Add special case to improve quality of generated code for simple functions

ir.py

@@ -116,10 +116,40 @@ class Function:
 
 	def codegen_inner(self) -> str:
 		return unwrap_r(self.eliminate(Variable('$'))).codegen()
+	def try_codegen_sp(self) -> Option[Tuple[str, str]]:
+		""" A special-case of codegen inner (see description)
+
+		In certain cases, starting a function with a full match tree may be unnecessary.
+		Specifically, if there exists only one possible branch and that branch binds only
+		one value and that value is equal to the whole entire input, rather than assigning
+		that input to a new variable, we may simply use argument variable instead.
+
+		This method returns the generated code for the inner branch in such a case.
+		Additionally, the second string returned represents the name of the variable which
+		ought to be bound as the argument.  If the argument is unused, this will be "$".
+		"""
+		match self.forms:
+			case [(patt, expr)]: # A single possible branch
+				match patt.bindings():
+					case []: # Binds nothing
+						return Some((expr.codegen(), '$'))
+					case [(var, [])]: # Binds a single variable to the entire input
+						return Some((expr.codegen(), var))
+		return None
 	def codegen(self) -> str:
-		return '$=>' + self.codegen_inner()
+		match self.try_codegen_sp():
+			case Some((codegen, var)):
+				return f'{var}=>{codegen}'
+			case None:
+				return '$=>' + self.codegen_inner()
+		raise Exception('Unreachable')
 	def codegen_named(self, name) -> str:
-		return f'function {name}($){{return {self.codegen_inner()}}}'
+		match self.try_codegen_sp():
+			case Some((codegen, var)):
+				return f'function {name}({var}){{return {codegen}}}'
+			case None:
+				return f'function {name}($){{return {self.codegen_inner()}}}'
+		raise Exception('Unreachable')
 	def __repr__(self) -> str:
 		return '{ ' + ', '.join('"' + repr(repr(p))[1:-1] + '" : ' + repr(e) for (p, e) in self.forms) + ' }'