Use ast walking to verify that identifiers have saved symbols and linking symbols are resolved.

src/ast/mod.rs

@@ -3,4 +3,4 @@ pub mod children;
 pub mod node;
 pub mod pretty_print;
 pub mod unparse;
-mod walk;
+pub mod walk;

src/name_analysis/gather.rs

@@ -250,9 +250,9 @@ fn gather_parameter(
 
     match insert_result {
         Ok(parameter_symbol) => {
-            parameter
-                .identifier_mut()
-                .set_scope_id(symbol_table.current_scope_id());
+            let mut identifier = parameter.identifier_mut();
+            identifier.set_scope_id(symbol_table.current_scope_id());
+            identifier.set_saved_symbol(Symbol::Parameter(parameter_symbol.clone()));
 
             gather_type_use(
                 parameter.type_use_mut(),
@@ -694,9 +694,9 @@ fn gather_function_definition(
 
     match insert_result {
         Ok(function_symbol) => {
-            function
-                .identifier_mut()
-                .set_scope_id(symbol_table.current_scope_id());
+            let mut identifier = function.identifier_mut();
+            identifier.set_saved_symbol(Symbol::Function(function_symbol.clone()));
+            identifier.set_scope_id(symbol_table.current_scope_id());
 
             symbol_table.push_scope(&format!("FunctionParameterScope({})", resolved_name));
 
@@ -1043,21 +1043,22 @@ fn gather_variable_declaration(
         Some(identifier),
     ));
 
-    if let Err(err) = insert_result {
-        handle_insert_error(
+    match insert_result {
+        Ok(variable_symbol) => {
+            let mut identifier = variable_declaration.identifier_mut();
+            identifier.set_saved_symbol(Symbol::Variable(variable_symbol));
+            identifier.set_scope_id(symbol_table.current_scope_id());
+        }
+        Err(err) => handle_insert_error(
             err,
             &variable_name,
             identifier.file_id(),
             identifier.range(),
             "function/variable",
             diagnostics,
-        )
+        ),
     }
 
-    variable_declaration
-        .identifier_mut()
-        .set_scope_id(symbol_table.current_scope_id());
-
     if let Some(initializer) = variable_declaration.initializer_mut() {
         gather_expression(initializer, symbol_table, diagnostics);
     }

src/name_analysis/mod.rs

@@ -55,6 +55,9 @@ pub fn analyze_names(
 mod tests {
     use super::*;
     use crate::ast::build::build_ast;
+    use crate::ast::children::NodeRef;
+    use crate::ast::node::use_statement::UseStatementLast;
+    use crate::ast::walk::walk_depth_first;
     use crate::parser::{DeimosParser, Rule};
     use crate::std_core::add_std_core_symbols;
     use codespan_reporting::files::SimpleFiles;
@@ -68,7 +71,7 @@ mod tests {
         sources: HashMap<&str, &str>,
         symbol_table: &mut SymbolTable,
         n_diagnostics: usize,
-    ) {
+    ) -> Vec<CompilationUnit> {
         let mut files = SimpleFiles::new();
         let mut compilation_units = vec![];
 
@@ -83,12 +86,12 @@ mod tests {
                 panic!("Parsing did not consume entire input.");
             }
 
-            compilation_units.push(build_ast(file_name, file_id, pairs.next().unwrap()))
+            compilation_units.push(build_ast(file_name, file_id, pairs.next().unwrap()));
         }
 
         let diagnostics = analyze_names(&mut compilation_units, symbol_table);
 
-        if !diagnostics.is_empty() {
+        if diagnostics.len() != n_diagnostics {
             let writer = StandardStream::stderr(ColorChoice::Always);
             let config = term::Config::default();
 
@@ -101,13 +104,88 @@ mod tests {
 
         assert_eq!(n_diagnostics, diagnostics.len());
 
-        for compilation_unit in &compilation_units {
-            dbg!(compilation_unit);
-        }
+        compilation_units
     }
 
