Use alternative way of ignoring measures when detecting integral types (#17040)

* Use alternative way of ignoring measures

* Use `typeEquivAux EraseMeasures` instead of calling
  `stripMeasuresFromTy` and passing the result into `typeEquiv` when
  determining whether the range operator's type argument is an integral
  type. I would have expected the outcome to be the same for both
  approaches, but that appears not always to be the case (though it
  often is).

* Update release notes

* Typo

Author: brianrourkeboll

docs/release-notes/.FSharp.Compiler.Service/8.0.400.md

@@ -1,3 +1,4 @@
 ### Fixed
 
 Various parenthesization API fixes. ([PR #16977](https://github.com/dotnet/fsharp/pull/16977))
+* Fix bug in optimization of for-loops over integral ranges with steps and units of measure. ([Issue #17025](https://github.com/dotnet/fsharp/issues/17025), [PR #17040](https://github.com/dotnet/fsharp/pull/17040))

src/Compiler/TypedTree/TypedTreeOps.fs

@@ -7417,39 +7417,37 @@ let mkTwo g m = mkInt g m 2
 let mkMinusOne g m = mkInt g m -1
 
 let mkTypedZero g m ty =
-    let underlyingTy = stripMeasuresFromTy g ty
-    if typeEquiv g underlyingTy g.int32_ty then Expr.Const (Const.Int32 0, m, ty)
-    elif typeEquiv g underlyingTy g.int64_ty then Expr.Const (Const.Int64 0L, m, ty)
-    elif typeEquiv g underlyingTy g.uint64_ty then Expr.Const (Const.UInt64 0UL, m, ty)
-    elif typeEquiv g underlyingTy g.uint32_ty then Expr.Const (Const.UInt32 0u, m, ty)
-    elif typeEquiv g underlyingTy g.nativeint_ty then Expr.Const (Const.IntPtr 0L, m, ty)
-    elif typeEquiv g underlyingTy g.unativeint_ty then Expr.Const (Const.UIntPtr 0UL, m, ty)
-    elif typeEquiv g underlyingTy g.int16_ty then Expr.Const (Const.Int16 0s, m, ty)
-    elif typeEquiv g underlyingTy g.uint16_ty then Expr.Const (Const.UInt16 0us, m, ty)
-    elif typeEquiv g underlyingTy g.sbyte_ty then Expr.Const (Const.SByte 0y, m, ty)
-    elif typeEquiv g underlyingTy g.byte_ty then Expr.Const (Const.Byte 0uy, m, ty)
-    elif typeEquiv g underlyingTy g.char_ty then Expr.Const (Const.Char '\000', m, ty)
-    elif typeEquiv g underlyingTy g.float32_ty then Expr.Const (Const.Single 0.0f, m, ty)
-    elif typeEquiv g underlyingTy g.float_ty then Expr.Const (Const.Double 0.0, m, ty)
-    elif typeEquiv g underlyingTy g.decimal_ty then Expr.Const (Const.Decimal 0m, m, ty)
+    if typeEquivAux EraseMeasures g ty g.int32_ty then Expr.Const (Const.Int32 0, m, ty)
+    elif typeEquivAux EraseMeasures g ty g.int64_ty then Expr.Const (Const.Int64 0L, m, ty)
+    elif typeEquivAux EraseMeasures g ty g.uint64_ty then Expr.Const (Const.UInt64 0UL, m, ty)
+    elif typeEquivAux EraseMeasures g ty g.uint32_ty then Expr.Const (Const.UInt32 0u, m, ty)
+    elif typeEquivAux EraseMeasures g ty g.nativeint_ty then Expr.Const (Const.IntPtr 0L, m, ty)
+    elif typeEquivAux EraseMeasures g ty g.unativeint_ty then Expr.Const (Const.UIntPtr 0UL, m, ty)
+    elif typeEquivAux EraseMeasures g ty g.int16_ty then Expr.Const (Const.Int16 0s, m, ty)
+    elif typeEquivAux EraseMeasures g ty g.uint16_ty then Expr.Const (Const.UInt16 0us, m, ty)
+    elif typeEquivAux EraseMeasures g ty g.sbyte_ty then Expr.Const (Const.SByte 0y, m, ty)
+    elif typeEquivAux EraseMeasures g ty g.byte_ty then Expr.Const (Const.Byte 0uy, m, ty)
+    elif typeEquivAux EraseMeasures g ty g.char_ty then Expr.Const (Const.Char '\000', m, ty)
+    elif typeEquivAux EraseMeasures g ty g.float32_ty then Expr.Const (Const.Single 0.0f, m, ty)
+    elif typeEquivAux EraseMeasures g ty g.float_ty then Expr.Const (Const.Double 0.0, m, ty)
+    elif typeEquivAux EraseMeasures g ty g.decimal_ty then Expr.Const (Const.Decimal 0m, m, ty)
     else error (InternalError ($"Unrecognized numeric type '{ty}'.", m))
 
