Sequre scoping fix (#121)

* Fix ABI incompatibilities

* Fix codon-jit on macOS

* Fix scoping bugs

codon/parser/visitors/simplify/assign.cpp

@@ -18,6 +18,8 @@ namespace codon::ast {
 void SimplifyVisitor::visit(AssignExpr *expr) {
   seqassert(expr->var->getId(), "only simple assignment expression are supported");
   StmtPtr s = N<AssignStmt>(clone(expr->var), expr->expr);
+  auto avoidDomination = false; // walruses always leak
+  std::swap(avoidDomination, ctx->avoidDomination);
   if (ctx->isConditionalExpr) {
     // Make sure to transform both suite _AND_ the expression in the same scope
     ctx->enterConditionalBlock();
@@ -33,6 +35,7 @@ void SimplifyVisitor::visit(AssignExpr *expr) {
     s = transform(s);
     transform(expr->var);
   }
+  std::swap(avoidDomination, ctx->avoidDomination);
   resultExpr = N<StmtExpr>(std::vector<StmtPtr>{s}, expr->var);
 }
 
@@ -155,7 +158,11 @@ StmtPtr SimplifyVisitor::transformAssignment(ExprPtr lhs, ExprPtr rhs, ExprPtr t
     val = ctx->addVar(e->value, canonical, lhs->getSrcInfo());
     if (auto st = getStaticGeneric(type.get()))
       val->staticType = st;
+    if (ctx->avoidDomination)
+      val->avoidDomination = true;
   }
+  // Clean up seen tags if shadowing a name
+  ctx->seenGlobalIdentifiers[ctx->getBaseName()].erase(e->value);
 
   // Register all toplevel variables as global in JIT mode
   bool isGlobal = (ctx->cache->isJit && val->isGlobal() && !val->isGeneric()) ||

codon/parser/visitors/simplify/collections.cpp

@@ -65,6 +65,8 @@ void SimplifyVisitor::visit(GeneratorExpr *expr) {
   }
 
   SuiteStmt *prev = nullptr;
+  auto avoidDomination = true;
+  std::swap(avoidDomination, ctx->avoidDomination);
   auto suite = transformGeneratorBody(loops, prev);
   ExprPtr var = N<IdExpr>(ctx->cache->getTemporaryVar("gen"));
   if (expr->kind == GeneratorExpr::ListGenerator) {
@@ -94,6 +96,7 @@ void SimplifyVisitor::visit(GeneratorExpr *expr) {
     stmts.push_back(suite);
     resultExpr = N<CallExpr>(N<DotExpr>(N<CallExpr>(makeAnonFn(stmts)), "__iter__"));
   }
+  std::swap(avoidDomination, ctx->avoidDomination);
 }
 
 /// Transform a dictionary comprehension to the corresponding statement expression.
@@ -102,6 +105,8 @@ void SimplifyVisitor::visit(GeneratorExpr *expr) {
 ///                                      for i in j: if a: gen.__setitem__(i+a, j+1)```
 void SimplifyVisitor::visit(DictGeneratorExpr *expr) {
   SuiteStmt *prev = nullptr;
+  auto avoidDomination = true;
+  std::swap(avoidDomination, ctx->avoidDomination);
   auto suite = transformGeneratorBody(expr->loops, prev);
 
   std::vector<StmtPtr> stmts;
@@ -111,6 +116,7 @@ void SimplifyVisitor::visit(DictGeneratorExpr *expr) {
                                                 clone(expr->key), clone(expr->expr))));
   stmts.push_back(transform(suite));
   resultExpr = N<StmtExpr>(stmts, transform(var));
+  std::swap(avoidDomination, ctx->avoidDomination);
 }
 
 /// Transforms a list of @c GeneratorBody loops to the corresponding set of for loops.
@@ -127,7 +133,8 @@ StmtPtr SimplifyVisitor::transformGeneratorBody(const std::vector<GeneratorBody>
     newSuite = N<SuiteStmt>();
     auto nextPrev = dynamic_cast<SuiteStmt *>(newSuite.get());
 
