diff --git a/Cargo.lock b/Cargo.lock
index e9bda67..3ae2be0 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -106,6 +106,17 @@ version = "0.7.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f46ad14479a25103f283c0f10005961cf086d8dc42205bb44c46ac563475dca6"
 
+[[package]]
+name = "codespan-reporting"
+version = "0.12.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fe6d2e5af09e8c8ad56c969f2157a3d4238cebc7c55f0a517728c38f7b200f81"
+dependencies = [
+ "serde",
+ "termcolor",
+ "unicode-width",
+]
+
 [[package]]
 name = "colorchoice"
 version = "1.0.3"
@@ -136,6 +147,7 @@ name = "deimos"
 version = "0.1.0"
 dependencies = [
  "clap",
+ "codespan-reporting",
  "pest",
  "pest_derive",
 ]
@@ -253,6 +265,26 @@ dependencies = [
  "proc-macro2",
 ]
 
+[[package]]
+name = "serde"
+version = "1.0.219"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5f0e2c6ed6606019b4e29e69dbaba95b11854410e5347d525002456dbbb786b6"
+dependencies = [
+ "serde_derive",
+]
+
+[[package]]
+name = "serde_derive"
+version = "1.0.219"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5b0276cf7f2c73365f7157c8123c21cd9a50fbbd844757af28ca1f5925fc2a00"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "sha2"
 version = "0.10.8"
@@ -281,6 +313,15 @@ dependencies = [
  "unicode-ident",
 ]
 
+[[package]]
+name = "termcolor"
+version = "1.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "06794f8f6c5c898b3275aebefa6b8a1cb24cd2c6c79397ab15774837a0bc5755"
+dependencies = [
+ "winapi-util",
+]
+
 [[package]]
 name = "thiserror"
 version = "1.0.69"
@@ -319,6 +360,12 @@ version = "1.0.14"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "adb9e6ca4f869e1180728b7950e35922a7fc6397f7b641499e8f3ef06e50dc83"
 
+[[package]]
+name = "unicode-width"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1fc81956842c57dac11422a97c3b8195a1ff727f06e85c84ed2e8aa277c9a0fd"
+
 [[package]]
 name = "utf8parse"
 version = "0.2.2"
@@ -331,6 +378,15 @@ version = "0.9.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0b928f33d975fc6ad9f86c8f283853ad26bdd5b10b7f1542aa2fa15e2289105a"
 
+[[package]]
+name = "winapi-util"
+version = "0.1.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cf221c93e13a30d793f7645a0e7762c55d169dbb0a49671918a2319d289b10bb"
+dependencies = [
+ "windows-sys",
+]
+
 [[package]]
 name = "windows-sys"
 version = "0.59.0"
diff --git a/Cargo.toml b/Cargo.toml
index c0e667e..a1d1c76 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -15,3 +15,4 @@ path = "src/bin/dmc/main.rs"
 pest = "2.7.14"
 clap = { version = "4.5.23", features = ["derive"] }
 pest_derive = "2.7.14"
+codespan-reporting = "0.12.0"
diff --git a/rust-toolchain.toml b/rust-toolchain.toml
new file mode 100644
index 0000000..5d56faf
--- /dev/null
+++ b/rust-toolchain.toml
@@ -0,0 +1,2 @@
+[toolchain]
+channel = "nightly"
diff --git a/sketching/may_2025/name_one.dm b/sketching/may_2025/name_one.dm
index 562c5b5..c94a645 100644
--- a/sketching/may_2025/name_one.dm
+++ b/sketching/may_2025/name_one.dm
@@ -4,7 +4,10 @@ fn main() {
     let x = 'Hello';
     let y = 'World';
     {
+        let x = 'Hello';
         let test = 'Test';
+        let test = 'Again';
     };
     x = y;
+    let x = 'Hello!';
 }
\ No newline at end of file
diff --git a/src/ast/build.rs b/src/ast/build.rs
index e2edddc..a4acfc7 100644
--- a/src/ast/build.rs
+++ b/src/ast/build.rs
@@ -14,10 +14,18 @@ pub fn build_ast(compilation_unit_pair: Pair<Rule>) -> CompilationUnit {
 }
 
