Bring back type test from Fable 2

src/Fable.Transforms/AST/AST.Babel.fs

@@ -482,22 +482,23 @@ type IfStatement(test, consequent, ?alternate, ?loc) =
     interface Statement with
         member _.Print(printer) =
             printer.AddLocation(loc)
-            match test, alternate with
-            | :? BooleanLiteral as b, _ when b.Value ->
-                printer.PrintProductiveStatements(consequent.Body)
-            | :? BooleanLiteral as b, Some(:? BlockStatement as alternate) when not b.Value ->
-                printer.PrintProductiveStatements(alternate.Body)
-            | _ ->
-                printer.Print("if (", ?loc=loc)
-                test.Print(printer)
-                printer.Print(") ")
-                printer.Print(consequent)
-                // TODO: Remove else clauses if they become empty after removing null statements (see PrintBlock)
-                printer.PrintOptional((if printer.Column > 0 then " else " else "else "), alternate)
-                // If the consequent/alternate is a block
-                // a new line should already be printed
-                if printer.Column > 0 then
-                    printer.PrintNewLine()
+            printer.Print("if (", ?loc=loc)
+            test.Print(printer)
+            printer.Print(") ")
+            printer.Print(consequent)
+            match alternate with
+            | None -> ()
+            | Some alternate ->
+                if printer.Column > 0 then printer.Print(" ")
+                printer.Print("else ")
+                match alternate with
+                | :? IfStatement
+                // TODO: Get productive statements and skip else if they're empty
+                | :? BlockStatement -> printer.Print(alternate)
+                // Make sure alternate is always printed as block
+                | _ -> printer.PrintBlock([|alternate|])
+            if printer.Column > 0 then
+                printer.PrintNewLine()
 
 /// A case (if test is an Expression) or default (if test === null) clause in the body of a switch statement.
 type SwitchCase(consequent, ?test, ?loc) =
@@ -849,6 +850,7 @@ type ConditionalExpression(test, consequent, alternate, ?loc) =
         member _.Print(printer) =
             printer.AddLocation(loc)
             match test with
+            // TODO: Move this optimization to Fable2Babel as with IfStatement?
             | :? BooleanLiteral as b ->
                 if b.Value then printer.Print(consequent)
                 else printer.Print(alternate)

src/Fable.Transforms/Fable2Babel.fs

@@ -247,61 +247,66 @@ module Reflection =
     let private ofString s = StringLiteral s :> Expression
     let private ofArray babelExprs = ArrayExpression(List.toArray babelExprs) :> Expression
 
-    let rec private toTypeTester com ctx r = function
-        | Fable.Regex -> Identifier "RegExp" :> Expression
-        | Fable.MetaType -> libValue com ctx "Reflection" "TypeInfo"
-        | Fable.LambdaType _ | Fable.DelegateType _ -> ofString "function"
-        | Fable.AnonymousRecordType _ -> ofString "unknown" // Recognize shape? (it's possible in F#)
-        | Fable.Any -> ofString "any"
-        | Fable.Unit -> ofString "undefined"
-        | Fable.Boolean -> ofString "boolean"
-        | Fable.Char
-        | Fable.String -> ofString "string"
-        | Fable.Number _ -> ofString "number"
-        | Fable.Enum _ -> ofString "number"
-        | Fable.Option t -> ofArray [ofString "option"; toTypeTester com ctx r t]
-        | Fable.Array t -> ofArray [ofString "array"; toTypeTester com ctx r t]
-        | Fable.List t -> ofArray [ofString "list"; toTypeTester com ctx r t]
-        | Fable.Tuple genArgs ->
-            let genArgs = List.map (toTypeTester com ctx r) genArgs
-            ofArray [ofString "tuple"; ofArray genArgs]
-        | Fable.GenericParam name ->
-            sprintf "Cannot resolve generic param %s for type testing, evals to true" name |> addWarning com [] r
-            ofString "any"
-        | Fable.DeclaredType(ent, _) when ent.IsInterface ->
-            "Cannot type test interfaces, evals to false" |> addWarning com [] r
-            ofString "unknown"
-        | Fable.DeclaredType(ent, genArgs) ->
-            match tryJsConstructor com ctx ent with
-            | Some cons ->
-                if not(List.isEmpty genArgs) then
-                    "Generic args are ignored in type testing" |> addWarning com [] r
-                cons
-            | None ->
-                sprintf "Cannot type test %s, evals to false" ent.FullName |> addWarning com [] r
-                ofString "unknown"
+    let transformTypeTest (com: IBabelCompiler) ctx range expr (typ: Fable.Type): Expression =
+        let warnAndEvalToFalse msg =
+            "Cannot type test (evals to false): " + msg
+            |> addWarning com [] range
+            BooleanLiteral false :> Expression
 
