Fix in nested block handling. @maydiscard and @nodiscard annotations. If the common type of int[x] and int[y] is int[]

lib/std/core/mem_allocator.c3

@@ -208,14 +208,14 @@ fn void DynamicArenaAllocator.destroy(DynamicArenaAllocator* this)
 	while (page)
 	{
 		DynamicArenaPage* next_page = page.prev_arena;
-		this.backing_allocator.free(page);
+		this.backing_allocator.free(page)!!;
 		page = next_page;
 	}
 	page = this.unused_page;
 	while (page)
 	{
 		DynamicArenaPage* next_page = page.prev_arena;
-		this.backing_allocator.free(page);
+		this.backing_allocator.free(page)!!;
 		page = next_page;
 	}
 	this.page = null;
@@ -297,7 +297,7 @@ private fn void*! DynamicArenaAllocator.alloc_new(DynamicArenaAllocator* this, u
 	DynamicArenaPage*! page = this.backing_allocator.alloc(DynamicArenaPage.sizeof);
 	if (catch err = page)
 	{
-		this.backing_allocator.free(mem);
+		this.backing_allocator.free(mem)?;
 		return err!;
 	}
     page.memory = mem;

lib/std/core/string.c3

@@ -196,7 +196,7 @@ fn void String.destroy(String* str)
 	if (!*str) return;
 	StringData* data = str.data();
 	if (!data) return;
-	data.allocator.free(data);
+	data.allocator.free(data)!!;
 	*str = (String)null;
 }
 

lib/std/io_printf.c3

@@ -542,7 +542,7 @@ private fn void! etoa(PrintParam* param, FloatType value)
 	if (minwidth)
 	{
 		// output the exponential symbol
-		param.out(param.flags.uppercase ? 'E' : 'e');
+		param.out(param.flags.uppercase ? 'E' : 'e')?;
 		// output the exponent value
 		param.flags = { .zeropad = true, .plus = true };
 		param.width = minwidth - 1;
@@ -653,7 +653,7 @@ private fn NtoaType int_from_variant(variant arg, bool *is_neg)
 }
 
 
-fn usize! printf(char[] format, args...)
+fn usize! printf(char[] format, args...) @maydiscard
 {
   return vsnprintf(&out_putchar_fn, " ", format, args);
 }

src/compiler/compiler_internal.h

@@ -458,6 +458,8 @@ typedef struct
 		bool attr_noinline : 1;
 		bool attr_extname : 1;
 		bool attr_naked : 1;
+		bool attr_nodiscard : 1;
+		bool attr_maydiscard: 1;
 	};
 	TypeInfoId type_parent;
 	FunctionSignature function_signature;
@@ -498,6 +500,8 @@ typedef struct
 	struct
 	{
 		bool attr_noreturn : 1;
+		bool attr_nodiscard : 1;
+		bool attr_maydiscard : 1;
 	};
 	TypeInfoId type_parent; // May be 0
 	TypeInfoId rtype; // May be 0
@@ -687,6 +691,7 @@ typedef struct
 	bool is_builtin : 1;
 	bool is_func_ref : 1;
 	bool attr_pure : 1;
+	bool result_unused : 1;
 	AstId body;
 	union
 	{
@@ -808,16 +813,27 @@ typedef struct
 } ExprBodyExpansion;
 
 
+typedef struct
+{
+	void *block_return_exit;
+	void *block_failable_exit;
+	void *block_error_var;
+	void *block_return_out;
+} BlockExit;
+
 typedef struct
 {
 	AstId first_stmt;
+	BlockExit **block_exit_ref;
 } ExprFuncBlock;
 
+
 typedef struct
 {
 	AstId first_stmt;
 	Expr **args;
 	Decl **params;
+	BlockExit **block_exit;
 } ExprMacroBlock;
 
 
@@ -982,6 +998,7 @@ typedef struct
 {
 	Expr *expr; // May be NULL
 	AstId cleanup;
+	BlockExit** block_exit_ref; // For block exits
 } AstReturnStmt;
 
 typedef struct
@@ -1412,6 +1429,7 @@ typedef struct SemaContext_
 		uint32_t original_inline_line;
 		Decl **yield_params;
 		Ast *yield_body;
+		BlockExit** block_exit_ref;
 		Type *expected_block_type;
 		Ast **returns;
 		// Reusable returns cache.

