Base compilation of some kind of file to a list of instructions seems to work(!)

I'm able to compile some basic expressions into instructions using the
`not` binary. Big first step, now we need to introduce branches and
loops to the syntax.

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

src/bin/not.rs

@@ -1,4 +1,4 @@
-use not_python::syn::ast;
+use not_python::{syn::ast, compile::Compile};
 
 use std::{fs, path::PathBuf};
 use structopt::StructOpt;
@@ -31,8 +31,14 @@ fn main() -> Result<()> {
             }
             return Err("errors reported, exiting".into());
         }
-    };
-    println!("{:#?}", ast);
+    }.unwrap();
+    //println!("{:#?}", ast);
+
+    let mut compile = Compile::new();
+    let (inst, const_pool) = compile.compile(&ast)?;
+
+    println!("{:#?}", inst);
+    println!("{:#?}", const_pool);
 
     Ok(())
 }

src/compile/basic_block.rs

@@ -69,7 +69,10 @@ impl BasicBlockList {
                         body.push(Inst::Jump(addr));
                     }
                 }
-                BasicBlock::Branch { block_true, block_false } => {
+                BasicBlock::Branch {
+                    block_true,
+                    block_false,
+                } => {
                     // insert conditional jump to true statement, and unconditional jump to false
                     // statement
                     let addr_true = addr_rev[&block_true];
@@ -96,10 +99,22 @@ impl BasicBlockList {
         let mut blocks = Vec::with_capacity(self.len());
         let mut entry_map = BTreeMap::new();
         // first pass: add blocks to the "blocks" list, and map block indices
+        let mut last_block_index = 0;
         for (new_index, (index, block)) in self.blocks.into_iter().enumerate() {
+            // search for the largest block index referred to in here - that is the last block
+            match block {
+                BasicBlock::Block { exit, .. } => last_block_index = exit.max(last_block_index),
+                BasicBlock::Branch {
+                    block_true,
+                    block_false,
+                } => last_block_index = block_true.max(block_false.max(last_block_index)),
+            }
             blocks.push(block);
             entry_map.insert(index, new_index);
         }
+        // this inserts a "dummy" mapping for the last block index because it will point out of bounds
+        let last_index = entry_map.len();
+        entry_map.insert(dbg!(last_block_index), dbg!(last_index));
         // second pass: update blocks in-place with their newly mapped addresses
         blocks
             .into_iter()

src/compile/mod.rs

@@ -3,9 +3,10 @@ pub mod error;
 mod locals;
 pub mod thunk;
 
-use crate::{syn::ast::Body, obj::prelude::*, vm::consts::*};
+use crate::{syn::ast::Body, obj::prelude::*, vm::{consts::*, inst::Inst}};
 use std::collections::{BTreeMap, HashMap};
 
+#[derive(Default)]
 pub struct Compile {
     const_data: ConstData,
     globals: BTreeMap<Sym, Local>,
@@ -16,12 +17,16 @@ pub struct Compile {
 impl Compile {
     /// Creates a new compiler using the given text.
     pub fn new() -> Self {
-        Compile {
-            const_data: Default::default(),
-            globals: Default::default(),
-            locals: Default::default(),
-            next_local: Default::default(),
+        Default::default()
     }
+
+    /// Compiles the given AST body.
+    pub fn compile<'c>(&'c mut self, body: &Body) -> error::Result<(Vec<Inst>, &'c ConstPool)> {
+        let main = thunk::CompileBody::new(self)
+            .compile(body)?
+            .flatten()
+            .to_vec();
+        Ok((main, &self.const_data.const_pool))
     }
 
     /// Gets the constant data that is interned in this compile session.

src/compile/thunk.rs

@@ -234,7 +234,7 @@ impl Visit for CompileBody<'_> {
         self.compile.collect_locals(body);
         let mut thunk = Thunk::Nop;
 
-        for stmt in body.body.iter() {
+        for stmt in body.iter() {
             thunk.push_thunk(stmt.accept(self)?);
         }
 
@@ -347,7 +347,13 @@ impl Visit for CompileBody<'_> {
         let thunk = match atom {
             Atom::Ident(ident) => {
                 let sym = global_sym(ident.to_string());
-                let local = self.compile.lookup_scope(sym).unwrap();
+                let local = if let Some(local) = self.compile.lookup_scope(sym) {
+                    local
+                } else {
+                    // create a global that gets looked up instead, since nothing with this name
+                    // has been declared/assigned in this scope
+                    self.compile.create_global(sym)
+                };
                 // get local
                 Inst::PushLocal(local).into()
             }

src/syn/ast.rs

@@ -2,10 +2,7 @@ use crate::syn::visit::*;
 
 // TODO : add locations to parsed items
 
-#[derive(Debug, Clone, PartialEq, Eq)]
-pub struct Body {
-    pub body: Vec<Stmt>,
-}
+pub type Body = Vec<Stmt>;
 
 //
 // impl Accept for Body
@@ -18,8 +15,7 @@ impl<V: Visit> Accept<V> for Body {
 
 impl<V: Visit<Out=()>> DefaultAccept<V> for Body {
     fn default_accept(&self, visitor: &mut V) -> V::Out {
-        self.body
-            .iter()
+        self.iter()
             .for_each(|stmt| visitor.visit_stmt(stmt));
     }
 }