From b6a5e047c231617d48a8c965b3dd8498d2f49cda Mon Sep 17 00:00:00 2001
From: Deukhoofd <Deukhoofd@gmail.com>
Date: Sun, 4 Oct 2020 19:38:13 +0200
Subject: [PATCH] Support for diagnostics system.

---
 src/Diagnostics/Diagnostic.hpp          |  23 ++
 src/Diagnostics/DiagnosticLevel.hpp     |  15 +
 src/Diagnostics/DiagnosticType.hpp      |  20 ++
 src/Diagnostics/Diagnostics.cpp         |   1 +
 src/Diagnostics/Diagnostics.hpp         |  25 ++
 src/Parser/Lexer/LexToken.hpp           |  20 +-
 src/Parser/Lexer/Lexer.cpp              | 379 ++++++++++++------------
 src/Parser/Lexer/Lexer.hpp              |  13 +-
 src/Parser/TextSpan.hpp                 |  19 ++
 tests/LexerTests/IdentifierLexTests.cpp |   8 +-
 tests/LexerTests/NumericalLexTests.cpp  |  22 +-
 tests/LexerTests/StringLexTests.cpp     |   9 +-
 tests/LexerTests/SymbolLexTests.cpp     |  10 +-
 13 files changed, 347 insertions(+), 217 deletions(-)
 create mode 100644 src/Diagnostics/Diagnostic.hpp
 create mode 100644 src/Diagnostics/DiagnosticLevel.hpp
 create mode 100644 src/Diagnostics/DiagnosticType.hpp
 create mode 100644 src/Diagnostics/Diagnostics.cpp
 create mode 100644 src/Diagnostics/Diagnostics.hpp
 create mode 100644 src/Parser/TextSpan.hpp

diff --git a/src/Diagnostics/Diagnostic.hpp b/src/Diagnostics/Diagnostic.hpp
new file mode 100644
index 0000000..81600bb
--- /dev/null
+++ b/src/Diagnostics/Diagnostic.hpp
@@ -0,0 +1,23 @@
+#ifndef ELOHIMSCRIPT_DIAGNOSTIC_HPP
+#define ELOHIMSCRIPT_DIAGNOSTIC_HPP
+
+#include "../Parser/TextSpan.hpp"
+#include "DiagnosticLevel.hpp"
+#include "DiagnosticType.hpp"
+namespace ElohimScript::Diagnostics {
+    class Diagnostic {
+        DiagnosticLevel _level;
+        DiagnosticType _type;
+        TextSpan _span;
+
+    public:
+        inline Diagnostic(DiagnosticLevel level, DiagnosticType type, TextSpan span)
+            : _level(level), _type(type), _span(span) {}
+
+        [[nodiscard]] inline DiagnosticLevel GetLevel() const noexcept { return _level; }
+        [[nodiscard]] inline DiagnosticType GetType() const noexcept { return _type; }
+        [[nodiscard]] inline const TextSpan& GetSpan() const noexcept { return _span; }
+    };
+}
+
+#endif // ELOHIMSCRIPT_DIAGNOSTIC_HPP
diff --git a/src/Diagnostics/DiagnosticLevel.hpp b/src/Diagnostics/DiagnosticLevel.hpp
new file mode 100644
index 0000000..382ce9c
--- /dev/null
+++ b/src/Diagnostics/DiagnosticLevel.hpp
@@ -0,0 +1,15 @@
+#ifndef ELOHIMSCRIPT_DIAGNOSTICLEVEL_HPP
+#define ELOHIMSCRIPT_DIAGNOSTICLEVEL_HPP
+
+#include <cstdint>
+namespace ElohimScript::Diagnostics {
+    enum class DiagnosticLevel : uint8_t {
+        Trace,
+        Information,
+        Warning,
+        Error,
+        Critical,
+    };
+}
+
+#endif // ELOHIMSCRIPT_DIAGNOSTICLEVEL_HPP
diff --git a/src/Diagnostics/DiagnosticType.hpp b/src/Diagnostics/DiagnosticType.hpp
new file mode 100644
index 0000000..f619ce1
--- /dev/null
+++ b/src/Diagnostics/DiagnosticType.hpp
@@ -0,0 +1,20 @@
+#ifndef ELOHIMSCRIPT_DIAGNOSTICTYPE_HPP
+#define ELOHIMSCRIPT_DIAGNOSTICTYPE_HPP
+#include <string>
+
+namespace ElohimScript::Diagnostics {
+    enum class DiagnosticType : uint8_t { UnknownToken, InvalidNumericalBase, ExpectedEndOfString };
+
+    class DiagnosticTypeHelper {
+        static std::string ToEnglishString(DiagnosticType type) {
+            switch (type) {
+                case DiagnosticType::UnknownToken: return "Unknown token";
+                case DiagnosticType::InvalidNumericalBase: return "Invalid numerical base";
+                case DiagnosticType::ExpectedEndOfString: return "Expected end of string";
+            }
+            return std::to_string((uint8_t)type);
+        }
+    };
+}
+
+#endif // ELOHIMSCRIPT_DIAGNOSTICTYPE_HPP
diff --git a/src/Diagnostics/Diagnostics.cpp b/src/Diagnostics/Diagnostics.cpp
new file mode 100644
index 0000000..f7c030d
--- /dev/null
+++ b/src/Diagnostics/Diagnostics.cpp
@@ -0,0 +1 @@
+#include "Diagnostics.hpp"
diff --git a/src/Diagnostics/Diagnostics.hpp b/src/Diagnostics/Diagnostics.hpp
new file mode 100644
index 0000000..013716b
--- /dev/null
+++ b/src/Diagnostics/Diagnostics.hpp
@@ -0,0 +1,25 @@
+#ifndef ELOHIMSCRIPT_DIAGNOSTICS_HPP
+#define ELOHIMSCRIPT_DIAGNOSTICS_HPP
+
+#include <vector>
+#include "Diagnostic.hpp"
+
+namespace ElohimScript::Diagnostics {
+    class Diagnostics {
+        std::vector<Diagnostic> _messages;
+
+    public:
+        inline void Log(DiagnosticLevel level, DiagnosticType type, TextSpan span) {
+            _messages.emplace_back(level, type, span);
+        }
+        inline void LogTrace(DiagnosticType type, TextSpan span) { Log(DiagnosticLevel::Trace, type, span); }
+        inline void LogInfo(DiagnosticType type, TextSpan span) { Log(DiagnosticLevel::Information, type, span); }
+        inline void LogWarning(DiagnosticType type, TextSpan span) { Log(DiagnosticLevel::Warning, type, span); }
+        inline void LogError(DiagnosticType type, TextSpan span) { Log(DiagnosticLevel::Error, type, span); }
+        inline void LogCritical(DiagnosticType type, TextSpan span) { Log(DiagnosticLevel::Critical, type, span); }
+
+        [[nodiscard]] const std::vector<Diagnostic>& GetMessages() const noexcept { return _messages; }
+    };
+}
+
+#endif // ELOHIMSCRIPT_DIAGNOSTICS_HPP
diff --git a/src/Parser/Lexer/LexToken.hpp b/src/Parser/Lexer/LexToken.hpp
index d98c18d..566ae80 100644
--- a/src/Parser/Lexer/LexToken.hpp
+++ b/src/Parser/Lexer/LexToken.hpp
@@ -10,16 +10,19 @@ namespace ElohimScript::Parser {
         friend class Lexer;
 
         std::unique_ptr<const LexToken> _next;
+        TextSpan _span;
 
     public:
+        LexToken(TextSpan span) : _span(span) {}
         virtual ~LexToken() = default;
         [[nodiscard]] virtual LexTokenKind GetKind() const noexcept = 0;
         [[nodiscard]] const std::unique_ptr<const LexToken>& GetNext() const noexcept { return _next; }
+        [[nodiscard]] const TextSpan& GetSpan() const noexcept { return _span; }
     };
 
     template <LexTokenKind kind> class LexTokenImpl : public LexToken {
     public:
-        LexTokenImpl() = default;
+        LexTokenImpl(TextSpan span) : LexToken(span){};
         [[nodiscard]] LexTokenKind GetKind() const noexcept override { return kind; }
     };
 
