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added inference context

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pca006132 2021-01-04 14:51:43 +08:00
parent 7523b43a08
commit 04e9f9c077
2 changed files with 230 additions and 0 deletions

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@ -0,0 +1,228 @@
use super::TopLevelContext;
use crate::typedef::*;
use std::boxed::Box;
use std::collections::HashMap;
struct ContextStack<'a> {
/// stack level, starts from 0
level: u32,
/// stack of variable definitions containing (id, def, level) where `def` is the original
/// definition in `level-1`.
var_defs: Vec<(usize, VarDef<'a>, u32)>,
/// stack of symbol definitions containing (name, level) where `level` is the smallest level
/// where the name is assigned a value
sym_def: Vec<(&'a str, u32)>,
}
pub struct InferenceContext<'a> {
/// top level context
top_level: TopLevelContext<'a>,
/// list of primitive instances
primitives: Vec<Type>,
/// list of variable instances
variables: Vec<Type>,
/// identifier to (type, readable) mapping.
/// an identifier might be defined earlier but has no value (for some code path), thus not
/// readable.
sym_table: HashMap<&'a str, (Type, bool)>,
/// resolution function reference, that may resolve unbounded identifiers to some type
resolution_fn: Box<dyn FnMut(&str) -> Result<Type, String>>,
/// stack
stack: ContextStack<'a>,
}
// non-trivial implementations here
impl<'a> InferenceContext<'a> {
/// return a new `InferenceContext` from `TopLevelContext` and resolution function.
pub fn new(
top_level: TopLevelContext,
resolution_fn: Box<dyn FnMut(&str) -> Result<Type, String>>,
) -> InferenceContext {
let primitives = (0..top_level.primitive_defs.len())
.map(|v| TypeEnum::PrimitiveType(PrimitiveId(v)).into())
.collect();
let variables = (0..top_level.var_defs.len())
.map(|v| TypeEnum::TypeVariable(VariableId(v)).into())
.collect();
InferenceContext {
top_level,
primitives,
variables,
sym_table: HashMap::new(),
resolution_fn,
stack: ContextStack {
level: 0,
var_defs: Vec::new(),
sym_def: Vec::new(),
},
}
}
/// execute the function with new scope.
/// variable assignment would be limited within the scope (not readable outside), and type
/// variable type guard would be limited within the scope.
/// returns the list of variables assigned within the scope, and the result of the function
pub fn with_scope<F, R>(&mut self, f: F) -> (Vec<&'a str>, R)
where
F: FnOnce(&mut Self) -> R,
{
self.stack.level += 1;
let result = f(self);
self.stack.level -= 1;
while !self.stack.var_defs.is_empty() {
let (_, _, level) = self.stack.var_defs.last().unwrap();
if *level > self.stack.level {
let (id, def, _) = self.stack.var_defs.pop().unwrap();
self.top_level.var_defs[id] = def;
} else {
break;
}
}
let mut poped_names = Vec::new();
while !self.stack.sym_def.is_empty() {
let (_, level) = self.stack.sym_def.last().unwrap();
if *level > self.stack.level {
let (name, _) = self.stack.sym_def.pop().unwrap();
self.sym_table.remove(name).unwrap();
poped_names.push(name);
} else {
break;
}
}
(poped_names, result)
}
/// assign a type to an identifier.
/// may return error if the identifier was defined but with different type
pub fn assign(&mut self, name: &'a str, ty: Type) -> Result<Type, String> {
if let Some((t, x)) = self.sym_table.get_mut(name) {
if t == &ty {
if !*x {
self.stack.sym_def.push((name, self.stack.level));
}
*x = true;
