diff --git a/src/buffer.cc b/src/buffer.cc
index aeff8400..398f7460 100644
--- a/src/buffer.cc
+++ b/src/buffer.cc
@@ -66,15 +66,10 @@ BufferCoord Buffer::line_and_column_at(const BufferIterator& iterator) const
     return iterator.m_coord;
 }
 
-BufferPos Buffer::line_at(const BufferIterator& iterator) const
-{
-    return iterator.line();
-}
-
-BufferSize Buffer::line_length(BufferPos line) const
+BufferSize Buffer::line_length(LineCount line) const
 {
     assert(line < line_count());
-    BufferPos end = (line < m_lines.size() - 1) ?
+    BufferPos end = (line < line_count() - 1) ?
                     m_lines[line + 1].start : character_count();
     return end - m_lines[line].start;
 }
@@ -86,7 +81,7 @@ BufferCoord Buffer::clamp(const BufferCoord& line_and_column,
         return BufferCoord();
 
     BufferCoord result(line_and_column.line, line_and_column.column);
-    result.line = Kakoune::clamp<int>(0, m_lines.size() - 1, result.line);
+    result.line = Kakoune::clamp(0_line, line_count() - 1, result.line);
     int max_col = std::max(0, line_length(result.line) - (avoid_eol ? 2 : 1));
     result.column = Kakoune::clamp<int>(0, max_col, result.column);
     return result;
@@ -97,35 +92,35 @@ BufferIterator Buffer::iterator_at_line_begin(const BufferIterator& iterator) co
     return BufferIterator(*this, { iterator.line(), 0 });
 }
 
-BufferIterator Buffer::iterator_at_line_begin(size_t line) const
+BufferIterator Buffer::iterator_at_line_begin(LineCount line) const
 {
-    return BufferIterator(*this, clamp({ (int)line, 0 }));
+    return BufferIterator(*this, clamp({ line, 0 }));
 }
 
 BufferIterator Buffer::iterator_at_line_end(const BufferIterator& iterator) const
 {
-    BufferPos line = iterator.line();
+    LineCount line = iterator.line();
     assert(line_length(line) > 0);
     return ++BufferIterator(*this, { line, line_length(line) - 1 });
 }
 
-BufferIterator Buffer::iterator_at_line_end(size_t line) const
+BufferIterator Buffer::iterator_at_line_end(LineCount line) const
 {
-    line = std::min(line, (size_t)line_count()-1);
+    line = std::min(line, line_count()-1);
     assert(line_length(line) > 0);
-    return ++BufferIterator(*this, { (int)line, line_length(line) - 1 });
+    return ++BufferIterator(*this, { line, line_length(line) - 1 });
 }
 
 BufferIterator Buffer::begin() const
 {
-    return BufferIterator(*this, { 0, 0 });
+    return BufferIterator(*this, { 0_line, 0 });
 }
 
 BufferIterator Buffer::end() const
 {
     if (m_lines.empty())
-        return BufferIterator(*this, { 0, 0 });
-    return BufferIterator(*this, { (int)line_count()-1, (int)m_lines.back().length() });
+        return BufferIterator(*this, { 0_line, 0 });
+    return BufferIterator(*this, { line_count()-1, (int)m_lines.back().length() });
 }
 
 BufferSize Buffer::character_count() const
@@ -135,15 +130,15 @@ BufferSize Buffer::character_count() const
     return m_lines.back().start + m_lines.back().length();
 }
 
-BufferSize Buffer::line_count() const
+LineCount Buffer::line_count() const
 {
-    return m_lines.size();
+    return LineCount(m_lines.size());
 }
 
 String Buffer::string(const BufferIterator& begin, const BufferIterator& end) const
 {
     String res;
-    for (BufferPos line = begin.line(); line <= end.line(); ++line)
+    for (LineCount line = begin.line(); line <= end.line(); ++line)
     {
        size_t start = 0;
        if (line == begin.line())
@@ -253,7 +248,7 @@ void Buffer::do_insert(const BufferIterator& pos, const String& content)
     BufferSize offset = pos.offset();
 
