# Mu - 055shape_shifting_container.cc

      1 //:: Container definitions can contain 'type ingredients'
      2
      3 //: pre-requisite: extend our notion of containers to not necessarily be
      4 //: atomic types
      5 :(after "Update GET base_type in Check")
      6 base_type = get_base_type(base_type);
      7 :(after "Update GET base_type in Run")
      8 base_type = get_base_type(base_type);
      9 :(after "Update PUT base_type in Check")
     10 base_type = get_base_type(base_type);
     11 :(after "Update PUT base_type in Run")
     12 base_type = get_base_type(base_type);
     13 :(after "Update MAYBE_CONVERT base_type in Check")
     14 base_type = get_base_type(base_type);
     15 :(after "Update base_type in element_type")
     16 base_type = get_base_type(base_type);
     17 :(after "Update base_type in skip_addresses")
     18 base_type = get_base_type(base_type);
     19 :(replace{} "const type_tree* get_base_type(const type_tree* t)")
     20 const type_tree* get_base_type(const type_tree* t) {
     21   const type_tree* result = t->atom ? t : t->left;
     22   if (!result->atom)
     23     raise << "invalid type " << to_string(t) << '\n' << end();
     24   return result;
     25 }
     26
     27 :(scenario ill_formed_container)
     28 % Hide_errors = true;
     29 def main [
     30   {1: ((foo) num)} <- copy 0
     31 ]
     32 # no crash
     33
     34 //: update size_of to handle non-atom container types
     35
     36 :(scenario size_of_shape_shifting_container)
     37 container foo:_t [
     38   x:_t
     39   y:num
     40 ]
     41 def main [
     42   1:foo:num <- merge 12, 13
     43   3:foo:point <- merge 14, 15, 16
     44 ]
     45 +mem: storing 12 in location 1
     46 +mem: storing 13 in location 2
     47 +mem: storing 14 in location 3
     48 +mem: storing 15 in location 4
     49 +mem: storing 16 in location 5
     50
     51 :(scenario size_of_shape_shifting_container_2)
     52 # multiple type ingredients
     53 container foo:_a:_b [
     54   x:_a
     55   y:_b
     56 ]
     57 def main [
     58   1:foo:num:bool <- merge 34, true
     59 ]
     60 $error: 0
     61
     62 :(scenario size_of_shape_shifting_container_3)
     63 container foo:_a:_b [
     64   x:_a
     65   y:_b
     66 ]
     67 def main [
     68   1:text <- new [abc]
     69   # compound types for type ingredients
     70   {3: (foo number (address array character))} <- merge 34/x, 1:text/y
     71 ]
     72 $error: 0
     73
     74 :(scenario size_of_shape_shifting_container_4)
     75 container foo:_a:_b [
     76   x:_a
     77   y:_b
     78 ]
     79 container bar:_a:_b [
     80   # dilated element
     81   {data: (foo _a (address _b))}
     82 ]
     83 def main [
     84   1:text <- new [abc]
     85   3:bar:num:@:char <- merge 34/x, 1:text/y
     86 ]
     87 $error: 0
     88
     89 :(scenario shape_shifting_container_extend)
     90 container foo:_a [
     91   x:_a
     92 ]
     93 container foo:_a [
     94   y:_a
     95 ]
     96 $error: 0
     97
     98 :(scenario shape_shifting_container_extend_error)
     99 % Hide_errors = true;
    100 container foo:_a [
    101   x:_a
    102 ]
    103 container foo:_b [
    104   y:_b
    105 ]
    106 +error: headers of container 'foo' must use identical type ingredients
    107
    108 :(scenario type_ingredient_must_start_with_underscore)
    109 % Hide_errors = true;
    110 container foo:t [
    111   x:num
    112 ]
    113 +error: foo: type ingredient 't' must begin with an underscore
    114
    115 :(before "End Globals")
    116 // We'll use large type ordinals to mean "the following type of the variable".
    117 // For example, if we have a generic type called foo:_elem, the type
    118 // ingredient _elem in foo's type_info will have value START_TYPE_INGREDIENTS,
    119 // and we'll handle it by looking in the current reagent for the next type
    120 // that appears after foo.
    121 extern const int START_TYPE_INGREDIENTS = 2000;
    122 :(before "End Commandline Parsing")  // after loading .mu files
    123 assert(Next_type_ordinal < START_TYPE_INGREDIENTS);
    124
    125 :(before "End type_info Fields")
    126 map<string, type_ordinal> type_ingredient_names;
    127
    128 //: Suppress unknown type checks in shape-shifting containers.
