Validate cast compatibility during semantic analysis

4 files changed, 327 insertions, 270 deletions

diff --git a/boot/ast.cc b/boot/ast.cc
index a2f108a..7f34243 100644
--- a/boot/ast.cc
+++ b/boot/ast.cc
@@ -1647,51 +1647,4 @@ namespace elna::boot
     {
         return *this->m_range;
     }
-
-    const char *print_binary_operator(const binary_operator operation)
-    {
-        switch (operation)
-        {
-            using enum binary_operator;
-            case sum:
-                return "+";
-            case subtraction: 
-                return "-";
-            case multiplication:
-                return "*";
-            case division:
-                return "/";
-            case remainder:
-                return "%";
-            case equals:
-                return "=";
-            case not_equals:
-                return "<>";
-            case less:
-                return "<";
-            case less_equal:
-                return "<=";
-            case greater:
-                return ">";
-            case greater_equal:
-                return ">=";
-            case conjunction:
-            case logical_conjunction:
-            case bitwise_conjunction:
-                return "&";
-            case disjunction:
-            case logical_disjunction:
-            case bitwise_disjunction:
-                return "or";
-            case exclusive_disjunction:
-            case logical_exclusive_disjunction:
-            case bitwise_exclusive_disjunction:
-                return "xor";
-            case shift_left:
-                return "<<";
-            case shift_right:
-                return ">>";
-        }
-        __builtin_unreachable();
-    };
 }
diff --git a/boot/name_analysis.cc b/boot/name_analysis.cc
index 077b5d6..89353e9 100644
--- a/boot/name_analysis.cc
+++ b/boot/name_analysis.cc
@@ -22,27 +22,35 @@ along with GCC; see the file COPYING3.  If not see
 
 namespace elna::boot
 {
-    declaration_error::declaration_error(const source_position position, payload_type payload)
-        : error(position), payload(std::move(payload))
+    declaration_error::declaration_error(const source_position position, const std::string& name, payload_type payload)
+        : error(position), name(name), payload(payload)
     {
     }
 
     std::string declaration_error::what() const
     {
-        return std::visit([](const auto& payload) -> std::string {
+        return std::visit([this](const auto& payload) -> std::string {
             using T = std::decay_t<decltype(payload)>;
 
-            if constexpr (std::is_same_v<T, undeclared>)
+            if constexpr (std::is_same_v<T, redefinition>)
             {
-                return "Type '" + payload.name + "' not declared";
+                return "Symbol '" + this->name + "' has been already defined";
             }
-            else if constexpr (std::is_same_v<T, local_export>)
+            else if constexpr (std::is_same_v<T, kind>)
             {
-                return "Local symbol '" + payload.name + "' cannot be exported";
-            }
-            else if constexpr (std::is_same_v<T, redefinition>)
-            {
-                return "Symbol '" + payload.name + "' has been already defined";
+                switch (payload)
+                {
+                    case kind::undeclared_type:
+                        return "Type '" + this->name + "' not declared";
+                    case kind::undeclared_trait:
+                        return "Trait '#" + this->name + "' not declared";
+                    case kind::undeclared_symbol:
+                        return "Symbol '" + this->name + "' not declared";
+                    case kind::local_export:
+                        return "Local symbol '" + this->name + "' cannot be exported";
+                    default:
+                        __builtin_unreachable();
+                }
             }
         }, this->payload);
     }
@@ -77,52 +85,54 @@ namespace elna::boot
         }
     }
 
-    member_error::member_error(const source_position position, payload_type payload)
-        : error(position), payload(std::move(payload))
+    member_error::member_error(const source_position position, const std::string& name,
+                const type& composite, payload_type payload)
+        : error(position), name(name), composite(composite), payload(std::move(payload))
     {
     }
 
     std::string member_error::what() const
     {
-        return std::visit([](const auto& pay) -> std::string {
-            using T = std::decay_t<decltype(pay)>;
+        return std::visit([this](const auto& payload) -> std::string {
+            using T = std::decay_t<decltype(payload)>;
+
             if constexpr (std::is_same_v<T, not_found>)
             {
-                const type resolved = resolve_underlying_type(pay.composite);
+                const type resolved = resolve_underlying_type(this->composite);
                 const bool is_enum = resolved.get<enumeration_type>() != nullptr;
                 const bool is_record = resolved.get<record_type>() != nullptr;
 
