implement type checking and constand folding for simple example

src/ast.rs

@@ -3,7 +3,8 @@ pub struct Position(pub usize);
 
 #[derive(Debug)]
 pub struct Script<'a> {
-    pub items: Vec<TopLevelItem<'a>>,
+    pub global_vars: Vec<GlobalVar<'a>>,
+    pub functions: Vec<Function<'a>>
 }
 
 #[derive(Debug)]
@@ -40,6 +41,7 @@ pub struct Block<'a> {
 pub enum Statement<'a> {
     LocalVariable(LocalVariable<'a>),
     Poke {
+        position: Position,
         mem_location: MemoryLocation<'a>,
         value: Expression<'a>,
     },
@@ -63,7 +65,19 @@ pub struct LocalVariable<'a> {
 }
 
 #[derive(Debug)]
-pub enum Expression<'a> {
+pub struct Expression<'a> {
+    pub type_: Option<Type>,
+    pub expr: Expr<'a>,
+}
+
+impl<'a> From<Expr<'a>> for Expression<'a> {
+    fn from(expr: Expr<'a>) -> Expression<'a> {
+        Expression { type_: None, expr }
+    }
+}
+
+#[derive(Debug)]
+pub enum Expr<'a> {
     I32Const(i32),
     Variable {
         position: Position,
@@ -92,7 +106,7 @@ pub enum Expression<'a> {
     },
 }
 
-#[derive(Debug)]
+#[derive(Debug, Clone, Copy)]
 pub enum BinOp {
     Add,
     Sub,

src/constfold.rs

@@ -0,0 +1,77 @@
+use crate::ast;
+
+pub fn fold_script(script: &mut ast::Script) {
+    for func in &mut script.functions {
+        fold_block(&mut func.body);
+    }
+}
+
+fn fold_block(block: &mut ast::Block) {
+    for stmt in &mut block.statements {
+        match stmt {
+            ast::Statement::LocalVariable(lv) => {
+                if let Some(ref mut expr) = lv.value {
+                    fold_expr(expr);
+                }
+            }
+            ast::Statement::Expression(expr) => fold_expr(expr),
+            ast::Statement::Poke {
+                mem_location,
+                value,
+                ..
+            } => {
+                fold_mem_location(mem_location);
+                fold_expr(value);
+            }
+        }
+    }
+    if let Some(ref mut expr) = block.final_expression {
+        fold_expr(expr);
+    }
+}
+
+fn fold_mem_location(mem_location: &mut ast::MemoryLocation) {
+    fold_expr(&mut mem_location.left);
+    fold_expr(&mut mem_location.right);
+}
+
+fn fold_expr(expr: &mut ast::Expression) {
+    use ast::BinOp::*;
+    match expr.expr {
+        ast::Expr::BinOp {
+            ref mut left, op, ref mut right, ..
+        } => {
+            fold_expr(left);
+            fold_expr(right);
+            dbg!(&left.expr, &right.expr);
+            match (&left.expr, &right.expr) {
+                (&ast::Expr::I32Const(left), &ast::Expr::I32Const(right)) => {
+                    let result = match op {
+                        Add => left.wrapping_add(right),
+                        Sub => left.wrapping_sub(right),
+                        Mul => left.wrapping_mul(right),
+                        Div => left / right, // TODO: protect agains division by zero
+                        Rem => left % right, // TODO: check correct behavior with negative operands
+                        And => left & right,
+                        Or => left | right,
+                        Xor => left ^ right,
+                        Eq => (left == right) as i32,
+                        Ne => (left != right) as i32,
+                        Lt => (left < right) as i32,
+                        Le => (left <= right) as i32,
+                        Gt => (left > right) as i32,
+                        Ge => (left >= right) as i32,
+                    };
+                    expr.expr = ast::Expr::I32Const(result);
+                }
+                _ => ()
+            }
+        }
+        ast::Expr::I32Const(_) | ast::Expr::Variable { .. } => (),
+        ast::Expr::LocalTee { ref mut value, .. } => fold_expr(value),
+        ast::Expr::Loop { ref mut block, .. } => fold_block(block),
+        ast::Expr::BranchIf {
+            ref mut condition, ..
+        } => fold_expr(condition),
+    }
+}

src/main.rs

@@ -1,11 +1,17 @@
 mod parser;
 mod ast;
+mod typecheck;
+mod constfold;
 
 fn main() {
     let input = include_str!("../test.hw");
     let result = parser::parse(input);
     match result {
-        Ok(script) => {dbg!(script);},
+        Ok(mut script) => {
+            constfold::fold_script(&mut script);
+            typecheck::tc_script(&mut script).unwrap();
+            dbg!(script);
+        },
         Err(err) => println!("error: {}", nom::error::convert_error(input, err))
     }
 }

