added some sort of error generation when parsing

errors occur

src/ast/errors/error.hpp

@@ -0,0 +1,25 @@
+#pragma once
+
+#include "token/type.hpp"
+
+namespace ast::error {
+    struct error : public std::runtime_error {
+        explicit error(const std::string& message)
+            : std::runtime_error(message) {}
+    };
+
+    struct parser_error : error {
+        explicit parser_error(const std::string& message): error(message) {}
+    };
+
+    struct expected_next : parser_error {
+        token::type expected_type;
+
+        explicit expected_next(
+            token::type expected_type, const std::string& message
+        )
+            : parser_error(message),
+              expected_type(expected_type) {}
+    };
+
+} // namespace ast::error

src/parser/parser.cpp

@@ -1,5 +1,6 @@
 #include "parser.hpp"
 
+#include "ast/errors/error.hpp"
 #include "token/type.hpp"
 
 #include <sstream>
@@ -27,7 +28,6 @@ namespace parser {
                 p->statements.push_back(stmt);
         }
 
-
         return p;
     }
 
@@ -45,6 +45,7 @@ namespace parser {
             next_token();
             return true;
         }
+        next_error(t);
         return false;
     }
 
@@ -73,6 +74,11 @@ namespace parser {
         std::stringstream ss;
         ss << "Expected next token to be " << t << " but instead got "
            << next.type;
-        errors.push_back(ss.str());
+        errors.push_back(new ast::error::expected_next(t, ss.str()));
+    }
+
+    parser::~parser() {
+        for (const auto& e : errors)
+            delete e;
     }
 } // namespace parser

src/parser/parser.hpp

@@ -1,6 +1,7 @@
 #pragma once
 
 #include "ast/ast.hpp"
+#include "ast/errors/error.hpp"
 #include "ast/statements/let.hpp"
 #include "lexer/lexer.hpp"
 #include "token/token.hpp"
@@ -8,7 +9,8 @@
 namespace parser {
     struct parser {
         parser(lexer::lexer& lexer);
-        std::vector<std::string> errors;
+        ~parser();
+        std::vector<ast::error::error*> errors;
 
         ast::program* parse_program();
 

test/parser.cpp

@@ -21,13 +21,49 @@ void test_let_statement(ast::statement* stmt, const std::string name) {
     REQUIRE(let_stmt->name->token_literal() == name);
 }
 
-void checkParserErrors(const std::vector<std::string>& errors) {
+void test_failing_let_parsing(
+    std::string input_s,
+    std::vector<token::type> expected_types,
+    int n_good_statements = 0
+) {
+    std::stringstream input(input_s);
+
+    lexer::lexer l{input};
+    parser::parser p{l};
+
+    ast::program* program = p.parse_program();
+
+    // Check for errors
+    REQUIRE(p.errors.size() == expected_types.size());
+
+    int i = 0;
+    for (auto& e : p.errors) {
+        ast::error::expected_next* en;
+
+        REQUIRE_NOTHROW(en = dynamic_cast<ast::error::expected_next*>(e));
+        REQUIRE_MESSAGE(
+            en != nullptr,
+            "Couldn't cast the error to an 'expected_next'"
+        );
+        REQUIRE(en->expected_type == expected_types[i++]);
+    }
+
+    // normal program check
+    REQUIRE_MESSAGE(
+        program != nullptr,
+        "parse_program() returned a null pointer"
+    );
+    REQUIRE(program->statements.size() == n_good_statements);
+    delete program;
+}
+
+void check_parser_errors(const std::vector<ast::error::error*>& errors) {
     if (errors.empty())
         return;
 
     std::cerr << "parser has " << errors.size() << " errors:\n";
-    for (const auto& msg : errors)
-        std::cerr << "parser error: \"" << msg << "\"\n";
+    for (const auto& error : errors)
+        std::cerr << '\t' << error->what() << "\n";
 
     // Use doctest's FAIL macro to immediately stop
     FAIL_CHECK("Parser had errors. See stderr for details.");
@@ -35,37 +71,26 @@ void checkParserErrors(const std::vector<std::string>& errors) {
 
 TEST_CASE("Malformed let statement (checking for memory leaks)") {
     SUBCASE("Second token not identifier") {
-        std::stringstream input("\
-let 5 = 5;\
-");
-
-        lexer::lexer l{input};
-        parser::parser p{l};
-
-        ast::program* program = p.parse_program();
-        REQUIRE_MESSAGE(
-            program != nullptr,
-            "parse_program() returned a null pointer"
-        );
-        REQUIRE(program->statements.size() == 0);
-        delete program;
+        test_failing_let_parsing("let 5 = 5;", {token::type::IDENTIFIER});
     }
 
     SUBCASE("Third token not '='") {
-        std::stringstream input("\
-let five ! 5;\
-");
+        test_failing_let_parsing("let five ! 5;", {token::type::ASSIGN});
+    }
 
-        lexer::lexer l{input};
-        parser::parser p{l};
+    SUBCASE("Missing both identifier and '='") {
+        test_failing_let_parsing("let 5;", {token::type::IDENTIFIER});
+    }
 
-        ast::program* program = p.parse_program();
-        REQUIRE_MESSAGE(
-            program != nullptr,
-            "parse_program() returned a null pointer"
+    SUBCASE("Multiple parsing errors") {
+        test_failing_let_parsing(
+            "let 5; let ! = 5; let five = 5; let five 5; let;",
+            {token::type::IDENTIFIER,
+             token::type::IDENTIFIER,
+             token::type::ASSIGN,
+             token::type::IDENTIFIER},
+            1
         );
-        REQUIRE(program->statements.size() == 0);
-        delete program;
     }
 }
 
@@ -80,6 +105,7 @@ let foobar = 103213;\
     parser::parser p{l};
 
     ast::program* program = p.parse_program();
+    check_parser_errors(p.errors);
 
     REQUIRE_MESSAGE(
         program != nullptr,