 fn build_identifier(identifier_pair: Pair<Rule>) -> Identifier {
-    Identifier::new(identifier_pair.as_span().as_str())
+    let as_span = identifier_pair.as_span();
+    Identifier::new(
+        as_span.as_str(),
+        Range {
+            start: as_span.start(),
+            end: as_span.end(),
+        },
+    )
 }
 
 fn build_fqn(fqn_pair: Pair<Rule>) -> FullyQualifiedName {
+    let as_span = fqn_pair.as_span();
     FullyQualifiedName::new(
         fqn_pair
             .into_inner()
@@ -25,6 +33,10 @@ fn build_fqn(fqn_pair: Pair<Rule>) -> FullyQualifiedName {
                 expect_and_use(identifier_pair, Rule::Identifier, build_identifier)
             })
             .collect(),
+        Range {
+            start: as_span.start(),
+            end: as_span.end(),
+        },
     )
 }
 
diff --git a/src/ast/mod.rs b/src/ast/mod.rs
index 8300d16..9548221 100644
--- a/src/ast/mod.rs
+++ b/src/ast/mod.rs
@@ -1,5 +1,6 @@
 use crate::compile::name_analysis::Symbol;
 use pest::Parser;
+use std::range::Range;
 
 pub mod build;
 pub mod named;
@@ -54,14 +55,16 @@ pub enum SuffixUnaryOperator {
 #[derive(Debug, Clone)]
 pub struct Identifier {
     pub name: String,
+    pub range: Range<usize>,
     scope_id: Option<usize>,
     symbol: Option<Symbol>,
 }
 
 impl Identifier {
-    pub fn new(name: &str) -> Self {
+    pub fn new(name: &str, range: Range<usize>) -> Self {
         Identifier {
             name: name.to_string(),
+            range,
             scope_id: None,
             symbol: None,
         }
@@ -87,14 +90,16 @@ impl Identifier {
 #[derive(Debug)]
 pub struct FullyQualifiedName {
     pub identifiers: Vec<Identifier>,
+    pub range: Range<usize>,
     scope_id: Option<usize>,
     symbol: Option<Symbol>,
 }
 
 impl FullyQualifiedName {
-    pub fn new(identifiers: Vec<Identifier>) -> Self {
+    pub fn new(identifiers: Vec<Identifier>, range: Range<usize>) -> Self {
         FullyQualifiedName {
             identifiers,
+            range,
             scope_id: None,
             symbol: None,
         }
diff --git a/src/bin/dmc/main.rs b/src/bin/dmc/main.rs
index bc3948a..ea350bf 100644
--- a/src/bin/dmc/main.rs
+++ b/src/bin/dmc/main.rs
@@ -46,7 +46,10 @@ fn main() {
         }
         Commands::NameAnalysis { paths } => {
             for path in paths {
-                name_analysis(&path)
+                let result = name_analysis(&path);
+                if let Err(e) = result {
+                    eprintln!("{}", e);
+                }
             }
         }
     }
diff --git a/src/bin/dmc/name_analysis.rs b/src/bin/dmc/name_analysis.rs
index 3a506b5..4aad6b3 100644
--- a/src/bin/dmc/name_analysis.rs
+++ b/src/bin/dmc/name_analysis.rs
@@ -1,36 +1,37 @@
+use codespan_reporting::files::SimpleFiles;
+use codespan_reporting::term;
+use codespan_reporting::term::termcolor::{ColorChoice, StandardStream};
 use deimos::ast::build::build_ast;
 use deimos::compile::name_analysis::{analyze_names, SymbolTable};
 use deimos::parser::{DeimosParser, Rule};
 use pest::Parser;
 use std::path::Path;
 
