Add variable resolution; the error behavior is pretty bad here.

src/passes.rs

@@ -0,0 +1,64 @@
+use codespan_reporting::files::SimpleFiles;
+use crate::asts::hil;
+use crate::errors::Error;
+use crate::syntax;
+use crate::syntax::Location;
+use crate::variable_map::VariableMap;
+use crate::warnings::Warning;
+use std::fs;
+
+mod syntax_to_hil;
+
+pub struct PassResult<T> {
+    pub result: T,
+    pub warnings: Vec<Warning>,
+    pub errors: Vec<Error>,
+}
+
+impl<T,E> From<E> for PassResult<Option<T>>
+ where
+  Error: From<E>
+{
+    fn from(x: E) -> Self {
+        PassResult {
+            result: None,
+            warnings: vec![],
+            errors: vec![Error::from(x)],
+        }
+    }
+}
+
+pub fn run_front_end(
+    file_database: &mut SimpleFiles<String, String>,
+    initial_file_name: &str,
+) -> PassResult<Option<(hil::Program<Location>, VariableMap)>> {
+    let initial_file_contents = match fs::read_to_string(initial_file_name) {
+        Ok(x) => x,
+        Err(e) => return PassResult::from(e),
+    };
+
+    let initial_file = file_database.add(initial_file_name.to_string(), initial_file_contents);
+    let db_version = match file_database.get(initial_file) {
+        Ok(x) => x,
+        Err(e) => return PassResult::from(e),
+    };
+    let db_version_source = db_version.source();
+    let raw_syntax = match syntax::Program::parse(initial_file, db_version_source) {
+        Ok(x) => x,
+        Err(e) => return PassResult::from(e),
+    };
+
+    let mut variable_map = VariableMap::empty();
+    let conversion_result = hil::Program::convert(raw_syntax, &mut variable_map);
+    let result = if conversion_result.errors.is_empty() {
+        Some((conversion_result.result, variable_map))
+    } else {
+        None
+    };
+
+    PassResult {
+        result,
+        warnings: conversion_result.warnings,
+        errors: conversion_result.errors,
+    }
+}