-    let transformTypeTest (com: IBabelCompiler) ctx range (expr': Fable.Expr) (typ: Fable.Type): Expression =
-        let (|EntityFullName|) (e: Fable.Entity) = e.FullName
+        let jsTypeof (primitiveType: string) (Util.TransformExpr com ctx expr): Expression =
+            let typeof = UnaryExpression(UnaryTypeof, expr)
+            upcast BinaryExpression(BinaryEqualStrict, typeof, StringLiteral primitiveType, ?loc=range)
 
-        let expr = com.TransformAsExpr(ctx, expr')
-        match typ with
-        // Special cases
-        | Fable.DeclaredType(EntityFullName Types.idisposable, _) ->
-            match expr' with
-            | MaybeCasted(ExprType(Fable.DeclaredType(ent2, _))) when FSharp2Fable.Util.hasInterface Types.idisposable ent2 ->
-                upcast BooleanLiteral true
-            | _ -> libCall com ctx None "Util" "isDisposable" [|expr|]
-        | Fable.DeclaredType(EntityFullName Types.ienumerable, _) ->
-            libCall com ctx None "Util" "isIterable" [|expr|]
-        | Fable.DeclaredType(EntityFullName Types.array, _) -> // Untyped array
-            libCall com ctx None "Util" "isArrayLike" [|expr|]
-        | Fable.DeclaredType(EntityFullName Types.exception_, _) ->
-            libCall com ctx None "Types" "isException" [|expr|]
-        | _ ->
-            let typeTester = toTypeTester com ctx range typ
-            libCall com ctx range "Reflection" "typeTest" [|expr; typeTester|]
+        let jsInstanceof consExpr (Util.TransformExpr com ctx expr): Expression =
+            upcast BinaryExpression(BinaryInstanceOf, expr, consExpr, ?loc=range)
 
+        match typ with
+        | Fable.Any -> upcast BooleanLiteral true
+        | Fable.Unit -> upcast BinaryExpression(BinaryEqual, com.TransformAsExpr(ctx, expr), Util.undefined None, ?loc=range)
+        | Fable.Boolean -> jsTypeof "boolean" expr
+        | Fable.Char | Fable.String _ -> jsTypeof "string" expr
+        | Fable.Number _ | Fable.Enum _ -> jsTypeof "number" expr
+        | Fable.Regex -> jsInstanceof (Identifier "RegExp") expr
+        | Fable.LambdaType _ | Fable.DelegateType _ -> jsTypeof "function" expr
+        | Fable.Array _ | Fable.Tuple _ ->
+            libCall com ctx None "Util" "isArrayLike" [|com.TransformAsExpr(ctx, expr)|]
+        | Fable.List _ ->
+            jsInstanceof (libValue com ctx "Types" "List") expr
+        | Fable.AnonymousRecordType _ ->
+            warnAndEvalToFalse "anonymous records"
+        | Fable.MetaType ->
+            jsInstanceof (libValue com ctx "Reflection" "TypeInfo") expr
+        | Fable.Option _ -> warnAndEvalToFalse "options" // TODO
+        | Fable.GenericParam _ -> warnAndEvalToFalse "generic parameters"
+        | Fable.DeclaredType (ent, genArgs) ->
+            match ent.FullName with
+            | Types.idisposable ->
+                match expr with
+                | MaybeCasted(ExprType(Fable.DeclaredType (ent2, _)))
+                        when FSharp2Fable.Util.hasInterface Types.idisposable ent2 ->
+                    upcast BooleanLiteral true
+                | _ -> libCall com ctx None "Util" "isDisposable" [|com.TransformAsExpr(ctx, expr)|]
+            | Types.ienumerable ->
+                [|com.TransformAsExpr(ctx, expr)|]
+                |> libCall com ctx None "Util" "isIterable"
+            | Types.array ->
+                [|com.TransformAsExpr(ctx, expr)|]
+                |> libCall com ctx None "Util" "isArrayLike"
+            | Types.exception_ ->
+                [|com.TransformAsExpr(ctx, expr)|]
+                |> libCall com ctx None "Types" "isException"
+            | _ when ent.IsInterface ->
+                warnAndEvalToFalse "interfaces"
+            | _ ->
+                match tryJsConstructor com ctx ent with
+                | Some cons ->
+                    // TODO: Emit warning only once per file?
+                    if not(List.isEmpty genArgs) then
+                        "Generic args are ignored in type testing"
+                        |> addWarning com [] range
+                    jsInstanceof cons expr
+                | None ->
+                    warnAndEvalToFalse ent.FullName
 
