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ToCsharpCode: format block inside expression in { ... } #354

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ToCsharpCode: format block inside expression in { ... } #354

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3369c2b
ToCsharpCode: format block inside expression in {}
exyi Dec 29, 2022
f0ca1d8
ToCSharpCode: add comments to invalid block expressions
exyi Oct 1, 2023
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21 changes: 17 additions & 4 deletions src/FastExpressionCompiler/FastExpressionCompiler.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -6948,7 +6948,8 @@ internal static StringBuilder ToCSharpString(this Expression e, StringBuilder sb
sb.NewLineIdentCs(body, EnclosedIn.LambdaBody, lineIdent + identSpaces, stripNamespace, printType, identSpaces, notRecognizedToCode);
else
{
sb.NewLine(lineIdent, identSpaces).Append('{');
sb.NewLineIdent(lineIdent).Append('{');

// Body handles `;` itself
if (body is BlockExpression bb)
bb.BlockToCSharpString(sb, lineIdent + identSpaces, stripNamespace, printType, identSpaces, notRecognizedToCode,
Expand All @@ -6959,7 +6960,7 @@ internal static StringBuilder ToCSharpString(this Expression e, StringBuilder sb
if (isBodyExpression)
sb.AddSemicolonIfFits();
}
sb.NewLine(lineIdent, identSpaces).Append('}');
sb.NewLineIdent(lineIdent).Append('}');
}
return sb.Append(')');
}
Expand All @@ -6977,7 +6978,6 @@ internal static StringBuilder ToCSharpString(this Expression e, StringBuilder sb
var x = (ConditionalExpression)e;
if (e.Type == typeof(void)) // otherwise output as ternary expression
{
sb.NewLine(lineIdent, identSpaces);
sb.Append("if (");
x.Test.ToCSharpString(sb, EnclosedIn.IfTest, lineIdent, stripNamespace, printType, identSpaces, notRecognizedToCode);
sb.Append(')');
Expand Down Expand Up @@ -7011,7 +7011,20 @@ internal static StringBuilder ToCSharpString(this Expression e, StringBuilder sb
}
case ExpressionType.Block:
{
return BlockToCSharpString((BlockExpression)e, sb, lineIdent, stripNamespace, printType, identSpaces, notRecognizedToCode: notRecognizedToCode);
if (enclosedIn == EnclosedIn.Block)
return BlockToCSharpString((BlockExpression)e, sb, lineIdent, stripNamespace, printType, identSpaces, notRecognizedToCode: notRecognizedToCode);
else
{
var isExpressionBlock = e.Type != typeof(void) && sb.Length > 0;
sb.Append("{");
if (isExpressionBlock)
sb.Append(" /* BlockExpression cannot be written in C#. Please rewrite the code inside these braces as a C# expression, or reorganize the parent expression as a block. */");
BlockToCSharpString((BlockExpression)e, sb, lineIdent + identSpaces, stripNamespace, printType, identSpaces, notRecognizedToCode: notRecognizedToCode);

if (isExpressionBlock)
sb.Append("/* <- block result */");
return sb.NewLineIdent(lineIdent).Append('}');
}
}
case ExpressionType.Loop:
{
Expand Down
78 changes: 77 additions & 1 deletion test/FastExpressionCompiler.UnitTests/ToCSharpStringTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -31,6 +31,82 @@ public void Outputs_closed_generic_type_constant_correctly()
Assert.AreEqual(typeof(A<string>), f());
}

[Test]
public void Lambda_with_block_body()
{
var variable = Parameter(typeof(int), "variable");
var e = Lambda<Func<int>>(Block(new [] { variable }, Assign(variable, Constant(1)), Add(variable, Constant(2))));

var cs = e.ToCSharpString();

Assert.AreEqual("""
(Func<int>)(() =>
{
int variable = default;
variable = 1;
return (variable + 2);
});
""", cs);
}

[Test]
public void Nested_blocks()
{
var v1 = Parameter(typeof(int), "v1");
var v2 = Parameter(typeof(int), "v2");
var cs = Block(new [] { v1 },
Assign(v1, Constant(2)),
Block(new [] { v2 },
Assign(v2, Constant(3)),
AddAssign(v1, v2),
IfThen(
Equal(v1, Constant(5)),
Block(
Assign(v2, Constant(7)),
AddAssign(v1, v2)
)
)
),
v1
).ToCSharpString();
Console.WriteLine(cs);
Assert.AreEqual("""
{
int v1 = default;
v1 = 2;
int v2 = default;
v2 = 3;
v1 += v2;
if (v1 == 5)
{
v2 = 7;
v1 += v2;
}
v1;
};
""", cs);
}


[Test]
public void Somehow_handles_block_in_expression()
{
// it's probably not possible to output compilable C# for expressions like this, but at least it can be easy to read
var variable = Parameter(typeof(int), "variable");
var cs = Add(Constant(1), Block(new [] { variable },
Assign(variable, Constant(2)),
variable
)).ToCSharpString();
Assert.AreEqual("""
(1 + { /* BlockExpression cannot be written in C#. Please rewrite the code inside these braces as a C# expression, or reorganize the parent expression as a block. */
int variable = default;
variable = 2;
variable;/* <- block result */
});
""", cs);
}


class A<X> {}
}
}
}