build.rs: Minor tweaks.

This uses the import of `std::env` in more places to shorten code
and fixes some things pointed out by clippy.

Also, since a const was only used in a single function, move it
inside that function.

z3-sys/build.rs

@@ -1,8 +1,5 @@
 use std::env;
 
-#[cfg(not(feature = "vcpkg"))]
-const Z3_HEADER_VAR: &str = "Z3_SYS_Z3_HEADER";
-
 fn main() {
  // Feature `vcpkg` is prior to `static-link-z3` as vcpkg-installed z3 is also statically linked.
 
@@ -47,7 +44,7 @@ fn link_against_cxx_stdlib() {
 
  println!("cargo:rerun-if-env-changed=CXXSTDLIB");
  if let Some(cxx) = cxx {
- println!("cargo:rustc-link-lib={}", cxx);
+ println!("cargo:rustc-link-lib={cxx}");
  }
 }
 
@@ -57,7 +54,7 @@ fn find_library_header_by_vcpkg() -> String {
  .emit_includes(true)
  .find_package("z3")
  .unwrap();
- for include in lib.include_paths.iter() {
+ for include in &lib.include_paths {
  let mut include = include.clone();
  include.push("z3.h");
  if include.exists() {
@@ -71,20 +68,21 @@ fn find_library_header_by_vcpkg() -> String {
 
 #[cfg(not(feature = "vcpkg"))]
 fn find_header_by_env() -> String {
+ const Z3_HEADER_VAR: &str = "Z3_SYS_Z3_HEADER";
  let header = if cfg!(feature = "static-link-z3") {
  "z3/src/api/z3.h".to_string()
- } else if let Ok(header_path) = std::env::var(Z3_HEADER_VAR) {
+ } else if let Ok(header_path) = env::var(Z3_HEADER_VAR) {
  header_path
  } else {
  "wrapper.h".to_string()
  };
- println!("cargo:rerun-if-env-changed={}", Z3_HEADER_VAR);
- println!("cargo:rerun-if-changed={}", header);
+ println!("cargo:rerun-if-env-changed={Z3_HEADER_VAR}");
+ println!("cargo:rerun-if-changed={header}");
  header
 }
 
 fn generate_binding(header: &str) {
- let out_path = std::path::PathBuf::from(std::env::var("OUT_DIR").unwrap());
+ let out_path = std::path::PathBuf::from(env::var("OUT_DIR").unwrap());
 
  for x in &[
  "ast_kind",
@@ -152,10 +150,7 @@ fn build_bundled_z3() {
  let full_lib_dir = dst.join(lib_dir);
  if full_lib_dir.exists() {
  if *lib_dir == "lib64" {
- assert_eq!(
- std::env::var("CARGO_CFG_TARGET_POINTER_WIDTH").unwrap(),
- "64"
- );
+ assert_eq!(env::var("CARGO_CFG_TARGET_POINTER_WIDTH").unwrap(), "64");
  }
  println!("cargo:rustc-link-search=native={}", full_lib_dir.display());
  found_lib_dir = true;