feat(ast): add initial AST implementation

compiler/CMakeLists.txt

@@ -4,6 +4,8 @@ add_library(phonkc STATIC
         src/diagnostics/diagnostic_engine.cpp
         src/lexer/lexer.cpp
         src/compiler.cpp
+        include/phonk/ast/expression.hpp
+        include/phonk/ast/statement.hpp
 )
 
 target_include_directories(phonkc PUBLIC include)

compiler/include/phonk/ast/expression.hpp

@@ -0,0 +1,63 @@
+//
+// Created by Maxwell Morgan on 9/5/26.
+//
+
+#ifndef PHONK_EXPRESSION_HPP
+#define PHONK_EXPRESSION_HPP
+
+#include <cstdint>
+#include <memory>
+#include <string>
+#include <variant>
+
+#include <phonk/lexer/token.hpp>
+#include <phonk/source/source_range.hpp>
+
+namespace phonk::ast {
+
+struct Expr;
+
+// Expressions can contain other expressions
+using ExprPtr = std::unique_ptr<Expr>;
+
+using LiteralValue = std::variant<
+    std::int64_t,
+    double,
+    std::string,
+    bool>;
+
+struct LiteralExpr {
+    LiteralValue value;
+};
+
+struct IdentifierExpr {
+    lexer::Token name;
+};
+
+struct UnaryExpr {
+    lexer::Token op;
+    ExprPtr operand;
+};
+
+struct BinaryExpr {
+    ExprPtr left;
+    lexer::Token op;
+    ExprPtr right;
+};
+
+
+// Eliminates need for many classes and inheritance
+using ExprNode = std::variant<
+    LiteralExpr,
+    IdentifierExpr,
+    UnaryExpr,
+    BinaryExpr>;
+
+struct Expr {
+    source::SourceRange range;
+    ExprNode node;
+};
+
+}
+
+#endif // PHONK_EXPRESSION_HPP

compiler/include/phonk/ast/statement.hpp

@@ -0,0 +1,45 @@
+//
+// Created by Maxwell Morgan on 9/5/26.
+//
+
+#ifndef PHONK_STATEMENT_HPP
+#define PHONK_STATEMENT_HPP
+
+#include <memory>
+#include <variant>
+#include <vector>
+
+#include <phonk/ast/expression.hpp>
+#include <phonk/source/source_range.hpp>
+
+namespace phonk::ast {
+
+struct Stmt;
+
+using StmtPtr = std::unique_ptr<Stmt>;
+
+struct ExprStmt {
+    ExprPtr expression;
+};
+
+struct BlockStmt {
+    std::vector<StmtPtr> statements;
+};
+
+struct ReturnStmt {
+    ExprPtr value;
+};
+
+using StmtNode = std::variant<
+    ExprStmt,
+    BlockStmt,
+    ReturnStmt>;
+
+struct Stmt {
+    source::SourceRange range;
+    StmtNode node;
+};
+
+}
+
+#endif // PHONK_STATEMENT_HPP