mkDummySrc: fix handling of bin targets

* First, bin targets go into `src/bin` not `bin`
* Second, the path fallback name needs a `rs` suffix

lib/mkDummySrc.nix

@@ -53,7 +53,7 @@ let
   safeStubList = attr: defaultPath:
     let
       targetList = trimmedCargoToml.${attr} or [ ];
-      paths = map (t: t.path or "${defaultPath}/${t.name}") targetList;
+      paths = map (t: t.path or "${defaultPath}/${t.name}.rs") targetList;
       commands = map cpDummy paths;
     in
     concatStringsSep "\n" commands;
@@ -73,7 +73,7 @@ runCommand name { } ''
   # Stub all other targets in case they have particular feature combinations
   ${safeStubLib}
   ${safeStubList "bench" "benches"}
-  ${safeStubList "bin" "bin"}
+  ${safeStubList "bin" "src/bin"}
   ${safeStubList "example" "examples"}
   ${safeStubList "test" "tests"}
 ''

tests/default.nix

@@ -41,6 +41,10 @@ pkgs.lib.makeScope myLib.newScope (self:
         touch $out
       '';
 
+    depsOnlyVariousTargets = myLib.buildDepsOnly {
+      src = ./various-targets;
+    };
+
     simple = myLib.buildWithCargo {
       doCopyTargetToOutput = false;
       src = ./simple;

tests/various-targets/Cargo.lock

@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "various-targets"
+version = "0.1.0"

tests/various-targets/Cargo.toml

@@ -0,0 +1,28 @@
+[package]
+name = "various-targets"
+version = "0.1.0"
+edition = "2021"
+
+[[bench]]
+name = "foo"
+
+[[bench]]
+name = "bar"
+
+[[bin]]
+name = "baz"
+
+[[bin]]
+name = "qux"
+
+[[example]]
+name = "zuul"
+
+[[example]]
+name = "corge"
+
+[[test]]
+name = "grault"
+
+[[test]]
+name = "garply"

tests/various-targets/benches/bar.rs

@@ -0,0 +1,4 @@
+#[test]
+fn foo() {
+}
+

tests/various-targets/benches/foo.rs

@@ -0,0 +1,4 @@
+#[test]
+fn foo() {
+}
+

tests/various-targets/examples/corge.rs

@@ -0,0 +1,4 @@
+fn main() {
+    println!("Hello, world!");
+}
+

tests/various-targets/examples/zuul.rs

@@ -0,0 +1,4 @@
+fn main() {
+    println!("Hello, world!");
+}
+

tests/various-targets/src/bin/baz.rs

@@ -0,0 +1,2 @@
+pub fn main() {
+}

tests/various-targets/src/bin/qux.rs

@@ -0,0 +1,3 @@
+pub fn main() {
+    println!("hello world");
+}