diff --git a/multiply_add.sus b/multiply_add.sus
index 9ada263..eb8086e 100644
--- a/multiply_add.sus
+++ b/multiply_add.sus
@@ -156,3 +156,7 @@ module test_exists : -> int result {
 	int x = exists(5);
 	int b = doesnt_exist(3);
 }
+
+module exists : duplicate a {
+	// Should be a duplicate of previous exists
+}
diff --git a/src/ast.rs b/src/ast.rs
index f142472..661114d 100644
--- a/src/ast.rs
+++ b/src/ast.rs
@@ -1,9 +1,9 @@
 
 use num_bigint::BigUint;
 
-use crate::{tokenizer::TokenTypeIdx, linker::GlobalValueUUID, linker::GlobalTypeUUID};
+use crate::{tokenizer::TokenTypeIdx, linker::ValueUUID, linker::TypeUUID};
 use core::ops::Range;
-use std::rc::Rc;
+use std::{rc::Rc, path::Path};
 
 // Token span. Indices are INCLUSIVE
 #[derive(Clone,Copy,Debug,PartialEq,Eq)]
@@ -105,7 +105,7 @@ pub enum Statement {
     TimelineStage(usize)
 }
 
-pub type FileName = Rc<String>;
+pub type FileName = Rc<Path>;
 
 #[derive(Debug)]
 pub struct Location {
@@ -118,8 +118,8 @@ pub struct Dependencies {
     pub global_references : Vec<GlobalReference>,
     pub type_references : Vec<GlobalReference>,
 
-    pub resolved_globals : Vec<GlobalValueUUID>,
-    pub resolved_types : Vec<GlobalTypeUUID>
+    pub resolved_globals : Vec<ValueUUID>,
+    pub resolved_types : Vec<TypeUUID>
 }
 
 #[derive(Debug)]
diff --git a/src/dev_aid/lsp.rs b/src/dev_aid/lsp.rs
index 918d42d..6518aa6 100644
--- a/src/dev_aid/lsp.rs
+++ b/src/dev_aid/lsp.rs
@@ -276,7 +276,7 @@ fn convert_diagnostic(err : ParsingError, severity : DiagnosticSeverity, token_p
     let mut related_info = Vec::new();
     for info in err.infos {
         let info_pos = cvt_span_to_lsp_range(info.position, token_positions);
-        let location = Location{uri : Url::parse(&info.file_name).unwrap(), range : info_pos};
+        let location = Location{uri : Url::from_file_path(info.file_name).unwrap(), range : info_pos};
         related_info.push(DiagnosticRelatedInformation { location, message: info.info });
     }
     Diagnostic::new(error_pos, Some(severity), None, None, err.reason, Some(related_info), None)
@@ -339,8 +339,7 @@ fn main_loop(
                         let path : PathBuf = params.text_document.uri.to_file_path().unwrap();
                         let file_data : Rc<LoadedFile> = file_cache.get(&path);
                         
-                        let file_uri_text = params.text_document.uri.to_string();
-                        let (full_parse, errors) = perform_full_semantic_parse(&file_data.file_text, Rc::from(file_uri_text));
+                        let (full_parse, errors) = perform_full_semantic_parse(&file_data.file_text, Rc::from(path));
                         
                         let (syntax_highlight, token_positions) = do_syntax_highlight(&file_data, &full_parse);
 
diff --git a/src/dev_aid/syntax_highlighting.rs b/src/dev_aid/syntax_highlighting.rs
index fb78b0d..3dcebd6 100644
--- a/src/dev_aid/syntax_highlighting.rs
+++ b/src/dev_aid/syntax_highlighting.rs
@@ -1,8 +1,9 @@
 
-use std::{ops::Range, rc::Rc};
+use std::{ops::Range, rc::Rc, collections::HashMap};
 
 use crate::{ast::*, tokenizer::*, parser::*, linker::Linker};
 
+use ariadne::FileCache;
 use console::Style;
 
 
@@ -178,13 +179,16 @@ fn generate_character_offsets(file_text : &str, tokens : &[Token]) -> Vec<Range<
     character_offsets
 }
 
-pub fn syntax_highlight_file(file_paths : &[String]) {
+pub fn syntax_highlight_file(file_paths : &[FileName]) {
     let mut linker : Linker = Linker::new();
-    let mut file_list = Vec::new();
+    let mut file_list = HashMap::new();
     for file_path in file_paths {
         let file_text = match std::fs::read_to_string(file_path) {
             Ok(file_text) => file_text,
-            Err(reason) => panic!("Could not open file '{file_path}' for syntax highlighting because {reason}")
+            Err(reason) => {
+                let file_path_disp = file_path.display();
+                panic!("Could not open file '{file_path_disp}' for syntax highlighting because {reason}")
+            }
         };
         
         let (full_parse, errors) = perform_full_semantic_parse(&file_text, Rc::from(file_path.to_owned()));
@@ -198,16 +202,19 @@ pub fn syntax_highlight_file(file_paths : &[String]) {
         
         println!("{:?}", full_parse.ast);
 
