std.testing: allow print() at comptime

This allows functions like expectEqual to be performed at comptime. If
an error is detected, the result is logged via a compile error.

1 files changed, 7 insertions, 3 deletions

diff --git a/lib/std/testing.zig b/lib/std/testing.zig
index 4dda8a0d0d..d4d162721d 100644
--- a/lib/std/testing.zig
+++ b/lib/std/testing.zig
@@ -22,10 +22,14 @@ pub var base_allocator_instance = std.heap.FixedBufferAllocator.init("");
 pub var log_level = std.log.Level.warn;
 
 fn print(comptime fmt: []const u8, args: anytype) void {
-    // Disable printing in tests for simple backends.
-    if (builtin.zig_backend == .stage2_spirv64) return;
+    if (@inComptime()) {
+        @compileError(std.fmt.comptimePrint(fmt, args));
+    } else {
+        // Disable printing in tests for simple backends.
+        if (builtin.zig_backend == .stage2_spirv64) return;
 
-    std.debug.print(fmt, args);
+        std.debug.print(fmt, args);
+    }
 }
 
 /// This function is intended to be used only in tests. It prints diagnostics to stderr