Make typing-asm match spec more closely around load/store, add more tests.

src/typing-asm.h

Index: src/typing-asm.h
diff --git a/src/typing-asm.h b/src/typing-asm.h
index 5f7a929a1e5bf99e7c8c1d4136ceb3a97e738d49..0834af7b92bdd610f070200fa7f3e5ff8d8d3f12 100644
--- a/src/typing-asm.h
+++ b/src/typing-asm.h
@@ -36,6 +36,7 @@ class AsmTyper : public AstVisitor {
   Type* expected_type_;
   Type* computed_type_;
   int intish_;  // How many ops we've gone without a x|0.
+  bool assigning_;  // Are we about to assign.
 
   Type* return_type_;  // Return type of last function.
   size_t array_size_;  // Array size of last ArrayLiteral.
@@ -65,7 +66,7 @@ class AsmTyper : public AstVisitor {
   void VisitDeclarations(ZoneList<Declaration*>* d) override;
   void VisitStatements(ZoneList<Statement*>* s) override;
 
-  void VisitExpressionAnnotation(Expression* e, bool is_return);
+  void VisitExpressionAnnotation(Expression* e, Variable* var, bool is_return);
   void VisitFunctionAnnotation(FunctionLiteral* f);
   void VisitAsmModule(FunctionLiteral* f);