[New Compiler] Produce an error / fail compilation if two variables share the same name within the same scope.

Author: cnf

nvse/nvse/Compiler/Passes/VariableResolution.cpp

@@ -26,6 +26,11 @@ namespace Compiler::Passes {
 					expr->Accept(this);
 				}
 			}
+			// Existing variable within the same scope, produce an error
+			else {
+				CompErr("[line %d:%d] Error - Variable name '%s' already exists in this scope.\n", token.line, token.column, token.lexeme.c_str());
+				this->had_error = true;
+			}
 		}
 	}
 

nvse/nvse/Compiler/Passes/VariableResolution.h

@@ -81,7 +81,7 @@ namespace Compiler::Passes {
 		static bool Resolve(Script *pScript, AST* pAST) {
 			auto resolver = VariableResolution{ pScript };
 			resolver.Visit(pAST);
-			return true;
+			return !resolver.HadError();
 		}
 
 		VariableResolution(Script* pScript) : pScript{ pScript } {

nvse/nvse/Compiler/Visitor.h

@@ -4,6 +4,8 @@
 
 namespace Compiler {
 	class Visitor {
+	protected:
+		boolean had_error = false;
 	public:
 		virtual ~Visitor() = default;
 
@@ -39,5 +41,9 @@ namespace Compiler {
 		virtual void VisitMapLiteralExpr(Expressions::MapLiteralExpr* expr);
 		virtual void VisitGroupingExpr(Expressions::GroupingExpr* expr);
 		virtual void VisitLambdaExpr(Expressions::LambdaExpr* expr);
+
+		virtual bool HadError() {
+			return had_error;
+		}
 	};
 }

nvse/nvse/Hooks_Script.cpp

@@ -544,7 +544,10 @@ PrecompileResult __stdcall HandleBeginCompile(ScriptBuffer* buf, Script* script)
 
 		if (auto astOpt = parser.Parse(); astOpt.has_value()) {
 			auto ast = std::move(astOpt.value());
-			Compiler::Passes::VariableResolution::Resolve(script, &ast);
+			const auto variablePass = Compiler::Passes::VariableResolution::Resolve(script, &ast);
+			if (!variablePass) {
+				return kPrecompile_Failure;
+			}
 
 			auto tc = Compiler::NVSETypeChecker(&ast, script);
 			bool typeCheckerPass = tc.check();

nvse/nvse/ScriptUtils.cpp

@@ -2289,7 +2289,10 @@ bool ExpressionParser::ParseUserFunctionParameters(std::vector<UserFunctionParam
 		Compiler::Lexer lexer{ funcScriptText };
 		Compiler::Parser parser{ lexer };
 		if (auto result = parser.Parse()) {
-			Compiler::Passes::VariableResolution::Resolve(nullptr, &*result);
+			const auto variablePass = Compiler::Passes::VariableResolution::Resolve(nullptr, &*result);
+			if (!variablePass) {
+				return false;
+			}
 
 			const auto blocks = result->blocks;
 			if (blocks.size() != 1) {