diff --git a/Cargo.toml b/Cargo.toml
index cb5cdd3..4254f3b 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "luau0-src"
-version = "0.5.0+luau555"
+version = "0.5.1+luau558"
 authors = ["Aleksandr Orlenko <zxteam@protonmail.com>"]
 edition = "2021"
 repository = "https://github.com/khvzak/luau-src-rs"
diff --git a/luau/Ast/include/Luau/Ast.h b/luau/Ast/include/Luau/Ast.h
index 0705116..aa87d9e 100644
--- a/luau/Ast/include/Luau/Ast.h
+++ b/luau/Ast/include/Luau/Ast.h
@@ -5,6 +5,7 @@
 
 #include <optional>
 #include <functional>
+#include <string>
 
 #include <string.h>
 
diff --git a/luau/Ast/include/Luau/Location.h b/luau/Ast/include/Luau/Location.h
index e39bbf8..dbe36be 100644
--- a/luau/Ast/include/Luau/Location.h
+++ b/luau/Ast/include/Luau/Location.h
@@ -1,8 +1,6 @@
 // This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
 #pragma once
 
-#include <string>
-
 namespace Luau
 {
 
@@ -10,130 +8,36 @@ struct Position
 {
     unsigned int line, column;
 
-    Position(unsigned int line, unsigned int column)
-        : line(line)
-        , column(column)
-    {
-    }
+    Position(unsigned int line, unsigned int column);
 
-    bool operator==(const Position& rhs) const
-    {
-        return this->column == rhs.column && this->line == rhs.line;
-    }
-    bool operator!=(const Position& rhs) const
-    {
-        return !(*this == rhs);
-    }
+    bool operator==(const Position& rhs) const;
+    bool operator!=(const Position& rhs) const;
+    bool operator<(const Position& rhs) const;
+    bool operator>(const Position& rhs) const;
+    bool operator<=(const Position& rhs) const;
+    bool operator>=(const Position& rhs) const;
 
-    bool operator<(const Position& rhs) const
-    {
-        if (line == rhs.line)
-            return column < rhs.column;
-        else
-            return line < rhs.line;
-    }
-
-    bool operator>(const Position& rhs) const
-    {
-        if (line == rhs.line)
-            return column > rhs.column;
-        else
-            return line > rhs.line;
-    }
-
-    bool operator<=(const Position& rhs) const
-    {
-        return *this == rhs || *this < rhs;
-    }
-
-    bool operator>=(const Position& rhs) const
-    {
-        return *this == rhs || *this > rhs;
-    }
-
-    void shift(const Position& start, const Position& oldEnd, const Position& newEnd)
-    {
-        if (*this >= start)
-        {
-            if (this->line > oldEnd.line)
-                this->line += (newEnd.line - oldEnd.line);
-            else
-            {
-                this->line = newEnd.line;
-                this->column += (newEnd.column - oldEnd.column);
-            }
-        }
-    }
+    void shift(const Position& start, const Position& oldEnd, const Position& newEnd);
 };
 
 struct Location
 {
     Position begin, end;
 
-    Location()
-        : begin(0, 0)
-        , end(0, 0)
-    {
-    }
+    Location();
+    Location(const Position& begin, const Position& end);
+    Location(const Position& begin, unsigned int length);
+    Location(const Location& begin, const Location& end);
 
-    Location(const Position& begin, const Position& end)
-        : begin(begin)
-        , end(end)
-    {
-    }
+    bool operator==(const Location& rhs) const;
+    bool operator!=(const Location& rhs) const;
 
-    Location(const Position& begin, unsigned int length)
-        : begin(begin)
-        , end(begin.line, begin.column + length)
-    {
-    }
-
-    Location(const Location& begin, const Location& end)
-        : begin(begin.begin)
-        , end(end.end)
-    {
-    }
-
-    bool operator==(const Location& rhs) const
-    {
-        return this->begin == rhs.begin && this->end == rhs.end;
-    }
-    bool operator!=(const Location& rhs) const
-    {
-        return !(*this == rhs);
-    }
-
-    bool encloses(const Location& l) const
-    {
-        return begin <= l.begin && end >= l.end;
-    }
-    bool overlaps(const Location& l) const
-    {
-        return (begin <= l.begin && end >= l.begin) || (begin <= l.end && end >= l.end) || (begin >= l.begin && end <= l.end);
-    }
-    bool contains(const Position& p) const
-    {
-        return begin <= p && p < end;
-    }
-    bool containsClosed(const Position& p) const
-    {
-        return begin <= p && p <= end;
-    }
-    void extend(const Location& other)
-    {
-        if (other.begin < begin)
-            begin = other.begin;
-        if (other.end > end)
-            end = other.end;
-    }
-    void shift(const Position& start, const Position& oldEnd, const Position& newEnd)
-    {
-        begin.shift(start, oldEnd, newEnd);
-        end.shift(start, oldEnd, newEnd);
-    }
+    bool encloses(const Location& l) const;
+    bool overlaps(const Location& l) const;
+    bool contains(const Position& p) const;
+    bool containsClosed(const Position& p) const;
+    void extend(const Location& other);
+    void shift(const Position& start, const Position& oldEnd, const Position& newEnd);
 };
 
