diff --git a/src/check_decl.cpp b/src/check_decl.cpp
index 28a3dadce..b23ab2b74 100644
--- a/src/check_decl.cpp
+++ b/src/check_decl.cpp
@@ -352,10 +352,6 @@ void check_const_decl(CheckerContext *ctx, Entity *e, AstNode *type_expr, AstNod
 		}
 	}
 
-	if (init != nullptr) {
-		check_expr_or_type(ctx, &operand, init, e->type);
-	}
-
 	check_init_constant(ctx, e, &operand);
 
 	if (operand.mode == Addressing_Invalid ||
diff --git a/src/check_expr.cpp b/src/check_expr.cpp
index f57b7095a..ea9936235 100644
--- a/src/check_expr.cpp
+++ b/src/check_expr.cpp
@@ -3632,7 +3632,7 @@ break;
 		isize variable_count = type->Struct.fields.count;
 		array_init(&tuple->Tuple.variables, a, variable_count);
 		// TODO(bill): Should I copy each of the entities or is this good enough?
-		gb_memcopy_array(tuple->Tuple.variables.data, type->Struct.fields.data, variable_count);
+		gb_memmove_array(tuple->Tuple.variables.data, type->Struct.fields.data, variable_count);
 
 		operand->type = tuple;
 		operand->mode = Addressing_Value;
diff --git a/src/check_type.cpp b/src/check_type.cpp
index 7151c9b6f..e4bd3dd2b 100644
--- a/src/check_type.cpp
+++ b/src/check_type.cpp
@@ -208,9 +208,7 @@ void add_polymorphic_struct_entity(CheckerContext *ctx, AstNode *node, Type *nam
 		token.kind = Token_String;
 		token.string = named_type->Named.name;
 
-		AstNode *node = gb_alloc_item(a, AstNode);
-		node->kind = AstNode_Ident;
-		node->Ident.token = token;
+		AstNode *node = ast_ident(nullptr, token);
 
 		e = alloc_entity_type_name(s, token, named_type);
 		e->state = EntityState_Resolved;
@@ -1634,8 +1632,7 @@ void init_map_entry_type(Type *type) {
 		value: Value;
 	}
 	*/
-	AstNode *dummy_node = gb_alloc_item(a, AstNode);
-	dummy_node->kind = AstNode_Invalid;
+	AstNode *dummy_node = alloc_ast_node(nullptr, AstNode_Invalid);
 	Scope *s = create_scope(universal_scope, a);
 
 	auto fields = array_make<Entity *>(a, 0, 3);
@@ -1670,8 +1667,7 @@ void init_map_internal_types(Type *type) {
 	}
 	*/
 	gbAllocator a = heap_allocator();
-	AstNode *dummy_node = gb_alloc_item(a, AstNode);
-	dummy_node->kind = AstNode_Invalid;
+	AstNode *dummy_node = alloc_ast_node(nullptr, AstNode_Invalid);
 	Scope *s = create_scope(universal_scope, a);
 
 	Type *hashes_type  = alloc_type_dynamic_array(t_int);
diff --git a/src/checker.cpp b/src/checker.cpp
index 0e8642c35..67ec7658d 100644
--- a/src/checker.cpp
+++ b/src/checker.cpp
@@ -241,7 +241,7 @@ Scope *create_scope_from_file(CheckerContext *c, AstFile *f) {
 	Scope *s = create_scope(f->pkg->scope, c->allocator);
 
 	array_reserve(&s->delayed_imports, f->imports.count);
-	array_reserve(&s->delayed_directives, f->assert_decl_count);
+	array_reserve(&s->delayed_directives, f->directive_count);
 
 	s->is_file = true;
 	s->file = f;
@@ -2652,7 +2652,7 @@ void check_add_foreign_import_decl(CheckerContext *ctx, AstNode *decl) {
 	if (fl->collection_name != "system") {
 		char *c_str = gb_alloc_array(heap_allocator(), char, fullpath.len+1);
 		defer (gb_free(heap_allocator(), c_str));
-		gb_memcopy(c_str, fullpath.text, fullpath.len);
+		gb_memmove(c_str, fullpath.text, fullpath.len);
 		c_str[fullpath.len] = '\0';
 