-    prev->stmts.push_back(N<ForStmt>(l.vars->clone(), l.gen->clone(), newSuite));
+    auto forStmt = N<ForStmt>(l.vars->clone(), l.gen->clone(), newSuite);
+    prev->stmts.push_back(forStmt);
     prev = nextPrev;
     for (auto &cond : l.conds) {
       newSuite = N<SuiteStmt>();

codon/parser/visitors/simplify/ctx.cpp

@@ -171,6 +171,8 @@ SimplifyContext::Item SimplifyContext::findDominatingBinding(const std::string &
   for (auto i = it->second.begin(); i != it->second.end(); i++) {
     if (i == lastGood)
       break;
+    if (!(*i)->canDominate())
+      continue;
     // These bindings (and their canonical identifiers) will be replaced by the
     // dominating binding during the type checking pass.
     cache->replacements[(*i)->canonicalName] = {canonicalName, hasUsed};

codon/parser/visitors/simplify/ctx.h

@@ -44,6 +44,9 @@ struct SimplifyItem : public SrcObject {
   bool generic = false;
   /// Set if an identifier is a static variable.
   char staticType = 0;
+  /// Set if an identifier should not be dominated
+  /// (e.g., a loop variable in a comprehension).
+  bool avoidDomination = false;
 
 public:
   SimplifyItem(Kind kind, std::string baseName, std::string canonicalName,
@@ -66,6 +69,8 @@ struct SimplifyItem : public SrcObject {
   bool isConditional() const { return scope.size() > 1; }
   bool isGeneric() const { return generic; }
   char isStatic() const { return staticType; }
+  /// True if an identifier is a loop variable in a comprehension
+  bool canDominate() const { return !avoidDomination; }
 };
 
 /** Context class that tracks identifiers during the simplification. **/
@@ -159,6 +164,8 @@ struct SimplifyContext : public Context<SimplifyItem> {
   /// Allow type() expressions. Currently used to disallow type() in class
   /// and function definitions.
   bool allowTypeOf;
+  /// Set if all assignments should not be dominated later on.
+  bool avoidDomination = false;
 
 public:
   SimplifyContext(std::string filename, Cache *cache);

codon/parser/visitors/simplify/loops.cpp

@@ -98,13 +98,14 @@ void SimplifyVisitor::visit(ForStmt *stmt) {
   ctx->getBase()->loops.push_back({breakVar, ctx->scope.blocks, {}});
   std::string varName;
   if (auto i = stmt->var->getId()) {
-    ctx->addVar(i->value, varName = ctx->generateCanonicalName(i->value),
-                stmt->var->getSrcInfo());
+    auto val = ctx->addVar(i->value, varName = ctx->generateCanonicalName(i->value),
+                           stmt->var->getSrcInfo());
+    val->avoidDomination = ctx->avoidDomination;
     transform(stmt->var);
     stmt->suite = transform(N<SuiteStmt>(stmt->suite));
   } else {
     varName = ctx->cache->getTemporaryVar("for");
-    ctx->addVar(varName, varName, stmt->var->getSrcInfo());
+    auto val = ctx->addVar(varName, varName, stmt->var->getSrcInfo());
     auto var = N<IdExpr>(varName);
     std::vector<StmtPtr> stmts;
     // Add for_var = [for variables]

codon/parser/visitors/typecheck/infer.cpp

@@ -325,6 +325,7 @@ types::TypePtr TypecheckVisitor::realizeFunc(types::FuncType *type, bool force)
         // Lambda typecheck failures are "ignored" as they are treated as statements,
         // not functions.
         // TODO: generalize this further.
+        // LOG("{}", ast->suite->toString(2));
         error("cannot typecheck the program");
       }
       ctx->realizationBases.pop_back();

test/parser/simplify_stmt.codon

@@ -1209,6 +1209,19 @@ for i in range(2):
 #: 1
 #: 1
 
+def comprehension_test(x):
+    for n in range(3):
+        print('>', n)
+    l = ['1', '2', str(x)]
+    x = [n for n in l]
+    print(x, n)
+comprehension_test(5)
+#: > 0
+#: > 1
+#: > 2
+#: ['1', '2', '5'] 2
+
+
 #%% block_unroll,barebones
 # Ensure that block unrolling is done in RAII manner on error
 def foo():