-        file_list.push(linker.add_file(file_text, full_parse.ast, errors, (full_parse.tokens, ide_tokens)));
+        let file_data = linker.add_file(file_text, full_parse.ast, errors, (full_parse.tokens, ide_tokens));
+        file_list.insert(file_path.clone(), file_data);
     }
 
     let linked = linker.link_all(file_list);
 
-    for f in &linked.files {
+    let mut file_cache : FileCache = Default::default();
+    
+    for (_file_name, f) in &linked.files {
         let token_offsets = generate_character_offsets(&f.file_text, &f.extra_data.0);
 
         for err in &f.errors.errors {
-            err.pretty_print_error(&f.errors.main_file, &f.file_text, &token_offsets);
+            err.pretty_print_error(&f.errors.main_file, &token_offsets, &mut file_cache);
         }
     }
 }
diff --git a/src/errors.rs b/src/errors.rs
index 19b1086..d4f0095 100644
--- a/src/errors.rs
+++ b/src/errors.rs
@@ -1,6 +1,6 @@
 
 
-use std::ops::Range;
+use std::{ops::Range, path::Path};
 
 use crate::ast::{Span, FileName};
 use ariadne::*;
@@ -19,27 +19,40 @@ pub struct ParsingError {
     pub infos : Vec<ErrorInfo>
 }
 
+struct CustomSpan<'a> {
+    file : &'a Path,
+    span : Range<usize>
+}
+impl<'a> ariadne::Span for CustomSpan<'a> {
+    type SourceId = Path;
+
+    fn source(&self) -> &Self::SourceId { &self.file }
+    fn start(&self) -> usize { self.span.start }
+    fn end(&self) -> usize { self.span.end }
+}
+
 impl ParsingError {
     // Requires that character_ranges.len() == tokens.len() + 1 to include EOF token
-    pub fn pretty_print_error(&self, main_file_name : &str, file_text : &str, character_ranges : &[Range<usize>]) {
+    pub fn pretty_print_error(&self, main_file : &Path, character_ranges : &[Range<usize>], file_cache : &mut FileCache) {
         // Generate & choose some colours for each of our elements
         let err_color = Color::Red;
         let info_color = Color::Blue;
 
         let error_span = self.position.to_range(character_ranges);
-        let mut report = Report::build(ReportKind::Error, main_file_name, error_span.start)
+
+        let mut report: ReportBuilder<'_, CustomSpan> = Report::build(ReportKind::Error, main_file, error_span.start);
+        report = report
             .with_message(&self.reason)
             .with_label(
-                Label::new((main_file_name, error_span))
+                Label::new(CustomSpan{file : main_file, span : error_span})
                     .with_message(&self.reason)
                     .with_color(err_color)
             );
 
         for info in &self.infos {
             let info_span = info.position.to_range(character_ranges);
-            let info_file : &str = &info.file_name;
             report = report.with_label(
-                Label::new((info_file, info_span))
+                Label::new(CustomSpan{file : &info.file_name, span : info_span})
                     .with_message(&info.info)
                     .with_color(info_color)
             )
@@ -49,7 +62,7 @@ impl ParsingError {
                 "match".fg(out)
             ))*/
         report.finish()
-        .print((main_file_name, Source::from(file_text)))
+        .eprint(file_cache)
         .unwrap();
     }
 }
diff --git a/src/linker.rs b/src/linker.rs
index 57d5d5d..7c07f6e 100644
--- a/src/linker.rs
+++ b/src/linker.rs
@@ -1,12 +1,12 @@
 use std::collections::HashMap;
 
-use crate::{ast::{Module, ASTRoot, Span, Location, Dependencies}, errors::{ErrorCollector, error_info}};
+use crate::{ast::{Module, ASTRoot, Span, Location, Dependencies, FileName}, errors::{ErrorCollector, error_info}};
 
 
-#[derive(Debug, Clone, Copy)]
-pub struct GlobalValueUUID(usize);
-#[derive(Debug, Clone, Copy)]
-pub struct GlobalTypeUUID(usize);
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct ValueUUID(usize);
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct TypeUUID(usize);
 
 const INVALID_UUID : usize = usize::MAX;
 
