From 90330b5330954d0e60b44c934e14f6323a759e1d Mon Sep 17 00:00:00 2001
From: Ivor Wanders <ivor@iwanders.net>
Date: Wed, 12 Jan 2022 19:04:16 -0500
Subject: [PATCH 1/5] Improve error message for cfg arguments.

This provides the user with a helpful error message in case a key="value"
message was specified but couldn't be parsed.
---
 compiler/rustc_interface/src/interface.rs | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/compiler/rustc_interface/src/interface.rs b/compiler/rustc_interface/src/interface.rs
index 3804e100307..8fa1e18df3c 100644
--- a/compiler/rustc_interface/src/interface.rs
+++ b/compiler/rustc_interface/src/interface.rs
@@ -124,7 +124,10 @@ macro_rules! error {
                     Err(errs) => errs.into_iter().for_each(|mut err| err.cancel()),
                 }
 
-                error!(r#"expected `key` or `key="value"`"#);
+                error!(concat!(
+                    r#"expected `key` or `key="value"`, ensure escaping is appropriate"#,
+                    r#" for your shell, try 'key="value"' or key=\"value\""#
+                ));
             })
             .collect::<CrateConfig>();
         cfg.into_iter().map(|(a, b)| (a.to_string(), b.map(|b| b.to_string()))).collect()

From db56c6d53adef72067f83f3d34b2881afe6b5d74 Mon Sep 17 00:00:00 2001
From: Ivor Wanders <ivor@iwanders.net>
Date: Wed, 12 Jan 2022 19:50:04 -0500
Subject: [PATCH 2/5] Update unit tests to accomodate for improved error.

---
 src/test/ui/conditional-compilation/cfg-arg-invalid-1.rs     | 2 +-
 src/test/ui/conditional-compilation/cfg-arg-invalid-1.stderr | 2 +-
 src/test/ui/conditional-compilation/cfg-arg-invalid-2.rs     | 2 +-
 src/test/ui/conditional-compilation/cfg-arg-invalid-2.stderr | 2 +-
 src/test/ui/conditional-compilation/cfg-arg-invalid-4.rs     | 2 +-
 src/test/ui/conditional-compilation/cfg-arg-invalid-4.stderr | 2 +-
 src/test/ui/conditional-compilation/cfg-arg-invalid-6.rs     | 2 +-
 src/test/ui/conditional-compilation/cfg-arg-invalid-6.stderr | 2 +-
 src/test/ui/conditional-compilation/cfg-arg-invalid-8.rs     | 2 +-
 src/test/ui/conditional-compilation/cfg-arg-invalid-8.stderr | 2 +-
 src/test/ui/conditional-compilation/cfg-empty-codemap.rs     | 2 +-
 src/test/ui/conditional-compilation/cfg-empty-codemap.stderr | 2 +-
 12 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/src/test/ui/conditional-compilation/cfg-arg-invalid-1.rs b/src/test/ui/conditional-compilation/cfg-arg-invalid-1.rs
index 36dd78dd2b1..d20e79b9db3 100644
--- a/src/test/ui/conditional-compilation/cfg-arg-invalid-1.rs
+++ b/src/test/ui/conditional-compilation/cfg-arg-invalid-1.rs
@@ -1,3 +1,3 @@
 // compile-flags: --cfg a(b=c)
-// error-pattern: invalid `--cfg` argument: `a(b=c)` (expected `key` or `key="value"`)
+// error-pattern: invalid `--cfg` argument: `a(b=c)` (expected `key` or `key="value"`, ensure escaping is appropriate for your shell, try 'key="value"' or key=\"value\")
 fn main() {}
diff --git a/src/test/ui/conditional-compilation/cfg-arg-invalid-1.stderr b/src/test/ui/conditional-compilation/cfg-arg-invalid-1.stderr
index 1e7922a9ff1..3a12e978680 100644
--- a/src/test/ui/conditional-compilation/cfg-arg-invalid-1.stderr
+++ b/src/test/ui/conditional-compilation/cfg-arg-invalid-1.stderr
@@ -1,2 +1,2 @@
-error: invalid `--cfg` argument: `a(b=c)` (expected `key` or `key="value"`)
+error: invalid `--cfg` argument: `a(b=c)` (expected `key` or `key="value"`, ensure escaping is appropriate for your shell, try 'key="value"' or key=\"value\")
 
