Fix domination within deeply nested blocks (#485)

Co-authored-by: Ibrahim Numanagić <ibrahimpasa@gmail.com>

codon/parser/visitors/simplify/ctx.cpp

@@ -126,11 +126,16 @@ SimplifyContext::Item SimplifyContext::findDominatingBinding(const std::string &
     // We went outside the function scope. Break.
     if (!isOutside && (*i)->getBaseName() != getBaseName())
       break;
+    bool completeDomination =
+        (*i)->scope.size() <= scope.blocks.size() &&
+        (*i)->scope.back() == scope.blocks[(*i)->scope.size() - 1];
+    if (!completeDomination && prefix < int(scope.blocks.size()) && prefix != p) {
+      break;
+    }
     prefix = p;
     lastGood = i;
     // The binding completely dominates the current scope. Break.
-    if ((*i)->scope.size() <= scope.blocks.size() &&
-        (*i)->scope.back() == scope.blocks[(*i)->scope.size() - 1])
+    if (completeDomination)
       break;
   }
   seqassert(lastGood != it->second.end(), "corrupted scoping ({})", name);

test/parser/types.codon

@@ -1998,3 +1998,35 @@ print(Tuple[-5, int].__class__.__name__)
 #: Tuple
 print(Tuple[5, int, str].__class__.__name__)
 #: Tuple[int,str,int,str,int,str,int,str,int,str]
+
+
+#%% domination_nested,barebones
+def correlate(a, b, mode = 'valid'):
+    if mode == 'valid':
+        if isinstance(a, List):
+            xret = '1'
+        else:
+            xret = '2'
+        for i in a:
+            for j in b:
+                xret += 'z'
+    elif mode == 'same':
+        if isinstance(a, List):
+            xret = '3'
+        else:
+            xret = '4'
+        for i in a:
+            for j in b:
+                xret += 'z'
+    elif mode == 'full':
+        if isinstance(a, List):
+            xret = '5'
+        else:
+            xret = '6'
+        for i in a:
+            for j in b:
+                xret += 'z'
+    else:
+        raise ValueError(f"mode must be one of 'valid', 'same', or 'full' (got {repr(mode)})")
+    return xret
+print(correlate([1], [2], 'full'))  # 5z