From b0711ef63501b7c29cb7c2014f3ceeaa399e3481 Mon Sep 17 00:00:00 2001
From: David Li <li.davidm96@gmail.com>
Date: Sun, 5 Nov 2017 09:27:10 -0500
Subject: Add stubbed out type checker

---
 src/ast.rs                  | 18 +++++++++++-------
 src/main.rs                 |  7 ++++++-
 src/semantic/environment.rs | 33 +++++++++++++++++++++++++++++++++
 src/semantic/mod.rs         |  3 +++
 src/semantic/translate.rs   | 39 +++++++++++++++++++++++++++++++++++++++
 src/semantic/types.rs       |  7 +++++++
 6 files changed, 99 insertions(+), 8 deletions(-)
 create mode 100644 src/semantic/environment.rs
 create mode 100644 src/semantic/mod.rs
 create mode 100644 src/semantic/translate.rs
 create mode 100644 src/semantic/types.rs

diff --git a/src/ast.rs b/src/ast.rs
index 7edf9c7..c3925b0 100644
--- a/src/ast.rs
+++ b/src/ast.rs
@@ -1,32 +1,36 @@
 #[derive(Debug)]
 pub struct WithLocation<T> {
-    value: T,
-    location: (usize, usize),
+    pub value: T,
+    pub start: usize,
+    pub end: usize,
 }
 
 impl<T> WithLocation<T> {
     pub fn new(value: T, start: usize, end: usize) -> WithLocation<T> {
         WithLocation {
             value: value,
-            location: (start, end),
+            start: start,
+            end: end,
         }
     }
 
     pub fn map<U, F: FnOnce(T) -> U>(self, f: F) -> WithLocation<U> {
         WithLocation {
             value: f(self.value),
-            location: self.location,
+            start: self.start,
+            end: self.end,
         }
     }
 
     pub fn join_map<U, V, F>(self, other: WithLocation<U>, f: F) -> WithLocation<V>
         where F: FnOnce(WithLocation<T>, WithLocation<U>) -> V
     {
-        let loc1 = self.location;
-        let loc2 = other.location;
+        let start = self.start;
+        let end = other.end;
         WithLocation {
             value: f(self, other),
-            location: (loc1.0, loc2.1),
+            start: start,
+            end: end,
         }
     }
 }
diff --git a/src/main.rs b/src/main.rs
index 8976597..8264f97 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,4 +1,5 @@
 pub mod ast;
+pub mod semantic;
 pub mod taiga;
 
 use std::io::{self, BufRead, Write};
@@ -12,7 +13,11 @@ fn main() {
         io::stdout().flush().unwrap();
         if let Ok(n) = handle.read_line(&mut input) {
             if n == 0 { break; }
-            println!("{:?}", taiga::parse_Program(&input));
+            let program = taiga::parse_Program(&input);
+            println!("{:?}", program);
+            if let Ok(program) = program {
+                println!("{:?}", semantic::translate::translate(&program));
+            }
         }
         else {
             break;
diff --git a/src/semantic/environment.rs b/src/semantic/environment.rs
new file mode 100644
index 0000000..fab16b3
--- /dev/null
+++ b/src/semantic/environment.rs
@@ -0,0 +1,33 @@
+use std::collections::HashMap;
+use std::hash::Hash;
+
+pub struct Environment<'a, T: 'a, U: 'a> {
+    pub parent: Option<&'a Environment<'a, T, U>>,
+    pub bindings: HashMap<T, U>,
+}
+
+impl<'a, T: 'a, U: 'a> Environment<'a, T, U>
+    where T: Eq + Hash {
+    pub fn new(parent: Option<&'a Environment<'a, T, U>>) -> Environment<'a, T, U> {
+        Environment {
+            parent: parent,
+            bindings: HashMap::new(),
+        }
+    }
+
+    pub fn add_binding(&mut self, key: T, value: U) {
+        self.bindings.insert(key, value);
+    }
+
+    pub fn lookup(&self, key: &T) -> Option<&U> {
+        if let Some(v) = self.bindings.get(key) {
+            Some(v)
+        }
+        else if let Some(p) = self.parent {
+            p.lookup(key)
+        }
+        else {
+            None
+        }
+    }
+}
diff --git a/src/semantic/mod.rs b/src/semantic/mod.rs
new file mode 100644
index 0000000..433a196
--- /dev/null
+++ b/src/semantic/mod.rs
@@ -0,0 +1,3 @@
+pub mod environment;
+pub mod translate;
+pub mod types;
diff --git a/src/semantic/translate.rs b/src/semantic/translate.rs
new file mode 100644
index 0000000..7bcd646
--- /dev/null
+++ b/src/semantic/translate.rs
@@ -0,0 +1,39 @@
+use ::ast::{self, WithLocation};
+use super::environment;
+use super::types::Ty;
+
+#[derive(Debug)]
+pub enum TypeError {
+    Unimplemented,
+}
+
+type TypeEnvironment<'a> = environment::Environment<'a, String, Ty>;
+pub type Result = ::std::result::Result<Ty, WithLocation<TypeError>>;
+
+pub fn translate(program: &ast::Program) -> Result {
+    trans_exp(TypeEnvironment::new(None), &*program.0)
+}
+
+fn trans_exp<'a>(venv: TypeEnvironment<'a>, exp: &WithLocation<ast::Expression>) -> Result {
+    use ast::Expression::*;
+
+    match &exp.value {
+        &Let(ref decls, ref body) => {
+            Err(WithLocation::new(TypeError::Unimplemented, exp.start, exp.end))
+        },
+        &UnaryOp(ref op, ref operand) => {
+            Err(WithLocation::new(TypeError::Unimplemented, exp.start, exp.end))
+        },
+        &BinOp(ref op, ref left, ref right) => {
+            Err(WithLocation::new(TypeError::Unimplemented, exp.start, exp.end))
+        },
+        &Number(_) => Ok(Ty::Int),
+        &String(_) => Ok(Ty::String),
+        &Name(ref name) => {
+            Err(WithLocation::new(TypeError::Unimplemented, exp.start, exp.end))
+        },
+        &Nil => {
+            Err(WithLocation::new(TypeError::Unimplemented, exp.start, exp.end))
+        },
+    }
+}
diff --git a/src/semantic/types.rs b/src/semantic/types.rs
new file mode 100644
index 0000000..2d76387
--- /dev/null
+++ b/src/semantic/types.rs
@@ -0,0 +1,7 @@
+#[derive(Debug)]
+pub enum Ty {
+    Int,
+    String,
+    Nil,
+    Unit,
+}
-- 
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