 		gbFile f = {};
diff --git a/src/common.cpp b/src/common.cpp
index 82a1685c4..686105dbb 100644
--- a/src/common.cpp
+++ b/src/common.cpp
@@ -211,7 +211,7 @@ String u64_to_string(u64 v, char *out_buf, isize out_buf_len) {
 	buf[--i] = gb__num_to_char_table[v%b];
 
 	isize len = gb_min(gb_size_of(buf)-i, out_buf_len);
-	gb_memcopy(out_buf, &buf[i], len);
+	gb_memmove(out_buf, &buf[i], len);
 	return make_string(cast(u8 *)out_buf, len);
 }
 String i64_to_string(i64 a, char *out_buf, isize out_buf_len) {
@@ -236,7 +236,7 @@ String i64_to_string(i64 a, char *out_buf, isize out_buf_len) {
 	}
 
 	isize len = gb_min(gb_size_of(buf)-i, out_buf_len);
-	gb_memcopy(out_buf, &buf[i], len);
+	gb_memmove(out_buf, &buf[i], len);
 	return make_string(cast(u8 *)out_buf, len);
 }
 
@@ -287,103 +287,115 @@ gb_global u64 const unsigned_integer_maxs[] = {
 gb_global String global_module_path = {0};
 gb_global bool global_module_path_set = false;
 
-#if 0
-struct Pool {
-	gbAllocator backing;
-	u8 *ptr;
-	u8 *end;
+// Arena from Per Vognsen
+#define ALIGN_DOWN(n, a)     ((n) & ~((a) - 1))
+#define ALIGN_UP(n, a)       ALIGN_DOWN((n) + (a) - 1, (a))
+#define ALIGN_DOWN_PTR(p, a) (cast(void *)ALIGN_DOWN(cast(uintptr)(p), (a)))
+#define ALIGN_UP_PTR(p, a)   (cast(void *)ALIGN_UP(cast(uintptr)(p), (a)))
+
+typedef struct Arena {
+	u8 *        ptr;
+	u8 *        end;
 	Array<u8 *> blocks;
-	isize block_size;
-	isize alignment;
-};
+	gbAllocator backing;
+	isize       block_size;
+	gbMutex     mutex;
 
-#define POOL_BLOCK_SIZE (8*1024*1024)
-#define POOL_ALIGNMENT  16
+	isize total_used;
+	isize possible_used;
+} Arena;
 
-#define ALIGN_DOWN(n, a) ((n) & ~((a) - 1))
-#define ALIGN_UP(n, a) ALIGN_DOWN((n) + (a) - 1, (a))
-#define ALIGN_DOWN_PTR(p, a) ((void *)ALIGN_DOWN((uintptr)(p), (a)))
-#define ALIGN_UP_PTR(p, a) ((void *)ALIGN_UP((uintptr)(p), (a)))
+#define ARENA_MIN_ALIGNMENT 16
+#define ARENA_DEFAULT_BLOCK_SIZE (8*1024*1024)
 
-void pool_init(Pool *pool, gbAllocator backing, isize block_size=POOL_BLOCK_SIZE, isize alignment=POOL_ALIGNMENT) {
-	pool->ptr = nullptr;
-	pool->end = nullptr;
-	pool->backing = backing;
-	pool->block_size = block_size;
-	pool->alignment = alignment;
-	array_init(&pool->blocks, backing);
+void arena_init(Arena *arena, gbAllocator backing, isize block_size=ARENA_DEFAULT_BLOCK_SIZE) {
+	arena->backing = backing;
+	arena->block_size = block_size;
+	array_init(&arena->blocks, backing);
+	gb_mutex_init(&arena->mutex);
 }
 
-void pool_free_all(Pool *pool) {
-	for_array(i, pool->blocks) {
-		gb_free(pool->backing, pool->blocks[i]);
-	}
-	array_clear(&pool->blocks);
+void arena_grow(Arena *arena, isize min_size) {
+	gb_mutex_lock(&arena->mutex);
+	defer (gb_mutex_unlock(&arena->mutex));
+
+	isize size = gb_max(arena->block_size, min_size);
+	size = ALIGN_UP(size, ARENA_MIN_ALIGNMENT);
+	void *new_ptr = gb_alloc(arena->backing, size);
+    arena->ptr = cast(u8 *)new_ptr;
+    gb_zero_size(arena->ptr, size);
+    GB_ASSERT(arena->ptr == ALIGN_DOWN_PTR(arena->ptr, ARENA_MIN_ALIGNMENT));
+    arena->end = arena->ptr + size;
+    array_add(&arena->blocks, arena->ptr);
 }
 
