Improve binop typechecking

src/ast.cpp

@@ -44,7 +44,7 @@ namespace AST {
 
     std::string CastExpression::formatted() {
         std::stringstream out{ "" };
-        out << "(" << this->m_ty->formatted() << ") ";
+        out << "(" << this->m_ty->formatted() << ")";
         out << this->m_expr->formatted();
         return out.str();
     }

src/casting.cpp

@@ -1,5 +1,6 @@
 
 #include "casting.h"
+#include <iostream>
 
 namespace types {
     std::vector<CastDefinition> create_casts() {
@@ -21,15 +22,21 @@ namespace types {
                         [](codegen::Builder&, std::shared_ptr<Type>, llvm::Value* value) {
                             return value;
                         } });
+                    continue;
                 }
-                else if (target_ty->is_signed()) {
-                    casts.push_back(CastDefinition{ source_ty, target_ty, false,
+
+                bool allow_implicit = false;
+                if (target_ty->size() >= source_ty->size())
+                    allow_implicit = true;
+
+                if (target_ty->is_signed()) {
+                    casts.push_back(CastDefinition{ source_ty, target_ty, allow_implicit,
                         [](codegen::Builder& builder, std::shared_ptr<Type> target, llvm::Value* value) {
                             return builder.builder->CreateSExtOrTrunc(value, target->codegen(builder), "cast");
                         } });
                 }
                 else {
-                    casts.push_back(CastDefinition{ source_ty, target_ty, false,
+                    casts.push_back(CastDefinition{ source_ty, target_ty, allow_implicit,
                         [](codegen::Builder& builder, std::shared_ptr<Type> target, llvm::Value* value) {
                             return builder.builder->CreateZExtOrTrunc(value, target->codegen(builder), "cast");
                         } });

src/main.cpp

@@ -117,6 +117,8 @@ std::optional<CompileOutput> compile(std::string_view in_filename) {
         return {};
     }
 
+    // Compile parsed output
+
     codegen::Scope cg_scope{
         .binops = typecheck_state.binops,
         .casts = typecheck_state.casts,
@@ -124,7 +126,6 @@ std::optional<CompileOutput> compile(std::string_view in_filename) {
         .is_lvalue = false,
     };
 
-    // Compile parsed output
     try {
         for (auto& tls : statements) {
             std::cout << tls->formatted() << std::endl;

src/typechecker.cpp

@@ -5,14 +5,31 @@
 #include "result.h"
 
 namespace {
-    enum class TypecheckRes {
+    enum class TypecheckResKind {
         Ok,
         Castable,
     };
 
-    Result<TypecheckRes, std::string> check_type(std::shared_ptr<types::Type> checked, std::shared_ptr<types::Type> target) {
+    struct TypecheckRes {
+        TypecheckResKind kind;
+        std::shared_ptr<types::Type> result;
+    };
+
+    Result<TypecheckRes, std::string> check_type(
+        typecheck::State& state,
+        std::shared_ptr<types::Type> checked,
+        std::shared_ptr<types::Type> target) {
+        auto potential_cast = types::find_cast(state.casts, checked, target);
+
+
         if (types::types_equal(checked, target)) {
-            return TypecheckRes::Ok;
+            return TypecheckRes{ TypecheckResKind::Ok, target };
+        }
+        else if (potential_cast.has_value()) {
+            if (potential_cast->allow_implicit)
+                return TypecheckRes{ TypecheckResKind::Castable, target };
+
+            return std::string{ "Type " + checked->formatted() + " not implicitly castable to " + target->formatted() };
         }
 