Ok(ty)
} else {
Err("different types".into())
}
} else {
self.stack.sym_def.push((name, self.stack.level));
self.sym_table.insert(name, (ty.clone(), true));
Ok(ty)
}
}
/// check if an identifier is already defined
pub fn defined(&self, name: &str) -> bool {
self.sym_table.get(name).is_some()
}
/// get the type of an identifier
/// may return error if the identifier is not defined, and cannot be resolved with the
/// resolution function.
pub fn resolve(&mut self, name: &str) -> Result<Type, String> {
if let Some((t, x)) = self.sym_table.get(name) {
if *x {
Ok(t.clone())
} else {
Err("may not have value".into())
}
} else {
self.resolution_fn.as_mut()(name)
}
}
/// restrict the bound of a type variable by replacing its definition.
/// used for implementing type guard
pub fn restrict(&mut self, id: VariableId, mut def: VarDef<'a>) {
std::mem::swap(self.top_level.var_defs.get_mut(id.0).unwrap(), &mut def);
self.stack.var_defs.push((id.0, def, self.stack.level));
}
}
// trivial getters:
impl<'a> InferenceContext<'a> {
pub fn get_primitive(&self, id: PrimitiveId) -> Type {
self.primitives.get(id.0).unwrap().clone()
}
pub fn get_variable(&self, id: VariableId) -> Type {
self.variables.get(id.0).unwrap().clone()
}
pub fn get_fn_def(&self, name: &str) -> Option<&FnDef> {
self.top_level.fn_table.get(name)
}
pub fn get_primitive_def(&self, id: PrimitiveId) -> &TypeDef {
self.top_level.primitive_defs.get(id.0).unwrap()
}
pub fn get_class_def(&self, id: ClassId) -> &ClassDef {
self.top_level.class_defs.get(id.0).unwrap()
}
pub fn get_parametric_def(&self, id: ParamId) -> &ParametricDef {
self.top_level.parametric_defs.get(id.0).unwrap()
}
pub fn get_variable_def(&self, id: VariableId) -> &VarDef {
self.top_level.var_defs.get(id.0).unwrap()
}
pub fn get_type(&self, name: &str) -> Option<Type> {
self.top_level.get_type(name)
}
}
impl TypeEnum {
pub fn subst(&self, map: &HashMap<VariableId, Type>) -> TypeEnum {
match self {
TypeEnum::TypeVariable(id) => map.get(id).map(|v| v.as_ref()).unwrap_or(self).clone(),
TypeEnum::ParametricType(id, params) => TypeEnum::ParametricType(
*id,
params
.iter()
.map(|v| v.as_ref().subst(map).into())
.collect(),
),
_ => self.clone(),
}
}
pub fn inv_subst(&self, map: &[(Type, Type)]) -> Type {
for (from, to) in map.iter() {
if self == from.as_ref() {
return to.clone();
}
}
match self {
TypeEnum::ParametricType(id, params) => TypeEnum::ParametricType(
*id,
params.iter().map(|v| v.as_ref().inv_subst(map)).collect(),
),
_ => self.clone(),
}
.into()
}
pub fn get_subst(&self, ctx: &InferenceContext) -> HashMap<VariableId, Type> {
match self {
TypeEnum::ParametricType(id, params) => {
let vars = &ctx.get_parametric_def(*id).params;
vars.iter()
.zip(params)
.map(|(v, p)| (*v, p.as_ref().clone().into()))
.collect()
}
// if this proves to be slow, we can use option type
_ => HashMap::new(),
}
}
pub fn get_base<'b: 'a, 'a>(&'a self, ctx: &'b InferenceContext) -> Option<&'b TypeDef> {
match self {
TypeEnum::PrimitiveType(id) => Some(ctx.get_primitive_def(*id)),
TypeEnum::ClassType(id) | TypeEnum::VirtualClassType(id) => {
Some(&ctx.get_class_def(*id).base)
}
TypeEnum::ParametricType(id, _) => Some(&ctx.get_parametric_def(*id).base),
_ => None,
}
}
}

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@ -1,2 +1,4 @@
mod inference_context;
mod top_level_context;
pub use inference_context::InferenceContext;
pub use top_level_context::TopLevelContext;