implement const

src/ast.rs

@@ -8,7 +8,8 @@ pub struct Script {
     pub global_vars: Vec<GlobalVar>,
     pub functions: Vec<Function>,
     pub data: Vec<Data>,
-    pub includes: Vec<Include>
+    pub includes: Vec<Include>,
+    pub consts: Vec<GlobalConst>,
 }
 
 impl Script {
@@ -17,6 +18,7 @@ impl Script {
         self.global_vars.append(&mut other.global_vars);
         self.functions.append(&mut other.functions);
         self.data.append(&mut other.data);
+        self.consts.append(&mut other.consts);
         assert!(other.includes.is_empty());
     }
 }
@@ -27,7 +29,8 @@ pub enum TopLevelItem {
     GlobalVar(GlobalVar),
     Function(Function),
     Data(Data),
-    Include(Include)
+    Include(Include),
+    Const(GlobalConst),
 }
 
 #[derive(Debug)]
@@ -67,6 +70,14 @@ pub struct GlobalVar {
     pub mutable: bool,
 }
 
+#[derive(Debug)]
+pub struct GlobalConst {
+    pub span: Span,
+    pub name: String,
+    pub value: Expression,
+    pub type_: Option<Type>,
+}
+
 #[derive(Debug)]
 pub struct Function {
     pub span: Span,
@@ -170,7 +181,7 @@ pub enum DataType {
     F64,
 }
 
-#[derive(Debug)]
+#[derive(Debug, Clone)]
 pub struct MemoryLocation {
     pub span: Span,
     pub size: MemSize,
@@ -178,7 +189,7 @@ pub struct MemoryLocation {
     pub right: Box<Expression>,
 }
 
-#[derive(Debug)]
+#[derive(Debug, Clone)]
 pub struct Expression {
     pub type_: Option<Type>,
     pub expr: Expr,
@@ -213,9 +224,16 @@ impl Expression {
             _ => panic!("Expected F64Const"),
         }
     }
+
+    pub fn is_const(&self) -> bool {
+        match self.expr {
+            Expr::I32Const(_) | Expr::I64Const(_) | Expr::F32Const(_) | Expr::F64Const(_) => true,
+            _ => false,
+        }
+    }
 }
 
-#[derive(Debug)]
+#[derive(Debug, Clone)]
 pub enum Expr {
     Block {
         statements: Vec<Expression>,
@@ -355,7 +373,7 @@ pub enum BinOp {
 pub enum MemSize {
     Byte,
     Word,
-    Float
+    Float,
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Ord, PartialOrd)]

src/constfold.rs

@@ -1,35 +1,103 @@
-use crate::ast;
+use std::collections::HashMap;
+
+use crate::{
+    ast,
+    parser::{Sources, Span},
+    typecheck::{report_duplicate_definition, report_error},
+};
+
+type Result<T> = std::result::Result<T, ()>;
+
+pub fn fold_script(script: &mut ast::Script, sources: &Sources) -> Result<()> {
+    let mut context = Context {
+        consts: HashMap::new(),
+        sources,
+    };
+    fold_consts(&mut context, &mut script.consts)?;
 
-pub fn fold_script(script: &mut ast::Script) {
     for var in &mut script.global_vars {
-        fold_expr(&mut var.value);
+        fold_expr(&context, &mut var.value);
     }
 
     for func in &mut script.functions {
-        fold_expr(&mut func.body);
+        fold_expr(&context, &mut func.body);
     }
 
     for data in &mut script.data {
-        fold_expr(&mut data.offset);
+        fold_expr(&context, &mut data.offset);
         for values in &mut data.data {
             match values {
                 ast::DataValues::Array { values, .. } => {
                     for value in values {
-                        fold_expr(value);
+                        fold_expr(&context, value);
                     }
                 }
                 ast::DataValues::String(_) | ast::DataValues::File { .. } => (),
             }
         }
     }
+
+    Ok(())
 }
 
-fn fold_mem_location(mem_location: &mut ast::MemoryLocation) {
-    fold_expr(&mut mem_location.left);
-    fold_expr(&mut mem_location.right);
+struct Context<'a> {
+    consts: HashMap<String, ast::Expr>,
+    sources: &'a Sources,
 }
 
