Merge pull request #21264 from mlugg/decl-literals

compiler: implement decl literals

lib/std/array_hash_map.zig

@@ -510,6 +510,8 @@ pub fn ArrayHashMap(
 /// `store_hash` is `false` and the number of entries in the map is less than 9,
 /// the overhead cost of using `ArrayHashMapUnmanaged` rather than `std.ArrayList` is
 /// only a single pointer-sized integer.
+///
+/// Default initialization of this struct is deprecated; use `.empty` instead.
 pub fn ArrayHashMapUnmanaged(
     comptime K: type,
     comptime V: type,
@@ -538,6 +540,12 @@ pub fn ArrayHashMapUnmanaged(
         /// Used to detect memory safety violations.
         pointer_stability: std.debug.SafetyLock = .{},
 
+        /// A map containing no keys or values.
+        pub const empty: Self = .{
+            .entries = .{},
+            .index_header = null,
+        };
+
         /// Modifying the key is allowed only if it does not change the hash.
         /// Modifying the value is allowed.
         /// Entry pointers become invalid whenever this ArrayHashMap is modified,

lib/std/array_list.zig

@@ -618,6 +618,8 @@ pub fn ArrayListUnmanaged(comptime T: type) type {
 /// Functions that potentially allocate memory accept an `Allocator` parameter.
 /// Initialize directly or with `initCapacity`, and deinitialize with `deinit`
 /// or use `toOwnedSlice`.
+///
+/// Default initialization of this struct is deprecated; use `.empty` instead.
 pub fn ArrayListAlignedUnmanaged(comptime T: type, comptime alignment: ?u29) type {
     if (alignment) |a| {
         if (a == @alignOf(T)) {
@@ -638,6 +640,12 @@ pub fn ArrayListAlignedUnmanaged(comptime T: type, comptime alignment: ?u29) typ
         /// additional memory.
         capacity: usize = 0,
 
+        /// An ArrayList containing no elements.
+        pub const empty: Self = .{
+            .items = &.{},
+            .capacity = 0,
+        };
+
         pub const Slice = if (alignment) |a| ([]align(a) T) else []T;
 
         pub fn SentinelSlice(comptime s: T) type {

lib/std/hash_map.zig

@@ -721,6 +721,8 @@ pub fn HashMap(
 /// the price of handling size with u32, which should be reasonable enough
 /// for almost all uses.
 /// Deletions are achieved with tombstones.
+///
+/// Default initialization of this struct is deprecated; use `.empty` instead.
 pub fn HashMapUnmanaged(
     comptime K: type,
     comptime V: type,
@@ -762,6 +764,13 @@ pub fn HashMapUnmanaged(
         /// Capacity of the first grow when bootstrapping the hashmap.
         const minimal_capacity = 8;
 
+        /// A map containing no keys or values.
+        pub const empty: Self = .{
+            .metadata = null,
+            .size = 0,
+            .available = 0,
+        };
+
         // This hashmap is specially designed for sizes that fit in a u32.
         pub const Size = u32;
 

lib/std/heap/general_purpose_allocator.zig

@@ -157,6 +157,7 @@ pub const Config = struct {
 
 pub const Check = enum { ok, leak };
 
+/// Default initialization of this struct is deprecated; use `.init` instead.
 pub fn GeneralPurposeAllocator(comptime config: Config) type {
     return struct {
         backing_allocator: Allocator = std.heap.page_allocator,
@@ -174,6 +175,16 @@ pub fn GeneralPurposeAllocator(comptime config: Config) type {
 
         const Self = @This();
 
+        /// The initial state of a `GeneralPurposeAllocator`, containing no allocations and backed by the system page allocator.
+        pub const init: Self = .{
+            .backing_allocator = std.heap.page_allocator,
+            .buckets = [1]Buckets{.{}} ** small_bucket_count,
+            .cur_buckets = [1]?*BucketHeader{null} ** small_bucket_count,
+            .large_allocations = .{},
+            .empty_buckets = if (config.retain_metadata) .{} else {},
+            .bucket_node_pool = .init(std.heap.page_allocator),
+        };
+
         const total_requested_bytes_init = if (config.enable_memory_limit) @as(usize, 0) else {};
         const requested_memory_limit_init = if (config.enable_memory_limit) @as(usize, math.maxInt(usize)) else {};
 