@@ -27,7 +30,8 @@ namespace ElohimScript::Parser {
         uint64_t _value;
 
     public:
-        IntegerLiteral(uint64_t value) : _value(value) {}
+        IntegerLiteral(TextSpan span, uint64_t value)
+            : LexTokenImpl<LexTokenKind::IntegerLiteral>(span), _value(value) {}
         [[nodiscard]] uint64_t GetValue() const noexcept { return _value; }
     };
 
@@ -35,7 +39,7 @@ namespace ElohimScript::Parser {
         double _value;
 
     public:
-        FloatLiteral(double value) : _value(value) {}
+        FloatLiteral(TextSpan span, double value) : LexTokenImpl<LexTokenKind::FloatLiteral>(span), _value(value) {}
         [[nodiscard]] double GetValue() const noexcept { return _value; }
     };
 
@@ -43,15 +47,17 @@ namespace ElohimScript::Parser {
         std::u8string _value;
 
     public:
-        StringLiteral(std::u8string value) : _value(std::move(value)) {}
+        StringLiteral(TextSpan span, std::u8string value)
+            : LexTokenImpl<LexTokenKind::StringLiteral>(span), _value(std::move(value)) {}
         [[nodiscard]] const std::u8string& GetValue() const noexcept { return _value; }
     };
 
-    class IdentifierToken : public LexTokenImpl<LexTokenKind::Identifier>{
-        std::u8string  _value;
+    class IdentifierToken : public LexTokenImpl<LexTokenKind::Identifier> {
+        std::u8string _value;
 
     public:
-        IdentifierToken(std::u8string value) : _value(std::move(value)) {}
+        IdentifierToken(TextSpan span, std::u8string value)
+            : LexTokenImpl<LexTokenKind::Identifier>(span), _value(std::move(value)) {}
         [[nodiscard]] const std::u8string& GetValue() const noexcept { return _value; }
     };
 }
diff --git a/src/Parser/Lexer/Lexer.cpp b/src/Parser/Lexer/Lexer.cpp
index cf9d891..29b890d 100644
--- a/src/Parser/Lexer/Lexer.cpp
+++ b/src/Parser/Lexer/Lexer.cpp
@@ -22,9 +22,10 @@ namespace ElohimScript::Parser {
     }
 