-pub fn name_analysis(path: &Path) {
+pub fn name_analysis(path: &Path) -> Result<(), Box<dyn std::error::Error>> {
     let src = std::fs::read_to_string(path).unwrap();
-    let parse_result = DeimosParser::parse(
-        Rule::CompilationUnit,
-        &src
-    );
+    let parse_result = DeimosParser::parse(Rule::CompilationUnit, &src);
+    let mut files = SimpleFiles::new();
+    let file_id = files.add(path.display().to_string(), &src);
+
     match parse_result {
         Ok(mut pairs) => {
             let compilation_unit_pair = pairs.next().unwrap();
             let mut compilation_unit = build_ast(compilation_unit_pair);
             let mut symbol_table = SymbolTable::new();
-            let name_analysis_result = analyze_names(
-                &mut compilation_unit,
-                &mut symbol_table,
-            );
-            match name_analysis_result {
-                Err(e) => {
-                    eprintln!("{}", e);
-                }
-                Ok(_) => {
-                    println!("name_analysis complete");
-                    println!("{}", symbol_table);
+            let diagnostics = analyze_names(file_id, &mut compilation_unit, &mut symbol_table);
+            if diagnostics.is_empty() {
+                println!("Name analysis complete.");
+                println!("Symbol table\n-------\n{}", symbol_table);
+                Ok(())
+            } else {
+                let writer = StandardStream::stderr(ColorChoice::Always);
+                let config = term::Config::default();
+                for diagnostic in diagnostics {
+                    term::emit(&mut writer.lock(), &config, &files, &diagnostic)?;
                 }
+                Ok(())
             }
         }
-        Err(e) => {
-            eprintln!("{}", e);
-        }
+        Err(e) => Err(e.into()),
     }
-}
\ No newline at end of file
+}
diff --git a/src/compile/name_analysis.rs b/src/compile/name_analysis.rs
index 39e6bb1..bf774e5 100644
--- a/src/compile/name_analysis.rs
+++ b/src/compile/name_analysis.rs
@@ -1,5 +1,6 @@
 use crate::ast::named::Named;
 use crate::ast::*;
+use codespan_reporting::diagnostic::{Diagnostic, Label};
 use std::collections::HashMap;
 use std::fmt::Display;
 
@@ -9,6 +10,15 @@ pub enum Symbol {
     Variable(VariableSymbol),
 }
 
+impl Symbol {
+    pub fn name(&self) -> &str {
+        match self {
+            Symbol::Function(s) => s.declared_name.as_str(),
+            Symbol::Variable(s) => s.name.as_str(),
+        }
+    }
+}
+
 impl Display for Symbol {
     fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
         use Symbol::*;
@@ -96,7 +106,10 @@ impl SymbolTable {
 
     pub fn insert(&mut self, name: String, symbol: Symbol) -> Result<(), String> {
         if let Some(current_symbol) = self.scopes[self.current_scope_id].symbols.get(&name) {
-            Err(format!("Symbol '{}' already defined", current_symbol))
+            Err(format!(
+                "Symbol '{}' already defined in current scope.",
+                current_symbol.name()
+            ))
         } else {
             self.scopes[self.current_scope_id]
                 .symbols
@@ -117,7 +130,7 @@ impl SymbolTable {
                 None
             };
         }
-        Err(format!("Symbol '{}' not found", name))
+        Err(format!("Symbol '{}' not found in current scope.", name))
     }
 }
 
@@ -173,101 +186,138 @@ impl FqnContext {
 }
 
 pub fn analyze_names(
+    file_id: usize,
     compilation_unit: &mut CompilationUnit,
     symbol_table: &mut SymbolTable,
-) -> Result<(), String> {
+) -> Vec<Diagnostic<usize>> {
+    let mut diagnostics = vec![];
+
     let mut fqn_context = FqnContext::new();
     if let Some(namespace) = &compilation_unit.namespace {
         fqn_context.push(namespace.name().to_string());
     }
 
     for declaration in &mut compilation_unit.declarations {
-        gather_module_level_declaration(declaration, symbol_table, &mut fqn_context)?;
+        diagnostics.extend(gather_module_level_declaration(
+            file_id,
+            declaration,
+            symbol_table,
+            &mut fqn_context,
+        ));
     }
 
     assert_eq!(symbol_table.current_scope_id, 0);
 
     for declaration in &mut compilation_unit.declarations {
-        resolve_module_level_declaration(declaration, symbol_table)?;
+        diagnostics.extend(resolve_module_level_declaration(file_id, declaration, symbol_table));
     }
 
