From 7871383a400f0a37dbd8459755aa9f98e2742f7a Mon Sep 17 00:00:00 2001
From: Tom Willemse
Date: Sat, 13 Aug 2022 14:52:57 -0700
Subject: Chapter 28.3

---
 clox/src/compiler.c | 35 ++++++++++++++++++++++++++++++-----
 clox/src/vm.c       |  1 +
 2 files changed, 31 insertions(+), 5 deletions(-)

diff --git a/clox/src/compiler.c b/clox/src/compiler.c
index 31a7937..a773e97 100644
--- a/clox/src/compiler.c
+++ b/clox/src/compiler.c
@@ -51,7 +51,7 @@ typedef struct {
   bool isLocal;
 } Upvalue;
 
-typedef enum { TYPE_FUNCTION, TYPE_SCRIPT } FunctionType;
+typedef enum { TYPE_FUNCTION, TYPE_METHOD, TYPE_SCRIPT } FunctionType;
 
 typedef struct Compiler {
   struct Compiler *enclosing;
@@ -64,10 +64,15 @@ typedef struct Compiler {
   int scopeDepth;
 } Compiler;
 
+typedef struct ClassCompiler {
+  struct ClassCompiler *enclosing;
+} ClassCompiler;
+
 static int resolveUpvalue(Compiler *, Token *);
 
 Parser parser;
 Compiler *current = NULL;
+ClassCompiler *currentClass = NULL;
 Chunk *compilingChunk;
 
 static Chunk *currentChunk() { return &current->function->chunk; }
@@ -200,8 +205,13 @@ static void initCompiler(Compiler *compiler, FunctionType type) {
   Local *local = &current->locals[current->localCount++];
   local->depth = 0;
   local->isCaptured = false;
-  local->name.start = "";
-  local->name.length = 0;
+  if (type != TYPE_FUNCTION) {
+    local->name.start = "this";
+    local->name.length = 4;
+  } else {
+    local->name.start = "";
+    local->name.length = 0;
+  }
 }
 
 static ObjFunction *endCompiler() {
@@ -378,7 +388,7 @@ static void method() {
   consume(TOKEN_IDENTIFIER, "Expect method name.");
   uint8_t constant = identifierConstant(&parser.previous);
 
-  FunctionType type = TYPE_FUNCTION;
+  FunctionType type = TYPE_METHOD;
   function(type);
   emitBytes(OP_METHOD, constant);
 }
@@ -453,6 +463,10 @@ static void classDeclaration() {
   emitBytes(OP_CLASS, nameConstant);
   defineVariable(nameConstant);
 
+  ClassCompiler classCompiler;
+  classCompiler.enclosing = currentClass;
+  currentClass = &classCompiler;
+
   namedVariable(className, false);
   consume(TOKEN_LEFT_BRACE, "Expect '{' before class body.");
   while (!check(TOKEN_RIGHT_BRACE) && !check(TOKEN_EOF)) {
@@ -460,6 +474,8 @@ static void classDeclaration() {
   }
   consume(TOKEN_RIGHT_BRACE, "Expect '}' after class body.");
   emitByte(OP_POP);
+
+  currentClass = currentClass->enclosing;
 }
 
 static void markInitialized() {
@@ -686,6 +702,15 @@ static void variable(bool canAssign) {
   namedVariable(parser.previous, canAssign);
 }
 
+static void this_(bool canAssign) {
+  if (currentClass == NULL) {
+    error("Can't use 'this' outside of a class.");
+    return;
+  }
+
+  variable(false);
+}
+
 static void unary(bool canAssign) {
   TokenType operatorType = parser.previous.type;
 
@@ -745,7 +770,7 @@ ParseRule rules[] = {
     [TOKEN_PRINT] = {NULL, NULL, PREC_NONE},
     [TOKEN_RETURN] = {NULL, NULL, PREC_NONE},
     [TOKEN_SUPER] = {NULL, NULL, PREC_NONE},
-    [TOKEN_THIS] = {NULL, NULL, PREC_NONE},
+    [TOKEN_THIS] = {this_, NULL, PREC_NONE},
     [TOKEN_TRUE] = {literal, NULL, PREC_NONE},
     [TOKEN_VAR] = {NULL, NULL, PREC_NONE},
     [TOKEN_WHILE] = {NULL, NULL, PREC_NONE},
diff --git a/clox/src/vm.c b/clox/src/vm.c
index 4b0fe48..6b15a3a 100644
--- a/clox/src/vm.c
+++ b/clox/src/vm.c
@@ -110,6 +110,7 @@ static bool callValue(Value callee, int argCount) {
     switch (OBJ_TYPE(callee)) {
     case OBJ_BOUND_METHOD: {
       ObjBoundMethod *bound = AS_BOUND_METHOD(callee);
+      vm.stackTop[-argCount - 1] = bound->receiver;
       return call(bound->method, argCount);
     }
     case OBJ_CLASS: {
-- 
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