Move trybuild_no_target logic to where --target is set

src/cargo.rs

@@ -123,8 +123,24 @@ fn features(project: &Project) -> Vec<String> {
 }
 
 fn target() -> Vec<&'static str> {
-    match crate::TARGET {
-        Some(target) => vec!["--target", target],
-        None => vec![],
+    // When --target flag is passed, cargo does not pass RUSTFLAGS to rustc when
+    // building proc-macro and build script even if the host and target triples
+    // are the same. Therefore, if we always pass --target to cargo, tools such
+    // as coverage that require RUSTFLAGS do not work for tests run by trybuild.
+    //
+    // To avoid that problem, do not pass --target to cargo if we know that it
+    // has not been passed.
+    //
+    // Currently, cargo does not have a way to tell the build script whether
+    // --target has been passed or not, and there is no heuristic that can
+    // handle this well.
+    //
+    // Therefore, expose a cfg to always treat the target as host.
+    if cfg!(trybuild_no_target) {
+        vec![]
+    } else if let Some(target) = crate::TARGET {
+        vec!["--target", target]
+    } else {
+        vec![]
     }
 }

src/lib.rs

@@ -245,22 +245,6 @@ mod normalize;
 mod run;
 mod rustflags;
 
-// When --target flag is passed, cargo does not pass RUSTFLAGS to rustc when
-// building proc-macro and build script even if the host and target triples are
-// the same. Therefore, if we always pass --target to cargo, tools such as
-// coverage that require RUSTFLAGS do not work for tests run by trybuild.
-//
-// To avoid that problem, do not pass --target to cargo if we know that it has
-// not been passed.
-//
-// Currently, cargo does not have a way to tell the build script whether
-// --target has been passed or not, and there is no heuristic that can handle
-// this well.
-//
-// Therefore, expose a cfg to always treat the target as host.
-#[cfg(trybuild_no_target)]
-const TARGET: Option<&str> = None;
-#[cfg(not(trybuild_no_target))]
 include!(concat!(env!("OUT_DIR"), "/target.rs"));
 
 use std::cell::RefCell;