src/parser.rs

@@ -19,7 +19,21 @@ pub fn parse(s: &str) -> Result<ast::Script, VerboseError<&str>> {
 
 fn script(s: &str) -> IResult<ast::Script> {
     let (s, items) = many0(top_level_item)(s)?;
-    Ok((s, ast::Script { items }))
+    let mut global_vars = vec![];
+    let mut functions = vec![];
+    for item in items {
+        match item {
+            ast::TopLevelItem::GlobalVar(v) => global_vars.push(v),
+            ast::TopLevelItem::Function(f) => functions.push(f),
+        }
+    }
+    Ok((
+        s,
+        ast::Script {
+            global_vars,
+            functions,
+        },
+    ))
 }
 
 fn top_level_item(s: &str) -> IResult<ast::TopLevelItem> {
@@ -88,7 +102,7 @@ fn block(s: &str) -> IResult<ast::Block> {
         s,
         ast::Block {
             statements,
-            final_expression,
+            final_expression: final_expression.map(|e| e.into()),
         },
     ))
 }
@@ -96,22 +110,25 @@ fn block(s: &str) -> IResult<ast::Block> {
 fn statement(s: &str) -> IResult<ast::Statement> {
     alt((
         map(local_var, ast::Statement::LocalVariable),
-        map(
-            terminated(expression, ws(char(';'))),
-            ast::Statement::Expression,
-        ),
+        map(terminated(expression, ws(char(';'))), |e| {
+            ast::Statement::Expression(e.into())
+        }),
         map(
             terminated(block_expression, not(peek(ws(char('}'))))),
-            ast::Statement::Expression,
+            |e| ast::Statement::Expression(e.into()),
         ),
         map(
             terminated(
-                pair(mem_location, preceded(ws(char('=')), expression)),
+                pair(
+                    mem_location,
+                    ws(pair(position, preceded(char('='), expression))),
+                ),
                 ws(char(';')),
             ),
-            |(mem_location, value)| ast::Statement::Poke {
+            |(mem_location, (position, value))| ast::Statement::Poke {
+                position,
                 mem_location,
-                value,
+                value: value.into(),
             },
         ),
     ))(s)
@@ -131,7 +148,7 @@ fn local_var(s: &str) -> IResult<ast::LocalVariable> {
             position,
             name: name,
             type_,
-            value,
+            value: value.map(|v| v.into()),
         },
     ))
 }
@@ -151,31 +168,31 @@ fn mem_location(s: &str) -> IResult<ast::MemoryLocation> {
         ast::MemoryLocation {
             position,
             size,
-            left,
-            right,
+            left: left.into(),
+            right: right.into(),
         },
     ))
 }
 
-fn expression(s: &str) -> IResult<ast::Expression> {
+fn expression(s: &str) -> IResult<ast::Expr> {
     expression_cmp(s)
 }
 
-fn expression_atom(s: &str) -> IResult<ast::Expression> {
+fn expression_atom(s: &str) -> IResult<ast::Expr> {
     alt((
         branch_if,
         block_expression,
         map(
             separated_pair(pair(ws(position), identifier), ws(tag(":=")), expression),
-            |((position, name), value)| ast::Expression::LocalTee {
+            |((position, name), value)| ast::Expr::LocalTee {
                 position,
                 name: name,
-                value: Box::new(value),
+                value: Box::new(value.into()),
             },
         ),
-        map(integer, |v| ast::Expression::I32Const(v)),
+        map(integer, |v| ast::Expr::I32Const(v)),
         map(ws(pair(position, identifier)), |(position, name)| {
-            ast::Expression::Variable {
+            ast::Expr::Variable {
                 position,
                 name: name,
             }
@@ -184,7 +201,7 @@ fn expression_atom(s: &str) -> IResult<ast::Expression> {
     ))(s)
 }
 
-fn branch_if(s: &str) -> IResult<ast::Expression> {
+fn branch_if(s: &str) -> IResult<ast::Expr> {
     let (s, position) = ws(position)(s)?;
     let (s, _) = tag("branch_if")(s)?;
     cut(move |s| {
@@ -194,16 +211,16 @@ fn branch_if(s: &str) -> IResult<ast::Expression> {
 
         Ok((
             s,
-            ast::Expression::BranchIf {
+            ast::Expr::BranchIf {
                 position,
-                condition: Box::new(condition),
+                condition: Box::new(condition.into()),
                 label: label,
             },
         ))
     })(s)
 }
 
