compiler: remove anonymous struct types, unify all tuples

This commit reworks how anonymous struct literals and tuples work.

Previously, an untyped anonymous struct literal
(e.g. `const x = .{ .a = 123 }`) was given an "anonymous struct type",
which is a special kind of struct which coerces using structural
equivalence. This mechanism was a holdover from before we used
RLS / result types as the primary mechanism of type inference. This
commit changes the language so that the type assigned here is a "normal"
struct type. It uses a form of equivalence based on the AST node and the
type's structure, much like a reified (`@Type`) type.

Additionally, tuples have been simplified. The distinction between
"simple" and "complex" tuple types is eliminated. All tuples, even those
explicitly declared using `struct { ... }` syntax, use structural
equivalence, and do not undergo staged type resolution. Tuples are very
restricted: they cannot have non-`auto` layouts, cannot have aligned
fields, and cannot have default values with the exception of `comptime`
fields. Tuples currently do not have optimized layout, but this can be
changed in the future.

This change simplifies the language, and fixes some problematic
coercions through pointers which led to unintuitive behavior.

Resolves: #16865

Author: mlugg

lib/compiler/aro/aro/Builtins.zig

@@ -157,7 +157,7 @@ fn createType(desc: TypeDescription, it: *TypeDescription.TypeIterator, comp: *c
                 .len = element_count,
                 .elem = child_ty,
             };
-            const vector_ty = .{ .specifier = .vector, .data = .{ .array = arr_ty } };
+            const vector_ty: Type = .{ .specifier = .vector, .data = .{ .array = arr_ty } };
             builder.specifier = Type.Builder.fromType(vector_ty);
         },
         .q => {

lib/compiler/aro/aro/Parser.zig

@@ -8095,7 +8095,7 @@ fn primaryExpr(p: *Parser) Error!Result {
 
 fn makePredefinedIdentifier(p: *Parser, strings_top: usize) !Result {
     const end: u32 = @intCast(p.strings.items.len);
-    const elem_ty = .{ .specifier = .char, .qual = .{ .@"const" = true } };
+    const elem_ty: Type = .{ .specifier = .char, .qual = .{ .@"const" = true } };
     const arr_ty = try p.arena.create(Type.Array);
     arr_ty.* = .{ .elem = elem_ty, .len = end - strings_top };
     const ty: Type = .{ .specifier = .array, .data = .{ .array = arr_ty } };

lib/compiler/aro/aro/text_literal.zig

@@ -188,7 +188,7 @@ pub const Parser = struct {
     pub fn err(self: *Parser, tag: Diagnostics.Tag, extra: Diagnostics.Message.Extra) void {
         if (self.errored) return;
         self.errored = true;
-        const diagnostic = .{ .tag = tag, .extra = extra };
+        const diagnostic: CharDiagnostic = .{ .tag = tag, .extra = extra };
         if (self.errors_len == self.errors_buffer.len) {
             self.errors_buffer[self.errors_buffer.len - 1] = diagnostic;
         } else {

lib/compiler/aro_translate_c.zig

@@ -749,7 +749,7 @@ fn transType(c: *Context, scope: *Scope, raw_ty: Type, qual_handling: Type.QualH
             const is_const = is_fn_proto or child_type.isConst();
             const is_volatile = child_type.qual.@"volatile";
             const elem_type = try transType(c, scope, child_type, qual_handling, source_loc);
-            const ptr_info = .{
+            const ptr_info: @FieldType(ast.Payload.Pointer, "data") = .{
                 .is_const = is_const,
                 .is_volatile = is_volatile,
                 .elem_type = elem_type,

lib/compiler/test_runner.zig

@@ -6,7 +6,7 @@ const io = std.io;
 const testing = std.testing;
 const assert = std.debug.assert;
 
-pub const std_options = .{
+pub const std_options: std.Options = .{
     .logFn = log,
 };
 

lib/std/SemanticVersion.zig

@@ -299,7 +299,7 @@ test "precedence" {
 
 test "zig_version" {
     // An approximate Zig build that predates this test.
-    const older_version = .{ .major = 0, .minor = 8, .patch = 0, .pre = "dev.874" };
+    const older_version: Version = .{ .major = 0, .minor = 8, .patch = 0, .pre = "dev.874" };
 
     // Simulated compatibility check using Zig version.
     const compatible = comptime @import("builtin").zig_version.order(older_version) == .gt;

lib/std/Target.zig

@@ -509,7 +509,7 @@ pub const Os = struct {
                             .max = .{ .major = 6, .minor = 10, .patch = 3 },
                         },
                         .glibc = blk: {
-                            const default_min = .{ .major = 2, .minor = 28, .patch = 0 };
+                            const default_min: std.SemanticVersion = .{ .major = 2, .minor = 28, .patch = 0 };
 
                             for (std.zig.target.available_libcs) |libc| {
                                 // We don't know the ABI here. We can get away with not checking it

lib/std/array_list.zig

@@ -100,7 +100,7 @@ pub fn ArrayListAligned(comptime T: type, comptime alignment: ?u29) type {
         /// of this ArrayList. Empties this ArrayList.
         pub fn moveToUnmanaged(self: *Self) ArrayListAlignedUnmanaged(T, alignment) {
             const allocator = self.allocator;
-            const result = .{ .items = self.items, .capacity = self.capacity };
+            const result: ArrayListAlignedUnmanaged(T, alignment) = .{ .items = self.items, .capacity = self.capacity };
             self.* = init(allocator);
             return result;
         }

lib/std/crypto/phc_encoding.zig

@@ -258,8 +258,7 @@ fn kvSplit(str: []const u8) !struct { key: []const u8, value: []const u8 } {
     var it = mem.splitScalar(u8, str, kv_delimiter_scalar);
     const key = it.first();
     const value = it.next() orelse return Error.InvalidEncoding;
-    const ret = .{ .key = key, .value = value };
-    return ret;
+    return .{ .key = key, .value = value };
 }
 
 test "phc format - encoding/decoding" {

lib/std/meta.zig

@@ -1018,7 +1018,7 @@ fn CreateUniqueTuple(comptime N: comptime_int, comptime types: [N]type) type {
             .type = T,
             .default_value = null,
             .is_comptime = false,
-            .alignment = if (@sizeOf(T) > 0) @alignOf(T) else 0,
+            .alignment = 0,
         };
     }