src/compiler/enums.h

@@ -701,6 +701,8 @@ typedef enum
 	ATTRIBUTE_OPERATOR,
 	ATTRIBUTE_PURE,
 	ATTRIBUTE_REFLECT,
+	ATTRIBUTE_MAYDISCARD,
+	ATTRIBUTE_NODISCARD,
 	ATTRIBUTE_NONE,
 	NUMBER_OF_ATTRIBUTES = ATTRIBUTE_NONE,
 } AttributeType;

src/compiler/linker.c

@@ -65,6 +65,20 @@ static void linker_setup_windows(const char ***args_ref, LinkerType linker_type)
 {
 	if (linker_type == LINKER_CC) return;
 	//add_arg("/MACHINE:X64");
+	switch (active_target.debug_info)
+	{
+		case DEBUG_INFO_NOT_SET:
+			break;
+		case DEBUG_INFO_NONE:
+			add_arg("/DEBUG:NONE");
+			break;
+		case DEBUG_INFO_LINE_TABLES:
+		case DEBUG_INFO_FULL:
+			add_arg("/DEBUG:FULL");
+			break;
+		default:
+			UNREACHABLE
+	}
 	if (active_target.win.sdk)
 	{
 		add_arg(str_printf("/LIBPATH:%s", active_target.win.sdk));

src/compiler/llvm_codegen_expr.c

@@ -4943,7 +4943,7 @@ static inline void gencontext_emit_expression_list_expr(GenContext *context, BEV
 	}
 }
 
-static inline void llvm_emit_return_block(GenContext *context, BEValue *be_value, Type *type, AstId current)
+static inline void llvm_emit_return_block(GenContext *context, BEValue *be_value, Type *type, AstId current, BlockExit **block_exit)
 {
 	// First case - an empty block
 	if (!current)
@@ -4954,25 +4954,26 @@ static inline void llvm_emit_return_block(GenContext *context, BEValue *be_value
 
 	Type *type_lowered = type_lowering(type);
 	LLVMValueRef old_ret_out = context->return_out;
-	LLVMBasicBlockRef saved_block_return_exit = context->block_return_exit;
-	LLVMBasicBlockRef saved_block_failable_exit = context->block_failable_exit;
-	LLVMValueRef saved_block_error = context->block_error_var;
 	context->in_block++;
 
-	LLVMBasicBlockRef expr_block = llvm_basic_block_new(context, "expr_block.exit");
-	context->block_return_exit = expr_block;
-
-	LLVMValueRef return_out = NULL;
 	LLVMValueRef error_out = context->error_var;
 	LLVMBasicBlockRef error_block = context->catch_block;
+	LLVMValueRef return_out = NULL;
+	LLVMBasicBlockRef expr_block = llvm_basic_block_new(context, "expr_block.exit");
+
+	BlockExit exit = {
+			.block_return_exit = expr_block,
+			.block_failable_exit = error_block,
+			.block_error_var = error_out,
+			.block_return_out = NULL,
+	};
+
+	*block_exit= &exit;
 
 	if (type_no_fail(type_lowered) != type_void)
 	{
-		return_out = llvm_emit_alloca_aligned(context, type_lowered, "blockret");
+		exit.block_return_out = llvm_emit_alloca_aligned(context, type_lowered, "blockret");
 	}
-	context->block_error_var = error_out;
-	context->block_failable_exit = error_block;
-	context->return_out = return_out;
 	context->error_var = NULL;
 	context->catch_block = NULL;
 
@@ -5013,7 +5014,7 @@ static inline void llvm_emit_return_block(GenContext *context, BEValue *be_value
 		// Optimization, emit directly to value
 		llvm_emit_expr(context, be_value, ret_expr);
 		// And remove the alloca
-		LLVMInstructionEraseFromParent(context->return_out);
+		LLVMInstructionEraseFromParent(exit.block_return_out);
 		goto DONE;
 
 	} while (0);
@@ -5034,9 +5035,9 @@ static inline void llvm_emit_return_block(GenContext *context, BEValue *be_value
 	// Emit the exit block.
 	llvm_emit_block(context, expr_block);
 
