Fix compilation when only the `serde-serialize` feature of nalgebra is enabled.

.github/workflows/nalgebra-ci-build.yml

@@ -34,6 +34,8 @@ jobs:
       run: cargo build --no-default-features;
     - name: Build (default features)
       run: cargo build;
+    - name: Build --features serde-serialize
+      run: cargo build --features serde-serialize
     - name: Build --all-features
       run: cargo build --all-features;
     - name: Build nalgebra-glm

Cargo.toml

@@ -23,10 +23,10 @@ path = "src/lib.rs"
 
 [features]
 default         = [ "std" ]
-std             = [ "matrixmultiply", "simba/std" ]
+std             = [ "matrixmultiply", "simba/std", "serde/std" ]
 sparse = [ ]
 debug = [ "approx/num-complex", "rand" ]
-alloc = [ ]
+alloc = [ "serde/alloc" ]
 io = [ "pest", "pest_derive" ]
 compare = [ "matrixcompare-core" ]
 libm = [ "simba/libm" ]