    129
    130 :(before "Check Container Field Types(info)")
    131 if (!info.type_ingredient_names.empty()) continue;
    132
    133 :(before "End container Name Refinements")
    134 if (name.find(':') != string::npos) {
    135   trace("parse") << "container has type ingredients; parsing" << end();
    136   if (!read_type_ingredients(name, command)) {
    137     // error; skip rest of the container definition and continue
    138     slurp_balanced_bracket(in);
    139     return;
    140   }
    141 }
    142
    143 :(code)
    144 bool read_type_ingredients(string& name, const string& command) {
    145   string save_name = name;
    146   istringstream in(save_name);
    147   name = slurp_until(in, ':');
    148   map<string, type_ordinal> type_ingredient_names;
    149   if (!slurp_type_ingredients(in, type_ingredient_names, name)) {
    150     return false;
    151   }
    152   if (contains_key(Type_ordinal, name)
    153       && contains_key(Type, get(Type_ordinal, name))) {
    154     const type_info& previous_info = get(Type, get(Type_ordinal, name));
    155     // we've already seen this container; make sure type ingredients match
    156     if (!type_ingredients_match(type_ingredient_names, previous_info.type_ingredient_names)) {
    157       raise << "headers of " << command << " '" << name << "' must use identical type ingredients\n" << end();
    158       return false;
    159     }
    160     return true;
    161   }
    162   // we haven't seen this container before
    163   if (!contains_key(Type_ordinal, name) || get(Type_ordinal, name) == 0)
    164     put(Type_ordinal, name, Next_type_ordinal++);
    165   type_info& info = get_or_insert(Type, get(Type_ordinal, name));
    166   info.type_ingredient_names.swap(type_ingredient_names);
    167   return true;
    168 }
    169
    170 bool slurp_type_ingredients(istream& in, map<string, type_ordinal>& out, const string& container_name) {
    171   int next_type_ordinal = START_TYPE_INGREDIENTS;
    172   while (has_data(in)) {
    173     string curr = slurp_until(in, ':');
    174     if (curr.empty()) {
    175       raise << container_name << ": empty type ingredients not permitted\n" << end();
    176       return false;
    177     }
    178     if (!starts_with(curr, "_")) {
    179       raise << container_name << ": type ingredient '" << curr << "' must begin with an underscore\n" << end();
    180       return false;
    181     }
    182     if (out.find(curr) != out.end()) {
    183       raise << container_name << ": can't repeat type ingredient name'" << curr << "' in a single container definition\n" << end();
    184       return false;
    185     }
    186     put(out, curr, next_type_ordinal++);
    187   }
    188   return true;
    189 }
    190
    191 bool type_ingredients_match(const map<string, type_ordinal>& a, const map<string, type_ordinal>& b) {
    192   if (SIZE(a) != SIZE(b)) return false;
    193   for (map<string, type_ordinal>::const_iterator p = a.begin();  p != a.end();  ++p) {
    194     if (!contains_key(b, p->first)) return false;
    195     if (p->second != get(b, p->first)) return false;
    196   }
    197   return true;
    198 }
    199
    200 :(before "End insert_container Special-cases")
    201 // check for use of type ingredients
    202 else if (is_type_ingredient_name(type->name)) {
    203   type->value = get(info.type_ingredient_names, type->name);
    204 }
    205 :(code)
    206 bool is_type_ingredient_name(const string& type) {
    207   return starts_with(type, "_");
    208 }
    209
    210 :(before "End Container Type Checks")
    211 if (type->value >= START_TYPE_INGREDIENTS
    212     && (type->value - START_TYPE_INGREDIENTS) < SIZE(get(Type, type->value).type_ingredient_names))
    213   return;
    214
    215 :(scenario size_of_shape_shifting_exclusive_container)
    216 exclusive-container foo:_t [
    217   x:_t
    218   y:num
    219 ]
    220 def main [
    221   1:foo:num <- merge 0/x, 34
    222   3:foo:point <- merge 0/x, 15, 16
    223   6:foo:point <- merge 1/y, 23
    224 ]
    225 +run: {1: ("foo" "number")} <- merge {0: "literal", "x": ()}, {34: "literal"}