-	if (return_out)
+	if (exit.block_return_out)
 	{
-		llvm_value_set_address_abi_aligned(be_value, return_out, type_lowered);
+		llvm_value_set_address_abi_aligned(be_value, exit.block_return_out, type_lowered);
 	}
 	else
 	{
@@ -5047,16 +5048,13 @@ DONE:
 	context->return_out = old_ret_out;
 	context->catch_block = error_block;
 	context->error_var = error_out;
-	context->block_return_exit = saved_block_return_exit;
-	context->block_failable_exit = saved_block_failable_exit;
-	context->block_error_var = saved_block_error;
 	context->in_block--;
 
 }
 
 static inline void llvm_emit_expr_block(GenContext *context, BEValue *be_value, Expr *expr)
 {
-	llvm_emit_return_block(context, be_value, expr->type, expr->expr_block.first_stmt);
+	llvm_emit_return_block(context, be_value, expr->type, expr->expr_block.first_stmt, expr->expr_block.block_exit_ref);
 }
 
 static inline void llvm_emit_macro_block(GenContext *context, BEValue *be_value, Expr *expr)
@@ -5098,7 +5096,8 @@ static inline void llvm_emit_macro_block(GenContext *context, BEValue *be_value,
 		llvm_emit_expr(context, &value, expr->macro_block.args[i]);
 		llvm_store_decl_raw(context, decl, llvm_load_value_store(context, &value));
 	}
-	llvm_emit_return_block(context, be_value, expr->type, expr->macro_block.first_stmt);
+
+	llvm_emit_return_block(context, be_value, expr->type, expr->macro_block.first_stmt, expr->macro_block.block_exit);
 }
 
 LLVMValueRef llvm_emit_call_intrinsic(GenContext *context, unsigned intrinsic, LLVMTypeRef *types, unsigned type_count,

src/compiler/llvm_codegen_function.c

@@ -437,7 +437,6 @@ void llvm_emit_function_body(GenContext *c, Decl *decl)
 	LLVMBasicBlockRef entry = LLVMAppendBasicBlockInContext(c->context, c->function, "entry");
 	c->current_block = entry;
 	c->current_block_is_target = true;
-	c->block_return_exit = NULL;
 	c->in_block = 0;
 	c->builder = LLVMCreateBuilderInContext(c->context);
 	LLVMPositionBuilderAtEnd(c->builder, entry);

src/compiler/llvm_codegen_internal.h

@@ -99,9 +99,6 @@ typedef struct
 	Module *code_module;
 	LLVMValueRef return_out;
 	LLVMValueRef failable_out;
-	LLVMBasicBlockRef block_return_exit;
-	LLVMBasicBlockRef block_failable_exit;
-	LLVMValueRef block_error_var;
 	BEValue retval;
 	int in_block;
 	bool current_block_is_target : 1;

src/compiler/llvm_codegen_stmt.c

@@ -228,8 +228,9 @@ static inline void llvm_emit_block_exit_return(GenContext *c, Ast *ast)
 
 	LLVMBasicBlockRef error_return_block = NULL;
 	LLVMValueRef error_out = NULL;
-	c->error_var = c->block_error_var;
+	BlockExit *exit = *ast->return_stmt.block_exit_ref;
-	c->catch_block = c->block_failable_exit;
+	c->error_var = exit->block_error_var;
+	c->catch_block = exit->block_failable_exit;
 
 	LLVMBasicBlockRef err_cleanup_block = NULL;
 	Expr *ret_expr = ast->return_stmt.expr;
@@ -250,21 +251,21 @@ static inline void llvm_emit_block_exit_return(GenContext *c, Ast *ast)
 	POP_ERROR();
 
 	llvm_emit_statement_chain(c, ast->return_stmt.cleanup);
-	if (c->return_out && return_value.value)
+	if (exit->block_return_out && return_value.value)
 	{
-		llvm_store_value_aligned(c, c->return_out, &return_value, type_alloca_alignment(return_value.type));
+		llvm_store_value_aligned(c, exit->block_return_out, &return_value, type_alloca_alignment(return_value.type));
 	}
 