     LexToken* Lexer::LexNext() {
+        auto start = _position;
         auto c = Consume();
         switch (c) {
-            case u8'\0': return new LexTokenImpl<LexTokenKind::EndOfFile>();
+            case u8'\0': return new LexTokenImpl<LexTokenKind::EndOfFile>(TextSpan(start, 1));
             case u8'*': {
                 auto n = Peek();
                 if (n == u8'*') {
@@ -32,177 +33,219 @@ namespace ElohimScript::Parser {
                     n = Peek();
                     if (n == u8'=') {
                         Progress();
-                        return new LexTokenImpl<LexTokenKind::StarStarEqualsSymbol>();
+                        // **=
+                        return new LexTokenImpl<LexTokenKind::StarStarEqualsSymbol>(TextSpan(start, 3));
                     }
-                    return new LexTokenImpl<LexTokenKind::StarStarSymbol>();
+                    // **
+                    return new LexTokenImpl<LexTokenKind::StarStarSymbol>(TextSpan(start, 2));
                 }
                 if (n == u8'=') {
                     Progress();
-                    return new LexTokenImpl<LexTokenKind::StarEqualsSymbol>();
+                    // *=
+                    return new LexTokenImpl<LexTokenKind::StarEqualsSymbol>(TextSpan(start, 2));
                 }
-                return new LexTokenImpl<LexTokenKind::StarSymbol>();
+                // *
+                return new LexTokenImpl<LexTokenKind::StarSymbol>(TextSpan(start, 1));
             }
             case u8'/':
                 if (Peek() == u8'=') {
                     Progress();
-                    return new LexTokenImpl<LexTokenKind::SlashEqualsSymbol>();
+                    // /=
+                    return new LexTokenImpl<LexTokenKind::SlashEqualsSymbol>(TextSpan(start, 2));
                 }
-                return new LexTokenImpl<LexTokenKind::SlashSymbol>();
+                // /
+                return new LexTokenImpl<LexTokenKind::SlashSymbol>(TextSpan(start, 1));
             case u8'%':
                 if (Peek() == u8'=') {
                     Progress();
-                    return new LexTokenImpl<LexTokenKind::PercentEqualsSymbol>();
+                    // %=
+                    return new LexTokenImpl<LexTokenKind::PercentEqualsSymbol>(TextSpan(start, 2));
                 }
-                return new LexTokenImpl<LexTokenKind::PercentSymbol>();
+                // %
+                return new LexTokenImpl<LexTokenKind::PercentSymbol>(TextSpan(start, 1));
             case u8'+': {
                 auto n = Peek();
                 if (n == u8'=') {
                     Progress();
-                    return new LexTokenImpl<LexTokenKind::PlusEqualsSymbol>();
+                    // +=
+                    return new LexTokenImpl<LexTokenKind::PlusEqualsSymbol>(TextSpan(start, 2));
                 }
                 if (n == u8'+') {
                     Progress();
-                    return new LexTokenImpl<LexTokenKind::PlusPlusSymbol>();
+                    // ++
+                    return new LexTokenImpl<LexTokenKind::PlusPlusSymbol>(TextSpan(start, 2));
                 }
-                return new LexTokenImpl<LexTokenKind::PlusSymbol>();
+                // +
+                return new LexTokenImpl<LexTokenKind::PlusSymbol>(TextSpan(start, 1));
             }
             case u8'-': {
                 auto n = Peek();
                 if (n == u8'=') {
                     Progress();
-                    return new LexTokenImpl<LexTokenKind::MinusEqualsSymbol>();
+                    // -=
+                    return new LexTokenImpl<LexTokenKind::MinusEqualsSymbol>(TextSpan(start, 2));
                 }
                 if (n == u8'-') {
                     Progress();
-                    return new LexTokenImpl<LexTokenKind::MinusMinusSymbol>();
+                    // --
+                    return new LexTokenImpl<LexTokenKind::MinusMinusSymbol>(TextSpan(start, 2));
                 }
-                return new LexTokenImpl<LexTokenKind::MinusSymbol>();
+                // -
+                return new LexTokenImpl<LexTokenKind::MinusSymbol>(TextSpan(start, 1));
             }
             case u8'<': {
                 auto n = Peek();
                 if (n == u8'=') {
                     Progress();
-                    return new LexTokenImpl<LexTokenKind::LessThanEqualsSymbol>();
+                    // <=
+                    return new LexTokenImpl<LexTokenKind::LessThanEqualsSymbol>(TextSpan(start, 2));
                 }
                 if (n == u8'<') {
                     Progress();
                     if (Peek() == u8'=') {
                         Progress();
-                        return new LexTokenImpl<LexTokenKind::LessThanLessThanEqualsSymbol>();
+                        // <<=
+                        return new LexTokenImpl<LexTokenKind::LessThanLessThanEqualsSymbol>(TextSpan(start, 3));
                     }
-                    return new LexTokenImpl<LexTokenKind::LessThanLessThanSymbol>();
+                    // <<
+                    return new LexTokenImpl<LexTokenKind::LessThanLessThanSymbol>(TextSpan(start, 2));
                 }
-                return new LexTokenImpl<LexTokenKind::LessThanSymbol>();
+                // <
+                return new LexTokenImpl<LexTokenKind::LessThanSymbol>(TextSpan(start, 1));
             }
             case u8'>': {
                 auto n = Peek();
                 if (n == u8'=') {
                     Progress();
-                    return new LexTokenImpl<LexTokenKind::GreaterThanEqualsSymbol>();
+                    // >=
+                    return new LexTokenImpl<LexTokenKind::GreaterThanEqualsSymbol>(TextSpan(start, 2));
                 }
                 if (n == u8'>') {
                     Progress();
                     n = Peek();
                     if (n == u8'=') {
                         Progress();
-                        return new LexTokenImpl<LexTokenKind::GreaterThanGreaterThanEqualsSymbol>();
+                        // >>=
+                        return new LexTokenImpl<LexTokenKind::GreaterThanGreaterThanEqualsSymbol>(TextSpan(start, 3));
                     }
                     if (n == u8'>') {
                         Progress();
                         if (Peek() == u8'=') {
                             Progress();
-                            return new LexTokenImpl<LexTokenKind::GreaterThanGreaterThanGreaterThanEqualsSymbol>();
+                            // >>>=
+                            return new LexTokenImpl<LexTokenKind::GreaterThanGreaterThanGreaterThanEqualsSymbol>(
+                                TextSpan(start, 4));
                         }
-                        return new LexTokenImpl<LexTokenKind::GreaterThanGreaterThanGreaterThanSymbol>();
+                        // >>>
+                        return new LexTokenImpl<LexTokenKind::GreaterThanGreaterThanGreaterThanSymbol>(
+                            TextSpan(start, 3));
                     }
-                    return new LexTokenImpl<LexTokenKind::GreaterThanGreaterThanSymbol>();
+                    // >>
+                    return new LexTokenImpl<LexTokenKind::GreaterThanGreaterThanSymbol>(TextSpan(start, 2));
                 }
-                return new LexTokenImpl<LexTokenKind::GreaterThanSymbol>();
+                // >
+                return new LexTokenImpl<LexTokenKind::GreaterThanSymbol>(TextSpan(start, 1));
             }
-            case u8'(': return new LexTokenImpl<LexTokenKind::OpenParenthesisSymbol>();
-            case u8')': return new LexTokenImpl<LexTokenKind::CloseParenthesisSymbol>();
+            case u8'(': return new LexTokenImpl<LexTokenKind::OpenParenthesisSymbol>(TextSpan(start, 1));
+            case u8')': return new LexTokenImpl<LexTokenKind::CloseParenthesisSymbol>(TextSpan(start, 1));
             case u8'=': {
                 if (Peek() == u8'=') {
                     Progress();
-                    return new LexTokenImpl<LexTokenKind::EqualsEqualsSymbol>();
+                    // ==
+                    return new LexTokenImpl<LexTokenKind::EqualsEqualsSymbol>(TextSpan(start, 2));
                 }
-                return new LexTokenImpl<LexTokenKind::EqualsSymbol>();
+                // =
+                return new LexTokenImpl<LexTokenKind::EqualsSymbol>(TextSpan(start, 1));
             }
             case u8'!': {
                 auto n = Peek();
                 if (n == u8'=') {
                     Progress();
-                    return new LexTokenImpl<LexTokenKind::ExclamationMarkEqualsSymbol>();
+                    // !=
+                    return new LexTokenImpl<LexTokenKind::ExclamationMarkEqualsSymbol>(TextSpan(start, 2));
                 }
                 if (n == u8'i' && Peek(2) == u8's') {
                     Progress(2);
-                    return new LexTokenImpl<LexTokenKind::ExclamationMarkIsSymbol>();
+                    // !is
+                    return new LexTokenImpl<LexTokenKind::ExclamationMarkIsSymbol>(TextSpan(start, 3));
                 }
-                return new LexTokenImpl<LexTokenKind::ExclamationMarkSymbol>();
+                // !
+                return new LexTokenImpl<LexTokenKind::ExclamationMarkSymbol>(TextSpan(start, 1));
             }
-            case u8'?': return new LexTokenImpl<LexTokenKind::QuestionMarkSymbol>();
+            case u8'?': return new LexTokenImpl<LexTokenKind::QuestionMarkSymbol>(TextSpan(start, 1));
             case u8':': {
                 if (Peek() == u8':') {
                     Progress();
-                    return new LexTokenImpl<LexTokenKind::ColonColonSymbol>();
+                    // ::
+                    return new LexTokenImpl<LexTokenKind::ColonColonSymbol>(TextSpan(start, 2));
                 }
-                return new LexTokenImpl<LexTokenKind::ColonSymbol>();
+                // :
+                return new LexTokenImpl<LexTokenKind::ColonSymbol>(TextSpan(start, 1));
             }
             case u8'&': {
                 auto n = Peek();
                 if (n == u8'=') {
                     Progress();
-                    return new LexTokenImpl<LexTokenKind::AmpersandEqualsSymbol>();
+                    // &=
+                    return new LexTokenImpl<LexTokenKind::AmpersandEqualsSymbol>(TextSpan(start, 2));
                 }
                 if (n == u8'&') {
                     Progress();
-                    return new LexTokenImpl<LexTokenKind::AmpersandAmpersandSymbol>();
+                    // &&
+                    return new LexTokenImpl<LexTokenKind::AmpersandAmpersandSymbol>(TextSpan(start, 2));
                 }
-                return new LexTokenImpl<LexTokenKind::AmpersandSymbol>();
+                // &
+                return new LexTokenImpl<LexTokenKind::AmpersandSymbol>(TextSpan(start, 1));
             }
-            case u8',': return new LexTokenImpl<LexTokenKind::CommaSymbol>();
-            case u8'{': return new LexTokenImpl<LexTokenKind::OpenCurlyParenthesisSymbol>();
-            case u8'}': return new LexTokenImpl<LexTokenKind::CloseCurlyParenthesisSymbol>();
-            case u8';': return new LexTokenImpl<LexTokenKind::SemicolonSymbol>();
+            case u8',': return new LexTokenImpl<LexTokenKind::CommaSymbol>(TextSpan(start, 1));
+            case u8'{': return new LexTokenImpl<LexTokenKind::OpenCurlyParenthesisSymbol>(TextSpan(start, 1));
+            case u8'}': return new LexTokenImpl<LexTokenKind::CloseCurlyParenthesisSymbol>(TextSpan(start, 1));
+            case u8';': return new LexTokenImpl<LexTokenKind::SemicolonSymbol>(TextSpan(start, 1));
             case u8'|': {
                 auto n = Peek();
                 if (n == u8'=') {
                     Progress();
-                    return new LexTokenImpl<LexTokenKind::VerticalLineEqualsSymbol>();
+                    // |=
+                    return new LexTokenImpl<LexTokenKind::VerticalLineEqualsSymbol>(TextSpan(start, 2));
                 }
                 if (n == u8'|') {
                     Progress();
-                    return new LexTokenImpl<LexTokenKind::VerticalLineVerticalLineSymbol>();
+                    // ||
+                    return new LexTokenImpl<LexTokenKind::VerticalLineVerticalLineSymbol>(TextSpan(start, 2));
                 }
-                return new LexTokenImpl<LexTokenKind::VerticalLineSymbol>();
+                // |
+                return new LexTokenImpl<LexTokenKind::VerticalLineSymbol>(TextSpan(start, 1));
             }
             case u8'^': {
                 auto n = Peek();
                 if (n == u8'=') {
                     Progress();
-                    return new LexTokenImpl<LexTokenKind::CaretEqualsSymbol>();
+                    // ^=
+                    return new LexTokenImpl<LexTokenKind::CaretEqualsSymbol>(TextSpan(start, start + 2));
                 }
                 if (n == u8'^') {
                     Progress();
-                    return new LexTokenImpl<LexTokenKind::CaretCaretSymbol>();
+                    // ^^
+                    return new LexTokenImpl<LexTokenKind::CaretCaretSymbol>(TextSpan(start, start + 2));
                 }
-                return new LexTokenImpl<LexTokenKind::CaretSymbol>();
+                // ^
+                return new LexTokenImpl<LexTokenKind::CaretSymbol>(TextSpan(start, start + 1));
             }
-            case u8'~': return new LexTokenImpl<LexTokenKind::TildeSymbol>();
-            case u8'.': return new LexTokenImpl<LexTokenKind::DotSymbol>();
-            case u8'[': return new LexTokenImpl<LexTokenKind::OpenBlockParenthesisSymbol>();
-            case u8']': return new LexTokenImpl<LexTokenKind::CloseBlockParenthesisSymbol>();
-            case u8'@': return new LexTokenImpl<LexTokenKind::AtSymbol>();
+            case u8'~': return new LexTokenImpl<LexTokenKind::TildeSymbol>(TextSpan(start, start + 1));
+            case u8'.': return new LexTokenImpl<LexTokenKind::DotSymbol>(TextSpan(start, start + 1));
+            case u8'[': return new LexTokenImpl<LexTokenKind::OpenBlockParenthesisSymbol>(TextSpan(start, start + 1));
+            case u8']': return new LexTokenImpl<LexTokenKind::CloseBlockParenthesisSymbol>(TextSpan(start, start + 1));
+            case u8'@': return new LexTokenImpl<LexTokenKind::AtSymbol>(TextSpan(start, start + 1));
 