                 if (is_enum || is_record)
                 {
                     std::string message = is_enum ? "Enumeration" : "Record";
-                    if (auto alias = pay.composite.template get<alias_type>())
+                    if (auto alias = this->composite.get<alias_type>())
                     {
                         message += " '" + alias->name + "'";
                     }
                     message += " does not have a ";
                     message += is_enum ? "member" : "field";
-                    message += " named '" + pay.name + "'";
+                    message += " named '" + this->name + "'";
                     return message;
                 }
-                return "Type '" + pay.composite.to_string()
-                    + "' does not have a field named '" + pay.name + "'";
+                return "Type '" + this->composite.to_string()
+                    + "' does not have a field named '" + this->name + "'";
             }
             else if constexpr (std::is_same_v<T, duplicate>)
             {
-                const type resolved = resolve_underlying_type(pay.aggregate);
+                const type resolved = resolve_underlying_type(this->composite);
                 const bool is_enum = resolved.get<enumeration_type>() != nullptr;
                 const std::string kind = is_enum ? "member" : "field";
                 std::string message = is_enum ? "Enumeration" : "Record";
 
-                if (auto alias = pay.aggregate.template get<alias_type>())
+                if (auto alias = this->composite.get<alias_type>())
                 {
                     message += " '" + alias->name + "'";
                 }
-                message += " already has a " + kind + " named '" + pay.name + "'";
+                message += " already has a " + kind + " named '" + this->name + "'";
 
-                if (pay.base.has_value())
+                if (payload.base.has_value())
                 {
-                    message += " (defined in base type '" + *pay.base + "')";
+                    message += " (defined in base type '" + *payload.base + "')";
                 }
                 return message;
             }
@@ -141,18 +151,6 @@ namespace elna::boot
         return std::nullopt;
     }
 
-    unsupported_trait_type_error::unsupported_trait_type_error(const identifier& trait,
-            type actual)
-        : error(trait.position()), actual(std::move(actual)), trait_name(trait.name())
-    {
-    }
-
-    std::string unsupported_trait_type_error::what() const
-    {
-        return "Type '" + actual.to_string()
-            + "' does not support trait '#" + trait_name + "'";
-    }
-
     // Members of a constant aggregate are constant themselves.
     static type qualify_member_type(const type& element, const type& aggregate)
     {
@@ -317,14 +315,12 @@ namespace elna::boot
         }
         for (auto& field : record->fields)
         {
-            names.insert(field.first, field_origin{ .declaration = std::nullopt, .base_type = composite_type });
+            names.insert(field.first, field_origin{ .position = std::nullopt, .base_type = composite_type });
         }
     }
 
-    ordered_map<type> name_analysis_visitor::build_composite_type(
-            const std::vector<field_declaration>& fields,
-            ordered_map<field_origin>& field_names,
-            const type& aggregate)
+    ordered_map<type> name_analysis_visitor::build_composite_type(const std::vector<field_declaration>& fields,
+            ordered_map<field_origin>& field_names, const type& aggregate)
     {
         ordered_map<type> result;
 
@@ -334,12 +330,12 @@ namespace elna::boot
             for (const auto& field_name : field.first)
             {
                 auto [existing, inserted] = field_names.insert(field_name.name(),
-                        field_origin{ .declaration = field.second->position(), .base_type = type() });
+                        field_origin{ .position = field.second->position(), .base_type = type() });
                 if (!inserted)
                 {
                     std::optional<std::string> base_name;
 
