Parenthesise a number literal used as a call receiver [patch]

Coder.Test/Languages/CallReceiverLiteralTests.cs

@@ -0,0 +1,77 @@
+// Copyright (c) 2023-2026 ktsu-dev contributors
+
+namespace ktsu.Coder.Test.Languages;
+
+using System.Linq;
+using ktsu.Coder.Ast;
+using ktsu.Coder.Languages;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+
+/// <summary>
+/// Tests that a number literal used as a call's receiver keeps its grouping.
+/// </summary>
+/// <remarks>
+/// <c>-2.5.abs()</c> is <c>-(2.5.abs())</c> in every target, because unary minus binds looser than
+/// member access, and <c>5.toString()</c> does not parse in JavaScript or Python.
+/// </remarks>
+[TestClass]
+public class CallReceiverLiteralTests
+{
+	/// <summary>
+	/// Every generator that writes a receiver in front of the callee. C passes it as an argument instead.
+	/// </summary>
+	private static readonly ILanguageGenerator[] Generators =
+	[
+		new CSharpGenerator(),
+		new CppGenerator(),
+		new GoGenerator(),
+		new RustGenerator(),
+		new PythonGenerator(),
+		new JavaScriptGenerator(),
+	];
+
+	/// <summary>
+	/// Tests that a negative literal receiver is parenthesised, so the call applies to the negative value.
+	/// </summary>
+	[TestMethod]
+	public void ANegativeLiteralReceiverIsParenthesised()
+	{
+		CallExpression call = new(Literal.DecimalValue(-2.5), "abs");
+
+		foreach (ILanguageGenerator generator in Generators)
+		{
+			string code = generator.Generate(call).Trim();
+
+			Assert.StartsWith("(-2.5", code, StringComparison.Ordinal, $"{generator.GetType().Name} wrote {code}");
+			Assert.EndsWith(").abs()", code, StringComparison.Ordinal, $"{generator.GetType().Name} wrote {code}");
+		}
+	}
+
+	/// <summary>
+	/// Tests that an integer literal receiver is parenthesised, so the dot is not read as a decimal point.
+	/// </summary>
+	[TestMethod]
+	public void AnIntegerLiteralReceiverIsParenthesised()
+	{
+		CallExpression call = new(Literal.Number(5), "toString");
+
+		foreach (ILanguageGenerator generator in Generators.Where(g => g is JavaScriptGenerator or PythonGenerator))
+		{
+			Assert.AreEqual("(5).toString()", generator.Generate(call).Trim(), generator.GetType().Name);
+		}
+	}
+
+	/// <summary>
+	/// Tests that a receiver that is not a literal is still written bare.
+	/// </summary>
+	[TestMethod]
+	public void ANameReceiverIsWrittenBare()
+	{
+		CallExpression call = new(new VariableReference("value"), "abs");
+
+		foreach (ILanguageGenerator generator in Generators)
+		{
+			Assert.AreEqual("value.abs()", generator.Generate(call).Trim(), generator.GetType().Name);
+		}
+	}
+}

Coder/Languages/LanguageGeneratorBase.cs

@@ -558,6 +558,12 @@
 	/// <see cref="CallExpression.Callee"/> is written verbatim. Nothing here maps a function's name
 	/// between languages, and nothing pretends to — see the node's own remarks for why.
 	/// </para>
+	/// <para>
+	/// A number literal receiver is parenthesised. A negative one would otherwise negate the call's
+	/// result rather than its receiver, since unary minus binds looser than member access, so
+	/// <c>-2.5.abs()</c> is <c>-(2.5.abs())</c>; and an integer one would run the dot into the
+	/// literal, which JavaScript and Python read as a malformed number rather than a member call.
+	/// </para>
 	/// </remarks>
 	protected virtual void GenerateCallExpression(CallExpression callExpr, CodeBlocker code)
 	{
@@ -566,7 +572,20 @@
 
 		if (callExpr.Receiver is not null)
 		{
+			bool parenthesise = IsNumberLiteral(callExpr.Receiver);
+
+			if (parenthesise)
+			{
+				code.Write("(");
+			}
+
 			GenerateInternal(callExpr.Receiver, code);
+
+			if (parenthesise)
+			{
+				code.Write(")");
+			}
+
 			code.Write(".");
 		}
 
@@ -714,6 +733,17 @@
 		_ => null,
 	};
 
+	/// <summary>
+	/// Reports whether a node is a number literal.
+	/// </summary>
+	/// <param name="node">The node to inspect.</param>
+	/// <returns>True for an integer or floating-point literal of any sign; otherwise false.</returns>
+	private static bool IsNumberLiteral(AstNode? node) => node is LiteralExpression<int>
+		or LiteralExpression<double>
+		or LiteralExpression<float>
+		or LiteralExpression<long>
+		or AstLeafNode<int>;
+
 	/// <summary>
 	/// Reports whether a node is one of the standard shapes a generator built on these helpers accepts.
 	/// </summary>
@@ -896,7 +926,7 @@
 		string? origin = null;
 		long offset = 0;
 
 		foreach (EnumMember member in enumDecl.Members)
 		{
 			if (member.Value is not null)
 			{