             case u8' ':
             case u8'\r':
             case u8'\n':
-            case u8'\t': return new LexTokenImpl<LexTokenKind::Whitespace>();
+            case u8'\t': return new LexTokenImpl<LexTokenKind::Whitespace>(TextSpan(start, start + 1));
             // Byte order mark
             case u8'\xEF': {
                 if (Peek() == u8'\xBB' && Peek(2) == u8'\xBF') {
                     Progress(2);
-                    return new LexTokenImpl<LexTokenKind::Whitespace>();
+                    return new LexTokenImpl<LexTokenKind::Whitespace>(TextSpan(start, start + 3));
                 }
             }
             case u8'0':
@@ -226,8 +269,8 @@ namespace ElohimScript::Parser {
             default:
                 if (IsAlphaNumericalOrUnderscore(c))
                     return LexKeywordOrIdentifier();
-                // TODO: Log error
-                return new LexTokenImpl<LexTokenKind::Unknown>();
+                _diagnostics->LogError(Diagnostics::DiagnosticType::UnknownToken, TextSpan(start, start + 1));
+                return new LexTokenImpl<LexTokenKind::Unknown>(TextSpan(start, start + 1));
         }
     }
 
@@ -248,7 +291,10 @@ namespace ElohimScript::Parser {
                         ;
                     case 'b': numericalSystem = 2; break;
                     default:
-                        // TODO: Log Invalid numerical system
+                        _diagnostics->LogError(Diagnostics::DiagnosticType::InvalidNumericalBase,
+                                               TextSpan(_position - 1, _position + 1));
+                        // Set to the largest numerical system, so we can prevent errors down the line.
+                        numericalSystem = 16;
                         break;
                 }
             }
@@ -287,6 +333,7 @@ namespace ElohimScript::Parser {
     }
 
     LexToken* Lexer::LexDecimal(uint64_t initial) {
+        auto start = _position;
         uint64_t value = initial;
         uint64_t decimalValue = 0;
         uint64_t exponentValue = 0;
@@ -327,12 +374,13 @@ namespace ElohimScript::Parser {
             if (isExponent) {
                 val *= pow(10, exponentValue);
             }
-            return new FloatLiteral(val);
+            return new FloatLiteral(TextSpan(start, _position), val);
         }
-        return new IntegerLiteral(value);
+        return new IntegerLiteral(TextSpan(start, _position), value);
     }
 
     IntegerLiteral* Lexer::LexHexadecimal() {
+        auto start = _position;
         uint64_t value = 0;
         while (true) {
             auto v = LexHexadecimalValue(Peek());
@@ -343,9 +391,10 @@ namespace ElohimScript::Parser {
             value <<= 4;
             value += v;
         }
-        return new IntegerLiteral(value);
+        return new IntegerLiteral(TextSpan(start, _position), value);
     }
     IntegerLiteral* Lexer::LexOctal() {
+        auto start = _position;
         uint64_t value = 0;
         while (true) {
             auto v = LexOctalValue(Peek());
@@ -356,9 +405,10 @@ namespace ElohimScript::Parser {
             value <<= 3;
             value += v;
         }
-        return new IntegerLiteral(value);
+        return new IntegerLiteral(TextSpan(start, _position), value);
     }
     IntegerLiteral* Lexer::LexBinary() {
+        auto start = _position;
         uint64_t value = 0;
         while (true) {
             auto v = LexBinaryValue(Peek());
@@ -369,7 +419,7 @@ namespace ElohimScript::Parser {
             value <<= 1;
             value += v;
         }
-        return new IntegerLiteral(value);
+        return new IntegerLiteral(TextSpan(start, _position), value);
     }
     StringLiteral* Lexer::LexString(char8_t opening, bool heredoc) {
         Progress();
@@ -388,11 +438,13 @@ namespace ElohimScript::Parser {
                 break;
             }
             if (current == u8'\0') {
-                // TODO: Log error
+                _diagnostics->LogError(Diagnostics::DiagnosticType::ExpectedEndOfString,
+                                       TextSpan(start, start + offset));
                 break;
             }
             if (!heredoc && (current == u8'\n' || current == u8'\r')) {
-                // TODO: log error
+                _diagnostics->LogError(Diagnostics::DiagnosticType::ExpectedEndOfString,
+                                       TextSpan(start, start + offset));
                 break;
             }
             offset++;
@@ -401,14 +453,15 @@ namespace ElohimScript::Parser {
         if (heredoc) {
             Progress(2);
         }
-        return new StringLiteral(std::u8string(_script.substr(start, offset)));
+        return new StringLiteral(TextSpan(start, start + _position), std::u8string(_script.substr(start, offset)));
     }
 