-fn expression_product(s: &str) -> IResult<ast::Expression> {
+fn expression_product(s: &str) -> IResult<ast::Expr> {
     let (s, mut init) = map(expression_atom, Some)(s)?;
     fold_many0(
         pair(
@@ -218,17 +235,17 @@ fn expression_product(s: &str) -> IResult<ast::Expression> {
                 '%' => ast::BinOp::Rem,
                 _ => unreachable!(),
             };
-            ast::Expression::BinOp {
+            ast::Expr::BinOp {
                 position,
                 op,
-                left: Box::new(left),
-                right: Box::new(right),
+                left: Box::new(left.into()),
+                right: Box::new(right.into()),
             }
         },
     )(s)
 }
 
-fn expression_sum(s: &str) -> IResult<ast::Expression> {
+fn expression_sum(s: &str) -> IResult<ast::Expr> {
     let (s, mut init) = map(expression_product, Some)(s)?;
     fold_many0(
         pair(
@@ -242,17 +259,17 @@ fn expression_sum(s: &str) -> IResult<ast::Expression> {
             } else {
                 ast::BinOp::Sub
             };
-            ast::Expression::BinOp {
+            ast::Expr::BinOp {
                 position,
                 op,
-                left: Box::new(left),
-                right: Box::new(right),
+                left: Box::new(left.into()),
+                right: Box::new(right.into()),
             }
         },
     )(s)
 }
 
-fn expression_bit(s: &str) -> IResult<ast::Expression> {
+fn expression_bit(s: &str) -> IResult<ast::Expr> {
     let (s, mut init) = map(expression_sum, Some)(s)?;
     fold_many0(
         pair(
@@ -267,17 +284,17 @@ fn expression_bit(s: &str) -> IResult<ast::Expression> {
                 '^' => ast::BinOp::Xor,
                 _ => unreachable!(),
             };
-            ast::Expression::BinOp {
+            ast::Expr::BinOp {
                 position,
                 op,
-                left: Box::new(left),
-                right: Box::new(right),
+                left: Box::new(left.into()),
+                right: Box::new(right.into()),
             }
         },
     )(s)
 }
 
-fn expression_cmp(s: &str) -> IResult<ast::Expression> {
+fn expression_cmp(s: &str) -> IResult<ast::Expr> {
     let (s, mut init) = map(expression_bit, Some)(s)?;
     fold_many0(
         pair(
@@ -305,21 +322,21 @@ fn expression_cmp(s: &str) -> IResult<ast::Expression> {
                 ">" => ast::BinOp::Gt,
                 _ => unreachable!(),
             };
-            ast::Expression::BinOp {
+            ast::Expr::BinOp {
                 position,
                 op,
-                left: Box::new(left),
-                right: Box::new(right),
+                left: Box::new(left.into()),
+                right: Box::new(right.into()),
             }
         },
     )(s)
 }
 
-fn block_expression(s: &str) -> IResult<ast::Expression> {
+fn block_expression(s: &str) -> IResult<ast::Expr> {
     loop_(s)
 }
 
-fn loop_(s: &str) -> IResult<ast::Expression> {
+fn loop_(s: &str) -> IResult<ast::Expr> {
     let (s, position) = ws(position)(s)?;
     let (s, _) = tag("loop")(s)?;
     cut(move |s| {
@@ -328,10 +345,10 @@ fn loop_(s: &str) -> IResult<ast::Expression> {
 
         Ok((
             s,
-            ast::Expression::Loop {
+            ast::Expr::Loop {
                 position,
                 label: label,
-                block: Box::new(block),
+                block: Box::new(block.into()),
             },
         ))
     })(s)

