Add unary minus to hauntedc parser and fix INT32_FITS macro

- Add Punct::Dash (unary minus) to the hauntedc parser's
  unary_expression, enabling expressions like -2147483647 in
  _requires/_ensures annotations
- Add SpecInt case for Neg in emit_unop, emitting op_Minus
- Fix INT32_FITS macro in malloc.c to use INT32_MIN properly

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: gebner

src/hauntedc.rs

@@ -709,6 +709,13 @@ fn expr_parser<
                             .with_loc(sift.resolve_source_info(&extra.span()))
                             .into()
                     }),
+                punct(Punct::Dash)
+                    .ignore_then(cast_expression.clone())
+                    .map_with(|e: Expr, extra| {
+                        ExprT::UnOp(UnOp::Neg, e.to_rvalue())
+                            .with_loc(sift.resolve_source_info(&extra.span()))
+                            .into()
+                    }),
             ));
 
             and_then!(type_name.delimited_by(punct(Punct::LParen), punct(Punct::RParen)), {

src/pass/emit.rs

@@ -768,6 +768,7 @@ fn emit_unop(env: &Env, op: UnOp, ty: MaybeRc<Type>) -> Option<Doc> {
             let modu = get_int_mod(signed, width)?;
             Doc::text(format!("{}.sub {}.zero", modu, modu))
         }
+        (UnOp::Neg, TypeT::SpecInt) => Doc::text("op_Minus"),
         (UnOp::Neg, _) => return None,
         (UnOp::BitNot, TypeT::Int { signed, width }) => {
             Doc::text(format!("{}.lognot", get_int_mod(signed, width)?))

test/malloc.c

@@ -23,8 +23,7 @@ point_ptr mk_point()
     return p;
 }
 
-// TODO: > INT32_MIN
-#define INT32_FITS(x) ((x) >= 0 && (x) < INT32_MAX)
+#define INT32_FITS(x) (INT32_MIN <= (x) && (x) <= INT32_MAX)
 
 int sum_point(const point_ptr p)
     _requires(INT32_FITS((_specint) p->x + p->y))