 	if (err_cleanup_block)
 	{
-		llvm_emit_br(c, c->block_return_exit);
+		llvm_emit_br(c, exit->block_return_exit);
 		llvm_emit_block(c, err_cleanup_block);
 		llvm_emit_statement_chain(c, ast->return_stmt.cleanup);
-		llvm_emit_jmp(c, c->block_failable_exit);
+		llvm_emit_jmp(c, exit->block_failable_exit);
 	}
 	else
 	{
-		llvm_emit_jmp(c, c->block_return_exit);
+		llvm_emit_jmp(c, exit->block_return_exit);
 	}
 }
 

src/compiler/sema_decls.c

@@ -1163,6 +1163,8 @@ static bool sema_analyse_attribute(SemaContext *context, Decl *decl, Attr *attr,
 			                    ATTR_MEMBER,
 			[ATTRIBUTE_INLINE] = ATTR_FUNC | ATTR_CALL,
 			[ATTRIBUTE_NOINLINE] = ATTR_FUNC | ATTR_CALL,
+			[ATTRIBUTE_NODISCARD] = ATTR_FUNC | ATTR_MACRO,
+			[ATTRIBUTE_MAYDISCARD] = ATTR_FUNC | ATTR_MACRO,
 			[ATTRIBUTE_BIGENDIAN] = ATTR_BITSTRUCT,
 			[ATTRIBUTE_LITTLEENDIAN] = ATTR_BITSTRUCT,
 			[ATTRIBUTE_USED] = (AttributeDomain)~ATTR_CALL,
@@ -1340,6 +1342,22 @@ static bool sema_analyse_attribute(SemaContext *context, Decl *decl, Attr *attr,
 			decl->func_decl.attr_noinline = true;
 			decl->func_decl.attr_inline = false;
 			break;
+		case ATTRIBUTE_NODISCARD:
+			if (domain == ATTR_MACRO)
+			{
+				decl->macro_decl.attr_nodiscard = true;
+				break;
+			}
+			decl->func_decl.attr_nodiscard = true;
+			break;
+		case ATTRIBUTE_MAYDISCARD:
+			if (domain == ATTR_MACRO)
+			{
+				decl->macro_decl.attr_maydiscard = true;
+				break;
+			}
+			decl->func_decl.attr_maydiscard = true;
+			break;
 		case ATTRIBUTE_INLINE:
 			decl->func_decl.attr_inline = true;
 			decl->func_decl.attr_noinline = false;
@@ -1689,9 +1707,27 @@ static inline bool sema_analyse_func(SemaContext *context, Decl *decl)
 	if (!sema_analyse_attributes(context, decl, decl->attributes, ATTR_FUNC)) return decl_poison(decl);
 
 	Type *func_type = sema_analyse_function_signature(context, decl->func_decl.function_signature.abi, &decl->func_decl.function_signature, true);
-	
 	decl->type = func_type;
 	if (!func_type) return decl_poison(decl);
+	TypeInfo *rtype_info = type_infoptr(decl->func_decl.function_signature.returntype);
+	assert(rtype_info);
+	Type *rtype = rtype_info->type->canonical;
+	if (decl->func_decl.attr_nodiscard)
+	{
+		if (rtype == type_void)
+		{
+			SEMA_ERROR(rtype_info, "@nodiscard cannot be used on functions returning 'void'.");
+			return decl_poison(decl);
+		}
+	}
+	if (decl->func_decl.attr_maydiscard)
+	{
+		if (!type_is_failable(rtype))
+		{
+			SEMA_ERROR(rtype_info, "@maydiscard can only be used on functions returning optional values.");
+			return decl_poison(decl);
+		}
+	}
 	if (decl->func_decl.type_parent)
 	{
 		if (!sema_analyse_method(context, decl)) return decl_poison(decl);
@@ -1749,9 +1785,28 @@ static inline bool sema_analyse_macro(SemaContext *context, Decl *decl)
 
 	if (!sema_analyse_attributes(context, decl, decl->attributes, ATTR_MACRO)) return decl_poison(decl);
 
