Commit 92915a42b55f2916f36ed6b1a2d51363331f47f8 | zig

author	Kendall Condon <goon.pri.low@gmail.com> 2026-03-22 17:39:43-04:00
committer	Kendall Condon <goon.pri.low@gmail.com> 2026-03-25 17:30:51-04:00
log	92915a42b55f2916f36ed6b1a2d51363331f47f8
tree	39d42e8f5e65576285c49aeacbf5a2de9c8c2e70
parent	ab237855b8df3f91f232c7e63eba7d21f166f75f

zig fmt: do not reorder pointer casts with comments

This was especially bad as it could crash or duplicate them due to
them being moved around "zig fmt: on/off".

As a bonus this fixes a crash from reordering at the start of the file.

2 files changed, 46 insertions(+), 12 deletions(-)

lib
- std
  - zig
    Ast
    Render.zig
    parser_test.zig

lib/std/zig/Ast/Render.zig+25-12

 @@ -800,34 +800,47 @@ fn renderExpression(r: *Render, node: Ast.Node.Index, space: Space) Error!void {
             canonicalize: {
                 if (params.len != 1) break :canonicalize;
-                const CastKind = enum {
+                const CastKind = enum(u8) {
                     ptrCast,
                     alignCast,
                     addrSpaceCast,
                     constCast,
                     volatileCast,
                 };
-                const kind = meta.stringToEnum(CastKind, tree.tokenSlice(builtin_token)[1..]) orelse break :canonicalize;
+                const kind = meta.stringToEnum(
+                    CastKind,
+                    tree.tokenSlice(builtin_token)[1..],
+                ) orelse break :canonicalize;
                 var cast_map = std.EnumMap(CastKind, Ast.TokenIndex).init(.{});
                 cast_map.put(kind, builtin_token);
                 var casts_before: usize = 0;
-                if (builtin_token >= 2) {
+                var prev_builtin_token = builtin_token;
-                    var prev_builtin_token = builtin_token - 2;
+                while (prev_builtin_token >= 2) {
-                    while (tree.tokenTag(prev_builtin_token) == .builtin) : (prev_builtin_token -= 2) {
+                    prev_builtin_token -= 2;
-                        const prev_kind = meta.stringToEnum(CastKind, tree.tokenSlice(prev_builtin_token)[1..]) orelse break;
+                    if (tree.tokenTag(prev_builtin_token) != .builtin) break;
-                        if (cast_map.contains(prev_kind)) break :canonicalize;
+                    const builtin_name = tree.tokenSlice(prev_builtin_token)[1..];
-                        cast_map.put(prev_kind, prev_builtin_token);
+                    const prev_kind = meta.stringToEnum(CastKind, builtin_name) orelse break;
-                        casts_before += 1;
+                    if (cast_map.contains(prev_kind)) break :canonicalize;
-                    }
+                    // This must be checked after so that cast builtins as arguments to other
+                    // builtins containing comments are reordered.
+                    if (hasComment(tree, prev_builtin_token, prev_builtin_token + 2))
+                        break :canonicalize;
+                    cast_map.put(prev_kind, prev_builtin_token);
+                    casts_before += 1;
                 }
                 var next_builtin_token = builtin_token + 2;
-                while (tree.tokenTag(next_builtin_token) == .builtin) : (next_builtin_token += 2) {
+                while (true) {
-                    const next_kind = meta.stringToEnum(CastKind, tree.tokenSlice(next_builtin_token)[1..]) orelse break;
+                    if (hasComment(tree, next_builtin_token - 2, next_builtin_token))
+                        break :canonicalize;
+                    if (tree.tokenTag(next_builtin_token) != .builtin) break;
+                    const builtin_name = tree.tokenSlice(next_builtin_token)[1..];
+                    const next_kind = meta.stringToEnum(CastKind, builtin_name) orelse break;
                     if (cast_map.contains(next_kind)) break :canonicalize;
                     cast_map.put(next_kind, next_builtin_token);
+                    next_builtin_token += 2;
                 }
                 var it = cast_map.iterator();

lib/std/zig/parser_test.zig+21

...	@@ -6133,6 +6133,16 @@ test "zig fmt: do not canonicalize invalid cast builtins" {	...	@@ -6133,6 +6133,16 @@ test "zig fmt: do not canonicalize invalid cast builtins" {
6133	);	6133	);
6134	}	6134	}
6135		6135
		6136	test "zig fmt: canonicalize cast builtins at file start" {
		6137	try testTransform(
		6138	\\@alignCast(@ptrCast(a)),
		6139	\\
		6140	,
		6141	\\@ptrCast(@alignCast(a)),
		6142	\\
		6143	);
		6144	}
		6145
6136	test "zig fmt: extern addrspace in struct" {	6146	test "zig fmt: extern addrspace in struct" {
6137	try testCanonical(	6147	try testCanonical(
6138	\\const namespace = struct {	6148	\\const namespace = struct {
...	@@ -6909,6 +6919,17 @@ test "zig fmt: render extra colons with comments" {	...	@@ -6909,6 +6919,17 @@ test "zig fmt: render extra colons with comments" {
6909	);	6919	);
6910	}	6920	}
6911		6921
		6922	test "zig fmt: cast builtins are not reordered with comments" {
		6923	try testCanonical(
		6924	\\const a = @volatileCast(@constCast( // ...
		6925	\\ @alignCast(@ptrCast(a))));
		6926	\\
		6927	\\const b = @alignCast(@ptrCast( // zig fmt: off
		6928	\\ c));
		6929	\\
		6930	);
		6931	}
		6932
6912	test "recovery: top level" {	6933	test "recovery: top level" {
6913	try testError(	6934	try testError(
6914	\\test "" {inline}	6935	\\test "" {inline}