Add a lot of new stuff to the compile mod

* compile::sym is now compile::name
* add basic block structure
* add visitor pattern
* some other minor things (e.g. syn::ast::prelude)

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

src/compile/ir.rs

@@ -0,0 +1,59 @@
+use crate::{
+    compile::Ctx,
+    obj::Sym,
+    syn::{ast, span::*},
+};
+
+pub type Body = Vec<Stmt>;
+
+#[derive(Debug, Clone)]
+pub enum Stmt {
+    Eval(Expr),
+    Assign(Lhs, Expr),
+}
+
+#[derive(Debug, Clone)]
+pub enum Lhs {
+    Sym(Sym),
+    Complex(Expr),
+}
+
+#[derive(Debug, Clone)]
+pub enum Expr {
+    Call(Box<Expr>, Vec<Expr>),
+    Base(BaseExpr),
+}
+
+#[derive(Debug, Clone)]
+pub enum BaseExprKind {
+    Num(i64),
+    Str(String),
+    Sym(Sym),
+    Ident(String),
+}
+
+#[derive(Debug, Clone)]
+pub struct BaseExpr {
+    pub kind: BaseExprKind,
+    pub span: Span,
+}
+
+// FromAst and IntoAst are just so we can use .into_ast(ctx, text)
+// some impls may not need ctx &mut ref - but probably needed for symbol resolution
+
+pub trait FromAst<A> {
+    fn from_ast(other: A, ctx: &mut Ctx, text: &str) -> Self;
+}
+
+pub trait IntoIr<I> {
+    fn into_ir(self, ctx: &mut Ctx, text: &str) -> I;
+}
+
+impl<A, I> IntoIr<I> for A
+where
+    I: FromAst<A>,
+{
+    fn into_ir(self, ctx: &mut Ctx, text: &str) -> I {
+        FromAst::from_ast(self, ctx, text)
+    }
+}