     static uint32_t constexpr Hash(const char8_t* input) {
-        return *input ? static_cast<uint32_t>(*input) + 33 * Hash(input + 1) : 5381;
+        return *input != 0U ? static_cast<uint32_t>(*input) + 33 * Hash(input + 1) : 5381;
     };
 
     LexToken* Lexer::LexKeywordOrIdentifier() {
+        auto start = _position;
         auto offset = 0;
         while (IsAlphaNumericalOrUnderscore(Peek(offset))) {
             offset++;
@@ -416,137 +469,75 @@ namespace ElohimScript::Parser {
         auto str = _script.substr(_position, offset);
         Progress(offset);
         switch (Hash(str.data())) {
-            case Hash(u8"and"):
-                return new LexTokenImpl<LexTokenKind::AndKeyword>();
-            case Hash(u8"abstract"):
-                return new LexTokenImpl<LexTokenKind::AbstractKeyword>();
-            case Hash(u8"auto"):
-                return new LexTokenImpl<LexTokenKind::AutoKeyword>();
-            case Hash(u8"bool"):
-                return new LexTokenImpl<LexTokenKind::BoolKeyword>();
-            case Hash(u8"break"):
-                return new LexTokenImpl<LexTokenKind::BreakKeyword>();
-            case Hash(u8"case"):
-                return new LexTokenImpl<LexTokenKind::CaseKeyword>();
-            case Hash(u8"cast"):
-                return new LexTokenImpl<LexTokenKind::CastKeyword>();
-            case Hash(u8"catch"):
-                return new LexTokenImpl<LexTokenKind::CatchKeyword>();
-            case Hash(u8"class"):
-                return new LexTokenImpl<LexTokenKind::ClassKeyword>();
-            case Hash(u8"const"):
-                return new LexTokenImpl<LexTokenKind::ConstKeyword>();
-            case Hash(u8"continue"):
-                return new LexTokenImpl<LexTokenKind::ContinueKeyword>();
-            case Hash(u8"default"):
-                return new LexTokenImpl<LexTokenKind::DefaultKeyword>();
-            case Hash(u8"do"):
-                return new LexTokenImpl<LexTokenKind::DoKeyword>();
-            case Hash(u8"double"):
-                return new LexTokenImpl<LexTokenKind::DoubleKeyword>();
-            case Hash(u8"else"):
-                return new LexTokenImpl<LexTokenKind::ElseKeyword>();
-            case Hash(u8"enum"):
-                return new LexTokenImpl<LexTokenKind::EnumKeyword>();
-            case Hash(u8"explicit"):
-                return new LexTokenImpl<LexTokenKind::ExplicitKeyword>();
-            case Hash(u8"external"):
-                return new LexTokenImpl<LexTokenKind::ExternalKeyword>();
-            case Hash(u8"false"):
-                return new LexTokenImpl<LexTokenKind::FalseKeyword>();
-            case Hash(u8"final"):
-                return new LexTokenImpl<LexTokenKind::FinalKeyword>();
-            case Hash(u8"float"):
-                return new LexTokenImpl<LexTokenKind::FloatKeyword>();
-            case Hash(u8"for"):
-                return new LexTokenImpl<LexTokenKind::ForKeyword>();
-            case Hash(u8"from"):
-                return new LexTokenImpl<LexTokenKind::FromKeyword>();
-            case Hash(u8"funcdef"):
-                return new LexTokenImpl<LexTokenKind::FuncdefKeyword>();
-            case Hash(u8"function"):
-                return new LexTokenImpl<LexTokenKind::FunctionKeyword>();
-            case Hash(u8"get"):
-                return new LexTokenImpl<LexTokenKind::GetKeyword>();
-            case Hash(u8"if"):
-                return new LexTokenImpl<LexTokenKind::IfKeyword>();
-            case Hash(u8"import"):
-                return new LexTokenImpl<LexTokenKind::ImportKeyword>();
-            case Hash(u8"in"):
-                return new LexTokenImpl<LexTokenKind::InKeyword>();
-            case Hash(u8"inout"):
-                return new LexTokenImpl<LexTokenKind::InoutKeyword>();
-            case Hash(u8"int"):
-                return new LexTokenImpl<LexTokenKind::IntKeyword>();
+            case Hash(u8"and"): return new LexTokenImpl<LexTokenKind::AndKeyword>(TextSpan(start, _position));
+            case Hash(u8"abstract"): return new LexTokenImpl<LexTokenKind::AbstractKeyword>(TextSpan(start, _position));
+            case Hash(u8"auto"): return new LexTokenImpl<LexTokenKind::AutoKeyword>(TextSpan(start, _position));
+            case Hash(u8"bool"): return new LexTokenImpl<LexTokenKind::BoolKeyword>(TextSpan(start, _position));
+            case Hash(u8"break"): return new LexTokenImpl<LexTokenKind::BreakKeyword>(TextSpan(start, _position));
+            case Hash(u8"case"): return new LexTokenImpl<LexTokenKind::CaseKeyword>(TextSpan(start, _position));
+            case Hash(u8"cast"): return new LexTokenImpl<LexTokenKind::CastKeyword>(TextSpan(start, _position));
+            case Hash(u8"catch"): return new LexTokenImpl<LexTokenKind::CatchKeyword>(TextSpan(start, _position));
+            case Hash(u8"class"): return new LexTokenImpl<LexTokenKind::ClassKeyword>(TextSpan(start, _position));
+            case Hash(u8"const"): return new LexTokenImpl<LexTokenKind::ConstKeyword>(TextSpan(start, _position));
+            case Hash(u8"continue"): return new LexTokenImpl<LexTokenKind::ContinueKeyword>(TextSpan(start, _position));
+            case Hash(u8"default"): return new LexTokenImpl<LexTokenKind::DefaultKeyword>(TextSpan(start, _position));
+            case Hash(u8"do"): return new LexTokenImpl<LexTokenKind::DoKeyword>(TextSpan(start, _position));
+            case Hash(u8"double"): return new LexTokenImpl<LexTokenKind::DoubleKeyword>(TextSpan(start, _position));
+            case Hash(u8"else"): return new LexTokenImpl<LexTokenKind::ElseKeyword>(TextSpan(start, _position));
+            case Hash(u8"enum"): return new LexTokenImpl<LexTokenKind::EnumKeyword>(TextSpan(start, _position));
+            case Hash(u8"explicit"): return new LexTokenImpl<LexTokenKind::ExplicitKeyword>(TextSpan(start, _position));
+            case Hash(u8"external"): return new LexTokenImpl<LexTokenKind::ExternalKeyword>(TextSpan(start, _position));
+            case Hash(u8"false"): return new LexTokenImpl<LexTokenKind::FalseKeyword>(TextSpan(start, _position));
+            case Hash(u8"final"): return new LexTokenImpl<LexTokenKind::FinalKeyword>(TextSpan(start, _position));
+            case Hash(u8"float"): return new LexTokenImpl<LexTokenKind::FloatKeyword>(TextSpan(start, _position));
+            case Hash(u8"for"): return new LexTokenImpl<LexTokenKind::ForKeyword>(TextSpan(start, _position));
+            case Hash(u8"from"): return new LexTokenImpl<LexTokenKind::FromKeyword>(TextSpan(start, _position));
+            case Hash(u8"funcdef"): return new LexTokenImpl<LexTokenKind::FuncdefKeyword>(TextSpan(start, _position));
+            case Hash(u8"function"): return new LexTokenImpl<LexTokenKind::FunctionKeyword>(TextSpan(start, _position));
+            case Hash(u8"get"): return new LexTokenImpl<LexTokenKind::GetKeyword>(TextSpan(start, _position));
+            case Hash(u8"if"): return new LexTokenImpl<LexTokenKind::IfKeyword>(TextSpan(start, _position));
+            case Hash(u8"import"): return new LexTokenImpl<LexTokenKind::ImportKeyword>(TextSpan(start, _position));
+            case Hash(u8"in"): return new LexTokenImpl<LexTokenKind::InKeyword>(TextSpan(start, _position));
+            case Hash(u8"inout"): return new LexTokenImpl<LexTokenKind::InoutKeyword>(TextSpan(start, _position));