     // all following lines advanced by length
-    for (size_t i = pos.line()+1; i < line_count(); ++i)
+    for (LineCount i = pos.line()+1; i < line_count(); ++i)
         m_lines[i].start += content.length();
 
     BufferIterator begin_it;
@@ -282,7 +277,7 @@ void Buffer::do_insert(const BufferIterator& pos, const String& content)
         String prefix = m_lines[pos.line()].content.substr(0, pos.column());
         String suffix = m_lines[pos.line()].content.substr(pos.column());
 
-        auto line_it = m_lines.begin() + pos.line();
+        auto line_it = m_lines.begin() + (int)pos.line();
         line_it = m_lines.erase(line_it);
 
         int start = 0;
@@ -313,7 +308,8 @@ void Buffer::do_insert(const BufferIterator& pos, const String& content)
             --line_it;
 
         begin_it = pos;
-        end_it = BufferIterator(*this, { int(line_it - m_lines.begin()), int(line_it->length() - suffix.length()) });
+        end_it = BufferIterator(*this, { LineCount(line_it - m_lines.begin()),
+                                         int(line_it->length() - suffix.length()) });
     }
 
     check_invariant();
@@ -331,11 +327,11 @@ void Buffer::do_erase(const BufferIterator& pos, BufferSize length)
     String suffix = m_lines[end.line()].content.substr(end.column());
     Line new_line = { m_lines[pos.line()].start, prefix + suffix };
 
-    m_lines.erase(m_lines.begin() + pos.line(), m_lines.begin() + end.line() + 1);
+    m_lines.erase(m_lines.begin() + (int)pos.line(), m_lines.begin() + (int)end.line() + 1);
     if (new_line.length())
-        m_lines.insert(m_lines.begin() + pos.line(), std::move(new_line));
+        m_lines.insert(m_lines.begin() + (int)pos.line(), std::move(new_line));
 
-    for (size_t i = pos.line()+1; i < line_count(); ++i)
+    for (LineCount i = pos.line()+1; i < line_count(); ++i)
         m_lines[i].start -= length;
 
     check_invariant();
diff --git a/src/buffer.hh b/src/buffer.hh
index 83bdcf22..971c731f 100644
--- a/src/buffer.hh
+++ b/src/buffer.hh
@@ -9,6 +9,7 @@
 #include "option_manager.hh"
 #include "hook_manager.hh"
 #include "string.hh"
+#include "units.hh"
 
 namespace Kakoune
 {
@@ -21,7 +22,7 @@ typedef int       BufferSize;
 
 struct BufferCoord : LineAndColumn<BufferCoord>
 {
-    BufferCoord(int line = 0, int column = 0)
+    BufferCoord(LineCount line = 0, int column = 0)
         : LineAndColumn(line, column) {}
 
     template<typename T>
@@ -72,7 +73,7 @@ public:
 
     const Buffer& buffer() const;
     const BufferCoord& coord() const { return m_coord; }
-    BufferSize line() const { return m_coord.line; }
+    LineCount  line() const { return m_coord.line; }
     BufferSize column() const { return m_coord.column; }
 
 private:
@@ -130,7 +131,7 @@ public:
     BufferIterator begin() const;
     BufferIterator end() const;
     BufferSize     character_count() const;
-    BufferSize     line_count() const;
+    LineCount      line_count() const;
 
     // returns an iterator at given coordinates. line_and_column is
     // clamped according to avoid_eol.
@@ -162,16 +163,17 @@ public:
     // iterator is on
     BufferIterator iterator_at_line_begin(const BufferIterator& iterator) const;
     // the same but taking a line number instead of an iterator
-    BufferIterator iterator_at_line_begin(size_t line) const;
+    BufferIterator iterator_at_line_begin(LineCount line) const;
 
     // returns an iterator pointing to the character after the last of the
     // line iterator is on (which is the first of the next line if iterator is
     // not on the last one)
     BufferIterator iterator_at_line_end(const BufferIterator& iterator) const;
     // the same but taking a line number instead of an iterator
-    BufferIterator iterator_at_line_end(size_t line) const;
+    BufferIterator iterator_at_line_end(LineCount line) const;
 