-                    if (!existing->second.declaration.has_value()
+                    if (!existing->second.position.has_value()
                             && !existing->second.base_type.empty())
                     {
                         if (auto alias = existing->second.base_type.get<alias_type>())
@@ -347,9 +343,8 @@ namespace elna::boot
                             base_name = alias->name;
                         }
                     }
-                    add_error<member_error>(field_name.position(),
-                            member_error::duplicate{.name = field_name.name(), .aggregate = aggregate,
-                                    .original = existing->second.declaration, .base = base_name});
+                    add_error<member_error>(field_name.position(), field_name.name(), aggregate,
+                            member_error::duplicate{ .original = existing->second.position, .base = base_name });
                 }
                 else
                 {
@@ -384,7 +379,7 @@ namespace elna::boot
             else
             {
                 add_error<declaration_error>(expression->base.value().position(),
-                    declaration_error::undeclared{.name = expression->base.value().name()});
+                    expression->base.value().name(), declaration_error::kind::undeclared_type);
                 this->current_type = type();
                 return;
             }
@@ -413,7 +408,7 @@ namespace elna::boot
         else
         {
             add_error<declaration_error>(expression->type_name.position(),
-                    declaration_error::undeclared{.name = expression->type_name.name()});
+                    expression->type_name.name(), declaration_error::kind::undeclared_type);
         }
         for (const field_initializer& initializer : expression->field_initializers)
         {
@@ -421,8 +416,8 @@ namespace elna::boot
             if (!expression->type_decoration.empty()
                     && lookup_field(expression->type_decoration, initializer.name()).empty())
             {
-                add_error<declaration_error>(initializer.id().position(),
-                        declaration_error::undeclared{.name = initializer.id().name()});
+                add_error<member_error>(initializer.id().position(), initializer.id().name(),
+                        expression->type_decoration, member_error::not_found{});
             }
         }
     }
@@ -469,7 +464,7 @@ namespace elna::boot
     {
         std::vector<std::string> member_names;
         member_names.reserve(expression->members.size());
-for (const auto& member : expression->members)
+        for (const auto& member : expression->members)
         {
             member_names.emplace_back(member.name());
         }
@@ -483,9 +478,8 @@ for (const auto& member : expression->members)
             auto existing = seen.find(member.name());
             if (existing != seen.end())
             {
-                add_error<member_error>(member.position(),
-                        member_error::duplicate{.name = member.name(), .aggregate = aggregate,
-                                .original = existing->second, .base = std::nullopt});
+                add_error<member_error>(member.position(), member.name(), aggregate,
+                        member_error::duplicate{ .original = existing->second, .base = std::nullopt });
             }
             else
             {
@@ -504,8 +498,8 @@ for (const auto& member : expression->members)
         if (!this->bag.enter(name, variable_symbol))
         {
             auto original = this->bag.lookup(name);
-            add_error<declaration_error>(position,
-                    declaration_error::redefinition{.name = name, .original = original->position});
+            add_error<declaration_error>(position, name,
+                    declaration_error::redefinition{ .original = original->position });
         }
         return variable_symbol;
     }
@@ -632,25 +626,11 @@ for (const auto& member : expression->members)
         else if (trait->name == "min" || trait->name == "max")
         {
             trait->type_decoration = trait->types.empty() ? type() : trait->types.front();
-
-            if (!trait->type_decoration.empty())
-            {
-                const type resolved = resolve_underlying_type(trait->type_decoration);
-
-                if (resolved.get<enumeration_type>() == nullptr
-                        && !is_primitive_type(resolved, "Float")
-                        && !is_discrete_type(resolved))
-                {
-                    add_error<unsupported_trait_type_error>(trait->name,
-                            trait->type_decoration);
-                    trait->type_decoration = type();
-                }
-            }
         }
         else
         {
             add_error<declaration_error>(trait->name.position(),
-                    declaration_error::undeclared{.name = trait->name.name()});
+                    trait->name.name(), declaration_error::kind::undeclared_trait);
         }
     }
 
@@ -730,8 +710,8 @@ for (const auto& member : expression->members)
         if (expression->type_decoration.empty())
         {
             add_error<member_error>(expression->field().position(),
-                    member_error::not_found{.name = expression->field().name(),
-                            .composite = expression->base().type_decoration});
+                    expression->field().name(), expression->base().type_decoration,
+                    member_error::not_found{});
         }
         else
         {
@@ -805,7 +785,7 @@ for (const auto& member : expression->members)
         else
         {
             add_error<declaration_error>(expression->position(),
-                    declaration_error::undeclared{.name = expression->name});
+                    expression->name, declaration_error::kind::undeclared_symbol);
         }
     }
 
@@ -882,8 +862,8 @@ for (const auto& member : expression->members)
         if (!this->unresolved.insert({ type_identifier, std::make_shared<alias_type>(type_identifier) }).second)
         {
             add_error<declaration_error>(declaration->identifier.id().position(),
-                    declaration_error::redefinition{.name = declaration->identifier.id().name(),
-                            .original = declaration->position()});
+                    declaration->identifier.id().name(),
+                    declaration_error::redefinition{ .original = declaration->position() });
         }
     }
 
@@ -906,7 +886,7 @@ for (const auto& member : expression->members)
             if (variable_identifier.exported())
             {
                 add_error<declaration_error>(variable_identifier.id().position(),
-                        declaration_error::local_export{.name = variable_identifier.id().name()});
+                        variable_identifier.id().name(), declaration_error::kind::local_export);
             }
         }
     }
diff --git a/boot/symbol.cc b/boot/symbol.cc
index e0a89e6..a51ee01 100644
--- a/boot/symbol.cc
+++ b/boot/symbol.cc
@@ -448,6 +448,14 @@ namespace elna::boot
             || is_primitive_type(checked, "Pointer");
     }
 