-fn fold_expr(expr: &mut ast::Expression) {
+fn fold_consts(context: &mut Context, consts: &mut [ast::GlobalConst]) -> Result<()> {
+    let mut spans: HashMap<&str, Span> = HashMap::new();
+
+    for cnst in consts.iter_mut() {
+        if let Some(prev_span) = spans.insert(&cnst.name, cnst.span.clone()) {
+            report_duplicate_definition(
+                "Const already defined",
+                &cnst.span,
+                &prev_span,
+                context.sources,
+            )?;
+        }
+    }
+
+    while context.consts.len() < consts.len() {
+        let mut making_progress = false;
+        for cnst in consts.iter_mut() {
+            if !context.consts.contains_key(&cnst.name) {
+                fold_expr(context, &mut cnst.value);
+                if cnst.value.is_const() {
+                    context
+                        .consts
+                        .insert(cnst.name.clone(), cnst.value.expr.clone());
+                    making_progress = true;
+                }
+            }
+        }
+
+        if !making_progress {
+            break;
+        }
+    }
+
+    let mut result = Ok(());
+    for cnst in consts {
+        if !context.consts.contains_key(&cnst.name) {
+            result = report_error(
+                &format!("Failed to fold const '{}'", cnst.name),
+                &cnst.span,
+                context.sources,
+            );
+        }
+    }
+
+    result
+}
+
+fn fold_mem_location(context: &Context, mem_location: &mut ast::MemoryLocation) {
+    fold_expr(context, &mut mem_location.left);
+    fold_expr(context, &mut mem_location.right);
+}
+
+fn fold_expr(context: &Context, expr: &mut ast::Expression) {
     use ast::BinOp::*;
     match expr.expr {
         ast::Expr::Block {
@@ -37,15 +105,15 @@ fn fold_expr(expr: &mut ast::Expression) {
             ref mut final_expression,
         } => {
             for stmt in statements {
-                fold_expr(stmt);
+                fold_expr(context, stmt);
             }
             if let Some(ref mut expr) = final_expression {
-                fold_expr(expr);
+                fold_expr(context, expr);
             }
         }
         ast::Expr::Let { ref mut value, .. } => {
             if let Some(ref mut expr) = value {
-                fold_expr(expr);
+                fold_expr(context, expr);
             }
         }
         ast::Expr::Poke {
@@ -53,12 +121,12 @@ fn fold_expr(expr: &mut ast::Expression) {
             ref mut value,
             ..
         } => {
-            fold_mem_location(mem_location);
-            fold_expr(value);
+            fold_mem_location(context, mem_location);
+            fold_expr(context, value);
         }
-        ast::Expr::Peek(ref mut mem_location) => fold_mem_location(mem_location),
+        ast::Expr::Peek(ref mut mem_location) => fold_mem_location(context, mem_location),
         ast::Expr::UnaryOp { op, ref mut value } => {
-            fold_expr(value);
+            fold_expr(context, value);
             let result = match (op, &value.expr) {
                 (ast::UnaryOp::Negate, ast::Expr::I32Const(value)) => {
                     Some(ast::Expr::I32Const(-*value))
@@ -90,8 +158,8 @@ fn fold_expr(expr: &mut ast::Expression) {
             ref mut right,
             ..
         } => {
-            fold_expr(left);
-            fold_expr(right);
+            fold_expr(context, left);
+            fold_expr(context, right);
             match (&left.expr, &right.expr) {
                 (&ast::Expr::I32Const(left), &ast::Expr::I32Const(right)) => {
                     let result = match op {
@@ -237,24 +305,28 @@ fn fold_expr(expr: &mut ast::Expression) {
         ast::Expr::I32Const(_)
         | ast::Expr::I64Const(_)
         | ast::Expr::F32Const(_)
-        | ast::Expr::F64Const(_)
-        | ast::Expr::Variable { .. } => (),
-        ast::Expr::Assign { ref mut value, .. } => fold_expr(value),
-        ast::Expr::LocalTee { ref mut value, .. } => fold_expr(value),
-        ast::Expr::Loop { ref mut block, .. } => fold_expr(block),
-        ast::Expr::LabelBlock { ref mut block, .. } => fold_expr(block),
+        | ast::Expr::F64Const(_) => (),
+        ast::Expr::Variable { ref name, .. } => {
+            if let Some(value) = context.consts.get(name) {
+                expr.expr = value.clone();
+            }
+        }
+        ast::Expr::Assign { ref mut value, .. } => fold_expr(context, value),
+        ast::Expr::LocalTee { ref mut value, .. } => fold_expr(context, value),
+        ast::Expr::Loop { ref mut block, .. } => fold_expr(context, block),
+        ast::Expr::LabelBlock { ref mut block, .. } => fold_expr(context, block),
         ast::Expr::Branch(_) => (),
         ast::Expr::BranchIf {
             ref mut condition, ..
-        } => fold_expr(condition),
-        ast::Expr::Cast { ref mut value, .. } => fold_expr(value),
+        } => fold_expr(context, condition),
+        ast::Expr::Cast { ref mut value, .. } => fold_expr(context, value),
         ast::Expr::FuncCall {
             ref name,
             ref mut params,
             ..
         } => {
             for param in params.iter_mut() {
-                fold_expr(param);
+                fold_expr(context, param);
             }
             use ast::Expr::*;
             let params: Vec<_> = params.iter().map(|e| &e.expr).collect();
@@ -269,31 +341,31 @@ fn fold_expr(expr: &mut ast::Expression) {
             ref mut if_false,
             ..
         } => {
-            fold_expr(condition);
-            fold_expr(if_true);
-            fold_expr(if_false);
+            fold_expr(context, condition);
+            fold_expr(context, if_true);
+            fold_expr(context, if_false);
         }
         ast::Expr::If {
             ref mut condition,
             ref mut if_true,
             ref mut if_false,
         } => {
-            fold_expr(condition);
-            fold_expr(if_true);
+            fold_expr(context, condition);
+            fold_expr(context, if_true);
             if let Some(ref mut if_false) = if_false {
-                fold_expr(if_false);
+                fold_expr(context, if_false);
             }
         }
         ast::Expr::Return {
             value: Some(ref mut value),
-        } => fold_expr(value),
+        } => fold_expr(context, value),
         ast::Expr::Return { value: None } => (),
         ast::Expr::First {
             ref mut value,
             ref mut drop,
         } => {
-            fold_expr(value);
-            fold_expr(drop);
+            fold_expr(context, value);
+            fold_expr(context, drop);
         }
         ast::Expr::Error => unreachable!(),
     }

