gnu: rust: Add 1.38

All packages are still built with rustc 1.37, but users will see rustc
1.38 in their profiles, and packages that require newer compiler
versions will be possible to add.

* gnu/packages/rust.scm (rust-1.31): Factor out the
  patch-command-exec-tests phase to a separate procedure.
  (patch-command-exec-tests-phase): New procedure.
  (rust): Rename to rust-1.37, make rust an alias.
  (rust-1.38): New variable.

gnu/packages/rust.scm

@@ -909,9 +909,30 @@ (define-public rust-1.30
              (replace 'disable-amd64-avx-test
                (lambda _
                  (substitute* "src/test/ui/run-pass/issues/issue-44056.rs"
-	          (("only-x86_64") "ignore-test"))
+                  (("only-x86_64") "ignore-test"))
                   #t)))))))))
 
+(define (patch-command-exec-tests-phase test-path)
+  "The command-exec.rs test moves around between releases.  We need to apply
+a Guix-specific patch to it for each release.  This function generates the phase
+that applies said patch, parametrized by the test-path.  This is done this way
+because the phase is more complex than the equivalents for other tests that
+move around."
+ `(lambda* (#:key inputs #:allow-other-keys)
+    (let ((coreutils (assoc-ref inputs "coreutils")))
+      (substitute* ,test-path
+        ;; This test suite includes some tests that the stdlib's
+        ;; `Command` execution properly handles situations where
+        ;; the environment or PATH variable are empty, but this
+        ;; fails since we don't have `echo` available in the usual
+        ;; Linux directories.
+        ;; NB: the leading space is so we don't fail a tidy check
+        ;; for trailing whitespace, and the newlines are to ensure
+        ;; we don't exceed the 100 chars tidy check as well
+        ((" Command::new\\(\"echo\"\\)")
+         (string-append "\nCommand::new(\"" coreutils "/bin/echo\")\n")))
+      #t)))
+
 (define-public rust-1.31
   (let ((base-rust
          (rust-bootstrapped-package rust-1.30 "1.31.1"
@@ -923,26 +944,14 @@ (define-public rust-1.31
          ((#:phases phases)
           `(modify-phases ,phases
              (add-after 'patch-tests 'patch-command-exec-tests
-               (lambda* (#:key inputs #:allow-other-keys)
-                 (let ((coreutils (assoc-ref inputs "coreutils")))
-                   (substitute* "src/test/run-pass/command-exec.rs"
-                     ;; This test suite includes some tests that the stdlib's
-                     ;; `Command` execution properly handles situations where
-                     ;; the environment or PATH variable are empty, but this
-                     ;; fails since we don't have `echo` available in the usual
-                     ;; Linux directories.
-                     ;; NB: the leading space is so we don't fail a tidy check
-                     ;; for trailing whitespace, and the newlines are to ensure
-                     ;; we don't exceed the 100 chars tidy check as well
-                     ((" Command::new\\(\"echo\"\\)")
-                      (string-append "\nCommand::new(\"" coreutils "/bin/echo\")\n")))
-                   #t)))
-	      ;; The test has been moved elsewhere.
-	      (replace 'disable-amd64-avx-test
-	        (lambda _
-	          (substitute* "src/test/ui/issues/issue-44056.rs"
-                   (("only-x86_64") "ignore-test"))
-                  #t))
+               ,(patch-command-exec-tests-phase
+                  "src/test/run-pass/command-exec.rs"))
+             ;; The test has been moved elsewhere.
+             (replace 'disable-amd64-avx-test
+               (lambda _
+                 (substitute* "src/test/ui/issues/issue-44056.rs"
+                  (("only-x86_64") "ignore-test"))
+                 #t))
              (add-after 'patch-tests 'patch-process-docs-rev-cmd
                (lambda* _
                  ;; Disable some doc tests which depend on the "rev" command
@@ -1084,7 +1093,7 @@ (define-public rust-1.36
           `(modify-phases ,phases
              (delete 'patch-process-docs-rev-cmd))))))))
 
-(define-public rust
+(define-public rust-1.37
   (let ((base-rust
          (rust-bootstrapped-package rust-1.36 "1.37.0"
            "1hrqprybhkhs6d9b5pjskfnc5z9v2l2gync7nb39qjb5s0h703hj")))
@@ -1100,3 +1109,25 @@ (define-public rust
                    (mkdir-p cargo-home)
                    (setenv "CARGO_HOME" cargo-home)
                    #t))))))))))
+
+(define-public rust-1.38
+  (let ((base-rust
+         (rust-bootstrapped-package rust-1.37 "1.38.0"
+           "101dlpsfkq67p0hbwx4acqq6n90dj4bbprndizpgh1kigk566hk4")))
+    (package
+      (inherit base-rust)
+      (arguments
+       (substitute-keyword-arguments (package-arguments base-rust)
+         ((#:phases phases)
+          `(modify-phases ,phases
+             (replace 'patch-command-exec-tests
+               ,(patch-command-exec-tests-phase
+                  "src/test/ui/command-exec.rs"))
+             (add-after 'patch-tests 'patch-command-uid-gid-test
+               (lambda _
+                 (substitute* "src/test/ui/command-uid-gid.rs"
+                   (("/bin/sh") (which "sh"))
+                   (("ignore-sgx") "ignore-sgx\n// ignore-tidy-linelength"))
+                 #t)))))))))
+
+(define-public rust rust-1.37)