+    bool is_scalar_type(const type& checked)
+    {
+        return is_discrete_type(checked)
+            || is_primitive_type(checked, "Float")
+            || is_any_pointer_type(checked)
+            || checked.get<enumeration_type>() != nullptr;
+    }
+
     type get_range_base_type(const type& range)
     {
         if (auto array = range.get<array_type>())
diff --git a/boot/type_check.cc b/boot/type_check.cc
index 343b5aa..07deb2d 100644
--- a/boot/type_check.cc
+++ b/boot/type_check.cc
@@ -22,9 +22,75 @@ along with GCC; see the file COPYING3.  If not see
 
 namespace elna::boot
 {
+    static char unary_operator_symbol(unary_operator operation)
+    {
+        switch (operation)
+        {
+            using enum unary_operator;
+            case reference:
+                return '@';
+            case negation:
+            case bitwise_negation:
+            case logical_negation:
+                return '~';
+            case minus:
+                return '-';
+            case plus:
+                return '+';
+        }
+        __builtin_unreachable();
+    }
+
+    static std::string print_binary_operator(const binary_operator operation)
+    {
+        switch (operation)
+        {
+            using enum binary_operator;
+            case sum:
+                return "+";
+            case subtraction: 
+                return "-";
+            case multiplication:
+                return "*";
+            case division:
+                return "/";
+            case remainder:
+                return "%";
+            case equals:
+                return "=";
+            case not_equals:
+                return "<>";
+            case less:
+                return "<";
+            case less_equal:
+                return "<=";
+            case greater:
+                return ">";
+            case greater_equal:
+                return ">=";
+            case conjunction:
+            case logical_conjunction:
+            case bitwise_conjunction:
+                return "&";
+            case disjunction:
+            case logical_disjunction:
+            case bitwise_disjunction:
+                return "or";
+            case exclusive_disjunction:
+            case logical_exclusive_disjunction:
+            case bitwise_exclusive_disjunction:
+                return "xor";
+            case shift_left:
+                return "<<";
+            case shift_right:
+                return ">>";
+        }
+        __builtin_unreachable();
+    };
+
     trait_error::trait_error(const source_position position, const std::string& trait_name,
             payload_type payload)
-        : error(position), trait_name(trait_name), m_payload(payload)
+        : error(position), trait_name(trait_name), payload(std::move(payload))
     {
     }
 
@@ -41,35 +107,94 @@ namespace elna::boot
                         + (payload.expected != 1 ? "s" : "") + ", got "
                         + std::to_string(payload.actual);
             }
-            else
+            else if constexpr (std::is_same_v<T, offset_not_field_name>)
             {
-                return "The second argument to the #" + this->trait_name + " trait must be a field name";
+                return "The second argument to the #" + this->trait_name
+                    + " trait must be a field name";
             }
-        }, this->m_payload);
+            else if constexpr (std::is_same_v<T, unsupported_type>)
+            {
+                return "Type '" + payload.actual.to_string()
+                    + "' does not support trait '#" + this->trait_name + "'";
+            }
+        }, this->payload);
     }
 
     type_mismatch_error::type_mismatch_error(const source_position position,
-            type expected, type actual)
-        : error(position), expected(std::move(expected)), actual(std::move(actual))
+            type actual, payload_type payload)
+        : error(position), actual(std::move(actual)), payload(std::move(payload))
     {
     }
 
     std::string type_mismatch_error::what() const
     {
-        return "Expected type '" + expected.to_string()
-            + "', but got '" + actual.to_string() + "'";
-    }
+        return std::visit([this](auto&& payload) -> std::string
+        {
+            using T = std::decay_t<decltype(payload)>;
 
-    constant_assignment_error::constant_assignment_error(const source_position position,
-            type assignee)
-        : error(position), assignee(std::move(assignee))
-    {
-    }
+            if constexpr (std::is_same_v<T, expected_type>)
+            {
+                return "Expected type '" + payload.value.to_string()
+                    + "', but got '" + this->actual.to_string() + "'";
+            }
+            else if constexpr (std::is_same_v<T, return_type>)
+            {
+                if (!this->actual.empty())
+                {
+                    return "Procedure '" + payload.identifier
+                        + "' does not return a value, but return expression has type '"
+                        + this->actual.to_string() + "'";
+                }
+                return "Procedure '" + payload.identifier
+                    + "' is expected to return, but does not have a return statement";
 