src/typecheck.rs

@@ -0,0 +1,217 @@
+use std::collections::HashMap;
+
+use crate::ast;
+use ast::Type::*;
+
+#[derive(Debug)]
+pub struct Error {
+    pub position: ast::Position,
+    pub message: String,
+}
+
+type Result<T> = std::result::Result<T, Error>;
+
+type Vars<'a> = HashMap<&'a str, ast::Type>;
+
+pub fn tc_script(script: &mut ast::Script) -> Result<()> {
+    let mut context = Context {
+        global_vars: HashMap::new(),
+        local_vars: HashMap::new(),
+    };
+
+    for v in &script.global_vars {
+        if context.global_vars.contains_key(v.name) {
+            return Err(Error {
+                position: v.position,
+                message: "Duplicate global variable".into(),
+            });
+        }
+        context.global_vars.insert(v.name, v.type_);
+    }
+
+    for f in &mut script.functions {
+        context.local_vars.clear();
+        for (name, type_) in &f.params {
+            if context.local_vars.contains_key(name) || context.global_vars.contains_key(name) {
+                return Err(Error {
+                    position: f.position,
+                    message: format!("Variable already defined '{}'", name),
+                });
+            }
+            context.local_vars.insert(name, *type_);
+        }
+
+        tc_block(&mut context, &mut f.body)?;
+    }
+
+    Ok(())
+}
+
+struct Context<'a> {
+    global_vars: Vars<'a>,
+    local_vars: Vars<'a>,
+}
+
+fn tc_block<'a>(context: &mut Context<'a>, block: &mut ast::Block<'a>) -> Result<()> {
+    for stmt in &mut block.statements {
+        match *stmt {
+            ast::Statement::Expression(ref mut expr) => tc_expression(context, expr)?,
+            ast::Statement::LocalVariable(ref mut lv) => {
+                if let Some(ref mut value) = lv.value {
+                    tc_expression(context, value)?;
+                    if lv.type_.is_none() {
+                        lv.type_ = value.type_;
+                    } else if lv.type_ != value.type_ {
+                        return Err(Error {
+                            position: lv.position,
+                            message: "Mismatched types".into(),
+                        });
+                    }
+                }
+                if let Some(type_) = lv.type_ {
+                    if context.local_vars.contains_key(lv.name)
+                        || context.global_vars.contains_key(lv.name)
+                    {
+                        return Err(Error {
+                            position: lv.position,
+                            message: format!("Variable '{}' already defined", lv.name),
+                        });
+                    }
+                    context.local_vars.insert(lv.name, type_);
+                } else {
+                    return Err(Error {
+                        position: lv.position,
+                        message: "Missing type".into(),
+                    });
+                }
+            }
+            ast::Statement::Poke {
+                position,
+                ref mut mem_location,
+                ref mut value,
+            } => {
+                tc_mem_location(context, mem_location)?;
+                tc_expression(context, value)?;
+                if value.type_ != Some(I32) {
+                    return Err(Error {
+                        position,
+                        message: "Type mismatch".into(),
+                    });
+                }
+            }
+        }
+    }
+    if let Some(ref mut expr) = block.final_expression {
+        tc_expression(context, expr)?;
+    }
+    Ok(())
+}
+
+fn tc_expression<'a>(context: &mut Context<'a>, expr: &mut ast::Expression<'a>) -> Result<()> {
+    expr.type_ = match expr.expr {
+        ast::Expr::I32Const(_) => Some(ast::Type::I32),
+        ast::Expr::BinOp {
+            position,
+            op,
+            ref mut left,
+            ref mut right,
+        } => {
+            tc_expression(context, left)?;
+            tc_expression(context, right)?;
+            if left.type_.is_none() || left.type_ != right.type_ {
+                return Err(Error {
+                    position,
+                    message: "Type mismatch".into(),
+                });
+            }
+            use ast::BinOp::*;
+            match op {
+                Add | Sub | Mul | Div => left.type_,
+                Rem | And | Or | Xor => {
+                    if left.type_ != Some(I32) {
+                        return Err(Error {
+                            position,
+                            message: "Unsupported type".into(),
+                        });
+                    } else {
+                        left.type_
+                    }
+                }
+                Eq | Ne | Lt | Le | Gt | Ge => Some(I32),
+            }
+        }
+        ast::Expr::Variable { position, name } => {
+            if let Some(&type_) = context
+                .global_vars
+                .get(name)
+                .or_else(|| context.local_vars.get(name))
+            {
+                Some(type_)
+            } else {
+                return Err(Error {
+                    position,
+                    message: "Variable not found".into(),
+                });
+            }
+        }
+        ast::Expr::LocalTee {
+            position,
+            name,
+            ref mut value,
+        } => {
+            tc_expression(context, value)?;
+            if let Some(&type_) = context.local_vars.get(name) {
+                if value.type_ != Some(type_) {
+                    return Err(Error {
+                        position,
+                        message: "Type mismatch".into(),
+                    });
+                }
+                Some(type_)
+            } else {
+                return Err(Error {
+                    position,
+                    message: format!("No local variable '{}' found", name),
+                });
+            }
+        }
+        ast::Expr::Loop {
+            position: _,
+            label: _,
+            ref mut block,
+        } => {
+            tc_block(context, block)?;
+            block.final_expression.as_ref().and_then(|e| e.type_)
+        }
+        ast::Expr::BranchIf {
+            position,
+            ref mut condition,
+            label: _,
+        } => {
+            tc_expression(context, condition)?;
+            if condition.type_ != Some(I32) {
+                return Err(Error {
+                    position,
+                    message: "Condition has to be i32".into(),
+                });
+            }
+            None
+        }
+    };
+    Ok(())
+}
+
+fn tc_mem_location<'a>(
+    context: &mut Context<'a>,
+    mem_location: &mut ast::MemoryLocation<'a>,
+) -> Result<()> {
+    tc_expression(context, &mut mem_location.left)?;
+    tc_expression(context, &mut mem_location.right)?;
+    if mem_location.left.type_ != Some(I32) || mem_location.right.type_ != Some(I32) {
+        return Err(Error {
+            position: mem_location.position,
+            message: "Type mismatch".into(),
+        });
+    }
+    Ok(())
+}