-
+	if (decl->macro_decl.rtype)
-	TypeInfo *rtype = type_infoptr(decl->macro_decl.rtype);
+	{
-	if (decl->macro_decl.rtype && !sema_resolve_type_info(context, rtype)) return decl_poison(decl);
+		TypeInfo *rtype_info = type_infoptr(decl->macro_decl.rtype);
+		if (!sema_resolve_type_info(context, rtype_info)) return decl_poison(decl);
+		Type *rtype = rtype_info->type;
+		if (decl->macro_decl.attr_nodiscard)
+		{
+			if (rtype == type_void)
+			{
+				SEMA_ERROR(rtype_info, "@nodiscard cannot be used on macros returning 'void'.");
+				return decl_poison(decl);
+			}
+		}
+		if (decl->macro_decl.attr_maydiscard)
+		{
+			if (!type_is_failable(rtype))
+			{
+				SEMA_ERROR(rtype_info, "@maydiscard can only be used on macros returning optional values.");
+				return decl_poison(decl);
+			}
+		}
+	}
 	decl->macro_decl.unit = context->unit;
 	Decl **parameters = decl->macro_decl.parameters;
 	unsigned param_count = vec_size(parameters);

src/compiler/sema_expr.c

@@ -1611,10 +1611,26 @@ static inline bool sema_expr_analyse_func_invocation(SemaContext *context, Funct
 		SEMA_ERROR(expr, "Only '@pure' functions may be called, you can override this with an attribute.");
 		return false;
 	}
+
+	bool is_unused = expr->call_expr.result_unused;
 	if (!sema_expr_analyse_call_invocation(context, expr, callee, &failable)) return false;
 
 	Type *rtype = prototype->rtype;
 
+	if (is_unused && rtype != type_void && decl && decl->decl_kind == DECL_FUNC)
+	{
+		if (decl->func_decl.attr_nodiscard)
+		{
+			SEMA_ERROR(expr, "The result of the function must be used.");
+			return false;
+		}
+		if (type_is_failable(rtype) && !decl->func_decl.attr_maydiscard)
+		{
+			SEMA_ERROR(expr, "The optional result of the macro must be used.");
+			return false;
+		}
+	}
+
 	expr->type = type_get_opt_fail(rtype, failable);
 
 	return true;
@@ -1882,6 +1898,9 @@ bool sema_expr_analyse_macro_call(SemaContext *context, Expr *call_expr, Expr *s
 	macro_context.yield_context = context;
 	macro_context.original_inline_line = context->original_inline_line ? context->original_inline_line : call_expr->span.row;
 
+	BlockExit** block_exit_ref = MALLOCS(BlockExit*);
+	macro_context.block_exit_ref = block_exit_ref;
+
 	VECEACH(params, i)
 	{
 		Decl *param = params[i];
@@ -1944,7 +1963,32 @@ bool sema_expr_analyse_macro_call(SemaContext *context, Expr *call_expr, Expr *s
 		if (!sum_returns) return SCOPE_POP_ERROR();
 		call_expr->type = type_get_opt_fail(sum_returns, failable);
 	}
-	if (vec_size(macro_context.returns) == 1)
+
+	if (call_expr->call_expr.result_unused)
+	{
+		Type *type = call_expr->type;
+		if (type != type_void)
+		{
+			if (decl->macro_decl.attr_nodiscard)
+			{
+				SEMA_ERROR(call_expr, "The result of the macro must be used.");
+				return SCOPE_POP_ERROR();
+			}
+			if (type_is_failable(type) && !decl->macro_decl.attr_maydiscard)
+			{
+				SEMA_ERROR(call_expr, "The optional result of the macro must be used.");
+				return SCOPE_POP_ERROR();
+			}
+		}
+	}
+	unsigned returns_found = vec_size(macro_context.returns);
+	// We may have zero normal macro returns but the active scope still has a "jump end".
+	// In this case it is triggered by the @body()
+	if (!returns_found && macro_context.active_scope.jump_end)
+	{
+		is_no_return = true;
+	}
+	if (returns_found == 1)
 	{
 		Ast *ret = macro_context.returns[0];
 		Expr *result = ret ? ret->return_stmt.expr : NULL;
@@ -1962,6 +2006,7 @@ bool sema_expr_analyse_macro_call(SemaContext *context, Expr *call_expr, Expr *s
 	call_expr->macro_block.first_stmt = body->compound_stmt.first_stmt;
 	call_expr->macro_block.params = params;
 	call_expr->macro_block.args = args;
+	call_expr->macro_block.block_exit = block_exit_ref;
 EXIT:
 	assert(context->active_scope.defer_last == context->active_scope.defer_start);
 	context->active_scope = old_scope;
@@ -2107,7 +2152,6 @@ static bool sema_analyse_body_expansion(SemaContext *macro_context, Expr *call)
 	SemaContext *context = macro_context->yield_context;
 	Decl **params = macro_context->yield_params;
 