-    std::string constant_assignment_error::what() const
-    {
-        return "Cannot assign to a value of type '" + assignee.to_string()
-            + "', because it is constant or contains constant members";
+            }
+            else if constexpr (std::is_same_v<T, unary>)
+            {
+                return "Type '" + this->actual.to_string() + "' cannot be used with unary '"
+                    + unary_operator_symbol(payload.operation) + "'";
+            }
+            else if constexpr (std::is_same_v<T, binary>)
+            {
+                return "Invalid operands of type '" + this->actual.to_string()
+                    + "' and '" + payload.right.to_string()
+                    + "' for operator " + print_binary_operator(payload.operation);
+            }
+            else if constexpr (std::is_same_v<T, invalid_cast>)
+            {
+                return "Type '" + this->actual.to_string()
+                    + "' cannot be converted to '" + payload.target.to_string() + "'";
+            }
+            else if constexpr (std::is_same_v<T, kind>)
+            {
+                switch (payload)
+                {
+                    case kind::record_base:
+                        return "Expected a record type, but got '"
+                            + this->actual.to_string() + "'";
+                    case kind::for_range:
+                        return "Expected an array or slice type, but got '"
+                            + this->actual.to_string() + "'";
+                    case kind::condition:
+                        return "Condition must be a boolean expression, but got '"
+                            + this->actual.to_string() + "'";
+                    case kind::constant_assignment:
+                        return "Cannot assign to a value of type '" + this->actual.to_string()
+                            + "', because it is constant or contains constant members";
+                    case kind::array_index:
+                        return "Array index must be an integral type, but got '"
+                            + this->actual.to_string() + "'";
+                    case kind::non_indexable:
+                        return "Indexing is not allowed on type '"
+                            + this->actual.to_string() + "'";
+                    case kind::dereference_of_non_pointer:
+                        return "Type '" + this->actual.to_string()
+                            + "' cannot be dereferenced, it is not a pointer";
+                    default:
+                        __builtin_unreachable();
+                }
+            }
+        }, this->payload);
     }
 
     cyclic_declaration_error::cyclic_declaration_error(const std::vector<std::string>& cycle,
@@ -91,46 +216,6 @@ namespace elna::boot
         return message;
     }
 
-    return_error::return_error(const std::string& identifier, const source_position position,
-            type return_type)
-        : error(position), identifier(identifier), return_type(std::move(return_type))
-    {
-    }
-
-    std::string return_error::what() const
-    {
-        if (!return_type.empty())
-        {
-            return "Procedure '" + this->identifier
-                + "' does not return a value, but return expression has type '"
-                + return_type.to_string() + "'";
-        }
-        return "Procedure '" + this->identifier
-            + "' is expected to return, but does not have a return statement";
-    }
-
-    type_kind_error::type_kind_error(const source_position position, kind type_kind, const type& actual)
-        : error(position), type_kind(type_kind), actual(actual)
-    {
-    }
-
-    std::string type_kind_error::what() const
-    {
-        switch (this->type_kind)
-        {
-            case kind::record_base:
-                return "'" + this->actual.to_string() + "' is not a record type";
-            case kind::for_loop:
-                return "for-loop variable must be an array or a slice, got '"
-                    + this->actual.to_string() + "'";
-            case kind::condition:
-                return "Condition must be a boolean, got '"
-                    + this->actual.to_string() + "'";
-            default:
-                __builtin_unreachable();
-        }
-    }
-
     argument_count_error::argument_count_error(std::size_t expected, std::size_t actual,
             const source_position position)
         : error(position), expected(expected), actual(actual)
@@ -151,43 +236,6 @@ namespace elna::boot
         }
     }
 
-    unary_operation_error::unary_operation_error(const source_position position,
-            type actual, unary_operator operation)
-        : error(position), actual(std::move(actual)), op(operation)
-    {
-    }
-
-    char unary_operation_error::unary_operator_symbol(unary_operator operation)
-    {
-        switch (operation)
-        {
-            using enum unary_operator;
-            case reference:
-                return '@';
-            case negation:
-            case bitwise_negation:
-            case logical_negation:
-                return '~';
-            case minus:
-                return '-';
-            case plus:
-                return '+';
-        }
-        __builtin_unreachable();
-    }
-
-    std::string unary_operation_error::what() const
-    {
-        return "Type '" + actual.to_string()
-            + "' cannot be used with unary '"
-            + unary_operator_symbol(op) + "'";
-    }
-
-    /*
-     * Whether the type itself is constant or has a constant member at any
-     * nesting level, so that values of this type cannot be reassigned as a
-     * whole. Pointers to constants do not make the type itself constant.
-     */
     static bool contains_constant_member(const type& checked)
     {
         auto referent = resolve_aliases(checked);
@@ -248,8 +296,8 @@ namespace elna::boot
         condition.accept(this);
         if (!is_primitive_type(condition.type_decoration, "Bool"))
         {
-            add_error<type_kind_error>(condition.position(),
-                    type_kind_error::kind::condition, condition.type_decoration);
+            add_error<type_mismatch_error>(condition.position(),
+                    condition.type_decoration, type_mismatch_error::kind::condition);
         }
     }
 