-void pool_destroy(Pool *pool) {
-	pool_free_all(pool);
-	array_free(&pool->blocks);
+void *arena_alloc(Arena *arena, isize size, isize alignment) {
+	gb_mutex_lock(&arena->mutex);
+	defer (gb_mutex_unlock(&arena->mutex));
+
+	arena->total_used += size;
+
+    if (size > (arena->end - arena->ptr)) {
+        arena_grow(arena, size);
+        GB_ASSERT(size <= (arena->end - arena->ptr));
+    }
+
+    isize align = gb_max(alignment, ARENA_MIN_ALIGNMENT);
+    void *ptr = arena->ptr;
+    arena->ptr = cast(u8 *)ALIGN_UP_PTR(arena->ptr + size, align);
+    GB_ASSERT(arena->ptr <= arena->end);
+    GB_ASSERT(ptr == ALIGN_DOWN_PTR(ptr, align));
+    gb_zero_size(ptr, size);
+    return ptr;
 }
 
-void pool_grow(Pool *pool, isize min_size) {
-	isize size = ALIGN_UP(gb_max(min_size, pool->block_size), pool->alignment);
-	pool->ptr = cast(u8 *)gb_alloc(pool->backing, size);
-	GB_ASSERT(pool->ptr == ALIGN_DOWN_PTR(pool->ptr, pool->alignment));
-	pool->end = pool->ptr + size;
-	array_add(&pool->blocks, pool->ptr);
+void arena_free_all(Arena *arena) {
+	gb_mutex_lock(&arena->mutex);
+	defer (gb_mutex_unlock(&arena->mutex));
+
+	for_array(i, arena->blocks) {
+        gb_free(arena->backing, arena->blocks[i]);
+    }
+    array_clear(&arena->blocks);
+    arena->ptr = nullptr;
+    arena->end = nullptr;
 }
 
-void *pool_alloc(Pool *pool, isize size, isize align) {
-	if (size > (pool->end - pool->ptr)) {
-		pool_grow(pool, size);
-		GB_ASSERT(size <= (pool->end - pool->ptr));
-	}
-	align = gb_max(align, pool->alignment);
-	void *ptr = pool->ptr;
-	pool->ptr = cast(u8 *)ALIGN_UP_PTR(pool->ptr + size, align);
-	GB_ASSERT(pool->ptr <= pool->end);
-	GB_ASSERT(ptr == ALIGN_DOWN_PTR(ptr, align));
-	return ptr;
-}
-
-GB_ALLOCATOR_PROC(pool_allocator_proc) {
-	void *ptr = nullptr;
-	Pool *pool = cast(Pool *)allocator_data;
 
 
-	switch (type) {
-	case gbAllocation_Alloc:
-		ptr = pool_alloc(pool, size, alignment);
-		break;
-	case gbAllocation_FreeAll:
-		pool_free_all(pool);
-		break;
 
-	case gbAllocation_Free:
-	case gbAllocation_Resize:
-		GB_PANIC("A pool allocator does not support free or resize");
-		break;
-	}
+GB_ALLOCATOR_PROC(arena_allocator_proc);
 
-	return ptr;
-}
-gbAllocator pool_allocator(Pool *pool) {
+gbAllocator arena_allocator(Arena *arena) {
 	gbAllocator a;
-	a.proc = pool_allocator_proc;
-	a.data = pool;
+	a.proc = arena_allocator_proc;
+	a.data = arena;
 	return a;
 }
 
 
-gb_global Pool global_pool = {};
+GB_ALLOCATOR_PROC(arena_allocator_proc) {
+	void *ptr = nullptr;
+	Arena *arena = cast(Arena *)allocator_data;
+	GB_ASSERT_NOT_NULL(arena);
 
