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copied!<p>Contrary to <a href="https://stackoverflow.com/questions/2850902/scala-coalesces-multiple-function-call-parameters-into-a-tuple-can-this-be-dis/2851212#2851212">this explanation</a>, Scala <em>parses</em> <code>println(1,2)</code> (or <code>Console println (1,2)</code> for that matter) the same way it parses any two-argument method call. Later, the compiler transforms the call by wrapping the method arguments in a tuple to match the actual method type signature.</p> <p>If the compiler did not do this, perfectly valid expressions like <code>Console println (1,2)</code> would fail to compile because <code>println</code> does not take multiple arguments. There are also <a href="https://stackoverflow.com/questions/5985076/scala-generic-class-supporting-function-of-multiple-arities">other valid use cases</a> for this behavior.</p> <p>Consider an expression like <code>foo bar (1,2)</code> from the compiler's point of view, keeping in mind that Scala has special syntax that allows you to drop the <code>.</code> and the parens on method calls. This could be a call to a two-argument <code>bar</code> method with arguments <code>1</code> and <code>2</code>, or it could be a call to a one-argument <code>bar</code> method with a single tuple-valued argument. The parser doesn't know anything about the <code>bar</code> method, so it just parses as a two-argument method call. </p> <p>During the type checking phase, suppose the compiler determines that <code>foo</code> has no two-argument <code>bar</code> method but that it does have a one-argument <code>bar</code> method whose signature is compatible with the tuple interpretation. Since there is no other valid interpretation, it assumes that this is what you meant and transforms the two arguments into a tuple. Note that if there is a two-argument <code>bar</code> method, even one that is incompatible with the actual arguments, the typer <em>will not</em> perform the auto-tupling transformation.</p>

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