 let mkTypedOne g m ty =
-    let underlyingTy = stripMeasuresFromTy g ty
-    if typeEquiv g underlyingTy g.int32_ty then Expr.Const (Const.Int32 1, m, ty)
-    elif typeEquiv g underlyingTy g.int64_ty then Expr.Const (Const.Int64 1L, m, ty)
-    elif typeEquiv g underlyingTy g.uint64_ty then Expr.Const (Const.UInt64 1UL, m, ty)
-    elif typeEquiv g underlyingTy g.uint32_ty then Expr.Const (Const.UInt32 1u, m, ty)
-    elif typeEquiv g underlyingTy g.nativeint_ty then Expr.Const (Const.IntPtr 1L, m, ty)
-    elif typeEquiv g underlyingTy g.unativeint_ty then Expr.Const (Const.UIntPtr 1UL, m, ty)
-    elif typeEquiv g underlyingTy g.int16_ty then Expr.Const (Const.Int16 1s, m, ty)
-    elif typeEquiv g underlyingTy g.uint16_ty then Expr.Const (Const.UInt16 1us, m, ty)
-    elif typeEquiv g underlyingTy g.sbyte_ty then Expr.Const (Const.SByte 1y, m, ty)
-    elif typeEquiv g underlyingTy g.byte_ty then Expr.Const (Const.Byte 1uy, m, ty)
-    elif typeEquiv g underlyingTy g.char_ty then Expr.Const (Const.Char '\001', m, ty)
-    elif typeEquiv g underlyingTy g.float32_ty then Expr.Const (Const.Single 1.0f, m, ty)
-    elif typeEquiv g underlyingTy g.float_ty then Expr.Const (Const.Double 1.0, m, ty)
-    elif typeEquiv g underlyingTy g.decimal_ty then Expr.Const (Const.Decimal 1m, m, ty)
+    if typeEquivAux EraseMeasures g ty g.int32_ty then Expr.Const (Const.Int32 1, m, ty)
+    elif typeEquivAux EraseMeasures g ty g.int64_ty then Expr.Const (Const.Int64 1L, m, ty)
+    elif typeEquivAux EraseMeasures g ty g.uint64_ty then Expr.Const (Const.UInt64 1UL, m, ty)
+    elif typeEquivAux EraseMeasures g ty g.uint32_ty then Expr.Const (Const.UInt32 1u, m, ty)
+    elif typeEquivAux EraseMeasures g ty g.nativeint_ty then Expr.Const (Const.IntPtr 1L, m, ty)
+    elif typeEquivAux EraseMeasures g ty g.unativeint_ty then Expr.Const (Const.UIntPtr 1UL, m, ty)
+    elif typeEquivAux EraseMeasures g ty g.int16_ty then Expr.Const (Const.Int16 1s, m, ty)
+    elif typeEquivAux EraseMeasures g ty g.uint16_ty then Expr.Const (Const.UInt16 1us, m, ty)
+    elif typeEquivAux EraseMeasures g ty g.sbyte_ty then Expr.Const (Const.SByte 1y, m, ty)
+    elif typeEquivAux EraseMeasures g ty g.byte_ty then Expr.Const (Const.Byte 1uy, m, ty)
+    elif typeEquivAux EraseMeasures g ty g.char_ty then Expr.Const (Const.Char '\001', m, ty)
+    elif typeEquivAux EraseMeasures g ty g.float32_ty then Expr.Const (Const.Single 1.0f, m, ty)
+    elif typeEquivAux EraseMeasures g ty g.float_ty then Expr.Const (Const.Double 1.0, m, ty)
+    elif typeEquivAux EraseMeasures g ty g.decimal_ty then Expr.Const (Const.Decimal 1m, m, ty)
     else error (InternalError ($"Unrecognized numeric type '{ty}'.", m))
 
 let destInt32 = function Expr.Const (Const.Int32 n, _, _) -> Some n | _ -> None

tests/FSharp.Compiler.ComponentTests/EmittedIL/ForLoop/RealInternalSignatureOff/ForEachRangeStep_UnitsOfMeasure.fs

@@ -0,0 +1,47 @@
+open FSharp.Data.UnitSystems.SI.UnitSymbols
+
+let mutable c = 0L<m>
+
+let f1 () =
+    for n in 10L<m>..1L<m>..1L<m> do
+        c <- n
+
+let f2 () =
+    for n in 1L<m>..1L<m>..10L<m> do
+        c <- n
+
+let f3 () =
+    for n in 1L<m>..2L<m>..10L<m> do
+        c <- n
+
+let f4 start =
+    for n in start..2L<m>..10L<m> do
+        c <- n
+
+let f5 step =
+    for n in 1L<m>..step..10L<m> do
+        c <- n
+
+let f6 finish =
+    for n in 1L<m>..2L<m>..finish do
+        c <- n
+
+let f7 start step finish =
+    for n in start..step..finish do
+        c <- n
+
+let f8 start finish =
+    for n in start..0L<m>..finish do
+        c <- n
+
+let f9 () =
+    for n in 1L<m>..0L<m>..10L<m> do
+        c <- n
+
+let f10 () =
+    for n in 10L<m> .. -1L<m>..1L<m> do
+        c <- n
+
+let f11 () =
+    for n in 10L<m> .. -2L<m>..1L<m> do
+        c <- n