From 4d9fd76d4031e2e4045b1a3195e66dea1033cac8 Mon Sep 17 00:00:00 2001
From: Per Lindgren <per.lindgren@ltu.se>
Date: Thu, 24 Sep 2020 16:08:33 +0200
Subject: [PATCH] borrow check, wip2
---
README.md | 26 ++++++++++++++++++++++++++
examples/borrow.rs | 6 ++++++
src/env.rs | 1 +
tests/test_check.rs | 5 +++++
4 files changed, 38 insertions(+)
create mode 100644 examples/borrow.rs
diff --git a/README.md b/README.md
index a8cb825..d4c4091 100644
--- a/README.md
+++ b/README.md
@@ -35,3 +35,29 @@ struct Mem(VecDeque<IdVal>);
On a function call, the parameters are pushed to the stack, and a new stack frame is generated (on entry of each sequence of statements).
References are handled through `Ref(Id)`, and are transitive. You cannot reference memory items in any other way (so this is a limitation compared to real Rust).
+
+## check
+
+The `check` module performs basic type checking and borrow checking. In the following the basic reasoning is discussed.
+
+``` Rust
+pub enum Type {
+ Unit, // (), // maybe just a special case of tuple, see todo
+ Never, // !
+ Bool, // bool
+ I32, // i32
+ Ref(Box<Type>), // & mut? Type -- used in parser
+ Mut(Box<Type>), // mut Type
+ Unknown, // Not yet assigned
+}
+
+pub type IdType = HashMap<Id, Type>;
+
+type Scope = i32;
+
+pub struct VarEnv(VecDeque<IdType>);
+```
+
+The `var_env : VarEnv` holds a stack of scopes. A lookup (`get(Id)-> Option<(Scope, &Type)>`), returns the type and what scope it is defined in (0, being arguments, 1, function body, 2 ... inner scopes). Inner scopes emerge from blocks, or block statements (if/while etc).
+
+
diff --git a/examples/borrow.rs b/examples/borrow.rs
new file mode 100644
index 0000000..3999f25
--- /dev/null
+++ b/examples/borrow.rs
@@ -0,0 +1,6 @@
+fn main() {
+ let mut a = 1;
+ let b = &mut a;
+ let c = &mut a;
+ let c: &mut i32 = b;
+}
diff --git a/src/env.rs b/src/env.rs
index 03f3ddc..1b48063 100644
--- a/src/env.rs
+++ b/src/env.rs
@@ -23,6 +23,7 @@ pub fn new_fn_env(v: &Vec<FnDecl>) -> FnEnv {
}
pub type IdType = HashMap<Id, Type>;
+
type Scope = i32;
#[derive(Debug)]
diff --git a/tests/test_check.rs b/tests/test_check.rs
index 72e0020..2c5e71d 100644
--- a/tests/test_check.rs
+++ b/tests/test_check.rs
@@ -170,3 +170,8 @@ fn check_let_if() {
fn wip() {
check(&read_file::parse("examples/wip.rs")).unwrap();
}
+
+#[test]
+fn borrow() {
+ check(&read_file::parse("examples/borrow.rs")).unwrap();
+}
--
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