-    Ok(())
+    diagnostics
 }
 
 fn gather_module_level_declaration(
+    file_id: usize,
     declaration: &mut ModuleLevelDeclaration,
     symbol_table: &mut SymbolTable,
     fqn_context: &mut FqnContext,
-) -> Result<(), String> {
+) -> Vec<Diagnostic<usize>> {
     use ModuleLevelDeclaration::*;
     match declaration {
         Function(function_definition) => {
-            gather_function_definition(function_definition, symbol_table, fqn_context)
+            gather_function_definition(file_id, function_definition, symbol_table, fqn_context)
         }
         _ => todo!(),
     }
 }
 
 fn gather_function_definition(
+    file_id: usize,
     function: &mut FunctionDefinition,
     symbol_table: &mut SymbolTable,
     fqn_context: &mut FqnContext,
-) -> Result<(), String> {
+) -> Vec<Diagnostic<usize>> {
+    let mut diagnostics = vec![];
+
     let declared_name = function.identifier.name().to_string();
     let resolved_name = fqn_context.resolve(&declared_name);
-    symbol_table.insert(
+
+    let insert_result = symbol_table.insert(
         declared_name.clone(),
         Symbol::Function(FunctionSymbol {
             fqn: resolved_name.clone(),
             declared_name,
             is_public: function.is_public,
         }),
-    )?;
+    );
+    if let Err(msg) = insert_result {
+        diagnostics.push(
+            Diagnostic::error()
+                .with_message(msg)
+                .with_label(Label::primary(file_id, function.identifier.range)),
+        )
+    }
+
     function
         .identifier
         .set_scope_id(symbol_table.current_scope_id());
+
     symbol_table.push_scope(&format!("FunctionScope({})", resolved_name));
     // TODO: params
-    gather_function_body(&mut function.body, symbol_table, fqn_context)?;
+    diagnostics.extend(gather_function_body(
+        file_id,
+        &mut function.body,
+        symbol_table,
+        fqn_context,
+    ));
     symbol_table.pop_scope();
-    Ok(())
+
+    diagnostics
 }
 
 fn gather_function_body(
+    file_id: usize,
     function_body: &mut FunctionBody,
     symbol_table: &mut SymbolTable,
     fqn_context: &mut FqnContext,
-) -> Result<(), String> {
+) -> Vec<Diagnostic<usize>> {
     use FunctionBody::*;
     match function_body {
-        Block(block) => gather_block_statement(block, symbol_table, fqn_context),
+        Block(block) => gather_block_statement(file_id, block, symbol_table, fqn_context),
         _ => todo!(),
     }
 }
 
 fn gather_block_statement(
+    file_id: usize,
     block: &mut BlockStatement,
     symbol_table: &mut SymbolTable,
     fqn_context: &mut FqnContext,
-) -> Result<(), String> {
+) -> Vec<Diagnostic<usize>> {
+    let mut diagnostics = vec![];
     symbol_table.push_scope("BlockStatementScope");
     for statement in &mut block.statements {
-        gather_statement(statement, symbol_table, fqn_context)?;
+        diagnostics.extend(gather_statement(
+            file_id,
+            statement,
+            symbol_table,
+            fqn_context,
+        ));
     }
     symbol_table.pop_scope();
-    Ok(())
+    diagnostics
 }
 
 fn gather_statement(
+    file_id: usize,
     statement: &mut Statement,
     symbol_table: &mut SymbolTable,
     fqn_context: &mut FqnContext,
-) -> Result<(), String> {
+) -> Vec<Diagnostic<usize>> {
     use Statement::*;
     match statement {
-        BlockStatement(block) => gather_block_statement(block, symbol_table, fqn_context),
+        BlockStatement(block) => gather_block_statement(file_id, block, symbol_table, fqn_context),
         VariableDeclarationStatement(variable_declaration) => {
-            gather_variable_declaration(variable_declaration, symbol_table, fqn_context)
+            gather_variable_declaration(file_id, variable_declaration, symbol_table)
         }
         AssignStatement(assign_statement) => {
             gather_assign_statement(assign_statement, symbol_table, fqn_context)
@@ -277,162 +327,198 @@ fn gather_statement(
 }
 
 fn gather_variable_declaration(
+    file_id: usize,
     variable_declaration: &mut VariableDeclarationStatement,
     symbol_table: &mut SymbolTable,
-    fqn_context: &mut FqnContext,
-) -> Result<(), String> {
+) -> Vec<Diagnostic<usize>> {
+    let mut diagnostics = vec![];
     let variable_name = variable_declaration.identifier.name().to_string();
-    symbol_table.insert(
+
+    let insert_result = symbol_table.insert(
         variable_name.clone(),
         Symbol::Variable(VariableSymbol {
             name: variable_name,
             is_mutable: variable_declaration.is_mutable,
         }),
-    )?;
+    );
+
+    if let Err(msg) = insert_result {
+        diagnostics.push(
+            Diagnostic::error()
+                .with_message(msg)
+                .with_label(Label::primary(
+                    file_id,
+                    variable_declaration.identifier.range,
+                )),
+        );
+    }
+
     variable_declaration
         .identifier
         .set_scope_id(symbol_table.current_scope_id());
-    Ok(())
+
+    diagnostics
 }
 