-
 	Expr *func_expr = exprptr(call_expr->function);
 	assert(func_expr->expr_kind == EXPR_MACRO_BODY_EXPANSION);
 	expr_replace(call, func_expr);
@@ -2115,6 +2159,7 @@ static bool sema_analyse_body_expansion(SemaContext *macro_context, Expr *call)
 	call->body_expansion_expr.declarations = macro_context->yield_params;
 	AstId last_defer = context->active_scope.defer_last;
 	bool success;
+	bool ends_in_jump;
 	SCOPE_START
 
 		if (macro_defer)
@@ -2133,15 +2178,20 @@ static bool sema_analyse_body_expansion(SemaContext *macro_context, Expr *call)
 			Decl *param = params[i];
 			if (!sema_add_local(context, param)) return SCOPE_POP_ERROR();
 		}
-		call->body_expansion_expr.ast = ast_macro_copy(macro_context->yield_body);
+		Ast *ast = call->body_expansion_expr.ast = ast_macro_copy(macro_context->yield_body);
-		success = sema_analyse_statement(context, call->body_expansion_expr.ast);
+		success = sema_analyse_statement(context, ast);
-
+		assert(ast->ast_kind == AST_COMPOUND_STMT);
+		if (context->active_scope.jump_end)
+		{
+			macro_context->active_scope.jump_end = true;
+		}
 		if (first_defer)
 		{
 			first_defer->defer_stmt.prev_defer = 0;
 			context->active_scope.defer_last = last_defer;
 		}
 	SCOPE_END;
+
 	return success;
 }
 
@@ -3473,6 +3523,7 @@ static inline bool sema_expr_analyse_access(SemaContext *context, Expr *expr)
 		if (parent->expr_kind != EXPR_TYPEINFO)
 		{
 			SEMA_ERROR(expr, "'typeid' can only be used with types, not values");
+			return false;
 		}
 
 		expr->type = type_typeid;
@@ -6439,6 +6490,10 @@ static inline bool sema_expr_analyse_expr_block(SemaContext *context, Type *infe
 	Ast **saved_returns = context_push_returns(context);
 	Type *stored_block_type = context->expected_block_type;
 	context->expected_block_type = infer_type;
+	BlockExit **ref = MALLOCS(BlockExit*);
+	BlockExit **stored_block_exit = context->block_exit_ref;
+	context->block_exit_ref = ref;
+	expr->expr_block.block_exit_ref = ref;
 	SCOPE_START_WITH_FLAGS(SCOPE_EXPR_BLOCK)
 
 		context->block_return_defer = context->active_scope.defer_last;
@@ -6487,6 +6542,7 @@ static inline bool sema_expr_analyse_expr_block(SemaContext *context, Type *infe
 		context_pop_defers(context, &stmt->next);
 	SCOPE_END;
 	context->expected_block_type = stored_block_type;
+	context->block_exit_ref = stored_block_exit;
 	context_pop_returns(context, saved_returns);
 
 	return success;

src/compiler/sema_stmts.c

@@ -126,6 +126,7 @@ static inline bool sema_analyse_block_exit_stmt(SemaContext *context, Ast *state
 			return false;
 		}
 	}
+	statement->return_stmt.block_exit_ref = context->block_exit_ref;
 	statement->return_stmt.cleanup = context_get_defers(context, context->active_scope.defer_last, context->block_return_defer);
 	vec_add(context->returns, statement);
 	return true;
@@ -706,10 +707,28 @@ static inline bool sema_analyse_declare_stmt(SemaContext *context, Ast *statemen
 	return sema_analyse_var_decl(context, statement->declare_stmt, true);
 }
 
