implementing inference

nac3type/src/inference.rs

@@ -0,0 +1,107 @@
+use super::types::{Type::*, *};
+use std::collections::HashMap;
+use std::rc::Rc;
+
+fn find_subst(
+    ctx: &GlobalContext,
+    assumptions: & HashMap<VariableId, Rc<Type>>,
+    sub: &mut HashMap<VariableId, Rc<Type>>,
+    mut a: Rc<Type>,
+    mut b: Rc<Type>,
+) -> Result<(), String> {
+    // TODO: fix error messages later
+    if let TypeVariable(id) = a.as_ref() {
+        if let Some(c) = assumptions.get(&id) {
+            a = c.clone();
+        }
+    }
+
+    if let TypeVariable(id) = b.as_ref() {
+        if let Some(c) = sub.get(&id) {
+            b = c.clone();
+        }
+    }
+
+    match (a.as_ref(), b.as_ref()) {
+        (BotType, _) => Ok(()),
+        (TypeVariable(id_a), TypeVariable(id_b)) => {
+            let v_a = ctx.get_variable(*id_a);
+            let v_b = ctx.get_variable(*id_b);
+            if v_b.bound.len() > 0 {
+                if v_a.bound.len() == 0 {
+                    return Err("unbounded a".to_string());
+                } else {
+                    let diff: Vec<_> = v_a
+                        .bound
+                        .iter()
+                        .filter(|x| !v_b.bound.contains(x))
+                        .collect();
+                    if diff.len() > 0 {
+                        return Err("different domain".to_string());
+                    }
+                }
+            }
+            sub.insert(*id_b, a.clone().into());
+            Ok(())
+        }
+        (TypeVariable(id_a), _) => {
+            let v_a = ctx.get_variable(*id_a);
+            if v_a.bound.len() == 1 && &v_a.bound[0] == b.as_ref() {
+                Ok(())
+            } else {
+                Err("different domain".to_string())
+            }
+        }
+        (_, TypeVariable(id_b)) => {
+            let v_b = ctx.get_variable(*id_b);
+            if v_b.bound.len() == 0 || v_b.bound.contains(&a) {
+                sub.insert(*id_b, a.clone().into());
+                Ok(())
+            } else {
+                Err("different domain".to_string())
+            }
+        }
+        (_, VirtualClassType(id_b)) => {
+            let mut parents;
+            match a.as_ref() {
+                ClassType(id_a) => {
+                    parents = [*id_a].to_vec();
+                }
+                VirtualClassType(id_a) => {
+                    let a = ctx.get_class(*id_a);
+                    parents = a.parents.clone();
+                }
+                _ => {
+                    return Err("cannot substitute non-class type into virtual class".to_string());
+                }
+            };
+            while !parents.is_empty() {
+                if *id_b == parents[0] {
+                    return Ok(());
+                }
+                let c = ctx.get_class(parents.remove(0));
+                parents.extend_from_slice(&c.parents);
+            }
+            Err("not subtype".to_string())
+        },
+        (ParametricType(id_a, param_a), ParametricType(id_b, param_b)) => {
+            if id_a != id_b || param_a.len() != param_b.len() {
+                Err("different parametric types".to_string())
+            } else {
+                for (x, y) in param_a.iter().zip(param_b.iter()) {
+                    find_subst(ctx, assumptions, sub, x.clone(), y.clone())?;
+                }
+                Ok(())
+            }
+        },
+        (_, _) => {
+            if a == b {
+                Ok(())
+            } else {
+                Err("not equal".to_string())
+            }
+        }
+    }
+}
+
+

nac3type/src/lib.rs

@@ -1,5 +1,5 @@
 extern crate rustpython_parser;
 
-
 mod types;
+mod inference;
 

nac3type/src/types.rs

@@ -1,25 +1,26 @@
 use std::collections::HashMap;
+use std::rc::Rc;
 
-#[derive(PartialEq, Eq, Copy, Clone)]
+#[derive(PartialEq, Eq, Copy, Clone, Hash)]
 pub struct PrimitiveId(usize);
 
-#[derive(PartialEq, Eq, Copy, Clone)]
+#[derive(PartialEq, Eq, Copy, Clone, Hash)]
 pub struct ClassId(usize);
 
-#[derive(PartialEq, Eq, Copy, Clone)]
+#[derive(PartialEq, Eq, Copy, Clone, Hash)]
 pub struct ParamId(usize);
 
 #[derive(PartialEq, Eq, Copy, Clone, Hash)]
 pub struct VariableId(usize);
 
-#[derive(PartialEq, Eq, Clone)]
+#[derive(PartialEq, Eq, Clone, Hash)]
 pub enum Type {
     BotType,
     SelfType,
     PrimitiveType(PrimitiveId),
     ClassType(ClassId),
     VirtualClassType(ClassId),
-    ParametricType(ParamId, Vec<Type>),
+    ParametricType(ParamId, Vec<Rc<Type>>),
     TypeVariable(VariableId),
 }
 
@@ -80,7 +81,11 @@ impl<'a> GlobalContext<'a> {
         self.class_defs.push(def);
     }
     pub fn add_parametric(&mut self, def: ParametricDef<'a>) {
-        let params = def.params.iter().map(|&v| Type::TypeVariable(v)).collect();
+        let params = def
+            .params
+            .iter()
+            .map(|&v| Type::TypeVariable(v).into())
+            .collect();
         self.sym_table.insert(
             def.base.name,
             Type::ParametricType(ParamId(self.parametric_defs.len()), params),
@@ -100,36 +105,36 @@ impl<'a> GlobalContext<'a> {
         self.var_defs.push(def);
     }
 
