Allow Void expressions to be used within ForAll (#1527)

If a ForAll expression is used within a context where its result is not needed, then it should be able to use void expressions, like in the example below. This change allows it, making the entire result of the ForAll expression a void result.

    ForAll(
        Sequence(4),
        If(
            Mod(Value, 2) = 1,
Patch( table, Index(table, Value), { IsOdd: true } ), // this returns a
record, incompatible with tables
Collect( table, { Value: Value, IsOdd: false }, { Value: Value + 1,
IsOdd: true } // this returns a table
        )
    )

Author: CarlosFigueiraMSFT

src/libraries/Microsoft.PowerFx.Core/Texl/Builtins/ForAll.cs

@@ -46,7 +46,8 @@ public override bool CheckTypes(CheckTypesContext context, TexlNode[] args, DTyp
             Contracts.Assert(args.Length == argTypes.Length);
             Contracts.AssertValue(errors);
 
-            var fArgsValid = base.CheckTypes(context, args, argTypes, errors, out returnType, out nodeToCoercedTypeMap);
+            nodeToCoercedTypeMap = null;
+            var fArgsValid = CheckType(context, args[0], argTypes[0], ParamTypes[0], errors, ref nodeToCoercedTypeMap);
 
             if (argTypes[1].IsRecord)
             {
@@ -56,6 +57,10 @@ public override bool CheckTypes(CheckTypesContext context, TexlNode[] args, DTyp
             {
                 returnType = DType.CreateTable(new TypedName(argTypes[1], ColumnName_Value));
             }
+            else if (argTypes[1].IsVoid)
+            {
+                returnType = argTypes[1];
+            }
             else
             {
                 returnType = DType.Error;
@@ -104,7 +109,8 @@ public override bool CheckTypes(CheckTypesContext context, TexlNode[] args, DTyp
             Contracts.Assert(args.Length == argTypes.Length);
             Contracts.AssertValue(errors);
 
-            var fArgsValid = base.CheckTypes(context, args, argTypes, errors, out returnType, out nodeToCoercedTypeMap);
+            nodeToCoercedTypeMap = null;
+            var fArgsValid = CheckType(context, args[0], argTypes[0], ParamTypes[0], errors, ref nodeToCoercedTypeMap);
 
             if (argTypes[1].IsRecord)
             {
@@ -114,6 +120,10 @@ public override bool CheckTypes(CheckTypesContext context, TexlNode[] args, DTyp
             {
                 returnType = DType.CreateTable(new TypedName(argTypes[1], ColumnName_Value));
             }
+            else if (argTypes[1].IsVoid)
+            {
+                returnType = argTypes[1];
+            }
             else
             {
                 returnType = DType.Error;

src/libraries/Microsoft.PowerFx.Interpreter/Functions/Library.cs

@@ -2485,7 +2485,12 @@ public static async ValueTask<FormulaValue> ForAll(EvalVisitor runner, EvalVisit
             if (errorRows.Any())
             {
                 return ErrorValue.Combine(irContext, errorRows);
-            }
+            }
+
+            if (irContext.ResultType is Types.Void)
+            {
+                return new VoidValue(irContext);
+            }
 
             return new InMemoryTableValue(irContext, StandardTableNodeRecords(irContext, rows.ToArray(), forceSingleColumn: false));
         }

src/libraries/Microsoft.PowerFx.Interpreter/Functions/LibraryUntypedObject.cs

@@ -555,7 +555,12 @@ public static async ValueTask<FormulaValue> ForAll_UO(EvalVisitor runner, EvalVi
             if (errorRows.Any())
             {
                 return ErrorValue.Combine(irContext, errorRows);
-            }
+            }
+
+            if (irContext.ResultType is Types.Void)
+            {
+                return new VoidValue(irContext);
+            }
 
             return new InMemoryTableValue(irContext, StandardTableNodeRecords(irContext, rows.ToArray(), forceSingleColumn: false));
         }

src/tests/Microsoft.PowerFx.Core.Tests/ExpressionTestCases/ForAll.txt

@@ -89,3 +89,23 @@ Table({Value:true})
 >> ForAll([Blank()],IsBlank(ThisRecord))
 Table({Value:false})
 
+// ************ ForAll and Void expressions ****************
+
+>> ForAll([1,2], If(Value = 1, Value * 2, {Result: Value}))
+If(true, {test:1}, "Mismatched args (result of the expression can't be used).")
+
+>> ForAll([1,2,3] As p, Switch(p.Value, 1, {a:1}, 2, [{a:2}], 3, "Hello"))
+If(true, {test:1}, "Mismatched args (result of the expression can't be used).")
+
+>> ForAll(ParseJSON("[1,2]"), If(Value(ThisRecord) = 1, Value(ThisRecord) * 2, {Result: Value(ThisRecord)}))
+If(true, {test:1}, "Mismatched args (result of the expression can't be used).")
+
+>> ForAll(ParseJSON("[1,2,3]"), Switch(Value(ThisRecord), 1, {a:1}, 2, [{a:2}], 3, "Hello"))
+If(true, {test:1}, "Mismatched args (result of the expression can't be used).")
+
+// Errors are returned
+>> ForAll([1,2], If(Value = 1, Sqrt(-Value), {Result: Value}))
+Error({Kind:ErrorKind.Numeric})
+
+>> ForAll(ParseJSON("[""1"",""a""]"), If(Text(ThisRecord) = "1", Value(ThisRecord) * 2, Value(ThisRecord)))
+Error({Kind:ErrorKind.InvalidArgument})

src/tests/Microsoft.PowerFx.Core.Tests/TexlTests.cs

@@ -589,7 +589,7 @@ public void TexlFunctionTypeSemanticsIf()
         [InlineData("Hour(If(1 < 0, [1], 2))", "n", false)]
 
         // ForAll([1,2,3], V)
-        [InlineData("ForAll([1,2,3], If(1 < 0, [1], 2))", "e", false)]
+        [InlineData("ForAll([1,2,3], If(1 < 0, [1], 2))", "-", true)]
         public void TexlFunctionTypeSemanticsIfWithArgumentCoercion(string expression, string expectedType, bool checkSuccess)
         {
             var symbol = new SymbolTable();