+            case Hash(u8"int"): return new LexTokenImpl<LexTokenKind::IntKeyword>(TextSpan(start, _position));
             case Hash(u8"interface"):
-                return new LexTokenImpl<LexTokenKind::InterfaceKeyword>();
-            case Hash(u8"int8"):
-                return new LexTokenImpl<LexTokenKind::Int8Keyword>();
-            case Hash(u8"int16"):
-                return new LexTokenImpl<LexTokenKind::Int16Keyword>();
-            case Hash(u8"int32"):
-                return new LexTokenImpl<LexTokenKind::Int32Keyword>();
-            case Hash(u8"int64"):
-                return new LexTokenImpl<LexTokenKind::Int64Keyword>();
-            case Hash(u8"is"):
-                return new LexTokenImpl<LexTokenKind::IsKeyword>();
-            case Hash(u8"mixin"):
-                return new LexTokenImpl<LexTokenKind::MixinKeyword>();
+                return new LexTokenImpl<LexTokenKind::InterfaceKeyword>(TextSpan(start, _position));
+            case Hash(u8"int8"): return new LexTokenImpl<LexTokenKind::Int8Keyword>(TextSpan(start, _position));
+            case Hash(u8"int16"): return new LexTokenImpl<LexTokenKind::Int16Keyword>(TextSpan(start, _position));
+            case Hash(u8"int32"): return new LexTokenImpl<LexTokenKind::Int32Keyword>(TextSpan(start, _position));
+            case Hash(u8"int64"): return new LexTokenImpl<LexTokenKind::Int64Keyword>(TextSpan(start, _position));
+            case Hash(u8"is"): return new LexTokenImpl<LexTokenKind::IsKeyword>(TextSpan(start, _position));
+            case Hash(u8"mixin"): return new LexTokenImpl<LexTokenKind::MixinKeyword>(TextSpan(start, _position));
             case Hash(u8"namespace"):
-                return new LexTokenImpl<LexTokenKind::NamespaceKeyword>();
-            case Hash(u8"not"):
-                return new LexTokenImpl<LexTokenKind::NotKeyword>();
-            case Hash(u8"null"):
-                return new LexTokenImpl<LexTokenKind::NullKeyword>();
-            case Hash(u8"or"):
-                return new LexTokenImpl<LexTokenKind::OrKeyword>();
-            case Hash(u8"out"):
-                return new LexTokenImpl<LexTokenKind::OutKeyword>();
-            case Hash(u8"override"):
-                return new LexTokenImpl<LexTokenKind::OverrideKeyword>();
-            case Hash(u8"private"):
-                return new LexTokenImpl<LexTokenKind::PrivateKeyword>();
-            case Hash(u8"property"):
-                return new LexTokenImpl<LexTokenKind::PropertyKeyword>();
+                return new LexTokenImpl<LexTokenKind::NamespaceKeyword>(TextSpan(start, _position));
+            case Hash(u8"not"): return new LexTokenImpl<LexTokenKind::NotKeyword>(TextSpan(start, _position));
+            case Hash(u8"null"): return new LexTokenImpl<LexTokenKind::NullKeyword>(TextSpan(start, _position));
+            case Hash(u8"or"): return new LexTokenImpl<LexTokenKind::OrKeyword>(TextSpan(start, _position));
+            case Hash(u8"out"): return new LexTokenImpl<LexTokenKind::OutKeyword>(TextSpan(start, _position));
+            case Hash(u8"override"): return new LexTokenImpl<LexTokenKind::OverrideKeyword>(TextSpan(start, _position));
+            case Hash(u8"private"): return new LexTokenImpl<LexTokenKind::PrivateKeyword>(TextSpan(start, _position));
+            case Hash(u8"property"): return new LexTokenImpl<LexTokenKind::PropertyKeyword>(TextSpan(start, _position));
             case Hash(u8"protected"):
-                return new LexTokenImpl<LexTokenKind::ProtectedKeyword>();
-            case Hash(u8"return"):
-                return new LexTokenImpl<LexTokenKind::ReturnKeyword>();
-            case Hash(u8"set"):
-                return new LexTokenImpl<LexTokenKind::SetKeyword>();
-            case Hash(u8"shared"):
-                return new LexTokenImpl<LexTokenKind::SharedKeyword>();
-            case Hash(u8"super"):
-                return new LexTokenImpl<LexTokenKind::SuperKeyword>();
-            case Hash(u8"switch"):
-                return new LexTokenImpl<LexTokenKind::SwitchKeyword>();
-            case Hash(u8"this"):
-                return new LexTokenImpl<LexTokenKind::ThisKeyword>();
-            case Hash(u8"true"):
-                return new LexTokenImpl<LexTokenKind::TrueKeyword>();
-            case Hash(u8"try"):
-                return new LexTokenImpl<LexTokenKind::TryKeyword>();
-            case Hash(u8"typedef"):
-                return new LexTokenImpl<LexTokenKind::TypedefKeyword>();
-            case Hash(u8"uint"):
-                return new LexTokenImpl<LexTokenKind::UintKeyword>();
-            case Hash(u8"uint8"):
-                return new LexTokenImpl<LexTokenKind::Uint8Keyword>();
-            case Hash(u8"uint16"):
-                return new LexTokenImpl<LexTokenKind::Uint16Keyword>();
-            case Hash(u8"uint32"):
-                return new LexTokenImpl<LexTokenKind::Uint32Keyword>();
-            case Hash(u8"uint64"):
-                return new LexTokenImpl<LexTokenKind::Uint64Keyword>();
-            case Hash(u8"void"):
-                return new LexTokenImpl<LexTokenKind::VoidKeyword>();
-            case Hash(u8"while"):
-                return new LexTokenImpl<LexTokenKind::WhileKeyword>();
-            case Hash(u8"xor"):
-                return new LexTokenImpl<LexTokenKind::XorKeyword>();
+                return new LexTokenImpl<LexTokenKind::ProtectedKeyword>(TextSpan(start, _position));
+            case Hash(u8"return"): return new LexTokenImpl<LexTokenKind::ReturnKeyword>(TextSpan(start, _position));
+            case Hash(u8"set"): return new LexTokenImpl<LexTokenKind::SetKeyword>(TextSpan(start, _position));
+            case Hash(u8"shared"): return new LexTokenImpl<LexTokenKind::SharedKeyword>(TextSpan(start, _position));
+            case Hash(u8"super"): return new LexTokenImpl<LexTokenKind::SuperKeyword>(TextSpan(start, _position));
+            case Hash(u8"switch"): return new LexTokenImpl<LexTokenKind::SwitchKeyword>(TextSpan(start, _position));
+            case Hash(u8"this"): return new LexTokenImpl<LexTokenKind::ThisKeyword>(TextSpan(start, _position));
+            case Hash(u8"true"): return new LexTokenImpl<LexTokenKind::TrueKeyword>(TextSpan(start, _position));
+            case Hash(u8"try"): return new LexTokenImpl<LexTokenKind::TryKeyword>(TextSpan(start, _position));
+            case Hash(u8"typedef"): return new LexTokenImpl<LexTokenKind::TypedefKeyword>(TextSpan(start, _position));
+            case Hash(u8"uint"): return new LexTokenImpl<LexTokenKind::UintKeyword>(TextSpan(start, _position));
+            case Hash(u8"uint8"): return new LexTokenImpl<LexTokenKind::Uint8Keyword>(TextSpan(start, _position));
+            case Hash(u8"uint16"): return new LexTokenImpl<LexTokenKind::Uint16Keyword>(TextSpan(start, _position));
+            case Hash(u8"uint32"): return new LexTokenImpl<LexTokenKind::Uint32Keyword>(TextSpan(start, _position));
+            case Hash(u8"uint64"): return new LexTokenImpl<LexTokenKind::Uint64Keyword>(TextSpan(start, _position));
+            case Hash(u8"void"): return new LexTokenImpl<LexTokenKind::VoidKeyword>(TextSpan(start, _position));
+            case Hash(u8"while"): return new LexTokenImpl<LexTokenKind::WhileKeyword>(TextSpan(start, _position));
+            case Hash(u8"xor"): return new LexTokenImpl<LexTokenKind::XorKeyword>(TextSpan(start, _position));
 