+static inline bool expr_is_assign(Expr *expr)
+{
+	switch (expr->expr_kind)
+	{
+		case EXPR_DECL:
+		case EXPR_BITASSIGN:
+		case EXPR_SLICE_ASSIGN:
+			return true;
+		case EXPR_BINARY:
+			return expr->binary_expr.operator >= BINARYOP_ASSIGN;
+		default:
+			return false;
+	}
+}
 static inline bool sema_analyse_expr_stmt(SemaContext *context, Ast *statement)
 {
-	if (!sema_analyse_expr(context, statement->expr_stmt)) return false;
+	Expr *expr = statement->expr_stmt;
-	return true;
+	if (expr->expr_kind == EXPR_CALL)
+	{
+		expr->call_expr.result_unused = true;
+	}
+	return sema_analyse_expr(context, expr);
 }
 
 bool sema_analyse_defer_stmt_body(SemaContext *context, Ast *statement, Ast *body)

src/compiler/symtab.c

@@ -230,6 +230,8 @@ void symtab_init(uint32_t capacity)
 	attribute_list[ATTRIBUTE_PURE] = kw_at_pure;
 	attribute_list[ATTRIBUTE_REFLECT] = KW_DEF("@reflect");
 	attribute_list[ATTRIBUTE_AUTOIMPORT] = KW_DEF("@autoimport");
+	attribute_list[ATTRIBUTE_MAYDISCARD] = KW_DEF("@maydiscard");
+	attribute_list[ATTRIBUTE_NODISCARD] = KW_DEF("@nodiscard");
 
 	for (unsigned i = 0; i < NUMBER_OF_ATTRIBUTES; i++)
 	{

src/compiler/types.c

@@ -1501,6 +1501,14 @@ Type *type_find_max_type(Type *type, Type *other)
 				{
 					return other;
 				}
+				if (other->type_kind == TYPE_POINTER)
+				{
+					Type *other_pointer = other->pointer;
+					if (other_pointer->type_kind == TYPE_ARRAY && other_pointer->array.base->canonical == array_base)
+					{
+						return type_get_subarray(array_base);
+					}
+				}
 			}
 			if (type->pointer->type_kind == TYPE_VECTOR)
 			{

test/test_suite/errors/error_regression_2.c3t

@@ -17,7 +17,7 @@ fn void Summary.print(Summary *s, CFile out)
 	// We don't have a native printf in C3 yet, so use libc,
 	// which is not all that nice for the strings but...
 	char[] title = s.title ? *s.title : "missing";
-	libc::fprintf(out, "Summary({ .title = %.*s, .ok = %s})", (int)title.len, title.ptr, s.ok ? "true" : "false");
+	libc::fprintf(out, "Summary({ .title = %.*s, .ok = %s})", (int)title.len, title.ptr, s.ok ? (char*)"true" : (char*)"false");
 }
 
 fn bool contains(char[] haystack, char[] needle)
@@ -144,7 +144,7 @@ fn void main()
         bool! has_title = readWhetherTitleNonEmpty(url);
         // This looks a bit less than elegant, but as you see it's mostly due to having to
         // use printf here.
-        libc::printf("  Has title: %s vs %s\n", bool_to_string(has_title) ?? nameFromError(catch(has_title)), (has_title ?? false) ? "true" : "false");
+        libc::printf("  Has title: %s vs %s\n", bool_to_string(has_title) ?? nameFromError(catch(has_title)), (has_title ?? false) ? (char*)"true" : (char*)"false");
     }
 }
 
@@ -757,8 +757,9 @@ err_retblock:                                     ; preds = %error3, %error
 define i8* @test.bool_to_string(i8 zeroext %0) #0 {
 entry:
   %1 = trunc i8 %0 to i1
-  %ternary = select i1 %1, i8* getelementptr inbounds ([5 x i8], [5 x i8]* @.str.7, i32 0, i32 0), i8* getelementptr inbounds ([6 x i8], [6 x i8]* @.str.8, i32 0, i32 0)
+  %ternary = select i1 %1, %"char[]" { i8* getelementptr inbounds ([5 x i8], [5 x i8]* @.str.7, i32 0, i32 0), i64 4 }, %"char[]" { i8* getelementptr inbounds ([6 x i8], [6 x i8]* @.str.8, i32 0, i32 0), i64 5 }
-  ret i8* %ternary
+  %2 = extractvalue %"char[]" %ternary, 0
+  ret i8* %2
 }
 