 fn gather_assign_statement(
     assign_statement: &mut AssignStatement,
     symbol_table: &mut SymbolTable,
     fqn_context: &mut FqnContext,
-) -> Result<(), String> {
-    gather_expression(&mut assign_statement.lhs, symbol_table, fqn_context)?;
-    gather_expression(&mut assign_statement.rhs, symbol_table, fqn_context)?;
-    Ok(())
+) -> Vec<Diagnostic<usize>> {
+    let mut diagnostics = vec![];
+    diagnostics.extend(gather_expression(
+        &mut assign_statement.lhs,
+        symbol_table,
+        fqn_context,
+    ));
+    diagnostics.extend(gather_expression(
+        &mut assign_statement.rhs,
+        symbol_table,
+        fqn_context,
+    ));
+    diagnostics
 }
 
 fn gather_expression(
     expression: &mut Expression,
     symbol_table: &mut SymbolTable,
     fqn_context: &mut FqnContext,
-) -> Result<(), String> {
+) -> Vec<Diagnostic<usize>> {
     use Expression::*;
     match expression {
         FullyQualifiedName(fully_qualified_name) => {
-            gather_fully_qualified_name(fully_qualified_name, symbol_table, fqn_context)?;
+            gather_fully_qualified_name(fully_qualified_name, symbol_table)
+        }
+        _ => {
+            vec![]
         }
-        _ => {}
     }
-    Ok(())
 }
 
 fn gather_fully_qualified_name(
     fully_qualified_name: &mut FullyQualifiedName,
     symbol_table: &mut SymbolTable,
-    fqn_context: &mut FqnContext,
-) -> Result<(), String> {
+) -> Vec<Diagnostic<usize>> {
     fully_qualified_name.set_scope_id(symbol_table.current_scope_id());
-    Ok(())
+    vec![]
 }
 
 /* Resolve */
 
 fn resolve_module_level_declaration(
+    file_id: usize,
     declaration: &mut ModuleLevelDeclaration,
     symbol_table: &mut SymbolTable,
-) -> Result<(), String> {
+) -> Vec<Diagnostic<usize>> {
     use ModuleLevelDeclaration::*;
     match declaration {
         Function(function_definition) => {
-            resolve_function_definition(function_definition, symbol_table)
+            resolve_function_definition(file_id, function_definition, symbol_table)
         }
         _ => todo!(),
     }
 }
 
 fn resolve_function_definition(
+    file_id: usize,
     function_definition: &mut FunctionDefinition,
     symbol_table: &mut SymbolTable,
-) -> Result<(), String> {
-    resolve_function_body(&mut function_definition.body, symbol_table)
+) -> Vec<Diagnostic<usize>> {
+    resolve_function_body(file_id, &mut function_definition.body, symbol_table)
 }
 
 fn resolve_function_body(
+    file_id: usize,
     function_body: &mut FunctionBody,
     symbol_table: &mut SymbolTable,
-) -> Result<(), String> {
+) -> Vec<Diagnostic<usize>> {
     use FunctionBody::*;
     match function_body {
-        Block(block) => resolve_block(block, symbol_table),
+        Block(block) => resolve_block(file_id, block, symbol_table),
         _ => todo!(),
     }
 }
 
 fn resolve_block(
+    file_id: usize,
     block_statement: &mut BlockStatement,
     symbol_table: &mut SymbolTable,
-) -> Result<(), String> {
-    for statement in &mut block_statement.statements {
-        resolve_statement(statement, symbol_table)?;
-    }
-    Ok(())
+) -> Vec<Diagnostic<usize>> {
+    block_statement
+        .statements
+        .iter_mut()
+        .flat_map(|statement| resolve_statement(file_id, statement, symbol_table))
+        .collect()
 }
 
