build-support/rustc-wrapper: use explicit substitution instead of substituteAll

The use of substituteAll is to be avoided and this fixes the wrapper
when structuredAttrs are enabled.

pkgs/build-support/rust/rustc-wrapper/default.nix

@@ -3,38 +3,38 @@
   runCommand,
   rustc-unwrapped,
   sysroot ? null,
+  stdenvNoCC,
+  shell ? stdenvNoCC.shell,
 }:
+let
+  sysrootFlag = lib.optionalString (sysroot != null) "--sysroot ${sysroot}";
 
+  # Upstream rustc still assumes that musl = static[1].  The fix for
+  # this is to disable crt-static by default for non-static musl
+  # targets.
+  #
+  # Even though Cargo will build build.rs files for the build platform,
+  # cross-compiling _from_ musl appears to work fine, so we only need
+  # to do this when rustc's target platform is dynamically linked musl.
+  #
+  # [1]: https://github.com/rust-lang/compiler-team/issues/422
+  #
+  # WARNING: using defaultArgs is dangerous, as it will apply to all
+  # targets used by this compiler (host and target).  This means
+  # that it can't be used to set arguments that should only be
+  # applied to the target.  It's fine to do this for -crt-static,
+  # because rustc does not support +crt-static host platforms
+  # anyway.
+  defaultArgs = lib.optionalString (
+    with rustc-unwrapped.stdenv.targetPlatform; isMusl && !isStatic
+  ) "-C target-feature=-crt-static";
+in
 runCommand "${rustc-unwrapped.pname}-wrapper-${rustc-unwrapped.version}"
   {
     preferLocalBuild = true;
     strictDeps = true;
     inherit (rustc-unwrapped) outputs;
 
-    env = {
-      sysroot = lib.optionalString (sysroot != null) "--sysroot ${sysroot}";
-
-      # Upstream rustc still assumes that musl = static[1].  The fix for
-      # this is to disable crt-static by default for non-static musl
-      # targets.
-      #
-      # Even though Cargo will build build.rs files for the build platform,
-      # cross-compiling _from_ musl appears to work fine, so we only need
-      # to do this when rustc's target platform is dynamically linked musl.
-      #
-      # [1]: https://github.com/rust-lang/compiler-team/issues/422
-      #
-      # WARNING: using defaultArgs is dangerous, as it will apply to all
-      # targets used by this compiler (host and target).  This means
-      # that it can't be used to set arguments that should only be
-      # applied to the target.  It's fine to do this for -crt-static,
-      # because rustc does not support +crt-static host platforms
-      # anyway.
-      defaultArgs = lib.optionalString (
-        with rustc-unwrapped.stdenv.targetPlatform; isMusl && !isStatic
-      ) "-C target-feature=-crt-static";
-    };
-
     passthru = {
       inherit (rustc-unwrapped)
         pname
@@ -58,10 +58,18 @@ runCommand "${rustc-unwrapped.pname}-wrapper-${rustc-unwrapped.version}"
     mkdir -p $out/bin
     ln -s ${rustc-unwrapped}/bin/* $out/bin
     rm $out/bin/{rustc,rustdoc}
-    prog=${rustc-unwrapped}/bin/rustc extraFlagsVar=NIX_RUSTFLAGS \
-        substituteAll ${./rustc-wrapper.sh} $out/bin/rustc
-    prog=${rustc-unwrapped}/bin/rustdoc extraFlagsVar=NIX_RUSTDOCFLAGS \
-        substituteAll ${./rustc-wrapper.sh} $out/bin/rustdoc
+    substitute ${./rustc-wrapper.sh} $out/bin/rustc \
+      --replace-fail "@shell@" ${lib.escapeShellArg shell} \
+      --replace-fail "@sysrootFlag@" ${lib.escapeShellArg sysrootFlag} \
+      --replace-fail "@defaultArgs@" ${lib.escapeShellArg defaultArgs} \
+      --replace-fail "@prog@" ${lib.escapeShellArg rustc-unwrapped}/bin/rustc \
+      --replace-fail "@extraFlagsVar@" "NIX_RUSTFLAGS"
+    substitute ${./rustc-wrapper.sh} $out/bin/rustdoc \
+      --replace-fail "@shell@" ${lib.escapeShellArg shell} \
+      --replace-fail "@sysrootFlag@" ${lib.escapeShellArg sysrootFlag} \
+      --replace-fail "@defaultArgs@" ${lib.escapeShellArg defaultArgs} \
+      --replace-fail "@prog@" ${lib.escapeShellArg rustc-unwrapped}/bin/rustdoc \
+      --replace-fail "@extraFlagsVar@" "NIX_RUSTDOCFLAGS"
     chmod +x $out/bin/{rustc,rustdoc}
     ${lib.concatMapStrings (output: "ln -s ${rustc-unwrapped.${output}} \$${output}\n") (
       lib.remove "out" rustc-unwrapped.outputs

pkgs/build-support/rust/rustc-wrapper/rustc-wrapper.sh

@@ -1,6 +1,6 @@
 #!@shell@
 
-defaultSysroot=(@sysroot@)
+defaultSysroot=(@sysrootFlag@)
 
 for arg; do
     case "$arg" in