feat(gs/achilles): Implement very basic monomorphization r/2296

Implement very basic monomorphization, by recording type variable
instantiations when typechecking Call nodes and then using those in a
new hir Visitor trait to copy the body of any generic decls for each
possible set of instantiation of the type variables.

Change-Id: Iab54030973e5d66e2b8bcd074b4cb6c001a90123
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2617
Reviewed-by: glittershark <grfn@gws.fyi>
Tested-by: BuildkiteCI

1 files changed, 179 insertions, 0 deletions

diff --git a/users/glittershark/achilles/src/passes/hir/mod.rs b/users/glittershark/achilles/src/passes/hir/mod.rs
new file mode 100644
index 000000000000..fb2f64e08591
--- /dev/null
+++ b/users/glittershark/achilles/src/passes/hir/mod.rs
@@ -0,0 +1,179 @@
+use std::collections::HashMap;
+
+use crate::ast::hir::{Binding, Decl, Expr};
+use crate::ast::{BinaryOperator, Ident, Literal, UnaryOperator};
+
+pub(crate) mod monomorphize;
+
+pub(crate) trait Visitor<'a, 'ast, T: 'ast>: Sized + 'a {
+    type Error;
+
+    fn visit_type(&mut self, _type: &mut T) -> Result<(), Self::Error> {
+        Ok(())
+    }
+
+    fn visit_ident(&mut self, _ident: &mut Ident<'ast>) -> Result<(), Self::Error> {
+        Ok(())
+    }
+
+    fn visit_literal(&mut self, _literal: &mut Literal<'ast>) -> Result<(), Self::Error> {
+        Ok(())
+    }
+
+    fn visit_unary_operator(&mut self, _op: &mut UnaryOperator) -> Result<(), Self::Error> {
+        Ok(())
+    }
+
+    fn visit_binary_operator(&mut self, _op: &mut BinaryOperator) -> Result<(), Self::Error> {
+        Ok(())
+    }
+
+    fn visit_binding(&mut self, binding: &mut Binding<'ast, T>) -> Result<(), Self::Error> {
+        self.visit_ident(&mut binding.ident)?;
+        self.visit_type(&mut binding.type_)?;
+        self.visit_expr(&mut binding.body)?;
+        Ok(())
+    }
+
+    fn post_visit_call(
+        &mut self,
+        _fun: &mut Expr<'ast, T>,
+        _type_args: &mut HashMap<Ident<'ast>, T>,
+        _args: &mut Vec<Expr<'ast, T>>,
+    ) -> Result<(), Self::Error> {
+        Ok(())
+    }
+
+    fn pre_visit_call(
+        &mut self,
+        _fun: &mut Expr<'ast, T>,
+        _type_args: &mut HashMap<Ident<'ast>, T>,
+        _args: &mut Vec<Expr<'ast, T>>,
+    ) -> Result<(), Self::Error> {
+        Ok(())
+    }
+
+    fn visit_expr(&mut self, expr: &mut Expr<'ast, T>) -> Result<(), Self::Error> {
+        match expr {
+            Expr::Ident(id, t) => {
+                self.visit_ident(id)?;
+                self.visit_type(t)?;
+            }
+            Expr::Literal(lit, t) => {
+                self.visit_literal(lit)?;
+                self.visit_type(t)?;
+            }
+            Expr::UnaryOp { op, rhs, type_ } => {
+                self.visit_unary_operator(op)?;
+                self.visit_expr(rhs)?;
+                self.visit_type(type_)?;
+            }
+            Expr::BinaryOp {
+                lhs,
+                op,
+                rhs,
+                type_,
+            } => {
+                self.visit_expr(lhs)?;
+                self.visit_binary_operator(op)?;
+                self.visit_expr(rhs)?;
+                self.visit_type(type_)?;
+            }
+            Expr::Let {
+                bindings,
+                body,
+                type_,
+            } => {
+                for binding in bindings.iter_mut() {
+                    self.visit_binding(binding)?;
+                }
+                self.visit_expr(body)?;
+                self.visit_type(type_)?;
+            }
+            Expr::If {
+                condition,
+                then,
+                else_,
+                type_,
+            } => {
+                self.visit_expr(condition)?;
+                self.visit_expr(then)?;
+                self.visit_expr(else_)?;
+                self.visit_type(type_)?;
+            }
+            Expr::Fun {
+                args,
+                body,
+                type_args,
+                type_,
+            } => {
+                for (ident, t) in args {
+                    self.visit_ident(ident)?;
+                    self.visit_type(t)?;
+                }
+                for ta in type_args {
+                    self.visit_ident(ta)?;
+                }
+                self.visit_expr(body)?;
+                self.visit_type(type_)?;
+            }
+            Expr::Call {
+                fun,
+                args,
+                type_args,
+                type_,
+            } => {
+                self.pre_visit_call(fun, type_args, args)?;
+                self.visit_expr(fun)?;
+                for arg in args.iter_mut() {
+                    self.visit_expr(arg)?;
+                }
+                self.visit_type(type_)?;
+                self.post_visit_call(fun, type_args, args)?;
+            }
+        }
+
+        Ok(())
+    }
+
+    fn post_visit_decl(&mut self, decl: &'a Decl<'ast, T>) -> Result<(), Self::Error> {
+        Ok(())
+    }
+
+    fn visit_decl(&mut self, decl: &'a mut Decl<'ast, T>) -> Result<(), Self::Error> {
+        match decl {
+            Decl::Fun {
+                name,
+                type_args,
+                args,
+                body,
+                type_,
+            } => {
+                self.visit_ident(name)?;
+                for type_arg in type_args {
+                    self.visit_ident(type_arg)?;
+                }
+                for (arg, t) in args {
+                    self.visit_ident(arg)?;
+                    self.visit_type(t)?;
+                }
+                self.visit_expr(body)?;
+                self.visit_type(type_)?;
+            }
+            Decl::Extern {
+                name,
+                arg_types,
+                ret_type,
+            } => {
+                self.visit_ident(name)?;
+                for arg_t in arg_types {
+                    self.visit_type(arg_t)?;
+                }
+                self.visit_type(ret_type)?;
+            }
+        }
+
+        self.post_visit_decl(decl)?;
+        Ok(())
+    }
+}