fix format bug for elsestme and stmt def in .g4

src/ASTPrinter.cpp

@@ -155,7 +155,7 @@ std::any ASTPrinter::visitStmt(SysYParser::StmtContext *ctx){
       cout << getIndent() << "}" << endl;
     }
     if (ctx->stmt().size() > 1) {
-      cout << getIndent() << "else" << endl;
+      cout << getIndent() << "else";
       if(ctx->stmt(1)->blockStmt())ctx->stmt(1)->accept(this);
       else{
         cout << " {"<< endl;

src/SysY.g4

@@ -137,6 +137,7 @@ blockStmt: LBRACE blockItem* RBRACE;
 blockItem: decl | stmt;
 
 stmt: lValue ASSIGN exp SEMICOLON
+		| exp? SEMICOLON
 		| blockStmt
 		| IF LPAREN cond RPAREN stmt (ELSE stmt)?
 		| WHILE LPAREN cond RPAREN stmt

src/SysYIRGenerator.cpp

@@ -6,7 +6,7 @@ using namespace std;
 
 namespace sysy {
 
-any SysYIRGenerator::visitModule(SysYParser::ModuleContext *ctx) {
+any SysYIRGenerator::visitCompUnit(SysYParser::CompUnitContext *ctx) {
   // create the IR module
   auto pModule = new Module();
   assert(pModule);

src/SysYIRGenerator.h

@@ -20,7 +20,7 @@ public:
   Module *get() const { return module.get(); }
 
 public:
-  std::any visitModule(SysYParser::ModuleContext *ctx) override;
+  std::any visitCompUnit(SysYParser::CompUnitContext *ctx) override;
   std::any visitFuncRParams(SysYParser::FuncRParamsContext *ctx) override;
   std::any visitNumber(SysYParser::NumberContext *ctx) override;
   std::any visitString(SysYParser::StringContext *ctx) override;