Function Expressions: first file is the grammar I want to use, demonstrating the problem. The second (example.eve) demonstrates what must be done currently in the language vs what I would like to achieve.

.gitignore

lib/
*.java
*.tokens

build.xml

<project xmlns:ivy="antlib:org.apache.ivy.ant" name="eve-interpreter" default="antlr" basedir=".">	
	<!-- Build macro for antlr code generation -->
	<macrodef name="antlr3">
		<attribute name="grammar"/>
		<attribute name="output" default="."/>
		<attribute name="lib" default="."/>
		<sequential>
			<java classname="org.antlr.Tool" fork="true" failonerror="true">
				<classpath>
					<fileset dir="lib/" includes="*.jar" />
				</classpath>
				<arg value="-o"/>
				<arg path="@{output}"/>
				<arg value="-verbose"/>
				<arg value="-make"/>
				<arg path="@{grammar}"/>
			</java>
		</sequential>
	</macrodef>
	
	<!-- resolve all dependencies via Ivy -->
    <target name="dependencies" description="--> retrieve dependencies with ivy">
        <ivy:retrieve />
    </target>
	
	<target name="antlr" depends="dependencies" description="--> antlr code generation">
		<antlr3 grammar="func.g" output="." />
	</target>
</project>

example.eve

//This is what must be done now, since functions can only be referenced by identifier.
var x = createFunction();
x();

//This is what I want to be able to do, among other things.
createFunction()();

func.g

grammar func;

options {
	language = Java;
	output = AST;
	ASTLabelType = CommonTree;
}

tokens {
	INVOKE_FUNCTION_STMT;
	INVOKE_FUNCTION_EXPR;
	NEGATION;
}

@header {
	package eve.core;
}

@lexer::header {
	package eve.core;
	import java.util.List;
	import java.util.ArrayList;
}

@lexer::members {
    public void displayRecognitionError(String[] tokenNames, RecognitionException e) {
        String hdr = getErrorHeader(e);
        String msg = getErrorMessage(e, tokenNames);
        throw new EveError(hdr + " " + msg);
    }
    
    public void recover(RecognitionException e) {
 	    String hdr = getErrorHeader(e);
        throw new EveError(hdr + " " + e.getMessage());
    }
}

@parser::members {
    private List<String> errors = new ArrayList<String>();
    public void displayRecognitionError(String[] tokenNames, RecognitionException e) {
        String hdr = getErrorHeader(e);
        String msg = getErrorMessage(e, tokenNames);
        errors.add(hdr + " " + msg);
    }
    
    public void recover(RecognitionException e) {
    	errors.add(e.getMessage());
    }
    
    public List<String> getErrors() {
        return errors;
    }
    
    public boolean hasErrors() {
    	return errors.size() > 0;
    }
}

//The original function invocation rules for expressions.
//Only identifies via identifier.
functionInvocationParameters
	:	expression (',' expression)* -> (expression)* //apparently this somehow rewrites the entire thing to "p1 p2 p3 ..."
	;
	
functionInvocationExpression
	:	IDENT '(' functionInvocationParameters ')' -> ^(INVOKE_FUNCTION_EXPR IDENT functionInvocationParameters)
	|	IDENT '(' ')' -> ^(INVOKE_FUNCTION_EXPR IDENT)
	;

//Expressions
term
	:	IDENT
	|	'('! expression ')'!
	|	INTEGER
	|	DOUBLE
	|	BOOLEAN
	//have this one commented out, because it's the old way.
	//|	functionInvocationExpression
	|	expression '(' ')' -> ^(INVOKE_FUNCTION_EXPR IDENT)
	|	expression '(' functionInvocationParameters ')' -> ^(INVOKE_FUNCTION_EXPR IDENT functionInvocationParameters)
	;
	
boolNegation
	:	'!'* term
	;
	
unary
	:	('+'! | negation^)* boolNegation
	;
		
negation
	:	'-' -> NEGATION
	;

mult
	:	unary (('*'^ | '/'^ | '%'^) unary)*
	;
	
add
	:	mult (('+'^ | '-'^ | '~'^) mult)*
	;

relation
	:	add (('=='^ | '!='^ | '<'^ | '<='^ | '>='^ | '>'^) add)*
	;
	
expression
	:	relation (('&&'^ | '||'^) relation)*
	;
	
// Tokens
fragment LETTER : ('a'..'z' | 'A'..'Z') ;
fragment DIGIT : '0'..'9';
INTEGER : DIGIT+ ;
DOUBLE : DIGIT+ '.' DIGIT+ ;
BOOLEAN : 'true' | 'false' ;
IDENT : LETTER (LETTER | DIGIT)*;

WS : (' ' | '\t' | '\n' | '\r' | '\f')+ {$channel = HIDDEN;};

ivy.xml

<ivy-module version="2.0">
    <info organisation="thermetics.eve" module="eve-interpreter" />
    <dependencies>
        <dependency org="org.antlr" name="antlr" rev="3.3" />
    </dependencies>
</ivy-module>