    226 +mem: storing 0 in location 1
    227 +mem: storing 34 in location 2
    228 +run: {3: ("foo" "point")} <- merge {0: "literal", "x": ()}, {15: "literal"}, {16: "literal"}
    229 +mem: storing 0 in location 3
    230 +mem: storing 15 in location 4
    231 +mem: storing 16 in location 5
    232 +run: {6: ("foo" "point")} <- merge {1: "literal", "y": ()}, {23: "literal"}
    233 +mem: storing 1 in location 6
    234 +mem: storing 23 in location 7
    235 +run: return
    236 # no other stores
    237 % CHECK_EQ(trace_count_prefix("mem", "storing"), 7);
    238
    239 :(before "End variant_type Special-cases")
    240 if (contains_type_ingredient(element))
    241   replace_type_ingredients(element.type, type->right, info, " while computing variant type of exclusive-container");
    242
    243 :(scenario get_on_shape_shifting_container)
    244 container foo:_t [
    245   x:_t
    246   y:num
    247 ]
    248 def main [
    249   1:foo:point <- merge 14, 15, 16
    250   4:num <- get 1:foo:point, y:offset
    251 ]
    252 +mem: storing 16 in location 4
    253
    254 :(scenario get_on_shape_shifting_container_2)
    255 container foo:_t [
    256   x:_t
    257   y:num
    258 ]
    259 def main [
    260   1:foo:point <- merge 14, 15, 16
    261   4:point <- get 1:foo:point, x:offset
    262 ]
    263 +mem: storing 14 in location 4
    264 +mem: storing 15 in location 5
    265
    266 :(scenario get_on_shape_shifting_container_3)
    267 container foo:_t [
    268   x:_t
    269   y:num
    270 ]
    271 def main [
    272   1:num/alloc-id, 2:num <- copy 0, 34
    273   3:foo:&:point <- merge 1:&:point, 48
    274   6:&:point <- get 1:foo:&:point, x:offset
    275 ]
    276 +mem: storing 0 in location 6
    277 +mem: storing 34 in location 7
    278
    279 :(scenario get_on_shape_shifting_container_inside_container)
    280 container foo:_t [
    281   x:_t
    282   y:num
    283 ]
    284 container bar [
    285   x:foo:point
    286   y:num
    287 ]
    288 def main [
    289   1:bar <- merge 14, 15, 16, 17
    290   5:num <- get 1:bar, 1:offset
    291 ]
    292 +mem: storing 17 in location 5
    293
    294 :(scenario get_on_complex_shape_shifting_container)
    295 container foo:_a:_b [
    296   x:_a
    297   y:_b
    298 ]
    299 def main [
    300   1:text <- new [abc]
    301   {3: (foo number (address array character))} <- merge 34/x, 1:text/y
    302   6:text <- get {3: (foo number (address array character))}, y:offset
    303   8:bool <- equal 1:text, 6:text
    304 ]
    305 +mem: storing 1 in location 8
    306
    307 :(before "End element_type Special-cases")
    308 replace_type_ingredients(element, type, info, " while computing element type of container");
    309
    310 :(before "End size_of(type) Non-atom Special-cases")
    311 assert(type->left->atom);
    312 if (!contains_key(Type, type->left->value)) {
    313   raise << "no such type " << type->left->value << '\n' << end();
    314   return 0;
    315 }
    316 type_info t = get(Type, type->left->value);
    317 if (t.kind == CONTAINER) {
    318   // size of a container is the sum of the sizes of its elements
    319   int result = 0;
    320   for (int i = 0; i < SIZE(t.elements); ++i) {
    321     // todo: strengthen assertion to disallow mutual type recursion
    322     if (get_base_type(t.elements.at(i).type)->value == get_base_type(type)->value) {
    323       raise << "container " << t.name << " can't include itself as a member\n" << end();
    324       return 0;
    325     }
    326     result += size_of(element_type(type, i));
    327   }
    328   return result;
    329 }
    330 if (t.kind == EXCLUSIVE_CONTAINER) {
    331   // size of an exclusive container is the size of its largest variant
    332   // (So like containers, it can't contain arrays.)
    333   int result = 0;
    334   for (int i = 0; i < SIZE(t.elements); ++i) {
    335     reagent tmp;
    336     tmp.type = new type_tree(*type);
    337     int size = size_of(variant_type(tmp, i));
    338     if (size > result) result = size;
    339   }
    340   // ...+1 for its tag.
