std.fmt: breaking API changes

added adapter to AnyWriter and GenericWriter to help bridge the gap
between old and new API

make std.testing.expectFmt work at compile-time

std.fmt no longer has a dependency on std.unicode. Formatted printing
was never properly unicode-aware. Now it no longer pretends to be.

Breakage/deprecations:
* std.fs.File.reader -> std.fs.File.deprecatedReader
* std.fs.File.writer -> std.fs.File.deprecatedWriter
* std.io.GenericReader -> std.io.Reader
* std.io.GenericWriter -> std.io.Writer
* std.io.AnyReader -> std.io.Reader
* std.io.AnyWriter -> std.io.Writer
* std.fmt.format -> std.fmt.deprecatedFormat
* std.fmt.fmtSliceEscapeLower -> std.ascii.hexEscape
* std.fmt.fmtSliceEscapeUpper -> std.ascii.hexEscape
* std.fmt.fmtSliceHexLower -> {x}
* std.fmt.fmtSliceHexUpper -> {X}
* std.fmt.fmtIntSizeDec -> {B}
* std.fmt.fmtIntSizeBin -> {Bi}
* std.fmt.fmtDuration -> {D}
* std.fmt.fmtDurationSigned -> {D}
* {} -> {f} when there is a format method
* format method signature
  - anytype -> *std.io.Writer
  - inferred error set -> error{WriteFailed}
  - options -> (deleted)
* std.fmt.Formatted
  - now takes context type explicitly
  - no fmt string

1 files changed, 11 insertions, 16 deletions

diff --git a/lib/std/Target.zig b/lib/std/Target.zig
index c3b37abb7e..91eed5fee9 100644
--- a/lib/std/Target.zig
+++ b/lib/std/Target.zig
@@ -301,29 +301,24 @@ pub const Os = struct {
 
         /// This function is defined to serialize a Zig source code representation of this
         /// type, that, when parsed, will deserialize into the same data.
-        pub fn format(
-            ver: WindowsVersion,
-            comptime fmt_str: []const u8,
-            _: std.fmt.FormatOptions,
-            writer: anytype,
-        ) @TypeOf(writer).Error!void {
+        pub fn format(ver: WindowsVersion, w: *std.io.Writer, comptime f: []const u8) std.io.Writer.Error!void {
             const maybe_name = std.enums.tagName(WindowsVersion, ver);
-            if (comptime std.mem.eql(u8, fmt_str, "s")) {
+            if (comptime std.mem.eql(u8, f, "s")) {
                 if (maybe_name) |name|
-                    try writer.print(".{s}", .{name})
+                    try w.print(".{s}", .{name})
                 else
-                    try writer.print(".{d}", .{@intFromEnum(ver)});
-            } else if (comptime std.mem.eql(u8, fmt_str, "c")) {
+                    try w.print(".{d}", .{@intFromEnum(ver)});
+            } else if (comptime std.mem.eql(u8, f, "c")) {
                 if (maybe_name) |name|
-                    try writer.print(".{s}", .{name})
+                    try w.print(".{s}", .{name})
                 else
-                    try writer.print("@enumFromInt(0x{X:0>8})", .{@intFromEnum(ver)});
-            } else if (fmt_str.len == 0) {
+                    try w.print("@enumFromInt(0x{X:0>8})", .{@intFromEnum(ver)});
+            } else if (f.len == 0) {
                 if (maybe_name) |name|
-                    try writer.print("WindowsVersion.{s}", .{name})
+                    try w.print("WindowsVersion.{s}", .{name})
                 else
-                    try writer.print("WindowsVersion(0x{X:0>8})", .{@intFromEnum(ver)});
-            } else std.fmt.invalidFmtError(fmt_str, ver);
+                    try w.print("WindowsVersion(0x{X:0>8})", .{@intFromEnum(ver)});
+            } else std.fmt.invalidFmtError(f, ver);
         }
     };