         return std::string{ "Types " + checked->formatted() + " and " + target->formatted() + " incompatible" };
@@ -24,12 +41,13 @@ namespace {
         typecheck::State& state) {
         if (res.ok()) {
             auto result = res.unwrap();
-            if (result == TypecheckRes::Ok) {
+            if (result.kind == TypecheckResKind::Ok) {
                 return expr;
             }
             else {
-                state.errors.push_back(CompileError("Casting not yet implemented", expr->m_meta));
-                return expr;
+                return std::unique_ptr<AST::Expression> {
+                    new AST::CastExpression{ expr->m_meta, result.result, std::move(expr) }
+                };
             }
         }
         else {
@@ -93,7 +111,7 @@ namespace AST {
     std::shared_ptr<types::Type> BinaryOperationExpression::typecheck(
         typecheck::State& state,
         typecheck::Scope& scope,
-        std::optional<std::shared_ptr<types::Type>>
+        std::optional<std::shared_ptr<types::Type>> expected_ty
     ) {
         auto lhs_ty = this->m_lhs->typecheck(state, scope, {});
         auto rhs_ty = this->m_rhs->typecheck(state, scope, {});
@@ -101,9 +119,12 @@ namespace AST {
         if (this->m_binop == types::BinOp::Assignment) {
             // Re-typecheck rhs to actually match lhs
             auto rhs_ty = this->m_rhs->typecheck(state, scope, lhs_ty);
+            auto rhs_ty_res = check_type(state, rhs_ty, lhs_ty);
+            this->m_rhs = handle_res(std::move(this->m_rhs), rhs_ty_res, state);
             return lhs_ty;
         }
 
+        // Try to find a binop that matches exactly
         auto binop = types::find_binop(
             state.binops,
             lhs_ty,
@@ -115,8 +136,53 @@ namespace AST {
             return binop->result;
         }
 
-        // TODO check for binops that may be implicitly castable
+        // If that fails, try to find binop that matches on one side perfectly
+        // and is castable on the other side, and would also be perfectly
+        // assignable to the expected value.
+        for (auto& binop : state.binops) {
+            if (expected_ty) {
+                // Skip any binops that would not be immediately assignable to
+                // the expected type
+                if (!types::types_equal(binop.result, *expected_ty)) {
+                    continue;
+                }
+            }
+            if (types::types_equal(binop.lhs, lhs_ty)) {
+                auto rhs_res = check_type(state, rhs_ty, binop.rhs);
+                if (!rhs_res.ok())
+                    // Skip if not implicitly castable to lhs
+                    continue;
+                this->m_rhs = handle_res(std::move(this->m_rhs), rhs_res, state);
+                return binop.result;
+            }
+            else if (types::types_equal(binop.rhs, rhs_ty)) {
+                auto lhs_res = check_type(state, lhs_ty, binop.lhs);
+                if (!lhs_res.ok())
+                    // Skip if not implicitly castable to rhs
+                    continue;
+                this->m_lhs = handle_res(std::move(this->m_lhs), lhs_res, state);
+                return binop.result;
+            }
+        }
 
+        // Finally check for any binop that allows the result to be implicitly
+        // casted to the result
+        for (auto& binop : state.binops) {
+            if (expected_ty) {
+                // Skip any binops that would not even be implicitly castable to
+                // the expected result
+                auto result_res = check_type(state, binop.result, *expected_ty);
+                if (!result_res.ok())
+                    continue;
+            }
+            auto lhs_result = check_type(state, lhs_ty, binop.lhs);
+            auto rhs_result = check_type(state, rhs_ty, binop.rhs);
+            this->m_lhs = handle_res(std::move(this->m_lhs), lhs_result, state);
+            this->m_rhs = handle_res(std::move(this->m_rhs), lhs_result, state);
+            return binop.result;
+        }
+
+        // No suitable binops found :(
         state.errors.push_back(CompileError(
             "No suitable binop between "
             + lhs_ty->formatted() + " "
@@ -156,7 +222,7 @@ namespace AST {
                     auto expected_param_ty = fn_ty->m_param_tys[i];
                     auto param_ty = this->m_args[i]->typecheck(state, scope, expected_param_ty);
 