-    const String& line_content(size_t l) const { return m_lines[l].content; }
+    const String& line_content(LineCount line) const
+    { return m_lines[line].content; }
 
     OptionManager&       option_manager()       { return m_option_manager; }
     const OptionManager& option_manager() const { return m_option_manager; }
@@ -190,13 +192,21 @@ private:
 
         size_t length() const { return content.length(); }
     };
-    std::vector<Line> m_lines;
+    struct LineList : std::vector<Line>
+    {
+    public:
+        Line& operator[](LineCount line)
+        { return std::vector<Line>::operator[]((int)line); }
+
+        const Line& operator[](LineCount line) const
+        { return std::vector<Line>::operator[]((int)line); }
+    };
+    LineList m_lines;
 
     void do_insert(const BufferIterator& pos, const String& content);
     void do_erase(const BufferIterator& pos, BufferSize length);
 
-    BufferPos line_at(const BufferIterator& iterator) const;
-    BufferSize line_length(BufferPos line) const;
+    BufferSize line_length(LineCount line) const;
 
     String  m_name;
     const Type   m_type;
diff --git a/src/buffer_iterator.inl.hh b/src/buffer_iterator.inl.hh
index eb9d5bcb..b91734dc 100644
--- a/src/buffer_iterator.inl.hh
+++ b/src/buffer_iterator.inl.hh
@@ -117,7 +117,8 @@ inline Character BufferIterator::operator*() const
 inline BufferSize BufferIterator::offset() const
 {
     assert(m_buffer);
-    return line() == 0 ? column() : m_buffer->m_lines[line()].start + column();
+    return line() == 0 ? column()
+                            : m_buffer->m_lines[line()].start + column();
 }
 
 inline BufferSize BufferIterator::operator-(const BufferIterator& iterator) const
@@ -132,12 +133,12 @@ inline BufferIterator BufferIterator::operator+(BufferSize size) const
     if (size >= 0)
     {
         BufferSize o = std::min(m_buffer->character_count(), offset() + size);
-        for (int i = line() + 1; i < m_buffer->line_count(); ++i)
+        for (LineCount i = line() + 1; i < m_buffer->line_count(); ++i)
         {
             if (m_buffer->m_lines[i].start > o)
                 return BufferIterator(*m_buffer, { i-1, o - m_buffer->m_lines[i-1].start });
         }
-        int last_line = std::max(0, m_buffer->line_count() - 1);
+        LineCount last_line = std::max(0_line, m_buffer->line_count() - 1);
         return BufferIterator(*m_buffer, { last_line, o - m_buffer->m_lines[last_line].start });
     }
     return operator-(-size);
@@ -149,7 +150,7 @@ inline BufferIterator BufferIterator::operator-(BufferSize size) const
     if (size >= 0)
     {
         BufferSize o = std::max(0, offset() - size);
-        for (int i = line(); i >= 0; --i)
+        for (LineCount i = line(); i >= 0; --i)
         {
             if (m_buffer->m_lines[i].start <= o)
                 return BufferIterator(*m_buffer, { i, o - m_buffer->m_lines[i].start });
diff --git a/src/commands.cc b/src/commands.cc
index c17dd0a9..0b73b164 100644
--- a/src/commands.cc
+++ b/src/commands.cc
@@ -259,7 +259,7 @@ void edit(const CommandParameters& params, Context& context)
         int column = param_count > 2 ?
                          std::max(0, str_to_int(parser[2]) - 1) : 0;
 
-        window.select(window.buffer().iterator_at({line, column}));
+        window.select(window.buffer().iterator_at({LineCount(line), column}));
         window.center_selection();
     }
 
diff --git a/src/display_buffer.hh b/src/display_buffer.hh
index f0a2bc1a..f48807c4 100644
--- a/src/display_buffer.hh
+++ b/src/display_buffer.hh
@@ -12,7 +12,7 @@ namespace Kakoune
 
 struct DisplayCoord : LineAndColumn<DisplayCoord>
 {
-    DisplayCoord(int line = 0, int column = 0)
+    DisplayCoord(LineCount line = 0, int column = 0)
         : LineAndColumn(line, column) {}
 
     template<typename T>
@@ -123,9 +123,9 @@ public:
     using iterator = AtomList::iterator;
     using const_iterator = AtomList::const_iterator;
 