-gbAllocator perm_allocator(void) {
-	return pool_allocator(&global_pool);
+	switch (type) {
+	case gbAllocation_Alloc:
+		ptr = arena_alloc(arena, size, alignment);
+		break;
+	case gbAllocation_Free:
+		GB_PANIC("gbAllocation_Free not supported");
+		break;
+	case gbAllocation_Resize:
+		GB_PANIC("gbAllocation_Resize: not supported");
+		break;
+	case gbAllocation_FreeAll:
+		arena_free_all(arena);
+		break;
+	}
+
+	return ptr;
 }
-#endif
-
-
 
 
 
diff --git a/src/integer128.cpp b/src/integer128.cpp
index 80f7e9cce..620ecb8a7 100644
--- a/src/integer128.cpp
+++ b/src/integer128.cpp
@@ -323,7 +323,7 @@ String u128_to_string(u128 v, char *out_buf, isize out_buf_len) {
 	buf[--i] = gb__num_to_char_table[u128_to_i64(u128_mod(v, b))];
 
 	isize len = gb_min(gb_size_of(buf)-i, out_buf_len);
-	gb_memcopy(out_buf, &buf[i], len);
+	gb_memmove(out_buf, &buf[i], len);
 	return make_string(cast(u8 *)out_buf, len);
 }
 String i128_to_string(i128 a, char *out_buf, isize out_buf_len) {
@@ -348,7 +348,7 @@ String i128_to_string(i128 a, char *out_buf, isize out_buf_len) {
 	}
 
 	isize len = gb_min(gb_size_of(buf)-i, out_buf_len);
-	gb_memcopy(out_buf, &buf[i], len);
+	gb_memmove(out_buf, &buf[i], len);
 	return make_string(cast(u8 *)out_buf, len);
 }
 
diff --git a/src/ir.cpp b/src/ir.cpp
index a2bb9808d..507cfd0fc 100644
--- a/src/ir.cpp
+++ b/src/ir.cpp
@@ -8550,7 +8550,7 @@ void ir_gen_tree(irGen *s) {
 		}
 		proc_type->Proc.abi_compat_result_type = proc_results->Tuple.variables[0]->type;
 
-		AstNode *body = gb_alloc_item(a, AstNode);
+		AstNode *body = alloc_ast_node(nullptr, AstNode_Invalid);
 		Entity *e = alloc_entity_procedure(nullptr, make_token_ident(name), proc_type, 0);
 		irValue *p = ir_value_procedure(a, m, e, proc_type, nullptr, body, name);
 
@@ -8628,7 +8628,7 @@ void ir_gen_tree(irGen *s) {
 		}
 		proc_type->Proc.abi_compat_result_type = proc_results->Tuple.variables[0]->type;
 
-		AstNode *body = gb_alloc_item(a, AstNode);
+		AstNode *body = alloc_ast_node(nullptr, AstNode_Invalid);
 		Entity *e     = alloc_entity_procedure(nullptr, make_token_ident(name), proc_type, 0);
 		irValue *p    = ir_value_procedure(a, m, e, proc_type, nullptr, body, name);
 
@@ -8692,7 +8692,7 @@ void ir_gen_tree(irGen *s) {
 		                                 proc_params, 4,
 		                                 proc_results, 1, false, ProcCC_Std);
 
-		AstNode *body = gb_alloc_item(a, AstNode);
+		AstNode *body = alloc_ast_node(nullptr, AstNode_Invalid);
 		Entity *e = alloc_entity_procedure(a, nullptr, make_token_ident(name), proc_type, 0);
 		irValue *p = ir_value_procedure(a, m, e, proc_type, nullptr, body, name);
 