-    fn assert_no_diagnostics(sources: HashMap<&str, &str>, symbol_table: &mut SymbolTable) {
-        assert_number_of_diagnostics(sources, symbol_table, 0);
+    fn assert_no_diagnostics(
+        sources: HashMap<&str, &str>,
+        symbol_table: &mut SymbolTable,
+    ) -> Vec<CompilationUnit> {
+        assert_number_of_diagnostics(sources, symbol_table, 0)
+    }
+
+    fn assert_saved_symbols(compilation_unit: &CompilationUnit) {
+        walk_depth_first(compilation_unit, &mut |node_ref| match node_ref {
+            NodeRef::Identifier(identifier) => {
+                if identifier.saved_symbol().is_none() {
+                    panic!("{:?} does not have a saved symbol.", identifier)
+                }
+            }
+            NodeRef::FullyQualifiedName(fqn) => {
+                if fqn.saved_symbol().is_none() {
+                    panic!("{:?} does not have a saved symbol.", fqn)
+                }
+            }
+            NodeRef::UseStatement(use_statement) => match use_statement.last() {
+                UseStatementLast::Identifier(identifier) => {
+                    if identifier.saved_symbol().is_none() {
+                        panic!(
+                            "UseStatement {:?} does not have a saved symbol.",
+                            identifier
+                        )
+                    }
+                }
+                UseStatementLast::Identifiers(identifiers) => {
+                    for identifier in identifiers {
+                        if identifier.saved_symbol().is_none() {
+                            panic!(
+                                "UseStatement {:?} does not have a saved symbol.",
+                                identifier
+                            )
+                        }
+                    }
+                }
+                _ => todo!(),
+            },
+            _ => {}
+        })
+    }
+
+    fn assert_resolved_symbols(compilation_unit: &CompilationUnit) {
+        walk_depth_first(compilation_unit, &mut |node_ref| match node_ref {
+            NodeRef::UseStatement(use_statement) => match use_statement.last() {
+                UseStatementLast::Identifier(identifier) => {
+                    let use_statement_symbol = identifier
+                        .saved_symbol()
+                        .unwrap()
+                        .unwrap_use_statement_symbol();
+                    let borrowed = use_statement_symbol.borrow();
+                    if borrowed.referenced_symbol().is_none() {
+                        panic!(
+                            "{:?} does not have a referenced symbol.",
+                            use_statement_symbol
+                        )
+                    }
+                }
+                UseStatementLast::Identifiers(identifiers) => {
+                    for identifier in identifiers {
+                        let use_statement_symbol = identifier
+                            .saved_symbol()
+                            .unwrap()
+                            .unwrap_use_statement_symbol();
+                        let borrowed = use_statement_symbol.borrow();
+                        if borrowed.referenced_symbol().is_none() {
+                            panic!(
+                                "{:?} does not have a referenced symbol.",
+                                use_statement_symbol
+                            )
+                        }
+                    }
+                }
+                _ => todo!(),
+            },
+            _ => {}
+        })
     }
 
     #[test]
@@ -120,7 +198,10 @@ mod tests {
             }"},
         )]);
 
-        assert_no_diagnostics(sources, &mut SymbolTable::new());
+        let cus = assert_no_diagnostics(sources, &mut SymbolTable::new());
+        for ref cu in cus {
+            assert_saved_symbols(cu);
+        }
     }
 
     #[test]
@@ -142,7 +223,11 @@ mod tests {
             ),
         ]);
 
-        assert_no_diagnostics(sources, &mut SymbolTable::new());
+        let cus = assert_no_diagnostics(sources, &mut SymbolTable::new());
+        for ref cu in cus {
+            assert_saved_symbols(cu);
+            assert_resolved_symbols(cu);
+        }
     }
 
     #[test]
@@ -158,7 +243,11 @@ mod tests {
 
         let mut symbol_table = SymbolTable::new();
         add_std_core_symbols(&mut symbol_table).expect("Failed to add std::core symbols.");
-        assert_no_diagnostics(sources, &mut symbol_table);
+        let cus = assert_no_diagnostics(sources, &mut symbol_table);
+        for ref cu in cus {
+            assert_saved_symbols(cu);
+            assert_resolved_symbols(cu);
+        }
     }
 
     #[test]
@@ -194,7 +283,11 @@ mod tests {
             ),
         ]);
         let mut symbol_table = SymbolTable::new();
-        assert_no_diagnostics(sources, &mut symbol_table);
+        let cus = assert_no_diagnostics(sources, &mut symbol_table);
+        for ref cu in cus {
+            assert_saved_symbols(cu);
+            assert_resolved_symbols(cu);
+        }
     }
 
     #[test]

src/name_analysis/symbol_table.rs

@@ -311,27 +311,31 @@ impl SymbolTable {
     pub fn insert_variable_symbol(
         &mut self,
         variable_symbol: VariableSymbol,
-    ) -> Result<(), SymbolInsertError> {
+    ) -> Result<Rc<VariableSymbol>, SymbolInsertError> {
         let current_scope = self.scopes.get_mut(self.current_scope_id).unwrap();
         if let Some(defined_symbol) =
             current_scope.get_value_symbol_by_declared_name(variable_symbol.declared_name())
         {
             Err(SymbolAlreadyDefined(defined_symbol))
         } else {
-            current_scope.variable_symbols.insert(
-                variable_symbol.declared_name().to_string(),
-                Rc::new(variable_symbol),
-            );
-            Ok(())
+            let declared_name = variable_symbol.declared_name().to_string();
+            let to_insert = Rc::new(variable_symbol);
+            let to_return = to_insert.clone();
+            current_scope
+                .variable_symbols
+                .insert(declared_name, to_insert);
+            Ok(to_return)
         }
     }
-    
+
     pub fn insert_class_member_symbol(
         &mut self,
         class_member_symbol: ClassMemberSymbol,
     ) -> Result<(), SymbolInsertError> {
         let current_scope = self.scopes.get_mut(self.current_scope_id).unwrap();
-        if let Some(defined_symbol) = current_scope.get_expressible_by_declared_name(class_member_symbol.declared_name()) {
+        if let Some(defined_symbol) =
+            current_scope.get_expressible_by_declared_name(class_member_symbol.declared_name())
+        {
             Err(SymbolAlreadyDefined(defined_symbol))
         } else {
             current_scope.class_member_symbols.insert(