Add if statement

Signed-off-by: CHatingPython <chatingpython@gmail.com>

furc/src/front/ir_generator.cpp

@@ -14,9 +14,9 @@ namespace ir = furlang::ir;
 }
 
 void ir_generator::visit_function_definition_node(const ast::function_definition_node& funcDef) {
-    auto func = std::make_unique<furlang::ir::function>(std::string(funcDef.name()->string));
+    m_currentFunction = std::make_unique<furlang::ir::function>(std::string(funcDef.name()->string));
 
-    m_currentBlock = func->push();
+    push_block();
     if (funcDef.body().has_error()) {
         std::cerr << funcDef.body().error() << '\n';
         return;
@@ -25,7 +25,7 @@ void ir_generator::visit_function_definition_node(const ast::function_definition
         stmt->accept(*this);
     }
 
-    m_module.push(std::move(func));
+    m_module.push(std::move(m_currentFunction));
 }
 
 void ir_generator::visit_return_statement_node(const ast::return_statement_node& returnStmt) {
@@ -41,6 +41,25 @@ void ir_generator::visit_return_statement_node(const ast::return_statement_node&
     }
 }
 
+void ir_generator::visit_if_statement_node(const ast::if_statement_node& node) {
+    node.cond()->accept(*this);
+    std::uint32_t cond = m_registerCounter - 1;
+    m_currentBlock->emplace<ir::branch_cond_instruction>(ir::operand::new_reg(cond),
+        m_currentFunction->blocks().size(),
+        m_currentFunction->blocks().size() + 1);
+
+    push_block(); // then block
+    node.then()->accept(*this);
+    if (node.elze().present()) {
+        m_currentBlock->emplace<ir::branch_instruction>(m_currentFunction->blocks().size() + 1);
+
+        push_block(); // else block
+        node.elze()->accept(*this);
+    }
+
+    push_block();
+}
+
 void ir_generator::visit_string_literal_node(const ast::string_literal_node& node) {
     m_currentBlock->emplace<furlang::ir::assign_instruction>(ir::operand::new_string(std::string(*node.value())),
         ir::operand::new_reg(m_registerCounter++));
@@ -93,4 +112,10 @@ void ir_generator::visit_var_assign_expression_node(const ast::var_assign_expres
     throw std::runtime_error("unimplemented");
 }
 
+furlang::ir::block_index ir_generator::push_block() {
+    ir::block_index index = m_currentFunction->blocks().size();
+    m_currentBlock        = m_currentFunction->push();
+    return index;
+}
+
 } // namespace furc::front

furc/src/front/lexer.cpp

@@ -90,6 +90,8 @@ token_handle<> lexer::next_token() {
             static std::unordered_map<std::string_view, keyword_token> s_keywords = {
                 { "func", keyword_token::Func },
                 { "return", keyword_token::Return },
+                { "if", keyword_token::If },
+                { "else", keyword_token::Else },
             };
 
             if (auto it = s_keywords.find(value); it != s_keywords.end()) return { location, it->second, value };

furc/src/front/parser.cpp

@@ -1,6 +1,6 @@
 #include "furc/front/parser.hpp"
 
-#include "furc/ast/declaration.hpp"
+// #include "furc/ast/declaration.hpp" // IWYU pragma: keep
 
 #include <fstream>
 #include <iostream>
@@ -55,7 +55,7 @@ ast::declaration_node_h parser::parse_declaration() {
             if (peek.has_error()) return peek;
             switch (peek->type) {
             case token_t::Lbrace: {
-                ast::function_body_h body = parse_body();
+                ast::body_h body = parse_body();
                 if (body.has_error()) return body;
                 return ast::function_definition_node_h{ first.location(), m_arena, *name, std::move(body) };
             }
@@ -91,16 +91,49 @@ ast::statement_node_h parser::parse_statement() {
     if (tok.has_error()) return tok;
     switch (tok->type) {
     case token_t::Keyword: {
-        auto tok = next_token();
-        if (peek_token()->type == token_t::Semicolon) {
-            next_token();
-            return ast::return_statement_node_h{ tok.location(), m_arena };
-        }
+        switch (tok->value.keyword) {
+        case keyword_token::Return: {
+            auto tok = next_token();
+            if (peek_token()->type == token_t::Semicolon) {
+                next_token();
+                return ast::return_statement_node_h{ tok.location(), m_arena };
+            }
 
-        auto value = parse_expression();
-        auto err   = eat_token(token_t::Semicolon);
-        if (err.has_error()) return err;
-        return ast::return_statement_node_h{ tok.location(), m_arena, std::move(value) };
+            auto value = parse_expression();
+            auto err   = eat_token(token_t::Semicolon);
+            if (err.has_error()) return err;
+            return ast::return_statement_node_h{ tok.location(), m_arena, std::move(value) };
+        }
+        case keyword_token::If: {
+            auto tok = next_token();
+            auto err = eat_token(token_t::Lparen);
+            if (err.has_error()) return err;
+
+            auto cond = parse_expression();
+
+            err = eat_token(token_t::Rparen);
+            if (err.has_error()) return err;
+
+            auto then = parse_statement();
+            if (then.has_error()) return then;
+
+            if (peek_token().present() && peek_token()->type == token_t::Keyword &&
+                peek_token()->value.keyword == keyword_token::Else) {
+                next_token();
+
+                return ast::if_statement_node_h{ tok.location(),
+                    m_arena,
+                    std::move(cond),
+                    std::move(then),
+                    std::move(parse_statement()) };
+            }
+
+            return ast::if_statement_node_h{ tok.location(), m_arena, std::move(cond), std::move(then) };
+        }
+        case keyword_token::None:
+        case keyword_token::Func:
+        default: break;
+        }
     }
     default: break;
     }
@@ -328,8 +361,8 @@ ast::expression_node_h parser::parse_expression_rhs(ast::expression_node_h&& ini
     return lhs;
 }
 
-ast::function_body_h parser::parse_body() {
-    ast::function_body body;
+ast::body_h parser::parse_body() {
+    ast::body body;
 
     token_handle<> begin = eat_token(token_t::Lbrace);
     if (begin.has_error()) return begin;