feat(furc): implement a basic parser

furc/src/front/parser.cpp

@@ -0,0 +1,133 @@
+#include "furc/front/parser.hpp"
+
+#include "furc/front/ast.hpp"
+#include "furc/front/token.hpp"
+
+#include <cassert>
+#include <stdexcept>
+#include <utility>
+
+namespace furc {
+
+ast parser::parse() {
+    ast tree;
+    while (m_lexer.peek_token().type != token::EndOfFile) {
+        auto* decl = parse_decl();
+        assert(decl);
+        tree.decls.push_back(decl);
+    }
+
+    return std::move(tree);
+}
+
+stmt_node* parser::parse_stmt() {
+    switch (m_lexer.peek_token().type) {
+    case token::LBrace: return m_arena->allocate<comp_stmt_node>(parse_comp());
+    default: break;
+    }
+
+    try {
+        return parse_decl();
+    } catch (...) {
+        return parse_expr();
+    }
+}
+
+decl_node* parser::parse_decl() {
+    auto first = eat_token(token::Identifier, token::Func);
+    if (first.type == token::Func) {
+        func_decl_node func;
+
+        func.name = std::string(eat_token(token::Identifier).value.string);
+        eat_token(token::LParen);
+        if (m_lexer.peek_token().type != token::RParen) {
+            do {
+                var_decl_node param;
+
+                param.name = std::string(eat_token(token::Identifier).value.string);
+                eat_token(token::Colon);
+                param.type = parse_type();
+                if (m_lexer.peek_token().type == token::Equals) {
+                    m_lexer.next_token();
+                    param.init = parse_expr();
+                }
+                func.params.emplace_back(std::move(param));
+            } while (eat_token(token::Comma, token::RParen).type == token::Comma);
+        } else {
+            eat_token(token::RParen);
+        }
+
+        if (m_lexer.peek_token().type == token::SlimArrow) {
+            m_lexer.next_token();
+            func.type = parse_type();
+        }
+
+        if (m_lexer.peek_token().type == token::Semicolon) {
+            m_lexer.next_token();
+            return m_arena->allocate<func_decl_node>(std::move(func));
+        }
+
+        func.body = parse_comp();
+
+        return m_arena->allocate<func_decl_node>(std::move(func));
+    }
+
+    var_decl_node var;
+    var.name = std::string(first.value.string);
+    eat_token(token::Colon); // TODO: Auto-deduce the type
+    var.type = parse_type();
+    if (eat_token(token::Equals, token::Semicolon).type == token::Equals) {
+        var.init = parse_expr();
+        eat_token(token::Semicolon);
+    }
+
+    return m_arena->allocate<var_decl_node>(std::move(var));
+}
+
+expr_node* parser::parse_expr() {
+    if (auto* lit = parse_lit(); lit != nullptr) return lit;
+    return nullptr;
+}
+
+lit_node* parser::parse_lit() {
+    auto token = eat_token(token::Integer, token::Char);
+    switch (token.type) {
+    case token::Integer: {
+        return m_arena->allocate<int_lit_node>(int_lit_node(token.value.integer));
+    }
+    case token::Char: {
+        return m_arena->allocate<char_lit_node>(char_lit_node(token.value.character));
+    }
+    default: throw std::runtime_error("unreachable");
+    }
+}
+
+ast_type parser::parse_type() {
+    auto token =
+        eat_token(token::S8, token::U8, token::S16, token::U16, token::S32, token::U32, token::S64, token::U64);
+    switch (token.type) {
+    case token::S8: return { ast_type::S8 };
+    case token::U8: return { ast_type::U8 };
+    case token::S16: return { ast_type::S16 };
+    case token::U16: return { ast_type::U16 };
+    case token::S32: return { ast_type::S32 };
+    case token::U32: return { ast_type::U32 };
+    case token::S64: return { ast_type::S64 };
+    case token::U64: return { ast_type::U64 };
+    default: throw std::runtime_error("unreachable");
+    }
+}
+
+comp_stmt_node parser::parse_comp() {
+    comp_stmt_node comp;
+
+    eat_token(token::LBrace);
+    while (m_lexer.peek_token().type != token::EndOfFile && m_lexer.peek_token().type != token::RBrace) {
+        comp.stmts.push_back(parse_stmt());
+    }
+    eat_token(token::RBrace);
+
+    return comp;
+}
+
+} // namespace furc