typecheck: infere type from rhs in assignments

3 files changed, 28 insertions, 3 deletions

diff --git a/src/compiler.rs b/src/compiler.rs
index 3a4181b..df816c9 100644
--- a/src/compiler.rs
+++ b/src/compiler.rs
@@ -504,8 +504,9 @@ impl Compiler {
     }
 
     fn definition_statement(&mut self, name: &str, typ: Type, block: &mut Block) {
-        let slot = self.define_variable(name, typ, block);
+        let slot = self.define_variable(name, typ.clone(), block);
         self.expression(block);
+        block.add(Op::Define(typ), self.line());
 
         if let Ok(slot) = slot {
             self.stack_mut()[slot].active = true;
diff --git a/src/typer.rs b/src/typer.rs
index 4e023e4..d6692d8 100644
--- a/src/typer.rs
+++ b/src/typer.rs
@@ -259,8 +259,28 @@ impl VM {
                             }
                         }
                         (lhs, rhs) if lhs == rhs => {},
-                        (lhs, rhs) => error!(self, ErrorKind::TypeError(op.clone(),
-                                            vec![lhs.clone(), rhs.clone()])),
+                        (lhs, rhs) => error!(self,
+                                             ErrorKind::TypeError(
+                                                 op.clone(),
+                                                 vec![lhs.clone(), rhs.clone()]
+                                             )),
+                    }
+                }
+
+                Op::Define(ref ty) => {
+                    let top_type = self.stack.last().unwrap();
+                    match (ty, top_type) {
+                        (Type::UnkownType, top_type)
+                            if top_type != &Type::UnkownType => {}
+                        (a, b) if a != b => {
+                            error!(self,
+                                   ErrorKind::TypeError(
+                                       op.clone(),
+                                       vec![a.clone(), b.clone()]),
+                                   format!("Tried to assign a type {:?} to type {:?}.", a, b)
+                            );
+                        }
+                        _ => {}
                     }
                 }
 
diff --git a/src/vm.rs b/src/vm.rs
index 3750690..0b9195d 100644
--- a/src/vm.rs
+++ b/src/vm.rs
@@ -69,6 +69,8 @@ pub enum Op {
     ReadLocal(usize),
     Assign(usize),
 
+    Define(Type),
+
     Call(usize),
 
     Print,
@@ -401,6 +403,8 @@ impl VM {
                     self.stack[slot] = self.stack.pop().unwrap();
                 }
 
+                Op::Define(_) => {}
+
                 Op::Call(num_args) => {
                     let new_base = self.stack.len() - 1 - num_args;
                     match &self.stack[new_base] {