@@ -91,16 +91,16 @@ impl Linkable for NamedType {
 
 #[derive(Debug, Clone, Copy)]
 pub enum GlobalNamespaceNode {
-    Value(GlobalValueUUID),
-    Type(GlobalTypeUUID),
+    Value(ValueUUID),
+    Type(TypeUUID),
 }
 
 pub struct FileData<T> {
     pub file_text : String,
     pub extra_data : T,
     pub errors : ErrorCollector,
-    associated_values : Vec<GlobalValueUUID>,
-    associated_types : Vec<GlobalTypeUUID>
+    associated_values : Vec<ValueUUID>,
+    associated_types : Vec<TypeUUID>
 }
 
 // All modules in the workspace
@@ -113,17 +113,17 @@ pub struct Linker {
 // All modules in the workspace
 pub struct FullyLinked<T> {
     pub data : Linker,
-    pub files : Vec<FileData<T>>
+    pub files : HashMap<FileName, FileData<T>>
 }
 
 impl Linker {
     // Returns None for builtins
     fn get_location(&self, node : GlobalNamespaceNode) -> Option<&Location> {
         match node {
-            GlobalNamespaceNode::Value(GlobalValueUUID(pos)) => {
+            GlobalNamespaceNode::Value(ValueUUID(pos)) => {
                 self.values[pos].get_location()
             },
-            GlobalNamespaceNode::Type(GlobalTypeUUID(pos)) => {
+            GlobalNamespaceNode::Type(TypeUUID(pos)) => {
                 self.types[pos].get_location()
             },
         }
@@ -136,7 +136,7 @@ impl Linker {
         let mut global_namespace = HashMap::new();
         
         for name in BUILTIN_TYPES {
-            let success = global_namespace.insert(name.to_owned(), GlobalNamespaceNode::Type(GlobalTypeUUID(named_types.len()))).is_none();
+            let success = global_namespace.insert(name.to_owned(), GlobalNamespaceNode::Type(TypeUUID(named_types.len()))).is_none();
             assert!(success);
             named_types.push(NamedType::Builtin(name));
         } 
@@ -159,8 +159,8 @@ impl Linker {
                     }
                 }
                 std::collections::hash_map::Entry::Vacant(vac) => {
-                    vac.insert(GlobalNamespaceNode::Value(GlobalValueUUID(self.values.len())));
-                    associated_values.push(GlobalValueUUID(self.values.len()));
+                    vac.insert(GlobalNamespaceNode::Value(ValueUUID(self.values.len())));
+                    associated_values.push(ValueUUID(self.values.len()));
                     self.values.push(NamedValue::Module(md));
                 }
             }
@@ -168,15 +168,15 @@ impl Linker {
         FileData{file_text, errors, associated_values, associated_types: Vec::new(), extra_data}
     }
 
-    fn link_dependencies(&self, file_text : &str, deps : &Dependencies, errors : &mut ErrorCollector) -> (Vec<GlobalValueUUID>, Vec<GlobalTypeUUID>) {
-        let value_references : Vec<GlobalValueUUID> = deps.global_references.iter().map(|reference| {
+    fn link_dependencies(&self, file_text : &str, deps : &Dependencies, errors : &mut ErrorCollector) -> (Vec<ValueUUID>, Vec<TypeUUID>) {
+        let value_references : Vec<ValueUUID> = deps.global_references.iter().map(|reference| {
             let reference_span = Span(reference.last().unwrap().position, reference[0].position);
             let reference_name_str = &file_text[reference[0].text.clone()];
             match self.global_namespace.get(reference_name_str) {
                 Some(GlobalNamespaceNode::Value(v)) => {
                     *v
                 }
-                Some(GlobalNamespaceNode::Type(GlobalTypeUUID(t))) => {
+                Some(GlobalNamespaceNode::Type(TypeUUID(t))) => {
                     let found_instead = &self.types[*t];
                     let found_full_name = found_instead.get_full_name();
                     let infos = if let Some(loc) = found_instead.get_location() {
@@ -185,23 +185,23 @@ impl Linker {
                         vec![]
                     };
                     errors.error_with_info(reference_span, format!("No Module or Constant of the name '{reference_name_str}' was found. Found type '{found_full_name}'"), infos);
-                    GlobalValueUUID(INVALID_UUID)
+                    ValueUUID(INVALID_UUID)
                 }
                 None => {
                     errors.error_basic(reference_span, format!("No Module or Constant of the name '{reference_name_str}' was found. Did you forget to import it?"));
-                    GlobalValueUUID(INVALID_UUID)
+                    ValueUUID(INVALID_UUID)
                 }
             }
         }).collect();
 