 // TODO: I'm trying to tell apart the code to generate annotations, but it's not a very clear distinction
 // as there are many dependencies from/to the Util module below
@@ -1119,20 +1124,19 @@ module Util =
         [|TryStatement(transformBlock com ctx returnStrategy body,
             ?handler=handler, ?finalizer=finalizer, ?loc=r) :> Statement|]
 
-    // Even if IfStatement doesn't enforce it, compile both branches as blocks
-    // to prevent conflict (e.g. `then` doesn't become a block while `else` does)
-    let rec transformIfStatement (com: IBabelCompiler) ctx r ret (guardExpr: Expression) thenStmnt elseStmnt =
-        let thenStmnt = transformBlock com ctx ret thenStmnt
-        match elseStmnt: Fable.Expr with
-        | Fable.IfThenElse(TransformExpr com ctx guardExpr', thenStmnt', elseStmnt', r2) ->
-            let elseStmnt = transformIfStatement com ctx r2 ret guardExpr' thenStmnt' elseStmnt'
-            IfStatement(guardExpr, thenStmnt, elseStmnt, ?loc=r)
-        | expr ->
-            match com.TransformAsStatements(ctx, ret, expr) with
-            | [||] -> IfStatement(guardExpr, thenStmnt, ?loc=r)
-            | [|:? ExpressionStatement as e|] when (e.Expression :? NullLiteral) ->
-                IfStatement(guardExpr, thenStmnt, ?loc=r)
-            | statements -> IfStatement(guardExpr, thenStmnt, BlockStatement statements, ?loc=r)
+    let rec transformIfStatement (com: IBabelCompiler) ctx r ret guardExpr thenStmnt elseStmnt =
+        match com.TransformAsExpr(ctx, guardExpr) with
+        | :? BooleanLiteral as b when b.Value ->
+            com.TransformAsStatements(ctx, ret, thenStmnt)
+        | :? BooleanLiteral as b when not b.Value ->
+            com.TransformAsStatements(ctx, ret, elseStmnt)
+        | guardExpr ->
+            let thenStmnt = transformBlock com ctx ret thenStmnt
+            match com.TransformAsStatements(ctx, ret, elseStmnt) with
+            | [||] -> IfStatement(guardExpr, thenStmnt, ?loc=r) :> Statement
+            | [|elseStmnt|] -> IfStatement(guardExpr, thenStmnt, elseStmnt, ?loc=r) :> Statement
+            | statements -> IfStatement(guardExpr, thenStmnt, BlockStatement statements, ?loc=r) :> Statement
+            |> Array.singleton
 
     let transformGet (com: IBabelCompiler) ctx range typ fableExpr (getKind: Fable.GetKind) =
         match getKind with
@@ -1579,8 +1583,6 @@ module Util =
                 | Some(Fable.FieldKey fi) -> get None expr fi.Name |> Assign
             com.TransformAsStatements(ctx, Some ret, value)
 
-        // Even if IfStatement doesn't enforce it, compile both branches as blocks
-        // to prevent conflicts (e.g. `then` doesn't become a block while `else` does)
         | Fable.IfThenElse(guardExpr, thenExpr, elseExpr, r) ->
             let asStatement =
                 match returnStrategy with
@@ -1591,10 +1593,7 @@ module Util =
                     Option.isSome ctx.TailCallOpportunity
                     || (isJsStatement ctx false thenExpr) || (isJsStatement ctx false elseExpr)
             if asStatement then
-                match com.TransformAsExpr(ctx, guardExpr) with
-                // In some situations (like some type tests) the condition may be always true
-                | :? BooleanLiteral as e when e.Value -> com.TransformAsStatements(ctx, returnStrategy, thenExpr)
-                | guardExpr -> [|transformIfStatement com ctx r returnStrategy guardExpr thenExpr elseExpr :> Statement|]
+                transformIfStatement com ctx r returnStrategy guardExpr thenExpr elseExpr
             else
                 let guardExpr' = transformAsExpr com ctx guardExpr
                 let thenExpr' = transformAsExpr com ctx thenExpr

src/Fable.Transforms/Replacements.fs

@@ -223,8 +223,6 @@ let (|ReplaceName|_|) (namesAndReplacements: (string*string) list) name =
     namesAndReplacements |> List.tryPick (fun (name2, replacement) ->
         if name2 = name then Some replacement else None)
 