lib/std/zig/AstGen.zig

@@ -1028,7 +1028,18 @@ fn expr(gz: *GenZir, scope: *Scope, ri: ResultInfo, node: Ast.Node.Index) InnerE
             const statements = tree.extra_data[node_datas[node].lhs..node_datas[node].rhs];
             return blockExpr(gz, scope, ri, node, statements, .normal);
         },
-        .enum_literal => return simpleStrTok(gz, ri, main_tokens[node], node, .enum_literal),
+        .enum_literal => if (try ri.rl.resultType(gz, node)) |res_ty| {
+            const str_index = try astgen.identAsString(main_tokens[node]);
+            const res = try gz.addPlNode(.decl_literal, node, Zir.Inst.Field{
+                .lhs = res_ty,
+                .field_name_start = str_index,
+            });
+            switch (ri.rl) {
+                .discard, .none, .ref => unreachable, // no result type
+                .ty, .coerced_ty => return res, // `decl_literal` does the coercion for us
+                .ref_coerced_ty, .ptr, .inferred_ptr, .destructure => return rvalue(gz, ri, res, node),
+            }
+        } else return simpleStrTok(gz, ri, main_tokens[node], node, .enum_literal),
         .error_value => return simpleStrTok(gz, ri, node_datas[node].rhs, node, .error_value),
         // TODO restore this when implementing https://github.com/ziglang/zig/issues/6025
         // .anyframe_literal => return rvalue(gz, ri, .anyframe_type, node),
@@ -2752,6 +2763,8 @@ fn addEnsureResult(gz: *GenZir, maybe_unused_result: Zir.Inst.Ref, statement: As
             .err_union_code_ptr,
             .ptr_type,
             .enum_literal,
+            .decl_literal,
+            .decl_literal_no_coerce,
             .merge_error_sets,
             .error_union_type,
             .bit_not,
@@ -2914,6 +2927,8 @@ fn addEnsureResult(gz: *GenZir, maybe_unused_result: Zir.Inst.Ref, statement: As
             .validate_array_init_result_ty,
             .validate_ptr_array_init,
             .validate_ref_ty,
+            .try_operand_ty,
+            .try_ref_operand_ty,
             => break :b true,
 
             .@"defer" => unreachable,
@@ -5887,13 +5902,21 @@ fn tryExpr(
     }
     const try_lc = LineColumn{ astgen.source_line - parent_gz.decl_line, astgen.source_column };
 
-    const operand_ri: ResultInfo = switch (ri.rl) {
-        .ref, .ref_coerced_ty => .{ .rl = .ref, .ctx = .error_handling_expr },
-        else => .{ .rl = .none, .ctx = .error_handling_expr },
+    const operand_rl: ResultInfo.Loc, const block_tag: Zir.Inst.Tag = switch (ri.rl) {
+        .ref => .{ .ref, .try_ptr },
+        .ref_coerced_ty => |payload_ptr_ty| .{
+            .{ .ref_coerced_ty = try parent_gz.addUnNode(.try_ref_operand_ty, payload_ptr_ty, node) },
+            .try_ptr,
+        },
+        else => if (try ri.rl.resultType(parent_gz, node)) |payload_ty| .{
+            // `coerced_ty` is OK due to the `rvalue` call below
+            .{ .coerced_ty = try parent_gz.addUnNode(.try_operand_ty, payload_ty, node) },
+            .@"try",
+        } else .{ .none, .@"try" },
     };
+    const operand_ri: ResultInfo = .{ .rl = operand_rl, .ctx = .error_handling_expr };
     // This could be a pointer or value depending on the `ri` parameter.
     const operand = try reachableExpr(parent_gz, scope, operand_ri, operand_node, node);
-    const block_tag: Zir.Inst.Tag = if (operand_ri.rl == .ref) .try_ptr else .@"try";
     const try_inst = try parent_gz.makeBlockInst(block_tag, node);
     try parent_gz.instructions.append(astgen.gpa, try_inst);
 
@@ -9905,7 +9928,7 @@ fn callExpr(
 ) InnerError!Zir.Inst.Ref {
     const astgen = gz.astgen;
 
-    const callee = try calleeExpr(gz, scope, call.ast.fn_expr);
+    const callee = try calleeExpr(gz, scope, ri.rl, call.ast.fn_expr);
     const modifier: std.builtin.CallModifier = blk: {
         if (gz.is_comptime) {
             break :blk .compile_time;
@@ -10033,6 +10056,7 @@ const Callee = union(enum) {
 fn calleeExpr(
     gz: *GenZir,
     scope: *Scope,
+    call_rl: ResultInfo.Loc,
     node: Ast.Node.Index,
 ) InnerError!Callee {
     const astgen = gz.astgen;
@@ -10059,6 +10083,19 @@ fn calleeExpr(
                 .field_name_start = str_index,
             } };
         },
+        .enum_literal => if (try call_rl.resultType(gz, node)) |res_ty| {
+            // Decl literal call syntax, e.g.
+            // `const foo: T = .init();`
+            // Look up `init` in `T`, but don't try and coerce it.
+            const str_index = try astgen.identAsString(tree.nodes.items(.main_token)[node]);
+            const callee = try gz.addPlNode(.decl_literal_no_coerce, node, Zir.Inst.Field{
+                .lhs = res_ty,
+                .field_name_start = str_index,
+            });
+            return .{ .direct = callee };
+        } else {
+            return .{ .direct = try expr(gz, scope, .{ .rl = .none }, node) };
+        },
         else => return .{ .direct = try expr(gz, scope, .{ .rl = .none }, node) },
     }
 }