-                    auto check_res = check_type(param_ty, expected_param_ty);
+                    auto check_res = check_type(state, param_ty, expected_param_ty);
                     this->m_args[i] = handle_res(std::move(this->m_args[i]), check_res, state);
                 }
                 else {
@@ -190,7 +256,7 @@ namespace AST {
     void ReturnStatement::typecheck(typecheck::State& state, typecheck::Scope& scope) {
         auto res_ty = this->m_expr->typecheck(state, scope, scope.return_ty);
         if (scope.return_ty) {
-            auto check_res = check_type(res_ty, *scope.return_ty);
+            auto check_res = check_type(state, res_ty, *scope.return_ty);
             this->m_expr = handle_res(std::move(this->m_expr), check_res, state);
         }
     }
@@ -211,7 +277,7 @@ namespace AST {
             new types::FundamentalType{ types::FundamentalTypeKind::Bool } };
         auto expr_ty = this->m_condition->typecheck(state, scope, bool_ty);
 
-        auto check_res = check_type(expr_ty, bool_ty);
+        auto check_res = check_type(state, expr_ty, bool_ty);
         this->m_condition = handle_res(std::move(this->m_condition), check_res, state);
 
         this->m_then->typecheck(state, scope);

src/types.cpp

@@ -76,7 +76,7 @@ namespace types {
     }
 
     bool Type::is_signed() {
-        false;
+        return false;
     }
 
     std::pair<llvm::Value*, std::shared_ptr<Type>> FundamentalType::load(codegen::Builder&, llvm::Value* ptr) {
@@ -140,6 +140,19 @@ namespace types {
         }
     }
 
+    uint32_t FundamentalType::size() {
+        switch (this->m_ty) {
+        case FundamentalTypeKind::Int:
+            return 32;
+        case FundamentalTypeKind::Bool:
+            return 1;
+        case FundamentalTypeKind::Char:
+            return 8;
+        default:
+            throw std::runtime_error("Invalid type");
+        }
+    }
+
     std::string FunctionType::formatted() {
         std::stringstream out{ "" };
         out << "(";
@@ -170,6 +183,10 @@ namespace types {
         return std::pair(ptr, self);
     }
 
+    uint32_t FunctionType::size() {
+        return 64;
+    }
+
     std::string PointerType::formatted() {
         std::stringstream out{ "" };
         out << this->m_inner->formatted() << "*";
@@ -183,6 +200,10 @@ namespace types {
         );
     }
 
+    uint32_t PointerType::size() {
+        return 64;
+    }
+
     bool types_equal(std::shared_ptr<types::Type> type1, std::shared_ptr<types::Type> type2) {
         if (type1->m_kind != type2->m_kind)
             return false;

src/types.h

@@ -34,6 +34,7 @@ namespace types {
         virtual llvm::Value* lt(codegen::Builder& builder, llvm::Value* lhs, llvm::Value* rhs);
         virtual llvm::Value* gt(codegen::Builder& builder, llvm::Value* lhs, llvm::Value* rhs);
         virtual bool is_signed();
+        virtual uint32_t size() = 0;
     };
 
     class FundamentalType : public Type {
@@ -49,6 +50,7 @@ namespace types {
         virtual llvm::Value* lt(codegen::Builder& builder, llvm::Value* lhs, llvm::Value* rhs) override;
         virtual llvm::Value* gt(codegen::Builder& builder, llvm::Value* lhs, llvm::Value* rhs) override;
         virtual bool is_signed() override;
+        virtual uint32_t size() override;
     };
 
 
@@ -68,6 +70,7 @@ namespace types {
         virtual llvm::Type* codegen(codegen::Builder& builder) override;
         virtual std::pair<llvm::Value*, std::shared_ptr<Type>> load(codegen::Builder& builder, llvm::Value* ptr) override;
         virtual std::optional<std::shared_ptr<Type>> return_type() override;
+        virtual uint32_t size() override;
     };
 
 
@@ -82,6 +85,7 @@ namespace types {
         virtual std::string formatted() override;
         virtual llvm::Type* codegen(codegen::Builder& builder) override;
         virtual std::pair<llvm::Value*, std::shared_ptr<Type>> load(codegen::Builder& builder, llvm::Value* ptr) override;
+        virtual uint32_t size() override;
     };
 
     bool types_equal(std::shared_ptr<types::Type> type1, std::shared_ptr<types::Type> type2);

test.c

@@ -10,5 +10,5 @@ int main() {
     printf("10th fibonacci number is %d!", fibonacci(10));
     char res = 0;
     res = 15;
-    return (int)res;
+    return res;
 }