Fix compiler handling of type params in stacks (issue #918)

src/libponyc/ast/ast.c

@@ -56,6 +56,13 @@ struct ast_t
   uint32_t flags;
 };
 
+static bool ast_cmp(ast_t* a, ast_t* b)
+{
+  return a == b;
+}
+
+DEFINE_LIST(astlist, astlist_t, ast_t, ast_cmp, NULL);
+
 static const char in[] = "  ";
 static const size_t in_len = 2;
 static size_t width = 80;

src/libponyc/ast/ast.h

@@ -45,6 +45,7 @@ enum
   AST_FLAG_ERROR_2      = 0x40000,
 };
 
+DECLARE_LIST(astlist, astlist_t, ast_t);
 
 ast_t* ast_new(token_t* t, token_id id);
 ast_t* ast_blank(token_id id);

src/libponyc/type/typeparam.c

@@ -500,17 +500,23 @@ ast_t* typeparam_constraint(ast_t* typeparamref)
   assert(ast_id(typeparamref) == TK_TYPEPARAMREF);
   ast_t* def = (ast_t*)ast_data(typeparamref);
   ast_t* constraint = ast_childidx(def, 1);
+  astlist_t* def_list = astlist_push(NULL, def);
 
-  while((constraint != NULL) && (ast_id(constraint) == TK_TYPEPARAMREF))
+  while(ast_id(constraint) == TK_TYPEPARAMREF)
   {
     ast_t* constraint_def = (ast_t*)ast_data(constraint);
 
-    if(constraint_def == def)
-      return NULL;
+    if(astlist_find(def_list, constraint_def))
+    {
+      constraint = NULL;
+      break;
+    }
 
+    def_list = astlist_push(def_list, constraint_def);
     constraint = ast_childidx(constraint_def, 1);
   }
 
+  astlist_free(def_list);
   return constraint;
 }
 

test/libponyc/type_check_bind.cc

@@ -0,0 +1,23 @@
+#include <gtest/gtest.h>
+#include <platform.h>
+#include <type/subtype.h>
+#include <type/typeparam.h>
+#include "util.h"
+
+#define TEST_COMPILE(src) DO(test_compile(src, "expr"))
+
+class BindTest: public PassTest
+{};
+
+
+TEST_F(BindTest, RecursiveConstraintIsUnbound)
+{
+  const char* src =
+    "class C1[A, B: A]\n"
+    "  var x: B\n"
+    "  new create(x': B) => x = consume x'\n";
+
+  TEST_COMPILE(src);
+  ast_t* x = lookup_member("C1", "x");
+  ASSERT_EQ(NULL, typeparam_constraint(ast_type(x)));
+}