-std::string toString(const Position& position);
-std::string toString(const Location& location);
-
 } // namespace Luau
diff --git a/luau/Ast/src/Location.cpp b/luau/Ast/src/Location.cpp
index d7a899e..d01d8a1 100644
--- a/luau/Ast/src/Location.cpp
+++ b/luau/Ast/src/Location.cpp
@@ -4,14 +4,128 @@
 namespace Luau
 {
 
-std::string toString(const Position& position)
+Position::Position(unsigned int line, unsigned int column)
+    : line(line)
+    , column(column)
 {
-    return "{ line = " + std::to_string(position.line) + ", col = " + std::to_string(position.column) + " }";
 }
 
-std::string toString(const Location& location)
+bool Position::operator==(const Position& rhs) const
 {
-    return "Location { " + toString(location.begin) + ", " + toString(location.end) + " }";
+    return this->column == rhs.column && this->line == rhs.line;
+}
+
+bool Position::operator!=(const Position& rhs) const
+{
+    return !(*this == rhs);
+}
+
+bool Position::operator<(const Position& rhs) const
+{
+    if (line == rhs.line)
+        return column < rhs.column;
+    else
+        return line < rhs.line;
+}
+
+bool Position::operator>(const Position& rhs) const
+{
+    if (line == rhs.line)
+        return column > rhs.column;
+    else
+        return line > rhs.line;
+}
+
+bool Position::operator<=(const Position& rhs) const
+{
+    return *this == rhs || *this < rhs;
+}
+
+bool Position::operator>=(const Position& rhs) const
+{
+    return *this == rhs || *this > rhs;
+}
+
+void Position::shift(const Position& start, const Position& oldEnd, const Position& newEnd)
+{
+    if (*this >= start)
+    {
+        if (this->line > oldEnd.line)
+            this->line += (newEnd.line - oldEnd.line);
+        else
+        {
+            this->line = newEnd.line;
+            this->column += (newEnd.column - oldEnd.column);
+        }
+    }
+}
+
+Location::Location()
+    : begin(0, 0)
+    , end(0, 0)
+{
+}
+
+Location::Location(const Position& begin, const Position& end)
+    : begin(begin)
+    , end(end)
+{
+}
+
+Location::Location(const Position& begin, unsigned int length)
+    : begin(begin)
+    , end(begin.line, begin.column + length)
+{
+}
+
+Location::Location(const Location& begin, const Location& end)
+    : begin(begin.begin)
+    , end(end.end)
+{
+}
+
+bool Location::operator==(const Location& rhs) const
+{
+    return this->begin == rhs.begin && this->end == rhs.end;
+}
+
+bool Location::operator!=(const Location& rhs) const
+{
+    return !(*this == rhs);
+}
+
+bool Location::encloses(const Location& l) const
+{
+    return begin <= l.begin && end >= l.end;
+}
+
+bool Location::overlaps(const Location& l) const
+{
+    return (begin <= l.begin && end >= l.begin) || (begin <= l.end && end >= l.end) || (begin >= l.begin && end <= l.end);
+}
+
+bool Location::contains(const Position& p) const
+{
+    return begin <= p && p < end;
+}
+
+bool Location::containsClosed(const Position& p) const
+{
+    return begin <= p && p <= end;
+}
+
+void Location::extend(const Location& other)
+{
+    if (other.begin < begin)
+        begin = other.begin;
+    if (other.end > end)
+        end = other.end;
+}
+
+void Location::shift(const Position& start, const Position& oldEnd, const Position& newEnd)
+{
+    begin.shift(start, oldEnd, newEnd);
+    end.shift(start, oldEnd, newEnd);
 }
 
 } // namespace Luau
diff --git a/luau/Compiler/src/Compiler.cpp b/luau/Compiler/src/Compiler.cpp
index 5d67236..8a1e80f 100644
--- a/luau/Compiler/src/Compiler.cpp
+++ b/luau/Compiler/src/Compiler.cpp
@@ -27,6 +27,7 @@ LUAU_FASTINTVARIABLE(LuauCompileInlineDepth, 5)
 
 LUAU_FASTFLAG(LuauInterpolatedStringBaseSupport)
 LUAU_FASTFLAGVARIABLE(LuauMultiAssignmentConflictFix, false)
+LUAU_FASTFLAGVARIABLE(LuauSelfAssignmentSkip, false)
 
 namespace Luau
 {
@@ -350,7 +351,7 @@ struct Compiler
     {
         LUAU_ASSERT(!multRet || unsigned(target + targetCount) == regTop);
 
-        setDebugLine(expr); // normally compileExpr sets up line info, but compileExprCall can be called directly
+        setDebugLine(expr); // normally compileExpr sets up line info, but compileExprVarargs can be called directly
 
         bytecode.emitABC(LOP_GETVARARGS, target, multRet ? 0 : uint8_t(targetCount + 1), 0);
     }
@@ -2027,7 +2028,9 @@ struct Compiler
             // note: this can't check expr->upvalue because upvalues may be upgraded to locals during inlining
             if (int reg = getExprLocalReg(expr); reg >= 0)
             {
-                bytecode.emitABC(LOP_MOVE, target, uint8_t(reg), 0);
+                // Optimization: we don't need to move if target happens to be in the same register
+                if (!FFlag::LuauSelfAssignmentSkip || options.optimizationLevel == 0 || target != reg)
+                    bytecode.emitABC(LOP_MOVE, target, uint8_t(reg), 0);
             }
             else
             {