Specify --print info=file syntax in --help

compiler/rustc_session/src/config.rs

@@ -1560,9 +1560,10 @@ The default is {DEFAULT_EDITION} and the latest stable edition is {LATEST_STABLE
     )
 });
 
-static PRINT_KINDS_STRING: LazyLock<String> = LazyLock::new(|| {
+static PRINT_HELP: LazyLock<String> = LazyLock::new(|| {
     format!(
-        "[{}]",
+        "Compiler information to print on stdout (or to a file)\n\
+        INFO may be one of ({}).",
         PRINT_KINDS.iter().map(|(name, _)| format!("{name}")).collect::<Vec<_>>().join("|")
     )
 });
@@ -1621,14 +1622,7 @@ pub fn rustc_optgroups() -> Vec<RustcOptGroup> {
             "Comma separated list of types of output for the compiler to emit",
             "[asm|llvm-bc|llvm-ir|obj|metadata|link|dep-info|mir]",
         ),
-        opt(
-            Stable,
-            Multi,
-            "",
-            "print",
-            "Compiler information to print on stdout",
-            &PRINT_KINDS_STRING,
-        ),
+        opt(Stable, Multi, "", "print", &PRINT_HELP, "INFO[=FILE]"),
         opt(Stable, FlagMulti, "g", "", "Equivalent to -C debuginfo=2", ""),
         opt(Stable, FlagMulti, "O", "", "Equivalent to -C opt-level=3", ""),
         opt(Stable, Opt, "o", "", "Write output to <filename>", "FILENAME"),

tests/run-make/rustc-help/help-v.diff

@@ -1,4 +1,4 @@
-@@ -51,10 +51,27 @@
+@@ -53,10 +53,27 @@
                          Set a codegen option
      -V, --version       Print version info and exit
      -v, --verbose       Use verbose output

tests/run-make/rustc-help/help-v.stdout

@@ -29,8 +29,10 @@ Options:
         --emit [asm|llvm-bc|llvm-ir|obj|metadata|link|dep-info|mir]
                         Comma separated list of types of output for the
                         compiler to emit
-        --print [all-target-specs-json|calling-conventions|cfg|check-cfg|code-models|crate-name|crate-root-lint-levels|deployment-target|file-names|host-tuple|link-args|native-static-libs|relocation-models|split-debuginfo|stack-protector-strategies|supported-crate-types|sysroot|target-cpus|target-features|target-libdir|target-list|target-spec-json|tls-models]
-                        Compiler information to print on stdout
+        --print INFO[=FILE]
+                        Compiler information to print on stdout (or to a file)
+                        INFO may be one of
+                        (all-target-specs-json|calling-conventions|cfg|check-cfg|code-models|crate-name|crate-root-lint-levels|deployment-target|file-names|host-tuple|link-args|native-static-libs|relocation-models|split-debuginfo|stack-protector-strategies|supported-crate-types|sysroot|target-cpus|target-features|target-libdir|target-list|target-spec-json|tls-models).
     -g                  Equivalent to -C debuginfo=2
     -O                  Equivalent to -C opt-level=3
     -o FILENAME         Write output to <filename>

tests/run-make/rustc-help/help.stdout

@@ -29,8 +29,10 @@ Options:
         --emit [asm|llvm-bc|llvm-ir|obj|metadata|link|dep-info|mir]
                         Comma separated list of types of output for the
                         compiler to emit
-        --print [all-target-specs-json|calling-conventions|cfg|check-cfg|code-models|crate-name|crate-root-lint-levels|deployment-target|file-names|host-tuple|link-args|native-static-libs|relocation-models|split-debuginfo|stack-protector-strategies|supported-crate-types|sysroot|target-cpus|target-features|target-libdir|target-list|target-spec-json|tls-models]
-                        Compiler information to print on stdout
+        --print INFO[=FILE]
+                        Compiler information to print on stdout (or to a file)
+                        INFO may be one of
+                        (all-target-specs-json|calling-conventions|cfg|check-cfg|code-models|crate-name|crate-root-lint-levels|deployment-target|file-names|host-tuple|link-args|native-static-libs|relocation-models|split-debuginfo|stack-protector-strategies|supported-crate-types|sysroot|target-cpus|target-features|target-libdir|target-list|target-spec-json|tls-models).
     -g                  Equivalent to -C debuginfo=2
     -O                  Equivalent to -C opt-level=3
     -o FILENAME         Write output to <filename>

tests/ui/invalid-compile-flags/print-without-arg.stderr

@@ -1,5 +1,6 @@
 error: Argument to option 'print' missing
        Usage:
-           --print [all-target-specs-json|calling-conventions|cfg|check-cfg|code-models|crate-name|crate-root-lint-levels|deployment-target|file-names|host-tuple|link-args|native-static-libs|relocation-models|split-debuginfo|stack-protector-strategies|supported-crate-types|sysroot|target-cpus|target-features|target-libdir|target-list|target-spec-json|tls-models]
-                               Compiler information to print on stdout
+           --print INFO[=FILE] Compiler information to print on stdout (or to a file)
+                               INFO may be one of
+                               (all-target-specs-json|calling-conventions|cfg|check-cfg|code-models|crate-name|crate-root-lint-levels|deployment-target|file-names|host-tuple|link-args|native-static-libs|relocation-models|split-debuginfo|stack-protector-strategies|supported-crate-types|sysroot|target-cpus|target-features|target-libdir|target-list|target-spec-json|tls-models).