Add build gate for nonzero signed integers so rustc <1.34 still works

serde/build.rs

@@ -69,11 +69,12 @@ fn main() {
         println!("cargo:rustc-cfg=num_nonzero");
     }
 
-    // TryFrom and Atomic types stabilized in Rust 1.34:
+    // TryFrom, Atomic types, and non-zero signed integers stabilized in Rust 1.34:
     // https://blog.rust-lang.org/2019/04/11/Rust-1.34.0.html#tryfrom-and-tryinto
     // https://blog.rust-lang.org/2019/04/11/Rust-1.34.0.html#library-stabilizations
     if minor >= 34 {
         println!("cargo:rustc-cfg=core_try_from");
+        println!("cargo:rustc-cfg=num_nonzero_signed");
 
         // Whitelist of archs that support std::sync::atomic module. Ideally we
         // would use #[cfg(target_has_atomic = "...")] but it is not stable yet.

serde/src/de/impls.rs

@@ -2409,6 +2409,10 @@ nonzero_integers! {
     NonZeroU32,
     NonZeroU64,
     NonZeroUsize,
+}
+
+#[cfg(num_nonzero_signed)]
+nonzero_integers! {
     NonZeroI8,
     NonZeroI16,
     NonZeroI32,
@@ -2421,6 +2425,10 @@ nonzero_integers! {
 serde_if_integer128! {
     nonzero_integers! {
         NonZeroU128,
+    }
+
+    #[cfg(num_nonzero_signed)]
+    nonzero_integers! {
         NonZeroI128,
     }
 }

serde/src/ser/impls.rs

@@ -486,6 +486,10 @@ nonzero_integers! {
     NonZeroU32,
     NonZeroU64,
     NonZeroUsize,
+}
+
+#[cfg(num_nonzero_signed)]
+nonzero_integers! {
     NonZeroI8,
     NonZeroI16,
     NonZeroI32,
@@ -498,6 +502,10 @@ nonzero_integers! {
 serde_if_integer128! {
     nonzero_integers! {
         NonZeroU128,
+    }
+
+    #[cfg(num_nonzero_signed)]
+    nonzero_integers! {
         NonZeroI128,
     }
 }