Add basic classes example.

dmc-lib/src/ast/class.rs

@@ -1,7 +1,7 @@
 use crate::ast::constructor::Constructor;
 use crate::ast::field::Field;
 use crate::ast::function::Function;
-use crate::diagnostic::Diagnostic;
+use crate::diagnostic::{Diagnostic, SecondaryLabel};
 use crate::source_range::SourceRange;
 use crate::symbol::class_symbol::ClassSymbol;
 use crate::symbol_table::{SymbolInsertError, SymbolTable};
@@ -48,6 +48,7 @@ impl Class {
             .insert_class_symbol(to_insert)
             .map_err(|e| match e {
                 SymbolInsertError::AlreadyDeclared(already_declared) => {
+                    let symbol = already_declared.symbol().borrow();
                     vec![
                         Diagnostic::new(
                             &format!(
@@ -57,6 +58,11 @@ impl Class {
                             self.declared_name_source_range.start(),
                             self.declared_name_source_range.end(),
                         )
+                        .with_secondary_labels(&[SecondaryLabel::new(
+                            symbol.declared_name_source_range().start(),
+                            symbol.declared_name_source_range().end(),
+                            Some("Symbol declared here.".to_string()),
+                        )])
                         .with_reporter(file!(), line!()),
                     ]
                 }
@@ -151,6 +157,10 @@ impl Class {
             .flatten()
             .for_each(|diagnostic| diagnostics.push(diagnostic));
 
+        if !diagnostics.is_empty() {
+            return Err(diagnostics);
+        }
+
         if let Some(constructor) = &mut self.constructor {
             match constructor.type_check(symbol_table) {
                 Ok(_) => {}
@@ -160,6 +170,10 @@ impl Class {
             }
         }
 
+        if !diagnostics.is_empty() {
+            return Err(diagnostics);
+        }
+
         self.functions
             .iter_mut()
             .map(|function| function.type_check(symbol_table))
@@ -167,6 +181,10 @@ impl Class {
             .flatten()
             .for_each(|diagnostic| diagnostics.push(diagnostic));
 
+        if !diagnostics.is_empty() {
+            return Err(diagnostics);
+        }
+
         // We need to determine if fields are initialized or not (the latter is an error).
         // First phase: check all fields, then check constructor, leaving pending those things that
         // are fields <- initialized by constructor. Then circle back to fields and check all are
@@ -199,6 +217,9 @@ impl Class {
                         field.declared_name_source_range().start(),
                         field.declared_name_source_range().end(),
                     )
+                    .with_primary_label_message(
+                        "Must be initialized in declaration or constructor.",
+                    )
                     .with_reporter(file!(), line!()),
                 )
             }

examples/basic_classes.dm

@@ -0,0 +1,20 @@
+class Foo
+    mut bar: Int = 42
+
+    ctor(_bar: Int)
+    end
+
+    fn baz() -> Int
+        bar
+    end
+end
+
+class Qux
+    fn foo() -> Foo
+        Foo(42)
+    end
+end
+
+fn main()
+    let crash = Qux()
+end