-            default:
-                return new IdentifierToken(std::u8string(str));
+            default: return new IdentifierToken(TextSpan(start, _position), std::u8string(str));
         }
     }
     bool Lexer::IsAlphaNumericalOrUnderscore(char8_t c) {
diff --git a/src/Parser/Lexer/Lexer.hpp b/src/Parser/Lexer/Lexer.hpp
index 391bc6a..1a4790f 100644
--- a/src/Parser/Lexer/Lexer.hpp
+++ b/src/Parser/Lexer/Lexer.hpp
@@ -2,19 +2,22 @@
 #define ELOHIMSCRIPT_LEXER_HPP
 
 #include <string_view>
+#include "../../Diagnostics/Diagnostics.hpp"
 #include "LexToken.hpp"
 
 namespace ElohimScript::Parser {
     class Lexer {
     public:
-        Lexer(const char* script) : _script(reinterpret_cast<const char8_t*>(script)) {}
-        Lexer(const char8_t* script) : _script(script) {}
-        Lexer(std::u8string_view script) : _script(script) {}
+        Lexer(const char* script, Diagnostics::Diagnostics* diag)
+            : Lexer(reinterpret_cast<const char8_t*>(script), diag) {}
+        Lexer(const char8_t* script, Diagnostics::Diagnostics* diag) : _script(script), _diagnostics(diag) {}
+        Lexer(std::u8string_view script, Diagnostics::Diagnostics* diag) : _script(script), _diagnostics(diag) {}
         const LexToken* Lex();
 
     private:
         std::u8string_view _script;
         size_t _position = -1;
+        Diagnostics::Diagnostics* _diagnostics;
 
         inline char8_t Consume() {
             if (++_position >= _script.size()) {
@@ -23,9 +26,7 @@ namespace ElohimScript::Parser {
             return _script[_position];
         }
 
-        inline void Progress(size_t steps = 1){
-            _position += steps;
-        }
+        inline void Progress(size_t steps = 1) { _position += steps; }
 
         inline char8_t Peek(size_t offset = 1) {
             auto pos = _position + offset;
diff --git a/src/Parser/TextSpan.hpp b/src/Parser/TextSpan.hpp
new file mode 100644
index 0000000..975de02
--- /dev/null
+++ b/src/Parser/TextSpan.hpp
@@ -0,0 +1,19 @@
+#ifndef ELOHIMSCRIPT_TEXTSPAN_HPP
+#define ELOHIMSCRIPT_TEXTSPAN_HPP
+
+#include <cstddef>
+namespace ElohimScript {
+    class TextSpan {
+        size_t _start;
+        size_t _end;
+
+    public:
+        inline TextSpan(size_t start, size_t end) : _start(start), _end(end) {}
+        [[nodiscard]] inline size_t GetStart() const noexcept { return _start; }
+        [[nodiscard]] inline size_t GetEnd() const noexcept { return _end; }
+        inline bool operator==(const TextSpan& rhs) const { return _start == rhs._start && _end == rhs._end; }
+        inline bool operator!=(const TextSpan& rhs) const { return !(rhs == *this); }
+    };
+}
+
+#endif // ELOHIMSCRIPT_TEXTSPAN_HPP
diff --git a/tests/LexerTests/IdentifierLexTests.cpp b/tests/LexerTests/IdentifierLexTests.cpp
index 491a48f..921cb3e 100644
--- a/tests/LexerTests/IdentifierLexTests.cpp
+++ b/tests/LexerTests/IdentifierLexTests.cpp
@@ -5,8 +5,10 @@ using namespace ElohimScript::Parser;
 
 #define KEYWORD_TEST(script, symbol)                                                                                   \
     TEST_CASE("Lex " script) {                                                                                         \
-        auto lexer = Lexer(script);                                                                                    \
+        ElohimScript::Diagnostics::Diagnostics diag;                                                                   \
+        auto lexer = Lexer(script, &diag);                                                                             \
         const auto* token = lexer.Lex();                                                                               \
+        CHECK(diag.GetMessages().empty());                                                                             \
         CHECK(token->GetKind() == LexTokenKind::symbol);                                                               \
         CHECK(token->GetNext()->GetKind() == LexTokenKind::EndOfFile);                                                 \
         delete token;                                                                                                  \
@@ -91,8 +93,10 @@ namespace doctest {
 
