improved error for match over union of different capabilities (#1516)

ponylang · Jan 18, 2017 · 8daa6ef · 8daa6ef
1 parent 3dfab96
commit 8daa6ef
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Showing 2 changed files with 43 additions and 6 deletions.
diff --git a/src/libponyc/expr/match.c b/src/libponyc/expr/match.c
@@ -333,12 +333,26 @@ bool expr_case(pass_opt_t* opt, ast_t* ast)
 
     case MATCHTYPE_DENY:
     {
-      ast_error(opt->check.errors, pattern,
-        "this capture violates capabilities");
-      ast_error_continue(opt->check.errors, match_type, "match type: %s",
-        ast_print_type(operand_type));
-      ast_error_continue(opt->check.errors, pattern, "pattern type: %s",
-        ast_print_type(pattern_type));
+      if(ast_id(match_type) == TK_UNIONTYPE) {
+        token_id cap = ast_id(ast_childidx(ast_child(match_type), 3));
+        for(size_t i=1; i<ast_childcount(match_type); i++) {
+          if(ast_id(ast_childidx(ast_childidx(match_type, i), 3)) != cap) {
+            ast_error(opt->check.errors, match_expr, 
+              "match type may not be a union of types with different "
+              "capabilities");
+            ast_error_continue(opt->check.errors, match_type, "match type: %s",
+              ast_print_type(operand_type));
+          }
+        }
+      } else {
+        ast_error(opt->check.errors, pattern,
+          "this capture violates capabilities");
+        ast_error_continue(opt->check.errors, match_type, "match type: %s",
+          ast_print_type(operand_type));
+        ast_error_continue(opt->check.errors, pattern, "pattern type: %s",
+          ast_print_type(pattern_type));
+      }
+
       ok = false;
       break;
     }

diff --git a/test/libponyc/badpony.cc b/test/libponyc/badpony.cc
@@ -315,3 +315,26 @@ TEST_F(BadPonyTest, IndexArrayWithBrackets)
 
   TEST_ERRORS_1(src, "Value formal parameters not yet supported");
 }
+
+TEST_F(BadPonyTest, MatchUnionOfDifferentCaps)
+{
+  // From issue #1506
+  const char* src =
+    "interface box Foo\n"
+      "fun foo(): None\n"
+
+    "interface ref Bar\n"
+      "fun ref bar(): None\n"
+
+    "actor Main\n"
+      "new create(env: Env) => None\n"
+
+      "fun apply(x: (Foo | Bar)) =>\n"
+        "match x\n"
+        "| let f: Foo => f.foo()\n"
+        "| let b: Bar => b.bar()\n"
+        "end";
+
+  TEST_ERRORS_1(src,
+    "match type may not be a union of types with different capabilities");
+}