Only inspect expressions for now

For `inspect` statements, we'll need to repeat the `if constexpr` rigamarole

Author: hsutter

source/lex.h

@@ -728,7 +728,7 @@ auto lex_line(
                 //G     
                 //G floating-point-literal:
                 //G     digit { ' | digit }* . digit { ' | digit }*
-                //GTODO TODO: full grammar
+                //GTODO full grammar
                 //G     
                 else if (is_digit(line[i])) {
                     auto j = 1;

source/parse.h

@@ -1949,7 +1949,7 @@ class parser
                 //  it doesn't destabilize any regression tests
             )
         {
-            error("expression-statement does not end with semicolon");
+            error("expected ; at end of statement");
             return {};
         }
         if (curr().type() == lexeme::Semicolon) {
@@ -2267,6 +2267,14 @@ class parser
             return {};
         }
 
+        if (!is_expression) {
+            errors.emplace_back(
+                curr().position(),
+                "(temporary alpha limitation) cppfront is still learning 'inspect' - only inspect expressions are currently supported"
+            );
+            return {};
+        }
+
         auto n = std::make_unique<inspect_expression_node>();
         n->identifier = &curr();
         next();