@@ -421,19 +469,22 @@ namespace elna::boot
                 {
                     if (!is_assignable_from(return_type, return_expr->type_decoration))
                     {
-                        add_error<type_mismatch_error>(
-                                return_expr->position(), return_type, return_expr->type_decoration);
+                        add_error<type_mismatch_error>(return_expr->position(),
+                                return_expr->type_decoration,
+                                type_mismatch_error::expected_type{ return_type });
                     }
                 }
                 else
                 {
-                    add_error<return_error>(declaration->identifier.name(),
-                            return_expr->position(), return_expr->type_decoration);
+                    add_error<type_mismatch_error>(return_expr->position(),
+                            return_expr->type_decoration,
+                            type_mismatch_error::return_type{ .identifier = declaration->identifier.name() });
                 }
             }
             else if (declaration->heading().return_type.proper_type != nullptr)
             {
-                add_error<return_error>(declaration->identifier.name(), declaration->position());
+                add_error<type_mismatch_error>(declaration->position(), type(),
+                        type_mismatch_error::return_type{ .identifier = declaration->identifier.name() });
             }
             this->bag.leave();
         }
@@ -451,13 +502,14 @@ namespace elna::boot
 
         if (contains_constant_member(statement->lvalue().type_decoration))
         {
-            add_error<constant_assignment_error>(statement->position(),
-                    statement->lvalue().type_decoration);
+            add_error<type_mismatch_error>(statement->position(), statement->lvalue().type_decoration,
+                    type_mismatch_error::kind::constant_assignment);
         }
         else if (!is_assignable_from(statement->lvalue().type_decoration, statement->rvalue().type_decoration))
         {
             add_error<type_mismatch_error>(statement->position(),
-                    statement->lvalue().type_decoration, statement->rvalue().type_decoration);
+                    statement->rvalue().type_decoration,
+                    type_mismatch_error::expected_type{ statement->lvalue().type_decoration });
         }
     }
 
@@ -475,7 +527,8 @@ namespace elna::boot
             if (!is_assignable_from(variable_symbol->symbol, declaration->initializer->type_decoration))
             {
                 add_error<type_mismatch_error>(declaration->initializer->position(),
-                        variable_symbol->symbol, declaration->initializer->type_decoration);
+                        declaration->initializer->type_decoration,
+                        type_mismatch_error::expected_type{ variable_symbol->symbol });
             }
         }
     }
@@ -491,9 +544,11 @@ namespace elna::boot
             {
                 if (!is_equality_compatible(condition_type, case_label->type_decoration))
                 {
-                    add_error<binary_operation_error>(
-                            case_label->position(), condition_type,
-                            case_label->type_decoration, binary_operator::equals);
+                    type_mismatch_error::binary binary_error{
+                        .right = case_label->type_decoration,
+                        .operation = binary_operator::equals
+                    };
+                    add_error<type_mismatch_error>(case_label->position(), condition_type, binary_error);
                 }
             }
         }
@@ -506,8 +561,8 @@ namespace elna::boot
 