@@ -8718,7 +8718,7 @@ void ir_gen_tree(irGen *s) {
 		                                  nullptr, 0,
 		                                  nullptr, 0, false,
 		                                  ProcCC_Contextless);
-		AstNode *body = gb_alloc_item(a, AstNode);
+		AstNode *body = alloc_ast_node(nullptr, AstNode_Invalid);
 		Entity *e = alloc_entity_procedure(nullptr, make_token_ident(name), proc_type, 0);
 		irValue *p = ir_value_procedure(a, m, e, proc_type, nullptr, body, name);
 
diff --git a/src/main.cpp b/src/main.cpp
index 1f8be7b91..749c4aae9 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -633,9 +633,9 @@ void remove_temp_files(String output_base) {
 	defer (array_free(&data));
 
 	isize n = output_base.len;
-	gb_memcopy(data.data, output_base.text, n);
+	gb_memmove(data.data, output_base.text, n);
 #define EXT_REMOVE(s) do {                         \
-		gb_memcopy(data.data+n, s, gb_size_of(s)); \
+		gb_memmove(data.data+n, s, gb_size_of(s)); \
 		gb_file_remove(cast(char *)data.data);     \
 	} while (0)
 	EXT_REMOVE(".ll");
@@ -718,6 +718,7 @@ int main(int arg_count, char **arg_ptr) {
 
 	init_string_buffer_memory();
 	init_global_error_collector();
+	arena_init(&global_ast_arena, heap_allocator());
 
 	array_init(&library_collections, heap_allocator());
 	// NOTE(bill): 'core' cannot be (re)defined by the user
diff --git a/src/parser.cpp b/src/parser.cpp
index 07996433a..75c9cfc75 100644
--- a/src/parser.cpp
+++ b/src/parser.cpp
@@ -113,7 +113,7 @@ AstNode *clone_ast_node(gbAllocator a, AstNode *node) {
 	if (node == nullptr) {
 		return nullptr;
 	}
-	AstNode *n = gb_alloc_item(a, AstNode);
+	AstNode *n = alloc_ast_node(node->file, node->kind);
 	gb_memmove(n, node, gb_size_of(AstNode));
 
 	switch (n->kind) {
@@ -422,12 +422,13 @@ bool ast_node_expect(AstNode *node, AstNodeKind kind) {
 
 // NOTE(bill): And this below is why is I/we need a new language! Discriminated unions are a pain in C/C++
 AstNode *alloc_ast_node(AstFile *f, AstNodeKind kind) {
-	gbArena *arena = &f->arena;
-	if (gb_arena_size_remaining(arena, GB_DEFAULT_MEMORY_ALIGNMENT) <= gb_size_of(AstNode)) {
-		// NOTE(bill): If a syntax error is so bad, just quit!
-		gb_exit(1);
-	}
-	AstNode *node = gb_alloc_item(gb_arena_allocator(arena), AstNode);
+	Arena *arena = &global_ast_arena;
+	gbAllocator a = arena_allocator(arena);
+	AstNode *node = gb_alloc_item(a, AstNode);
+	gb_mutex_lock(&arena->mutex);
+	defer (gb_mutex_unlock(&arena->mutex));
+	arena->possible_used += ALIGN_UP(24 + ast_node_sizes[kind], 8);
+
 	node->kind = kind;
 	node->file = f;
 	return node;
@@ -3865,10 +3866,6 @@ ParseFileError init_ast_file(AstFile *f, String fullpath, TokenPos *err_pos) {
 	f->prev_token = f->tokens[f->curr_token_index];
 	f->curr_token = f->tokens[f->curr_token_index];
 
-	// NOTE(bill): Is this big enough or too small?
-	isize arena_size = gb_size_of(AstNode);
-	arena_size *= 2*f->tokens.count;
-	gb_arena_init_from_allocator(&f->arena, heap_allocator(), arena_size);
 	array_init(&f->comments, heap_allocator());
 	array_init(&f->imports, heap_allocator());
 
@@ -3879,7 +3876,6 @@ ParseFileError init_ast_file(AstFile *f, String fullpath, TokenPos *err_pos) {
 
 void destroy_ast_file(AstFile *f) {
 	GB_ASSERT(f != nullptr);
-	gb_arena_free(&f->arena);
 	array_free(&f->tokens);
 	array_free(&f->comments);
 	array_free(&f->imports);
@@ -4197,10 +4193,8 @@ void parse_setup_file_decls(Parser *p, AstFile *f, String base_dir, Array<AstNod
 			if (node->kind == AstNode_ExprStmt) {
 				AstNode *expr = node->ExprStmt.expr;
 				if (expr->kind == AstNode_CallExpr &&
-				    expr->CallExpr.proc->kind == AstNode_BasicDirective &&
-				    expr->CallExpr.proc->BasicDirective.name == "assert") {
-
-					f->assert_decl_count += 1;
+				    expr->CallExpr.proc->kind == AstNode_BasicDirective) {
+					f->directive_count += 1;
 					continue;
 				}
 			}
@@ -4224,7 +4218,6 @@ void parse_setup_file_decls(Parser *p, AstFile *f, String base_dir, Array<AstNod
 			ast_node(fl, ForeignImportDecl, node);
 