lib/std/zig/Zir.zig

@@ -651,6 +651,14 @@ pub const Inst = struct {
         err_union_code_ptr,
         /// An enum literal. Uses the `str_tok` union field.
         enum_literal,
+        /// A decl literal. This is similar to `field`, but unwraps error unions and optionals,
+        /// and coerces the result to the given type.
+        /// Uses the `pl_node` union field. Payload is `Field`.
+        decl_literal,
+        /// The same as `decl_literal`, but the coercion is omitted. This is used for decl literal
+        /// function call syntax, i.e. `.foo()`.
+        /// Uses the `pl_node` union field. Payload is `Field`.
+        decl_literal_no_coerce,
         /// A switch expression. Uses the `pl_node` union field.
         /// AST node is the switch, payload is `SwitchBlock`.
         switch_block,
@@ -684,6 +692,14 @@ pub const Inst = struct {
         /// operator. Emit a compile error if not.
         /// Uses the `un_tok` union field. Token is the `&` operator. Operand is the type.
         validate_ref_ty,
+        /// Given a type `T`, construct the type `E!T`, where `E` is this function's error set, to be used
+        /// as the result type of a `try` operand. Generic poison is propagated.
+        /// Uses the `un_node` union field. Node is the `try` expression. Operand is the type `T`.
+        try_operand_ty,
+        /// Given a type `*T`, construct the type `*E!T`, where `E` is this function's error set, to be used
+        /// as the result type of a `try` operand whose address is taken with `&`. Generic poison is propagated.
+        /// Uses the `un_node` union field. Node is the `try` expression. Operand is the type `*T`.
+        try_ref_operand_ty,
 
         // The following tags all relate to struct initialization expressions.
 
@@ -1136,6 +1152,8 @@ pub const Inst = struct {
                 .err_union_code_ptr,
                 .ptr_type,
                 .enum_literal,
+                .decl_literal,
+                .decl_literal_no_coerce,
                 .merge_error_sets,
                 .error_union_type,
                 .bit_not,
@@ -1254,6 +1272,8 @@ pub const Inst = struct {
                 .array_init_elem_type,
                 .array_init_elem_ptr,
                 .validate_ref_ty,
+                .try_operand_ty,
+                .try_ref_operand_ty,
                 .restore_err_ret_index_unconditional,
                 .restore_err_ret_index_fn_entry,
                 => false,
@@ -1324,6 +1344,8 @@ pub const Inst = struct {
                 .validate_array_init_result_ty,
                 .validate_ptr_array_init,
                 .validate_ref_ty,
+                .try_operand_ty,
+                .try_ref_operand_ty,
                 => true,
 
                 .param,
@@ -1430,6 +1452,8 @@ pub const Inst = struct {
                 .err_union_code_ptr,
                 .ptr_type,
                 .enum_literal,
+                .decl_literal,
+                .decl_literal_no_coerce,
                 .merge_error_sets,
                 .error_union_type,
                 .bit_not,
@@ -1685,6 +1709,8 @@ pub const Inst = struct {
                 .err_union_code = .un_node,
                 .err_union_code_ptr = .un_node,
                 .enum_literal = .str_tok,
+                .decl_literal = .pl_node,
+                .decl_literal_no_coerce = .pl_node,
                 .switch_block = .pl_node,
                 .switch_block_ref = .pl_node,
                 .switch_block_err_union = .pl_node,
@@ -1698,6 +1724,8 @@ pub const Inst = struct {
                 .opt_eu_base_ptr_init = .un_node,
                 .coerce_ptr_elem_ty = .pl_node,
                 .validate_ref_ty = .un_tok,
+                .try_operand_ty = .un_node,
+                .try_ref_operand_ty = .un_node,
 
                 .int_from_ptr = .un_node,
                 .compile_error = .un_node,
@@ -3828,12 +3856,16 @@ fn findDeclsInner(
         .err_union_code,
         .err_union_code_ptr,
         .enum_literal,
+        .decl_literal,
+        .decl_literal_no_coerce,
         .validate_deref,
         .validate_destructure,
         .field_type_ref,
         .opt_eu_base_ptr_init,
         .coerce_ptr_elem_ty,
         .validate_ref_ty,
+        .try_operand_ty,
+        .try_ref_operand_ty,
         .struct_init_empty,
         .struct_init_empty_result,
         .struct_init_empty_ref_result,