    341   return result+1;
    342 }
    343
    344 :(scenario complex_shape_shifting_exclusive_container)
    345 exclusive-container foo:_a [
    346   x:_a
    347   y:num
    348 ]
    349 def main [
    350   1:text <- new [abc]
    351   3:foo:point <- merge 0/variant, 34/xx, 35/xy
    352   10:point, 20:bool <- maybe-convert 3:foo:point, 0/variant
    353 ]
    354 +mem: storing 1 in location 20
    355 +mem: storing 35 in location 11
    356
    357 :(code)
    358 bool contains_type_ingredient(const reagent& x) {
    359   return contains_type_ingredient(x.type);
    360 }
    361
    362 bool contains_type_ingredient(const type_tree* type) {
    363   if (!type) return false;
    364   if (type->atom) return type->value >= START_TYPE_INGREDIENTS;
    365   return contains_type_ingredient(type->left) || contains_type_ingredient(type->right);
    366 }
    367
    368 void replace_type_ingredients(reagent& element, const type_tree* caller_type, const type_info& info, const string& location_for_error_messages) {
    369   if (contains_type_ingredient(element)) {
    370     if (!caller_type->right)
    371       raise << "illegal type " << names_to_string(caller_type) << " seems to be missing a type ingredient or three" << location_for_error_messages << '\n' << end();
    372     replace_type_ingredients(element.type, caller_type->right, info, location_for_error_messages);
    373   }
    374 }
    375
    376 // replace all type_ingredients in element_type with corresponding elements of callsite_type
    377 void replace_type_ingredients(type_tree* element_type, const type_tree* callsite_type, const type_info& container_info, const string& location_for_error_messages) {
    378   if (!callsite_type) return;  // error but it's already been raised above
    379   if (!element_type) return;
    380   if (!element_type->atom) {
    381     if (element_type->right == NULL && is_type_ingredient(element_type->left)) {
    382       int type_ingredient_index = to_type_ingredient_index(element_type->left);
    383       if (corresponding(callsite_type, type_ingredient_index, is_final_type_ingredient(type_ingredient_index, container_info))->right) {
    384         // replacing type ingredient at end of list, and replacement is a non-degenerate compound type -- (a b) but not (a)
    385         replace_type_ingredient_at(type_ingredient_index, element_type, callsite_type, container_info, location_for_error_messages);
    386         return;
    387       }
    388     }
    389     replace_type_ingredients(element_type->left, callsite_type, container_info, location_for_error_messages);
    390     replace_type_ingredients(element_type->right, callsite_type, container_info, location_for_error_messages);
    391     return;
    392   }
    393   if (is_type_ingredient(element_type))
    394     replace_type_ingredient_at(to_type_ingredient_index(element_type), element_type, callsite_type, container_info, location_for_error_messages);
    395 }
    396
    397 const type_tree* corresponding(const type_tree* type, int index, bool final) {
    398   for (const type_tree* curr = type;  curr;  curr = curr->right, --index) {
    399     assert_for_now(!curr->atom);
    400     if (index == 0)
    401       return final ? curr : curr->left;
    402   }
    403   assert_for_now(false);
    404 }
    405
    406 bool is_type_ingredient(const type_tree* type) {
    407   return type->atom && type->value >= START_TYPE_INGREDIENTS;
    408 }
    409
    410 int to_type_ingredient_index(const type_tree* type) {
    411   assert(type->atom);
    412   return type->value-START_TYPE_INGREDIENTS;
    413 }
    414
    415 void replace_type_ingredient_at(const int type_ingredient_index, type_tree* element_type, const type_tree* callsite_type, const type_info& container_info, const string& location_for_error_messages) {
    416   if (!has_nth_type(callsite_type, type_ingredient_index)) {
    417     raise << "illegal type " << names_to_string(callsite_type) << " seems to be missing a type ingredient or three" << location_for_error_messages << '\n' << end();
    418     return;
    419   }
    420   *element_type = *nth_type_ingredient(callsite_type, type_ingredient_index, container_info);
    421 }
    422
    423 const type_tree* nth_type_ingredient(const type_tree* callsite_type, int type_ingredient_index, const type_info& container_info) {