src/lib.rs

@@ -1,7 +1,7 @@
 use anyhow::{bail, Result};
+use parser::Sources;
 use std::ffi::OsStr;
 use std::path::Path;
-use parser::Sources;
 
 mod ast;
 mod constfold;
@@ -36,15 +36,18 @@ pub fn compile_file<P: AsRef<Path>>(path: P, options: Options) -> Result<Vec<u8>
                     Ok(script) => script,
                     Err(_) => bail!("Parse failed"),
                 };
-            
+
                 includes::resolve_includes(&mut new_script, &path)?;
-    
+
                 for include in std::mem::take(&mut new_script.includes) {
-                    let mut path = path.parent().expect("Script path has no parent").to_path_buf();
+                    let mut path = path
+                        .parent()
+                        .expect("Script path has no parent")
+                        .to_path_buf();
                     path.push(include.path);
                     pending_files.push((path, Some(include.span)));
                 }
-    
+
                 script.merge(new_script);
             }
             Ok((_, false)) => (), // already parsed this include
@@ -59,8 +62,9 @@ pub fn compile_file<P: AsRef<Path>>(path: P, options: Options) -> Result<Vec<u8>
         }
     }
 
-
-    constfold::fold_script(&mut script);
+    if constfold::fold_script(&mut script, &sources).is_err() {
+        bail!("Constant folding failed");
+    }
     if typecheck::tc_script(&mut script, &sources).is_err() {
         bail!("Type check failed");
     }

src/parser.rs

@@ -925,6 +925,21 @@ fn script_parser() -> impl Parser<Token, ast::Script, Error = ScriptError> + Clo
             })
             .boxed();
 
+        let global_const = just(Token::Ident("const".to_string()))
+            .ignore_then(identifier)
+            .then(just(Token::Ctrl(':')).ignore_then(type_parser()).or_not())
+            .then(just(Token::Op("=".to_string())).ignore_then(expression.clone()))
+            .then_ignore(just(Token::Ctrl(';')))
+            .map_with_span(|((name, type_), value), span| {
+                ast::TopLevelItem::Const(ast::GlobalConst {
+                    name,
+                    type_,
+                    value,
+                    span,
+                })
+            })
+            .boxed();
+
         let data_i8 = just(Token::Ident("i8".to_string()))
             .to(ast::DataType::I8)
             .or(just(Token::Ident("i16".to_string())).to(ast::DataType::I16))
@@ -975,17 +990,17 @@ fn script_parser() -> impl Parser<Token, ast::Script, Error = ScriptError> + Clo
                 |path, span| ast::TopLevelItem::Include(ast::Include { span, path }),
             ));
 
-        import.or(function).or(global).or(data).or(include).boxed()
+        import
+            .or(function)
+            .or(global)
+            .or(data)
+            .or(include)
+            .or(global_const)
+            .boxed()
     };
 
     top_level_item.repeated().then_ignore(end()).map(|items| {
-        let mut script = ast::Script {
-            imports: Vec::new(),
-            global_vars: Vec::new(),
-            functions: Vec::new(),
-            data: Vec::new(),
-            includes: Vec::new(),
-        };
+        let mut script = ast::Script::default();
         for item in items {
             match item {
                 ast::TopLevelItem::Import(i) => script.imports.push(i),
@@ -993,6 +1008,7 @@ fn script_parser() -> impl Parser<Token, ast::Script, Error = ScriptError> + Clo
                 ast::TopLevelItem::Function(f) => script.functions.push(f),
                 ast::TopLevelItem::Data(d) => script.data.push(d),
                 ast::TopLevelItem::Include(i) => script.includes.push(i),
+                ast::TopLevelItem::Const(c) => script.consts.push(c),
             }
         }
         script

src/typecheck.rs

@@ -298,7 +298,7 @@ impl LocalVars {
     }
 }
 
-fn report_duplicate_definition(
+pub fn report_duplicate_definition(
     msg: &str,
     span: &Span,
     prev_span: &Span,