-    explicit DisplayLine(size_t buffer_line) : m_buffer_line(buffer_line) {}
+    explicit DisplayLine(LineCount buffer_line) : m_buffer_line(buffer_line) {}
 
-    size_t buffer_line() const { return m_buffer_line; }
+    LineCount buffer_line() const { return m_buffer_line; }
 
     iterator begin() { return m_atoms.begin(); }
     iterator end() { return m_atoms.end(); }
@@ -140,8 +140,8 @@ public:
     void     push_back(DisplayAtom atom) { m_atoms.push_back(std::move(atom)); }
 
 private:
-    size_t   m_buffer_line;
-    AtomList m_atoms;
+    LineCount m_buffer_line;
+    AtomList  m_atoms;
 };
 
 using BufferRange = std::pair<BufferIterator, BufferIterator>;
diff --git a/src/file.cc b/src/file.cc
index 33c543a3..ec6a4f67 100644
--- a/src/file.cc
+++ b/src/file.cc
@@ -173,7 +173,7 @@ void write_buffer_to_file(const Buffer& buffer, const String& filename)
     if (buffer.option_manager()["BOM"].as_string() == "utf-8")
         ::write(fd, "\xEF\xBB\xBF", 3);
 
-    for (size_t i = 0; i < buffer.line_count(); ++i)
+    for (LineCount i = 0; i < buffer.line_count(); ++i)
     {
         // end of lines are written according to eolformat but always
         // stored as \n
diff --git a/src/highlighters.cc b/src/highlighters.cc
index 3313eaa8..92de5c08 100644
--- a/src/highlighters.cc
+++ b/src/highlighters.cc
@@ -213,9 +213,9 @@ void expand_tabulations(Window& window, DisplayBuffer& display_buffer)
 
 void show_line_numbers(Window& window, DisplayBuffer& display_buffer)
 {
-    int last_line = window.buffer().line_count();
+    LineCount last_line = window.buffer().line_count();
     int digit_count = 0;
-    for (int c = last_line; c > 0; c /= 10)
+    for (LineCount c = last_line; c > 0; c /= 10)
         ++digit_count;
 
     char format[] = "%?d ";
@@ -224,7 +224,7 @@ void show_line_numbers(Window& window, DisplayBuffer& display_buffer)
     for (auto& line : display_buffer.lines())
     {
         char buffer[10];
-        snprintf(buffer, 10, format, line.buffer_line() + 1);
+        snprintf(buffer, 10, format, (int)line.buffer_line() + 1);
         DisplayAtom atom = DisplayAtom(AtomContent(buffer));
         atom.fg_color = Color::Black;
         atom.bg_color = Color::White;
diff --git a/src/line_and_column.hh b/src/line_and_column.hh
index bc19becf..3e03d1b9 100644
--- a/src/line_and_column.hh
+++ b/src/line_and_column.hh
@@ -1,16 +1,18 @@
 #ifndef line_and_column_hh_INCLUDED
 #define line_and_column_hh_INCLUDED
 
+#include "units.hh"
+
 namespace Kakoune
 {
 
 template<typename EffectiveType>
 struct LineAndColumn
 {
-    int line;
+    LineCount line;
     int column;
 
-    LineAndColumn(int line = 0, int column = 0)
+    LineAndColumn(LineCount line = 0, int column = 0)
         : line(line), column(column) {}
 