         if (!get_range_base_type(resolved_range))
         {
-            add_error<type_kind_error>(statement->range().position(), type_kind_error::kind::for_loop,
-                    statement->range().type_decoration);
+            add_error<type_mismatch_error>(statement->range().position(),
+                    statement->range().type_decoration, type_mismatch_error::kind::for_range);
         }
         this->bag.enter(statement->symbols);
         for (auto *body_statement : statement->body)
@@ -594,16 +649,16 @@ namespace elna::boot
             auto const base_symbol = this->bag.lookup(expression->base.value().name());
             if (base_symbol == nullptr || base_symbol->is_type() == nullptr)
             {
-                add_error<type_kind_error>(expression->position(),
-                        type_kind_error::kind::record_base, type());
+                add_error<type_mismatch_error>(expression->position(),
+                        type(), type_mismatch_error::kind::record_base);
             }
             else
             {
                 type const base_type = resolve_underlying_type(base_symbol->is_type()->symbol);
                 if (base_type.get<record_type>() == nullptr)
                 {
-                    add_error<type_kind_error>(expression->position(),
-                            type_kind_error::kind::record_base, base_type);
+                    add_error<type_mismatch_error>(expression->position(),
+                            base_type, type_mismatch_error::kind::record_base);
                 }
             }
         }
@@ -626,8 +681,9 @@ namespace elna::boot
                 if (!is_assignable_from(*type_iterator, (*argument_iterator)->type_decoration))
                 {
                     add_error<type_mismatch_error>(
-                            (*argument_iterator)->position(), *type_iterator,
-                            (*argument_iterator)->type_decoration);
+                            (*argument_iterator)->position(),
+                            (*argument_iterator)->type_decoration,
+                            type_mismatch_error::expected_type{ *type_iterator });
                 }
                 ++argument_iterator;
                 ++type_iterator;
@@ -641,8 +697,8 @@ namespace elna::boot
         else if (!call->callable().type_decoration.empty())
         {
             add_error<type_mismatch_error>(call->position(),
-                    type(std::make_shared<procedure_type>()),
-                    call->callable().type_decoration);
+                    call->callable().type_decoration,
+                    type_mismatch_error::expected_type{ type(std::make_shared<procedure_type>()) });
         }
         // else callable is not declared which is already reported.
     }
@@ -654,8 +710,8 @@ namespace elna::boot
         if (record == nullptr)
         {
             add_error<type_mismatch_error>(
-                    expression->position(), type(std::make_shared<record_type>()),
-                    expression->type_decoration);
+                    expression->position(), expression->type_decoration,
+                    type_mismatch_error::expected_type{ type(std::make_shared<record_type>()) });
             return;
         }
         for (const field_initializer& initializer : expression->field_initializers)
@@ -667,8 +723,7 @@ namespace elna::boot
                     if (!is_assignable_from(field_type, initializer.value().type_decoration))
                     {
                         add_error<type_mismatch_error>(
-                                initializer.value().position(), field_type,
-                                initializer.value().type_decoration);
+                                initializer.value().position(), initializer.value().type_decoration, type_mismatch_error::expected_type{field_type});
                     }
                     break;
                 }
@@ -683,8 +738,8 @@ namespace elna::boot
         if (array == nullptr)
         {
             add_error<type_mismatch_error>(
-                    expression->position(), type(std::make_shared<array_type>(type(), 0)),
-                    expression->type_decoration);
+                    expression->position(), expression->type_decoration,
+                    type_mismatch_error::expected_type{ type(std::make_shared<array_type>(type(), 0)) });
             return;
         }
         if (expression->elements.size() > array->size)
@@ -698,7 +753,8 @@ namespace elna::boot
             if (!is_assignable_from(array->base, element->type_decoration))
             {
                 add_error<type_mismatch_error>(
-                        element->position(), array->base, element->type_decoration);
+                        element->position(), element->type_decoration,
+                        type_mismatch_error::expected_type{ array->base });
             }
         }
     }
@@ -708,6 +764,24 @@ namespace elna::boot
         walking_visitor::visit(expression);
     }
 
+    void type_analysis_visitor::visit(array_access_expression *expression)
+    {
+        walking_visitor::visit(expression);
+
+        auto resolved_base = resolve_underlying_type(expression->base().type_decoration);
+        if (resolved_base.get<array_type>() == nullptr
+                && resolved_base.get<slice_type>() == nullptr)
+        {
+            add_error<type_mismatch_error>(expression->position(),
+                    expression->base().type_decoration, type_mismatch_error::kind::non_indexable);
+        }
+        if (!is_integral_type(resolve_underlying_type(expression->index().type_decoration)))
+        {
+            add_error<type_mismatch_error>(expression->index().position(),
+                    expression->index().type_decoration, type_mismatch_error::kind::array_index);
+        }
+    }
+
     void type_analysis_visitor::visit(unary_expression *expression)
     {
         walking_visitor::visit(expression);
@@ -719,8 +793,9 @@ namespace elna::boot
         {
             if (!is_numeric_type(resolved))
             {
-                add_error<unary_operation_error>(expression->position(),
-                        expression->operand().type_decoration, operation);
+                add_error<type_mismatch_error>(expression->position(),
+                        expression->operand().type_decoration,
+                        type_mismatch_error::unary{ .operation = operation });
             }
         }
         else if (operation == unary_operator::minus)
@@ -728,8 +803,9 @@ namespace elna::boot
             if (!is_primitive_type(resolved, "Int")
                     && !is_primitive_type(resolved, "Float"))
             {
-                add_error<unary_operation_error>(expression->position(),
-                        expression->operand().type_decoration, operation);
+                add_error<type_mismatch_error>(expression->position(),
+                        expression->operand().type_decoration,
+                        type_mismatch_error::unary{ .operation = operation });
             }
         }
         else if (operation == unary_operator::negation)
@@ -744,8 +820,9 @@ namespace elna::boot
             }
             else
             {
-                add_error<unary_operation_error>(expression->position(),
-                        expression->operand().type_decoration, operation);
+                add_error<type_mismatch_error>(expression->position(),
+                        expression->operand().type_decoration,
+                        type_mismatch_error::unary{ .operation = operation });
             }
         }
         else if (operation == unary_operator::reference)
@@ -753,23 +830,40 @@ namespace elna::boot
             auto *designator = expression->operand().is_designator();
             if (designator == nullptr || designator->is_slicing() != nullptr)
             {
-                add_error<unary_operation_error>(expression->position(),
-                        expression->operand().type_decoration, operation);
+                add_error<type_mismatch_error>(expression->position(),
+                        expression->operand().type_decoration,
+                        type_mismatch_error::unary{ .operation = operation });
             }
         }
     }
 
