From a12cf52c48ed1bd1b5f42789276b0aa2035a148e Mon Sep 17 00:00:00 2001
From: Sofia <sofia@teascade.net>
Date: Wed, 15 Apr 2026 20:01:20 +0300
Subject: [PATCH] Add FieldAccessExpression

---
 src/ast.cpp         |  7 +++++
 src/ast.h           | 26 ++++++++++++++++++
 src/codegen.cpp     | 66 +++++++++++++++++++++++++++++++++++++++++++++
 src/typechecker.cpp | 33 +++++++++++++++++++++++
 test.c              |  2 ++
 5 files changed, 134 insertions(+)

diff --git a/src/ast.cpp b/src/ast.cpp
index 3e68664..4284ded 100644
--- a/src/ast.cpp
+++ b/src/ast.cpp
@@ -68,6 +68,13 @@ namespace AST {
         return out.str();
     }
 
+    std::string FieldAccessExpression::formatted() {
+        std::stringstream out{ "" };
+        out << this->m_expr->formatted();
+        out << "." << this->m_field;
+        return out.str();
+    }
+
     std::string ListInitializerExpression::formatted() {
         std::stringstream out{ "" };
         out << "{ ";
diff --git a/src/ast.h b/src/ast.h
index 5538827..13f0d35 100644
--- a/src/ast.h
+++ b/src/ast.h
@@ -245,6 +245,32 @@ namespace AST {
         ) override;
     };
 
+    /// @brief Same as value.field
+    class FieldAccessExpression : public Expression {
+    private:
+        std::unique_ptr<Expression> m_expr;
+        std::string m_field;
+    public:
+        FieldAccessExpression(
+            token::Metadata meta,
+            std::unique_ptr<Expression> expr,
+            std::string field)
+            : Expression{ meta }
+            , m_expr{ std::move(expr) }
+            , m_field{ field } {
+        }
+        virtual ~FieldAccessExpression() override = default;
+        virtual std::string formatted() override;
+        virtual codegen::StackValue codegen(codegen::Builder& builder, codegen::Scope& scope) override;
+        virtual std::shared_ptr<types::Type> get_codegen_type(codegen::Scope& scope) override;
+        virtual std::shared_ptr<types::Type> typecheck(
+            typecheck::State& state,
+            typecheck::Scope& scope,
+            std::optional<std::shared_ptr<types::Type>> expected_ty
+        ) override;
+    };
+
+    /// @brief Same as {value1, value2}
     class ListInitializerExpression : public Expression {
     private:
         std::vector<std::unique_ptr<Expression>> m_expressions;
diff --git a/src/codegen.cpp b/src/codegen.cpp
index 4182ee6..37b6533 100644
--- a/src/codegen.cpp
+++ b/src/codegen.cpp
@@ -323,6 +323,72 @@ namespace AST {
     }
 
 
+    std::shared_ptr<types::Type> FieldAccessExpression::get_codegen_type(codegen::Scope& scope) {
+        auto ty = this->m_expr->get_codegen_type(scope);
+        if (ty->m_kind == types::TypeKind::Struct) {
+            auto struct_ty = dynamic_cast<types::StructType*>(ty.get());
+            if (struct_ty->m_fields) {
+                for (auto& field : *struct_ty->m_fields) {
+                    if (field.first == this->m_field)
+                        return field.second;
+                }
+                throw CompileError("Unknown field", this->m_meta);
+            }
+            throw CompileError("Cannot access a field of opaque struct", this->m_meta);
+        }
+        else {
+            throw CompileError("Tried accessing a non-struct", this->m_meta);
+        }
+    }
+
+    codegen::StackValue FieldAccessExpression::codegen(codegen::Builder& builder, codegen::Scope& scope) {
+        auto lvalued = scope.with_lvalue();
+        auto struct_ptr = this->m_expr->codegen(builder, lvalued);
+        if (struct_ptr.ty->m_kind == types::TypeKind::Pointer) {
+            auto ptr_ty = dynamic_cast<types::PointerType*>(struct_ptr.ty.get());
+            if (ptr_ty->m_inner->m_kind == types::TypeKind::Struct) {
+                auto struct_ty = dynamic_cast<types::StructType*>(ptr_ty->m_inner.get());
+
+                int idx = -1;
+                auto field_ty = std::shared_ptr<types::Type>{};
+
+                for (int i = 0; i < static_cast<int>(struct_ty->m_fields->size()); i++) {
+                    auto field = (*struct_ty->m_fields)[i];
+                    if (field.first == this->m_field) {
+                        idx = i;
+                        field_ty = field.second;
+                        break;
+                    }
+                }
+
+                auto gep = builder.builder->CreateStructGEP(
+                    ptr_ty->m_inner->codegen(builder, scope.structs), struct_ptr.value, idx);
+
+                auto ptr_ty = std::shared_ptr<types::Type>{
+                    new types::PointerType { field_ty }
+                };
+
+                if (scope.is_lvalue) {
+                    return codegen::StackValue{
+                        gep,
+                        ptr_ty
+                    };
+                }
+                else {
+                    auto loaded = ptr_ty->load(builder, gep, scope.structs);
+                    return codegen::StackValue{ loaded.first, loaded.second };
+                }
+            }
+            else {
+                throw CompileError("Tried field-accessing a non-struct-pointer", this->m_meta);
+            }
+        }
+        else {
+            throw CompileError("Tried field-accessing a non-pointer", this->m_meta);
+        }
+    }
+
+
 
     std::shared_ptr<types::Type> ListInitializerExpression::get_codegen_type(codegen::Scope&) {
         return this->m_ty;
diff --git a/src/typechecker.cpp b/src/typechecker.cpp
index 91630f6..c0fb498 100644
--- a/src/typechecker.cpp
+++ b/src/typechecker.cpp
@@ -309,6 +309,39 @@ namespace AST {
         };
     }
 
+    std::shared_ptr<types::Type> FieldAccessExpression::typecheck(
+        typecheck::State& state,
+        typecheck::Scope& scope,
+        std::optional<std::shared_ptr<types::Type>>
+    ) {
+        auto expr_ty = this->m_expr->typecheck(state, scope, {});
+        if (expr_ty->m_kind != types::TypeKind::Struct) {
+            state.errors.push_back(
+                CompileError("Tried to access " + expr_ty->formatted() + "." + this->m_field, this->m_meta));
+            return std::shared_ptr<types::Type> {
+                new types::FundamentalType{ types::FundamentalTypeKind::Void }
+            };
+        }
+
+        auto struct_ty = dynamic_cast<types::StructType*>(expr_ty.get());
+        if (struct_ty->m_fields) {
+            for (auto& field : *struct_ty->m_fields) {
+                if (field.first == this->m_field) {
+                    return field.second;
+                }
+            }
+            state.errors.push_back(CompileError("No such field", this->m_meta));
+            return std::shared_ptr<types::Type> {
+                new types::FundamentalType{ types::FundamentalTypeKind::Void }
+            };
+        }
+
+        state.errors.push_back(CompileError("Cannot access fields of opaque struct", this->m_meta));
+        return std::shared_ptr<types::Type> {
+            new types::FundamentalType{ types::FundamentalTypeKind::Void }
+        };
+    }
+
     std::shared_ptr<types::Type> ListInitializerExpression::typecheck(
         typecheck::State& state,
         typecheck::Scope& scope,
diff --git a/test.c b/test.c
index 2efd44c..04f99bc 100644
--- a/test.c
+++ b/test.c
@@ -26,5 +26,7 @@ int main() {
 
     struct Otus otus = { 5 };
 
+    printf(" first field: %d!", otus.field);
+
     return 0;
 }
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