[fine] Empty blocks generate nothing

fine/src/semantics.rs

@@ -347,10 +347,10 @@ impl<'a> Semantics<'a> {
             return None;
         }
 
-        // if tree.children.len() == 2 {
-        //     // Empty blocks generate Nothing.
-        //     return Some(Type::Nothing);
-        // }
+        if tree.children.len() == 2 {
+            // Empty blocks generate Nothing.
+            return Some(Type::Nothing);
+        }
 
         // The type of the block is the type of the last expression.
         // (But the last child is the closing brace probably?)
@@ -359,6 +359,9 @@ impl<'a> Semantics<'a> {
 
         let mut is_unreachable = false;
         for i in 1..last_index {
+            // TODO: if `is_unreachable` here then we actually have
+            // unreachable code here! We should warn about it I guess.
+
             is_unreachable = self
                 .type_of(tree.nth_tree(i)?)
                 .map(|t| matches!(t, Type::Unreachable))

fine/tests/example_tests.rs

@@ -16,7 +16,7 @@ fn rebase_concrete(source_path: &str, dump: &str) {
         result.push_str(line);
         result.push_str("\n");
 
-        if line == "// concrete:" {
+        if line == "// @concrete:" {
             found_concrete_section = true;
             break;
         }

fine/tests/expression/block.fine

@@ -0,0 +1,10 @@
+// @concrete:
+// | File
+// |   Block
+// |     LeftBrace:'"{"'
+// |     RightBrace:'"}"'
+// |
+
+{}
+
+// @type: 94 ()