     EffectiveType operator+(const EffectiveType& other) const
diff --git a/src/main.cc b/src/main.cc
index 34952491..dd24571c 100644
--- a/src/main.cc
+++ b/src/main.cc
@@ -344,15 +344,15 @@ Repeated<T> repeated(T func) { return Repeated<T>(func); }
 
 std::unordered_map<Key, std::function<void (Context& context)>> keymap =
 {
-    { { Key::Modifiers::None, 'h' }, [](Context& context) { context.editor().move_selections(BufferCoord(0, -std::max(context.numeric_param(),1))); } },
-    { { Key::Modifiers::None, 'j' }, [](Context& context) { context.editor().move_selections(BufferCoord( std::max(context.numeric_param(),1), 0)); } },
-    { { Key::Modifiers::None, 'k' }, [](Context& context) { context.editor().move_selections(BufferCoord(-std::max(context.numeric_param(),1), 0)); } },
-    { { Key::Modifiers::None, 'l' }, [](Context& context) { context.editor().move_selections(BufferCoord(0,  std::max(context.numeric_param(),1))); } },
+    { { Key::Modifiers::None, 'h' }, [](Context& context) { context.editor().move_selections({  0, -std::max(context.numeric_param(),1) }); } },
+    { { Key::Modifiers::None, 'j' }, [](Context& context) { context.editor().move_selections({  std::max(context.numeric_param(),1), 0  }); } },
+    { { Key::Modifiers::None, 'k' }, [](Context& context) { context.editor().move_selections({ -std::max(context.numeric_param(),1), 0 }); } },
+    { { Key::Modifiers::None, 'l' }, [](Context& context) { context.editor().move_selections({  0,  std::max(context.numeric_param(),1) }); } },
 
-    { { Key::Modifiers::None, 'H' }, [](Context& context) { context.editor().move_selections(BufferCoord(0, -std::max(context.numeric_param(),1)), true); } },
-    { { Key::Modifiers::None, 'J' }, [](Context& context) { context.editor().move_selections(BufferCoord( std::max(context.numeric_param(),1), 0), true); } },
-    { { Key::Modifiers::None, 'K' }, [](Context& context) { context.editor().move_selections(BufferCoord(-std::max(context.numeric_param(),1), 0), true); } },
-    { { Key::Modifiers::None, 'L' }, [](Context& context) { context.editor().move_selections(BufferCoord(0,  std::max(context.numeric_param(),1)), true); } },
+    { { Key::Modifiers::None, 'H' }, [](Context& context) { context.editor().move_selections({  0, -std::max(context.numeric_param(),1) }, true); } },
+    { { Key::Modifiers::None, 'J' }, [](Context& context) { context.editor().move_selections({  std::max(context.numeric_param(),1), 0 }, true); } },
+    { { Key::Modifiers::None, 'K' }, [](Context& context) { context.editor().move_selections({ -std::max(context.numeric_param(),1), 0 }, true); } },
+    { { Key::Modifiers::None, 'L' }, [](Context& context) { context.editor().move_selections({  0,  std::max(context.numeric_param(),1) }, true); } },
 
     { { Key::Modifiers::None, 't' }, [](Context& context) { context.editor().select(std::bind(select_to, _1, context.client().get_key().key, context.numeric_param(), false)); } },
     { { Key::Modifiers::None, 'f' }, [](Context& context) { context.editor().select(std::bind(select_to, _1, context.client().get_key().key, context.numeric_param(), true)); } },
diff --git a/src/ncurses.cc b/src/ncurses.cc
index f85eb408..b18e048e 100644
--- a/src/ncurses.cc
+++ b/src/ncurses.cc
@@ -93,7 +93,7 @@ void NCursesClient::draw_window(Window& window)
     getmaxyx(stdscr, max_y, max_x);
     max_y -= 1;
 
-    window.set_dimensions(DisplayCoord(max_y, max_x));
+    window.set_dimensions(DisplayCoord(LineCount(max_y), max_x));
     window.update_display_buffer();
 
