Add structures we'll need for the first parser iteration

src/parser/cst.h

@@ -0,0 +1,62 @@
+/**
+ * The structures for a concrete syntax tree.
+ * For now, the subset of C we are parsing is quite simple:
+ * - Parameterless functions.
+ * - Return statements, which accept integers or function calls.
+ */
+
+#pragma once
+
+#include "list.h"
+
+// A list of all node types.
+typedef enum {
+    NT_STMT,
+    NT_EXPR,
+    NT_BLOCK_STMT,
+    NT_RETURN_STMT,
+    NT_FUNCDECL,
+    NT_FUNCCALL,
+    NT_LITERAL,
+} NodeType;
+
+// A block statement is just a list of statements.
+typedef struct {
+    List* stmts; // A list of Statement structs.
+} BlockStatement;
+
+typedef struct {
+    // TODO -- add parameters whe we get there
+    BlockStatement body;
+    char name[256]; // The actual name of the function.
+} FunctionDeclaration;
+
+// An entire program is just a list of top level declarations.
+// For now, such declarations are only functions.
+typedef struct {
+    union {
+        FunctionDeclaration fd;
+        // VariableDeclaration vd; when we get there
+    } u;
+    NodeType type;
+} TopLevelDeclaration;
+
+// Right now, a function call doesn't have any parameters so it's just the name
+// of the function being called.
+typedef struct {
+    char name[256];
+} FunctionCall;
+
+// An expression for now is an integer or a function call.
+typedef struct {
+    union {
+        FunctionCall fc;
+        char literal[256];
+    } u;
+    NodeType type;
+} Expression;
+
+// Finally, an entire source file is a list of top-level declarations.
+typedef struct {
+    List* decls; // list of TopLevelDeclaration
+} ConcreteFileTree;