 fn resolve_statement(
+    file_id: usize,
     statement: &mut Statement,
     symbol_table: &mut SymbolTable,
-) -> Result<(), String> {
+) -> Vec<Diagnostic<usize>> {
     use Statement::*;
     match statement {
-        BlockStatement(block) => resolve_block(block, symbol_table),
+        BlockStatement(block) => resolve_block(file_id, block, symbol_table),
         VariableDeclarationStatement(variable_declaration) => {
-            resolve_variable_declaration(variable_declaration, symbol_table)
+            resolve_variable_declaration(file_id, variable_declaration, symbol_table)
         }
         AssignStatement(assign_statement) => {
-            resolve_assign_statement(assign_statement, symbol_table)
+            resolve_assign_statement(file_id, assign_statement, symbol_table)
         }
-        CallStatement(call_statement) => resolve_call_statement(call_statement, symbol_table),
+        CallStatement(call_statement) => resolve_call_statement(file_id, call_statement, symbol_table),
         _ => todo!(),
     }
 }
 
 fn resolve_variable_declaration(
+    file_id: usize,
     variable_declaration: &mut VariableDeclarationStatement,
     symbol_table: &mut SymbolTable,
-) -> Result<(), String> {
+) -> Vec<Diagnostic<usize>> {
     if let Some(initializer) = &mut variable_declaration.initializer {
-        resolve_expression(initializer, symbol_table)
+        resolve_expression(file_id, initializer, symbol_table)
     } else {
-        Ok(())
+        vec![]
     }
 }
 
 fn resolve_assign_statement(
+    file_id: usize,
     assign_statement: &mut AssignStatement,
     symbol_table: &mut SymbolTable,
-) -> Result<(), String> {
-    resolve_expression(&mut assign_statement.lhs, symbol_table)?;
-    resolve_expression(&mut assign_statement.rhs, symbol_table)?;
-    Ok(())
+) -> Vec<Diagnostic<usize>> {
+    let mut diagnostics = vec![];
+    diagnostics.extend(resolve_expression(file_id, &mut assign_statement.lhs, symbol_table));
+    diagnostics.extend(resolve_expression(file_id, &mut assign_statement.rhs, symbol_table));
+    diagnostics
 }
 
 fn resolve_call_statement(
+    file_id: usize,
     call_statement: &mut CallStatement,
     symbol_table: &mut SymbolTable,
-) -> Result<(), String> {
-    resolve_expression(&mut call_statement.0, symbol_table)
+) -> Vec<Diagnostic<usize>> {
+    resolve_expression(file_id, &mut call_statement.0, symbol_table)
 }
 
 fn resolve_expression(
+    file_id: usize,
     expression: &mut Expression,
     symbol_table: &mut SymbolTable,
-) -> Result<(), String> {
+) -> Vec<Diagnostic<usize>> {
     use Expression::*;
     match expression {
-        FullyQualifiedName(fqn) => resolve_fully_qualified_name(fqn, symbol_table),
-        Literal(_) => Ok(()),
+        FullyQualifiedName(fqn) => resolve_fully_qualified_name(file_id, fqn, symbol_table),
+        Literal(_) => vec![],
         _ => todo!(),
     }
 }
 
 fn resolve_fully_qualified_name(
+    file_id: usize,
     fully_qualified_name: &mut FullyQualifiedName,
     symbol_table: &mut SymbolTable,
-) -> Result<(), String> {
+) -> Vec<Diagnostic<usize>> {
     let lookup_result = symbol_table.lookup(
         fully_qualified_name.name().as_ref(),
         fully_qualified_name.scope_id().expect(&format!(
@@ -443,8 +529,12 @@ fn resolve_fully_qualified_name(
     match lookup_result {
         Ok(symbol) => {
             fully_qualified_name.set_symbol(symbol.clone());
-            Ok(())
+            vec![]
         }
-        Err(e) => Err(e),
+        Err(e) => vec![
+            Diagnostic::error()
+            .with_message(e)
+                .with_label(Label::primary(file_id, fully_qualified_name.range))
+        ],
     }
 }
diff --git a/src/lib.rs b/src/lib.rs
index c0a8b56..44f09d1 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,3 +1,4 @@
+#![feature(new_range_api)]
 #![allow(warnings)]
 pub mod ast;
 pub mod compile;