parser: improve error message for missing semicolon in inherit

Before:
  error: syntax error, expecting ';'

After:
  error: syntax error, expecting ';' to end 'inherit' bindings


Change-Id: I47c633cb5c696b646840c58e03270a7d6a6a6964

lix/libexpr/parser/grammar.hh

@@ -203,6 +203,14 @@ struct sep : sor<
 
 using seps = star<t::sep>;
 
+// Delimiters.
+namespace d {
+    // Terminators.
+    namespace t {
+        struct inherit : one<';'> { };
+    }
+}
+
 
 // marker for semantic rules. not handling one of these in an action that cares about
 // semantics is probably an error.
@@ -411,7 +419,7 @@ struct inherit : _inherit, seq<
     t::kw_inherit, seps,
     opt<one<'('>, seps, _inherit::from, seps, must<one<')'>>, seps>,
     opt<_inherit::attrs, seps>,
-    must<one<';'>>
+    must<d::t::inherit>
 > {};
 
 struct _binding {

lix/libexpr/parser/parser-impl1.inc.cc

@@ -56,6 +56,7 @@ error_message_for(grammar::v1::expr::select) = "expecting selection expression";
 error_message_for(grammar::v1::t::kw_then) = "expecting 'then'";
 error_message_for(grammar::v1::t::kw_else) = "expecting 'else'";
 error_message_for(grammar::v1::t::kw_in) = "expecting 'in'";
+error_message_for(grammar::v1::d::t::inherit) = "expecting ';' to end 'inherit' bindings";
 
 struct SyntaxErrors
 {

tests/functional2/lang/inherit/in-unterminated.nix

@@ -0,0 +1,8 @@
+let
+  c = { };
+  b = 2;
+in {
+  a = b;
+  inherit c b
+  d = 5;
+}

tests/functional2/lang/inherit/parse-fail-unterminated.err.exp

@@ -0,0 +1,6 @@
+error: syntax error, expecting ';' to end 'inherit' bindings
+       at /pwd/in.nix:7:5:
+            6|   inherit c b
+            7|   d = 5;
+             |     ^
+            8| }