    424   bool final = is_final_type_ingredient(type_ingredient_index, container_info);
    425   const type_tree* curr = callsite_type;
    426   for (int i = 0;  i < type_ingredient_index;  ++i) {
    427     assert(curr);
    428     assert(!curr->atom);
    429 //?     cerr << "type ingredient " << i << " is " << to_string(curr->left) << '\n';
    430     curr = curr->right;
    431   }
    432   assert(curr);
    433   if (curr->atom) return curr;
    434   if (!final) return curr->left;
    435   if (!curr->right) return curr->left;
    436   return curr;
    437 }
    438
    439 bool is_final_type_ingredient(int type_ingredient_index, const type_info& container_info) {
    440   for (map<string, type_ordinal>::const_iterator p = container_info.type_ingredient_names.begin();
    441        p != container_info.type_ingredient_names.end();
    442        ++p) {
    443     if (p->second > START_TYPE_INGREDIENTS+type_ingredient_index) return false;
    444   }
    445   return true;
    446 }
    447
    448 :(before "End Unit Tests")
    449 void test_replace_type_ingredients_entire() {
    450   run("container foo:_elem [\n"
    451       "  x:_elem\n"
    452       "  y:num\n"
    453       "]\n");
    454   reagent callsite("x:foo:point");
    455   reagent element = element_type(callsite.type, 0);
    456   CHECK_EQ(to_string(element), "{x: \"point\"}");
    457 }
    458
    459 void test_replace_type_ingredients_tail() {
    460   run("container foo:_elem [\n"
    461       "  x:_elem\n"
    462       "]\n"
    463       "container bar:_elem [\n"
    464       "  x:foo:_elem\n"
    465       "]\n");
    466   reagent callsite("x:bar:point");
    467   reagent element = element_type(callsite.type, 0);
    468   CHECK_EQ(to_string(element), "{x: (\"foo\" \"point\")}");
    469 }
    470
    471 void test_replace_type_ingredients_head_tail_multiple() {
    472   run("container foo:_elem [\n"
    473       "  x:_elem\n"
    474       "]\n"
    475       "container bar:_elem [\n"
    476       "  x:foo:_elem\n"
    477       "]\n");
    478   reagent callsite("x:bar:address:array:character");
    479   reagent element = element_type(callsite.type, 0);
    480   CHECK_EQ(to_string(element), "{x: (\"foo\" \"address\" \"array\" \"character\")}");
    481 }
    482
    483 void test_replace_type_ingredients_head_middle() {
    484   run("container foo:_elem [\n"
    485       "  x:_elem\n"
    486       "]\n"
    487       "container bar:_elem [\n"
    488       "  x:foo:_elem:num\n"
    489       "]\n");
    490   reagent callsite("x:bar:address");
    491   reagent element = element_type(callsite.type, 0);
    492   CHECK_EQ(to_string(element), "{x: (\"foo\" \"address\" \"number\")}");
    493 }
    494
    495 void test_replace_last_type_ingredient_with_multiple() {
    496   run("container foo:_a:_b [\n"
    497       "  x:_a\n"
    498       "  y:_b\n"
    499       "]\n");
    500   reagent callsite("{f: (foo number (address array character))}");
    501   reagent element1 = element_type(callsite.type, 0);
    502   CHECK_EQ(to_string(element1), "{x: \"number\"}");
    503   reagent element2 = element_type(callsite.type, 1);
    504   CHECK_EQ(to_string(element2), "{y: (\"address\" \"array\" \"character\")}");
    505 }
    506
    507 void test_replace_last_type_ingredient_inside_compound() {
    508   run("container foo:_a:_b [\n"
    509       "  {x: (bar _a (address _b))}\n"
    510       "]\n");
    511   reagent callsite("f:foo:number:array:character");
    512   reagent element = element_type(callsite.type, 0);
    513   CHECK_EQ(names_to_string_without_quotes(element.type), "(bar number (address array character))");
    514 }
    515
    516 void test_replace_middle_type_ingredient_with_multiple() {
    517   run("container foo:_a:_b:_c [\n"
    518       "  x:_a\n"
    519       "  y:_b\n"
    520       "  z:_c\n"
    521       "]\n");
    522   reagent callsite("{f: (foo number (address array character) boolean)}");
    523   reagent element1 = element_type(callsite.type, 0);
    524   CHECK_EQ(to_string(element1), "{x: \"number\"}");
    525   reagent element2 = element_type(callsite.type, 1);
    526   CHECK_EQ(to_string(element2), "{y: (\"address\" \"array\" \"character\")}");
    527   reagent element3 = element_type(callsite.type, 2);
    528   CHECK_EQ(to_string(element3), "{z: \"boolean\"}");