-    pub fn get_primitive_mut(&mut self, id: PrimitiveId) -> Option<&mut TypeDef<'a>> {
-        self.primitive_defs.get_mut(id.0)
+    pub fn get_primitive_mut(&mut self, id: PrimitiveId) -> &mut TypeDef<'a> {
+        self.primitive_defs.get_mut(id.0).unwrap()
     }
 
-    pub fn get_primitive(&self, id: PrimitiveId) -> Option<&TypeDef> {
-        self.primitive_defs.get(id.0)
+    pub fn get_primitive(&self, id: PrimitiveId) -> &TypeDef {
+        self.primitive_defs.get(id.0).unwrap()
     }
 
-    pub fn get_class_mut(&mut self, id: ClassId) -> Option<&mut ClassDef<'a>> {
-        self.class_defs.get_mut(id.0)
+    pub fn get_class_mut(&mut self, id: ClassId) -> &mut ClassDef<'a> {
+        self.class_defs.get_mut(id.0).unwrap()
     }
 
-    pub fn get_class(&self, id: ClassId) -> Option<&ClassDef> {
-        self.class_defs.get(id.0)
+    pub fn get_class(&self, id: ClassId) -> &ClassDef {
+        self.class_defs.get(id.0).unwrap()
     }
 
-    pub fn get_parametric_mut(&mut self, id: ParamId) -> Option<&mut ParametricDef<'a>> {
-        self.parametric_defs.get_mut(id.0)
+    pub fn get_parametric_mut(&mut self, id: ParamId) -> &mut ParametricDef<'a> {
+        self.parametric_defs.get_mut(id.0).unwrap()
     }
 
-    pub fn get_parametric(&self, id: ParamId) -> Option<&ParametricDef> {
-        self.parametric_defs.get(id.0)
+    pub fn get_parametric(&self, id: ParamId) -> &ParametricDef {
+        self.parametric_defs.get(id.0).unwrap()
     }
 
-    pub fn get_variable_mut(&mut self, id: VariableId) -> Option<&mut VarDef<'a>> {
-        self.var_defs.get_mut(id.0)
+    pub fn get_variable_mut(&mut self, id: VariableId) -> &mut VarDef<'a> {
+        self.var_defs.get_mut(id.0).unwrap()
     }
 
-    pub fn get_variable(&self, id: VariableId) -> Option<&VarDef> {
-        self.var_defs.get(id.0)
+    pub fn get_variable(&self, id: VariableId) -> &VarDef {
+        self.var_defs.get(id.0).unwrap()
     }
 
     pub fn get_type(&self, name: &str) -> Option<Type> {
@@ -139,41 +144,49 @@ impl<'a> GlobalContext<'a> {
 }
 
 impl Type {
-    pub fn subst(&self, map: &Option<HashMap<VariableId, Type>>) -> Type {
-        if let Some(m) = map {
-            match self {
-                Type::TypeVariable(id) => m.get(id).unwrap_or(self).clone(),
-                Type::ParametricType(id, params) => {
-                    Type::ParametricType(*id, params.iter().map(|v| v.subst(map)).collect())
-                }
-                _ => self.clone(),
-            }
-        } else {
-            self.clone()
+    pub fn subst(&self, map: &HashMap<VariableId, Type>) -> Type {
+        match self {
+            Type::TypeVariable(id) => map.get(id).unwrap_or(self).clone(),
+            Type::ParametricType(id, params) => Type::ParametricType(
+                *id,
+                params
+                    .iter()
+                    .map(|v| v.as_ref().subst(map).into())
+                    .collect(),
+            ),
+            _ => self.clone(),
         }
     }
 
     pub fn inv_subst(&self, map: &Vec<(Type, Type)>) -> Type {
         for (from, to) in map.iter() {
             if self == from {
-                return to.clone()
+                return to.clone();
             }
         }
         match self {
-            Type::ParametricType(id, params) => {
-                Type::ParametricType(*id, params.iter().map(|v| v.inv_subst(map)).collect())
-            },
-            _ => self.clone()
+            Type::ParametricType(id, params) => Type::ParametricType(
+                *id,
+                params
+                    .iter()
+                    .map(|v| v.as_ref().inv_subst(map).into())
+                    .collect(),
+            ),
+            _ => self.clone(),
         }
     }
 
-    pub fn get_subst(&self, ctx: &GlobalContext) -> Option<HashMap<VariableId, Type>> {
+    pub fn get_subst(&self, ctx: &GlobalContext) -> HashMap<VariableId, Type> {
         match self {
             Type::ParametricType(id, params) => {
-                let vars = &ctx.get_parametric(*id).unwrap().params;
-                Some(vars.iter().zip(params).map(|(v, p)| (*v, p.clone())).collect())
-            },
-            _ => None
+                let vars = &ctx.get_parametric(*id).params;
+                vars.iter()
+                    .zip(params)
+                    .map(|(v, p)| (*v, p.as_ref().clone()))
+                    .collect()
+            }
+            // if this proves to be slow, we can use option type
+            _ => HashMap::new(),
         }
     }
 }