 ; Function Attrs: nounwind

test/test_suite/errors/failable_inits.c3t

@@ -13,13 +13,13 @@ struct Bar
     int x;
 }
 
-fn void! test1()
+fn void! test1() @maydiscard
 {
     Bar! x = Foo.MY_VAL1!;
     Bar y = x?;
 }
 
-fn void! test2()
+fn void! test2() @maydiscard
 {
     Bar! x = {};
     Bar y = x?;

test/test_suite/macros/macro_body_defer.c3t

@@ -87,17 +87,17 @@ loop.exit:                                        ; preds = %loop.body
   br label %loop.body2
 
 loop.body2:                                       ; preds = %loop.exit
-  call void (i8*, ...) @printf(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str.13, i32 0, i32 0))
+  call void (i8*, ...) @printf(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str.10, i32 0, i32 0))
   store i32 3, i32* %i3, align 4
-  call void (i8*, ...) @printf(i8* getelementptr inbounds ([5 x i8], [5 x i8]* @.str.14, i32 0, i32 0))
+  call void (i8*, ...) @printf(i8* getelementptr inbounds ([5 x i8], [5 x i8]* @.str.11, i32 0, i32 0))
-  call void (i8*, ...) @printf(i8* getelementptr inbounds ([22 x i8], [22 x i8]* @.str.15, i32 0, i32 0))
+  call void (i8*, ...) @printf(i8* getelementptr inbounds ([22 x i8], [22 x i8]* @.str.12, i32 0, i32 0))
   %3 = load i32, i32* %i3, align 4
-  call void (i8*, ...) @printf(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str.16, i32 0, i32 0), i32 %3)
+  call void (i8*, ...) @printf(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str.13, i32 0, i32 0), i32 %3)
-  call void (i8*, ...) @printf(i8* getelementptr inbounds ([10 x i8], [10 x i8]* @.str.17, i32 0, i32 0))
+  call void (i8*, ...) @printf(i8* getelementptr inbounds ([10 x i8], [10 x i8]* @.str.14, i32 0, i32 0))
   ret i64 0
 
 loop.exit4:                                       ; No predecessors!
-  call void (i8*, ...) @printf(i8* getelementptr inbounds ([18 x i8], [18 x i8]* @.str.21, i32 0, i32 0))
+  call void (i8*, ...) @printf(i8* getelementptr inbounds ([18 x i8], [18 x i8]* @.str.15, i32 0, i32 0))
   ret i64 0
 }
 

test/test_suite2/errors/failable_inits.c3t

@@ -13,13 +13,13 @@ struct Bar
     int x;
 }
 
-fn void! test1()
+fn void! test1() @maydiscard
 {
     Bar! x = Foo.MY_VAL1!;
     Bar y = x?;
 }
 
-fn void! test2()
+fn void! test2() @maydiscard
 {
     Bar! x = {};
     Bar y = x?;

test/test_suite2/macros/macro_body_defer.c3t

@@ -87,17 +87,17 @@ loop.exit:                                        ; preds = %loop.body
   br label %loop.body2
 
 loop.body2:                                       ; preds = %loop.exit
-  call void (ptr, ...) @printf(ptr @.str.13)
+  call void (ptr, ...) @printf(ptr @.str.10)
   store i32 3, ptr %i3, align 4
-  call void (ptr, ...) @printf(ptr @.str.14)
+  call void (ptr, ...) @printf(ptr @.str.11)
-  call void (ptr, ...) @printf(ptr @.str.15)
+  call void (ptr, ...) @printf(ptr @.str.12)
   %3 = load i32, ptr %i3, align 4
-  call void (ptr, ...) @printf(ptr @.str.16, i32 %3)
+  call void (ptr, ...) @printf(ptr @.str.13, i32 %3)
-  call void (ptr, ...) @printf(ptr @.str.17)
+  call void (ptr, ...) @printf(ptr @.str.14)
   ret i64 0
 
 loop.exit4:                                       ; No predecessors!
-  call void (ptr, ...) @printf(ptr @.str.21)
+  call void (ptr, ...) @printf(ptr @.str.15)
   ret i64 0
 }