-        let type_references : Vec<GlobalTypeUUID> = deps.type_references.iter().map(|reference| {
+        let type_references : Vec<TypeUUID> = deps.type_references.iter().map(|reference| {
             let reference_span = Span(reference.last().unwrap().position, reference[0].position);
             let reference_name_str = &file_text[reference[0].text.clone()];
             match self.global_namespace.get(reference_name_str) {
                 Some(GlobalNamespaceNode::Type(v)) => {
                     *v
                 }
-                Some(GlobalNamespaceNode::Value(GlobalValueUUID(idx))) => {
+                Some(GlobalNamespaceNode::Value(ValueUUID(idx))) => {
                     let found_instead = &self.values[*idx];
                     let found_full_name = found_instead.get_full_name();
                     let infos = if let Some(loc) = found_instead.get_location() {
@@ -210,11 +210,11 @@ impl Linker {
                         vec![]
                     };
                     errors.error_with_info(reference_span, format!("No Type of the name '{reference_name_str}' was found. Found type '{found_full_name}'"), infos);
-                    GlobalTypeUUID(INVALID_UUID)
+                    TypeUUID(INVALID_UUID)
                 }
                 None => {
                     errors.error_basic(reference_span, format!("No Type of the name '{reference_name_str}' was found. Did you forget to import it?"));
-                    GlobalTypeUUID(INVALID_UUID)
+                    TypeUUID(INVALID_UUID)
                 }
             }
         }).collect();
@@ -223,16 +223,16 @@ impl Linker {
     }
 
     // This should be called once all modules have been added. Adds errors for globals it couldn't match
-    pub fn link_all<T>(mut self, mut files : Vec<FileData<T>>) -> FullyLinked<T> {
-        for file in &mut files {
-            for GlobalValueUUID(idx) in &file.associated_values {
+    pub fn link_all<T>(mut self, mut files : HashMap<FileName, FileData<T>>) -> FullyLinked<T> {
+        for (_file_name, file) in &mut files {
+            for ValueUUID(idx) in &file.associated_values {
                 let deps = self.values[*idx].get_dependencies();
                 let (vals_this_refers_to, types_this_refers_to) = self.link_dependencies(&file.file_text, deps, &mut file.errors);
                 let deps_mut = self.values[*idx].get_dependencies_mut();
                 deps_mut.resolved_globals = vals_this_refers_to;
                 deps_mut.resolved_types = types_this_refers_to;
             }
-            for GlobalTypeUUID(idx) in &file.associated_types {
+            for TypeUUID(idx) in &file.associated_types {
                 let deps = self.types[*idx].get_dependencies();
                 let (vals_this_refers_to, types_this_refers_to) = self.link_dependencies(&file.file_text, deps, &mut file.errors);
                 let deps_mut = self.types[*idx].get_dependencies_mut();
diff --git a/src/main.rs b/src/main.rs
index 91caea5..2ca91ad 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -10,6 +10,9 @@ mod linker;
 
 use std::env;
 use std::error::Error;
+use std::path::PathBuf;
+use std::rc::Rc;
+use ast::FileName;
 use dev_aid::syntax_highlighting::*;
 
 
@@ -18,13 +21,13 @@ fn main() -> Result<(), Box<dyn Error + Sync + Send>> {
 
     let _executable_path = args.next();
 
-    let mut file_paths : Vec<String> = Vec::new();
+    let mut file_paths : Vec<FileName> = Vec::new();
     let mut is_lsp : bool = false;
     for arg in args {
         if arg == "--lsp" {
             is_lsp = true;
         } else {
-            file_paths.push(arg);
+            file_paths.push(Rc::from(PathBuf::from(arg)));
         }
     }
     #[cfg(feature = "lsp")]
@@ -33,7 +36,7 @@ fn main() -> Result<(), Box<dyn Error + Sync + Send>> {
     }
     if file_paths.len() == 0 {
         // Quick debug file
-        file_paths.push("multiply_add.sus".to_owned());
+        file_paths.push(Rc::from(PathBuf::from("multiply_add.sus")));
     }
     syntax_highlight_file(&file_paths);
 
diff --git a/src/parser.rs b/src/parser.rs
index 5f53e0f..7d7c300 100644
--- a/src/parser.rs
+++ b/src/parser.rs
@@ -672,7 +672,7 @@ impl<'g, 'file> ASTParserContext<'g, 'file> {
             type_references : replace(&mut self.type_references, Vec::new()),
             ..Default::default()
         };
-        let full_name : String = [self.errors.main_file.as_ref(), &self.file_text[name.text.clone()]].join("::");
+        let full_name : String = [&self.errors.main_file.as_ref().to_string_lossy(), &self.file_text[name.text.clone()]].join("::");
         Some(Module{name, declarations, code, full_name, location : Location{span, file_name : self.errors.main_file.clone()}, dependencies})
     }