    529 }
    530
    531 void test_replace_middle_type_ingredient_with_multiple2() {
    532   run("container foo:_key:_value [\n"
    533       "  key:_key\n"
    534       "  value:_value\n"
    535       "]\n");
    536   reagent callsite("{f: (foo (address array character) number)}");
    537   reagent element = element_type(callsite.type, 0);
    538   CHECK_EQ(to_string(element), "{key: (\"address\" \"array\" \"character\")}");
    539 }
    540
    541 void test_replace_middle_type_ingredient_with_multiple3() {
    542   run("container foo_table:_key:_value [\n"
    543       "  data:&:@:foo_table_row:_key:_value\n"
    544       "]\n"
    545       "\n"
    546       "container foo_table_row:_key:_value [\n"
    547       "  key:_key\n"
    548       "  value:_value\n"
    549       "]\n");
    550   reagent callsite("{f: (foo_table (address array character) number)}");
    551   reagent element = element_type(callsite.type, 0);
    552   CHECK_EQ(to_string(element), "{data: (\"address\" \"array\" \"foo_table_row\" (\"address\" \"array\" \"character\") \"number\")}");
    553 }
    554
    555 :(code)
    556 bool has_nth_type(const type_tree* base, int n) {
    557   assert(n >= 0);
    558   if (!base) return false;
    559   if (n == 0) return true;
    560   return has_nth_type(base->right, n-1);
    561 }
    562
    563 :(scenario get_on_shape_shifting_container_error)
    564 % Hide_errors = true;
    565 container foo:_t [
    566   x:_t
    567   y:num
    568 ]
    569 def main [
    570   1:foo:point <- merge 14, 15, 16
    571   10:num <- get 1:foo, 1:offset
    572 ]
    573 # todo: improve error message
    574 +error: illegal type "foo" seems to be missing a type ingredient or three while computing element type of container
    575
    576 :(scenario typos_in_container_definitions)
    577 % Hide_errors = true;
    578 container foo:_t [
    579   x:adress:_t  # typo
    580 ]
    581 def main [
    582   local-scope
    583   x:address:foo:num <- new {(foo num): type}
    584 ]
    585 # no crash
    586
    587 :(scenario typos_in_recipes)
    588 % Hide_errors = true;
    589 def foo [
    590   local-scope
    591   x:adress:array:number <- copy null  # typo
    592 ]
    593 # shouldn't crash
    594
    595 //:: 'merge' on shape-shifting containers
    596
    597 :(scenario merge_check_shape_shifting_container_containing_exclusive_container)
    598 container foo:_elem [
    599   x:num
    600   y:_elem
    601 ]
    602 exclusive-container bar [
    603   x:num
    604   y:num
    605 ]
    606 def main [
    607   1:foo:bar <- merge 23, 1/y, 34
    608 ]
    609 +mem: storing 23 in location 1
    610 +mem: storing 1 in location 2
    611 +mem: storing 34 in location 3
    612 $error: 0
    613
    614 :(scenario merge_check_shape_shifting_container_containing_exclusive_container_2)
    615 % Hide_errors = true;
    616 container foo:_elem [
    617   x:num
    618   y:_elem
    619 ]
    620 exclusive-container bar [
    621   x:num
    622   y:num
    623 ]
    624 def main [
    625   1:foo:bar <- merge 23, 1/y, 34, 35
    626 ]
    627 +error: main: too many ingredients in '1:foo:bar <- merge 23, 1/y, 34, 35'
    628
    629 :(scenario merge_check_shape_shifting_exclusive_container_containing_container)
    630 exclusive-container foo:_elem [
    631   x:num
    632   y:_elem
    633 ]
    634 container bar [
    635   x:num
    636   y:num
    637 ]
    638 def main [
    639   1:foo:bar <- merge 1/y, 23, 34
    640 ]
    641 +mem: storing 1 in location 1
    642 +mem: storing 23 in location 2
    643 +mem: storing 34 in location 3
    644 $error: 0
    645
    646 :(scenario merge_check_shape_shifting_exclusive_container_containing_container_2)
    647 exclusive-container foo:_elem [
    648   x:num
    649   y:_elem
    650 ]
    651 container bar [
    652   x:num
    653   y:num
    654 ]
    655 def main [
    656   1:foo:bar <- merge 0/x, 23
    657 ]
    658 $error: 0
    659
    660 :(scenario merge_check_shape_shifting_exclusive_container_containing_container_3)
    661 % Hide_errors = true;
    662 exclusive-container foo:_elem [
    663   x:num
    664   y:_elem
    665 ]
    666 container bar [
    667   x:num
    668   y:num
    669 ]
    670 def main [
    671   1:foo:bar <- merge 1/y, 23
    672 ]
    673 +error: main: too few ingredients in '1:foo:bar <- merge 1/y, 23'