-    binary_operation_error::binary_operation_error(const source_position position,
-            type left, type right, binary_operator operation)
-        : error(position), left(std::move(left)), right(std::move(right)), op(operation)
+    void type_analysis_visitor::visit(dereference_expression *expression)
     {
+        walking_visitor::visit(expression);
+
+        if (resolve_underlying_type(expression->base().type_decoration).get<pointer_type>() == nullptr)
+        {
+            add_error<type_mismatch_error>(expression->position(),
+                    expression->base().type_decoration,
+                    type_mismatch_error::kind::dereference_of_non_pointer);
+        }
     }
 
-    std::string binary_operation_error::what() const
+    void type_analysis_visitor::visit(cast_expression *expression)
     {
-        return "Invalid operands of type '" + left.to_string()
-            + "' and '" + right.to_string()
-            + "' for operator " + print_binary_operator(op);
+        walking_visitor::visit(expression);
+
+        auto source = resolve_underlying_type(expression->value().type_decoration);
+        auto target = resolve_underlying_type(expression->type_decoration);
+
+        if (source != target // const cast.
+                && (!is_scalar_type(source) || !is_scalar_type(target))
+                && (source.get<slice_type>() == nullptr || target.get<slice_type>() == nullptr))
+        {
+            add_error<type_mismatch_error>(expression->position(),
+                    expression->value().type_decoration,
+                    type_mismatch_error::invalid_cast{ expression->type_decoration });
+        }
     }
 
     void type_analysis_visitor::visit(binary_expression *expression)
@@ -860,8 +954,11 @@ namespace elna::boot
         }
         if (!valid)
         {
-            add_error<binary_operation_error>(expression->position(),
-                    expression->lhs().type_decoration, expression->rhs().type_decoration, operation);
+            type_mismatch_error::binary binary_error{
+                .right = expression->rhs().type_decoration,
+                .operation = operation
+            };
+            add_error<type_mismatch_error>(expression->position(), expression->lhs().type_decoration, binary_error);
         }
     }
 
@@ -869,8 +966,7 @@ namespace elna::boot
     {
         walking_visitor::visit(trait);
 
-        if (trait->name == "size" || trait->name == "alignment"
-                || trait->name == "min" || trait->name == "max")
+        if (trait->name == "size" || trait->name == "alignment")
         {
             if (trait->arguments.size() != 1)
             {
@@ -878,6 +974,26 @@ namespace elna::boot
                         trait_error::argument_count{ .expected = 1, .actual = trait->arguments.size() });
             }
         }
+        else if ((trait->name == "min" || trait->name == "max") && !trait->type_decoration.empty())
+        {
+            if (trait->arguments.size() != 1)
+            {
+                add_error<trait_error>(trait->position(), trait->name.name(),
+                        trait_error::argument_count{ .expected = 1, .actual = trait->arguments.size() });
+            }
+            else
+            {
+                const type resolved = resolve_underlying_type(trait->type_decoration);
+
+                if (resolved.get<enumeration_type>() == nullptr
+                        && !is_primitive_type(resolved, "Float")
+                        && !is_discrete_type(resolved))
+                {
+                    add_error<trait_error>(trait->name.position(), trait->name.name(),
+                            trait_error::unsupported_type{ trait->type_decoration });
+                }
+            }
+        }
         else if (trait->name == "offset")
         {
             if (trait->arguments.size() != 2)