-let inline (|ExprType|) (e: Expr) = e.Type
-
 let (|OrDefault|) (def:'T) = function
     | Some v -> v
     | None -> def

src/fable-library/BigInt.fs

@@ -2,6 +2,8 @@ module BigInt.Exports
 
 type bigint = BigInt.BigInteger
 
+let isBigInt (x: obj) = x :? bigint
+
 let tryParse str res =
     try
         res := bigint.Parse str

src/fable-library/Reflection.ts

@@ -1,6 +1,5 @@
-import { value as getOptionValue } from "./Option.js";
-import { FSharpRef, List } from "./Types.js";
-import { compareArraysWith, equalArraysWith, isArrayLike, isUnionLike } from "./Util.js";
+import { FSharpRef } from "./Types.js";
+import { compareArraysWith, equalArraysWith, isUnionLike } from "./Util.js";
 
 export type FieldInfo = [string, TypeInfo];
 export type PropertyInfo = FieldInfo;
@@ -417,50 +416,3 @@ export function getCaseFields(x: any): any[] {
   assertUnion(x);
   return x.fields;
 }
-
-type TypeTester =
-  | "any"
-  | "unknown"
-  | "undefined"
-  | "function"
-  | "boolean"
-  | "number"
-  | "string"
-  | ["tuple", TypeTester[]]
-  | ["array", TypeTester | undefined]
-  | ["list", TypeTester]
-  | ["option", TypeTester]
-  | FunctionConstructor
-
-export function typeTest(x: any, typeTester: TypeTester): boolean {
-  if (typeof typeTester === "string") {
-    if (typeTester === "any") {
-      return true;
-    } else if (typeTester === "unknown") {
-      return false;
-    } else {
-      return typeof x === typeTester;
-    }
-  } else if (Array.isArray(typeTester)) {
-    switch (typeTester[0]) {
-      case "tuple":
-        return Array.isArray(x)
-          && x.length === typeTester[1].length
-          && x.every((x, i) => typeTest(x, typeTester[1][i]));
-      case "array":
-        return isArrayLike(x)
-          && (x.length === 0
-            || typeTester[1] == null
-            || typeTest(x[0], typeTester[1]));
-      case "list":
-        return x instanceof List
-          && (x.tail == null || typeTest(x.head, typeTester[1]));
-      case "option":
-        return x == null || typeTest(getOptionValue(x), typeTester[1]);
-      default:
-        return false
-    }
-  } else {
-    return x instanceof typeTester;
-  }
-}

src/quicktest/QuickTest.fs

@@ -66,3 +66,20 @@ let measureTime (f: unit -> unit) = emitJsStatement () """
 // to Fable.Tests project. For example:
 // testCase "Addition works" <| fun () ->
 //     2 + 2 |> equal 4
+
+let test (exn: exn) =
+    match exn with
+    | :? System.NotSupportedException  -> ()
+    | :? System.SystemException -> ()
+    | Failure _ -> raise exn
+    | _ -> ()
+
+let test2 () =
+    printfn "foo"
+    if 3 > 2 then
+        "foo"
+    elif false then
+        "bar"
+    else
+        "baz"
+

tests/Main/TypeTests.fs

@@ -454,8 +454,7 @@ let tests =
             | :? bool -> "boolean"
             | :? unit -> "unit"
             | :? System.Text.RegularExpressions.Regex -> "RegExp"
-            | :? (int[]) -> "int array"
-            | :? (string[]) -> "string array"
+            | :? (int[]) | :? (string[]) -> "Array"
             | _ -> "unknown"
         "A" :> obj |> test |> equal "string"
         3. :> obj |> test |> equal "number"
@@ -464,8 +463,8 @@ let tests =
         // Workaround to make sure Fable is passing the argument
         let a = () :> obj in test a |> equal "unit"
         System.Text.RegularExpressions.Regex(".") :> obj |> test |> equal "RegExp"
-        [|"A"|] :> obj |> test |> equal "string array"
-        [|1;2|] :> obj |> test |> equal "int array"
+        [|"A"|] :> obj |> test |> equal "Array"
+        [|1;2|] :> obj |> test |> equal "Array"
 
     testCase "Type test with Date" <| fun () ->
         let isDate (x: obj) =