     int line_index = 0;
diff --git a/src/units.hh b/src/units.hh
new file mode 100644
index 00000000..8a1180de
--- /dev/null
+++ b/src/units.hh
@@ -0,0 +1,88 @@
+#ifndef units_hh_INCLUDED
+#define units_hh_INCLUDED
+
+namespace Kakoune
+{
+
+template<typename RealType, typename ValueType = int>
+class StronglyTypedInteger
+{
+public:
+    explicit StronglyTypedInteger(ValueType value)
+         : m_value(value) {}
+
+    RealType operator+(const RealType& other) const
+    { return RealType(m_value + other.m_value); }
+
+    RealType operator-(const RealType& other) const
+    { return RealType(m_value - other.m_value); }
+
+    RealType operator*(const RealType& other) const
+    { return RealType(m_value * other.m_value); }
+
+    RealType operator/(const RealType& other) const
+    { return RealType(m_value / other.m_value); }
+
+    RealType& operator+=(const RealType& other)
+    { m_value += other.m_value; return static_cast<RealType&>(*this); }
+
+    RealType& operator-=(const RealType& other)
+    { m_value -= other.m_value; return static_cast<RealType&>(*this); }
+
+    RealType& operator*=(const RealType& other)
+    { m_value *= other.m_value; return static_cast<RealType&>(*this); }
+
+    RealType& operator/=(const RealType& other)
+    { m_value /= other.m_value; return static_cast<RealType&>(*this); }
+
+    RealType& operator++()
+    { ++m_value; return static_cast<RealType&>(*this); }
+
+    RealType& operator--()
+    { --m_value; return static_cast<RealType&>(*this); }
+
+    RealType operator++(int)
+    { RealType backup(*this); ++m_value; return backup; }
+
+    RealType operator--(int)
+    { RealType backup(*this); --m_value; return backup; }
+
+    RealType operator-() { return RealType(-m_value); }
+
+    bool operator==(const RealType& other) const
+    { return m_value == other.m_value; }
+
+    bool operator!=(const RealType& other) const
+    { return m_value != other.m_value; }
+
+    bool operator<(const RealType& other) const
+    { return m_value < other.m_value; }
+
+    bool operator<=(const RealType& other) const
+    { return m_value <= other.m_value; }
+
+    bool operator>(const RealType& other) const
+    { return m_value > other.m_value; }
+
+    bool operator>=(const RealType& other) const
+    { return m_value >= other.m_value; }
+
+    explicit operator ValueType() const { return m_value; }
+private:
+   ValueType m_value;
+};
+
+struct LineCount : public StronglyTypedInteger<LineCount, int>
+{
+    LineCount(int value) : StronglyTypedInteger<LineCount>(value) {}
+};
+
+inline LineCount operator"" _line(unsigned long long int value)
+{
+    return LineCount(value);
+}
+
+}
+
+#endif // units_hh_INCLUDED
+
diff --git a/src/window.cc b/src/window.cc
index c5ee5c1a..cc60d1f1 100644
--- a/src/window.cc
+++ b/src/window.cc
@@ -13,8 +13,6 @@ namespace Kakoune
 
 Window::Window(Buffer& buffer)
     : Editor(buffer),
-      m_position(0, 0),
-      m_dimensions(0, 0),
       m_hook_manager(buffer.hook_manager()),
       m_option_manager(buffer.option_manager())
 {
@@ -38,7 +36,7 @@ Window::~Window()
 void Window::center_selection()
 {
     BufferIterator cursor = selections().back().last();
-    m_position.line = std::max(0, cursor.line() - m_dimensions.line/2);
+    m_position.line = std::max(0_line, cursor.line() - m_dimensions.line/2_line);
 }
 
 void Window::update_display_buffer()
@@ -48,9 +46,9 @@ void Window::update_display_buffer()
     DisplayBuffer::LineList& lines = m_display_buffer.lines();
     lines.clear();
 
-    for (auto line = 0; line < m_dimensions.line; ++line)
+    for (LineCount line = 0; line < m_dimensions.line; ++line)
     {
-        auto buffer_line = m_position.line + line;
+        LineCount buffer_line = m_position.line + line;
         if (buffer_line >= buffer().line_count())
             break;
         BufferIterator pos        = buffer().iterator_at({ buffer_line, m_position.column });
@@ -138,7 +136,7 @@ String Window::status_line() const
     oss << buffer().name();
     if (buffer().is_modified())
         oss << " [+]";
-    oss << " -- " << cursor.line+1 << "," << cursor.column+1
+    oss << " -- " << (int)cursor.line+1 << "," << cursor.column+1
         << " -- " << selections().size() << " sel -- ";
     if (is_editing())
         oss << "[Insert]";