 #define IDENTIFIER_TEST(identifier)                                                                                    \
     TEST_CASE("Lex identifier " identifier) {                                                                          \
-        auto lexer = Lexer(identifier);                                                                                \
+        ElohimScript::Diagnostics::Diagnostics diag;                                                                   \
+        auto lexer = Lexer(identifier, &diag);                                                                         \
         const auto* token = lexer.Lex();                                                                               \
+        CHECK(diag.GetMessages().empty());                                                                             \
         REQUIRE(token->GetKind() == LexTokenKind::Identifier);                                                         \
         auto value = ((IdentifierToken*)token)->GetValue();                                                            \
         CHECK(value == std::u8string(reinterpret_cast<const char8_t*>(identifier)));                                   \
diff --git a/tests/LexerTests/NumericalLexTests.cpp b/tests/LexerTests/NumericalLexTests.cpp
index d2ffcaf..028cac4 100644
--- a/tests/LexerTests/NumericalLexTests.cpp
+++ b/tests/LexerTests/NumericalLexTests.cpp
@@ -5,8 +5,10 @@ using namespace ElohimScript::Parser;
 
 #define INTEGER_TEST(script, expected)                                                                                 \
     TEST_CASE("Lex " script) {                                                                                         \
-        auto lexer = Lexer(script);                                                                                    \
+        ElohimScript::Diagnostics::Diagnostics diag;                                                                   \
+        auto lexer = Lexer(script, &diag);                                                                             \
         const auto* token = lexer.Lex();                                                                               \
+        CHECK(diag.GetMessages().empty());                                                                             \
         REQUIRE(token->GetKind() == LexTokenKind::IntegerLiteral);                                                     \
         auto value = ((const IntegerLiteral*)token)->GetValue();                                                       \
         CHECK(value == (expected));                                                                                    \
@@ -16,8 +18,10 @@ using namespace ElohimScript::Parser;
 
 #define FLOAT_TEST(script, expected)                                                                                   \
     TEST_CASE("Lex " script) {                                                                                         \
-        auto lexer = Lexer(script);                                                                                    \
+        ElohimScript::Diagnostics::Diagnostics diag;                                                                   \
+        auto lexer = Lexer(script, &diag);                                                                             \
         const auto* token = lexer.Lex();                                                                               \
+        CHECK(diag.GetMessages().empty());                                                                             \
         REQUIRE(token->GetKind() == LexTokenKind::FloatLiteral);                                                       \
         auto value = ((const FloatLiteral*)token)->GetValue();                                                         \
         CHECK(value == (expected));                                                                                    \
@@ -63,4 +67,16 @@ INTEGER_TEST("0b1111", 15);
 INTEGER_TEST("0b110011", 51);
 
 #undef INTEGER_TEST
-#undef FLOAT_TEST
\ No newline at end of file
+#undef FLOAT_TEST
+
+TEST_CASE("Lex invalid numerical base") {
+    ElohimScript::Diagnostics::Diagnostics diag;
+    auto lexer = Lexer("0f553", &diag);
+    const auto* token = lexer.Lex();
+    const auto& messages = diag.GetMessages();
+    REQUIRE(messages.size() == 1);
+    CHECK(messages[0].GetType() == ElohimScript::Diagnostics::DiagnosticType::InvalidNumericalBase);
+    CHECK(messages[0].GetLevel() == ElohimScript::Diagnostics::DiagnosticLevel::Error);
+    CHECK(messages[0].GetSpan() == ElohimScript::TextSpan(0, 2));
+    delete token;
+}
diff --git a/tests/LexerTests/StringLexTests.cpp b/tests/LexerTests/StringLexTests.cpp
index e1a8a47..3df238f 100644
--- a/tests/LexerTests/StringLexTests.cpp
+++ b/tests/LexerTests/StringLexTests.cpp
@@ -5,8 +5,10 @@ using namespace ElohimScript::Parser;
 
 #define STRING_TEST(str, constraint)                                                                                   \
     TEST_CASE("Lex string " constraint str constraint) {                                                               \
-        auto lexer = Lexer(constraint str constraint);                                                                 \
+        ElohimScript::Diagnostics::Diagnostics diag;                                                                   \
+        auto lexer = Lexer(constraint str constraint, &diag);                                                          \
         const auto* token = lexer.Lex();                                                                               \
+        CHECK(diag.GetMessages().empty());                                                                             \
         REQUIRE(token->GetKind() == LexTokenKind::StringLiteral);                                                      \
         auto value = ((const StringLiteral*)token)->GetValue();                                                        \
         CHECK(value == std::u8string(reinterpret_cast<const char8_t*>(str)));                                          \
@@ -21,9 +23,12 @@ STRING_TEST("\"foo bar\"", "\"\"\"");
 STRING_TEST("\"\"foo bar\"\"", "\"\"\"");
 
 TEST_CASE("Lex multiline string") {
+    ElohimScript::Diagnostics::Diagnostics diag;
     auto lexer = Lexer(R"("""foo
-bar""")");
+bar""")",
+                       &diag);
     const auto* token = lexer.Lex();
+    CHECK(diag.GetMessages().empty());
     REQUIRE(token->GetKind() == LexTokenKind::StringLiteral);
     auto value = (dynamic_cast<const StringLiteral*>(token))->GetValue();
     CHECK(value == std::u8string(reinterpret_cast<const char8_t*>(R"(foo
diff --git a/tests/LexerTests/SymbolLexTests.cpp b/tests/LexerTests/SymbolLexTests.cpp
index 0d61e27..fecf65f 100644
--- a/tests/LexerTests/SymbolLexTests.cpp
+++ b/tests/LexerTests/SymbolLexTests.cpp
@@ -6,8 +6,10 @@ using namespace ElohimScript::Parser;
 
 #define SYMBOL_TEST(script, symbol)                                                                                    \
     TEST_CASE("Lex " script) {                                                                                         \
-        auto lexer = Lexer(script);                                                                                    \
+        ElohimScript::Diagnostics::Diagnostics diag;                                                                   \
+        auto lexer = Lexer(script, &diag);                                                                             \
         const auto* token = lexer.Lex();                                                                               \
+        CHECK(diag.GetMessages().empty());                                                                             \
         CHECK(token->GetKind() == LexTokenKind::symbol);                                                               \
         CHECK(token->GetNext()->GetKind() == LexTokenKind::EndOfFile);                                                 \
         delete token;                                                                                                  \
@@ -71,9 +73,11 @@ SYMBOL_TEST(" ", Whitespace)
 
 TEST_CASE("Lex whitespace") {
     auto whitespace = {" ", "\t", "\n", "\r", "\xef\xbb\xbf"};
-    for (auto v : whitespace) {
-        auto lexer = Lexer(v);
+    for (const auto *v : whitespace) {
+        ElohimScript::Diagnostics::Diagnostics diag;
+        auto lexer = Lexer(v, &diag);
         const auto* token = lexer.Lex();
+        CHECK(diag.GetMessages().empty());
         CHECK(token->GetKind() == LexTokenKind::Whitespace);
         CHECK(token->GetNext()->GetKind() == LexTokenKind::EndOfFile);
         delete token;