trashcan 0.1.0

a simple language which compiles to Visual Basic 6 / VBA
Documentation 
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//! code generation for trashcan bits/atoms

use std::io;
use std::io::Write;

use ast::*;
use super::*;

pub enum TypePos {
    Decl,
    FunParam,
    FunRet,
}

// TODO: need context here (are we in fn-ret, param, or decl position?)
impl Emit<TypePos> for Type {
    fn emit<W: Write>(&self, out: &mut W, symtab: &SymbolTable,
      ctxt: TypePos, _indent: u32) -> io::Result<()> {
        match *self {
            Type::Deferred(ref i) =>
                panic!("dumpster fire: unresolved type \
                  {:?} in codegen", i),

            Type::Array(_, ref bounds) => {
                match ctxt {
                    TypePos::Decl => {
                        emit_bounds(out, bounds, symtab)?;
                        out.write_all(b" As ")?;
                        emit_basename(out, symtab, self)
                    },

                    TypePos::FunParam => {
                        out.write_all(b"() As ")?;
                        emit_basename(out, symtab, self)
                    },

                    TypePos::FunRet => {
                        out.write_all(b" As ")?;
                        emit_basename(out, symtab, self)?;
                        out.write_all(b"()")
                    },
                }
            },

            _ => {
                out.write_all(b" As ")?;
                emit_basename(out, symtab, self)
            }
        }
    }
}

fn emit_basename<W: Write>(out: &mut W, symtab: &SymbolTable, ty: &Type)
  -> io::Result<()> {
    match ty {
        &Type::Bool => out.write_all(b"Boolean"),
        &Type::UInt8 => out.write_all(b"Byte"),
        &Type::Int16 => out.write_all(b"Integer"),
        &Type::Int32 => out.write_all(b"Long"),
        &Type::IntPtr => out.write_all(b"LongPtr"),
        &Type::Float32 => out.write_all(b"Single"),
        &Type::Float64 => out.write_all(b"Double"),
        &Type::String => out.write_all(b"String"),
        &Type::Currency => out.write_all(b"Currency"),
        &Type::Date => out.write_all(b"Date"),
        &Type::Variant => out.write_all(b"Variant"),
        &Type::Obj => out.write_all(b"Object"),
        &Type::Array(ref basety, _) => emit_basename(out, symtab, basety),
        &Type::VarArgsArray => out.write_all(b"Variant"),
        &Type::Object(ref path) => path.emit(out, symtab, (), 0),
        &Type::Struct(ref path) => path.emit(out, symtab, (), 0),
        &Type::Enum(ref path) => path.emit(out, symtab, (), 0),
        &Type::Deferred(ref path) => path.emit(out, symtab, (), 0),
        &Type::Void =>
            panic!("dumpster fire: tried to emit void type"),
    }
}

fn emit_bounds<W: Write>(out: &mut W, bounds: &ArrayBounds,
  symtab: &SymbolTable) -> io::Result<()> {
    out.write_all(b"(")?;
    match *bounds {
        ArrayBounds::Static(ref bounds) => {
            for (i, bound) in bounds.iter().enumerate() {
                if i != 0 {
                    out.write_all(b", ")?;
                }

                match *bound {
                    StaticArrayBound::Range(ref first, ref end) => {
                        emit_static_dim(out, first, symtab, false)?;
                        out.write_all(b" To ")?;
                        emit_static_dim(out, end, symtab, false)?;
                    },

                    StaticArrayBound::Length(ref len) => {
                        out.write_all(b"0 To ")?;
                        emit_static_dim(out, len, symtab, true)?;
                    },
                }
            }
        },

        ArrayBounds::Dynamic(_) => {},
    };
    out.write_all(b")")
}

fn emit_static_dim<W: Write>(out: &mut W, dim: &StaticArrayDim,
  symtab: &SymbolTable, subtract_one: bool) -> io::Result<()> {
    match *dim {
        StaticArrayDim::Lit(ref lit) => {
            match *lit {
                Literal::UInt8(i) =>
                    write!(out, "{}", if subtract_one { i - 1 } else { i }),
                Literal::Int16(i) =>
                    write!(out, "{}", if subtract_one { i - 1 } else { i }),
                Literal::Int32(i) =>
                    write!(out, "{}", if subtract_one { i - 1 } else { i }),
                _ => panic!("dumpster fire: invalid literal type in static \
                  array bound during codegen"),
            }?;
        },

        StaticArrayDim::Named(ref path) => {
            path.emit(out, symtab, (), 0)?;
            if subtract_one {
                out.write_all(b" - 1")?;
            }
        },
    }

    Ok(())
}