 			String file_str = fl->filepath.string;
-			fl->base_dir = base_dir;
 			fl->fullpath = file_str;
 
 			if (fl->collection_name != "system") {
diff --git a/src/parser.hpp b/src/parser.hpp
index f15aad756..4428c67b6 100644
--- a/src/parser.hpp
+++ b/src/parser.hpp
@@ -54,7 +54,6 @@ struct AstFile {
 
 	AstNode *           pkg_decl;
 	String              fullpath;
-	gbArena             arena;
 	Tokenizer           tokenizer;
 	Array<Token>        tokens;
 	isize               curr_token_index;
@@ -74,7 +73,7 @@ struct AstFile {
 
 	Array<AstNode *>    decls;
 	Array<AstNode *>    imports; // 'import' 'using import'
-	isize               assert_decl_count;
+	isize               directive_count;
 
 
 	AstNode *           curr_proc;
@@ -388,7 +387,6 @@ AST_NODE_KIND(_DeclBegin,      "", struct {}) \
 		Token    token;           \
 		Token    filepath;        \
 		Token    library_name;    \
-		String   base_dir;        \
 		String   collection_name; \
 		String   fullpath;        \
 		CommentGroup docs;        \
@@ -505,10 +503,19 @@ String const ast_node_strings[] = {
 #undef AST_NODE_KIND
 };
 
+
 #define AST_NODE_KIND(_kind_name_, name, ...) typedef __VA_ARGS__ GB_JOIN2(AstNode, _kind_name_);
 	AST_NODE_KINDS
 #undef AST_NODE_KIND
 
+
+isize const ast_node_sizes[] = {
+	0,
+#define AST_NODE_KIND(_kind_name_, name, ...) gb_size_of(GB_JOIN2(AstNode, _kind_name_)),
+	AST_NODE_KINDS
+#undef AST_NODE_KIND
+};
+
 struct AstNode {
 	AstNodeKind kind;
 	u32         stmt_state_flags;
@@ -523,7 +530,9 @@ struct AstNode {
 };
 
 
-#define ast_node(n_, Kind_, node_) GB_JOIN2(AstNode, Kind_) *n_ = &(node_)->Kind_; GB_ASSERT((node_)->kind == GB_JOIN2(AstNode_, Kind_))
+#define ast_node(n_, Kind_, node_) GB_JOIN2(AstNode, Kind_) *n_ = &(node_)->Kind_; GB_ASSERT_MSG((node_)->kind == GB_JOIN2(AstNode_, Kind_), \
+	"expected '%.*s' got '%.*s'", \
+	LIT(ast_node_strings[GB_JOIN2(AstNode_, Kind_)]), LIT(ast_node_strings[(node_)->kind]))
 #define case_ast_node(n_, Kind_, node_) case GB_JOIN2(AstNode_, Kind_): { ast_node(n_, Kind_, node_);
 #ifndef case_end
 #define case_end } break;
@@ -549,4 +558,6 @@ gb_inline bool is_ast_node_when_stmt(AstNode *node) {
 	return node->kind == AstNode_WhenStmt;
 }
 
+gb_global Arena global_ast_arena = {};
 
+AstNode *alloc_ast_node(AstFile *f, AstNodeKind kind);
diff --git a/src/string.cpp b/src/string.cpp
index 96e17f58f..0db54d6df 100644
--- a/src/string.cpp
+++ b/src/string.cpp
@@ -96,7 +96,7 @@ String substring(String const &s, isize lo, isize hi) {
 
 char *alloc_cstring(gbAllocator a, String s) {
 	char *c_str = gb_alloc_array(a, char, s.len+1);
-	gb_memcopy(c_str, s.text, s.len);
+	gb_memmove(c_str, s.text, s.len);
 	c_str[s.len] = '\0';
 	return c_str;
 }