVoid

match expr with
| ValUseAtApp(valRef, _) -> TailCall.Yes(TailCall.IsVoidRet g valRef.Deref)
| Expr.Const(constType = constType) -> yesFromTType constType
| Expr.Match(exprType = exprType) -> yesFromTType exprType
| _ -> TailCall.Yes TailCallReturnType.NonVoid

member x.AtExprLambda =
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19 changes: 19 additions & 0 deletions tests/FSharp.Compiler.ComponentTests/ErrorMessages/TailCallAttribute.fs
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Original file line number Diff line number Diff line change
Expand Up @@ -1722,3 +1722,22 @@ module M =
|> withLangVersion80
|> compile
|> shouldSucceed

[<FSharp.Test.FactForNETCOREAPP>]
let ``Don't warn for tail rec call returning unit`` () =
"""
namespace N

module M =

[<TailCall>]
let rec go (args: string list) =
match args with
| [] -> ()
| "--" :: _ -> ()
| arg :: args -> go args
"""
|> FSharp
|> withLangVersion80
|> compile
|> shouldSucceed
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