diff --git a/src/test/ui/conditional-compilation/cfg-arg-invalid-2.rs b/src/test/ui/conditional-compilation/cfg-arg-invalid-2.rs
index 48d656a4a28..660d5d1b1ea 100644
--- a/src/test/ui/conditional-compilation/cfg-arg-invalid-2.rs
+++ b/src/test/ui/conditional-compilation/cfg-arg-invalid-2.rs
@@ -1,3 +1,3 @@
 // compile-flags: --cfg a{b}
-// error-pattern: invalid `--cfg` argument: `a{b}` (expected `key` or `key="value"`)
+// error-pattern: invalid `--cfg` argument: `a{b}` (expected `key` or `key="value"`, ensure escaping is appropriate for your shell, try 'key="value"' or key=\"value\")
 fn main() {}
diff --git a/src/test/ui/conditional-compilation/cfg-arg-invalid-2.stderr b/src/test/ui/conditional-compilation/cfg-arg-invalid-2.stderr
index b92e1fd3d97..2e141137129 100644
--- a/src/test/ui/conditional-compilation/cfg-arg-invalid-2.stderr
+++ b/src/test/ui/conditional-compilation/cfg-arg-invalid-2.stderr
@@ -1,2 +1,2 @@
-error: invalid `--cfg` argument: `a{b}` (expected `key` or `key="value"`)
+error: invalid `--cfg` argument: `a{b}` (expected `key` or `key="value"`, ensure escaping is appropriate for your shell, try 'key="value"' or key=\"value\")
 
diff --git a/src/test/ui/conditional-compilation/cfg-arg-invalid-4.rs b/src/test/ui/conditional-compilation/cfg-arg-invalid-4.rs
index e7dfa17b4b6..d8b3c0284cc 100644
--- a/src/test/ui/conditional-compilation/cfg-arg-invalid-4.rs
+++ b/src/test/ui/conditional-compilation/cfg-arg-invalid-4.rs
@@ -1,3 +1,3 @@
 // compile-flags: --cfg a(b)
-// error-pattern: invalid `--cfg` argument: `a(b)` (expected `key` or `key="value"`)
+// error-pattern: invalid `--cfg` argument: `a(b)` (expected `key` or `key="value"`, ensure escaping is appropriate for your shell, try 'key="value"' or key=\"value\")
 fn main() {}
diff --git a/src/test/ui/conditional-compilation/cfg-arg-invalid-4.stderr b/src/test/ui/conditional-compilation/cfg-arg-invalid-4.stderr
index 6853a69b9eb..52685d7b4a2 100644
--- a/src/test/ui/conditional-compilation/cfg-arg-invalid-4.stderr
+++ b/src/test/ui/conditional-compilation/cfg-arg-invalid-4.stderr
@@ -1,2 +1,2 @@
-error: invalid `--cfg` argument: `a(b)` (expected `key` or `key="value"`)
+error: invalid `--cfg` argument: `a(b)` (expected `key` or `key="value"`, ensure escaping is appropriate for your shell, try 'key="value"' or key=\"value\")
 
diff --git a/src/test/ui/conditional-compilation/cfg-arg-invalid-6.rs b/src/test/ui/conditional-compilation/cfg-arg-invalid-6.rs
index 9fa726f93e3..4a0d116e644 100644
--- a/src/test/ui/conditional-compilation/cfg-arg-invalid-6.rs
+++ b/src/test/ui/conditional-compilation/cfg-arg-invalid-6.rs
@@ -1,3 +1,3 @@
 // compile-flags: --cfg a{
-// error-pattern: invalid `--cfg` argument: `a{` (expected `key` or `key="value"`)
+// error-pattern: invalid `--cfg` argument: `a{` (expected `key` or `key="value"`, ensure escaping is appropriate for your shell, try 'key="value"' or key=\"value\")
 fn main() {}
diff --git a/src/test/ui/conditional-compilation/cfg-arg-invalid-6.stderr b/src/test/ui/conditional-compilation/cfg-arg-invalid-6.stderr
index 7d2087b4b71..618d12aba68 100644
--- a/src/test/ui/conditional-compilation/cfg-arg-invalid-6.stderr
+++ b/src/test/ui/conditional-compilation/cfg-arg-invalid-6.stderr
@@ -1,2 +1,2 @@
-error: invalid `--cfg` argument: `a{` (expected `key` or `key="value"`)
+error: invalid `--cfg` argument: `a{` (expected `key` or `key="value"`, ensure escaping is appropriate for your shell, try 'key="value"' or key=\"value\")
 
diff --git a/src/test/ui/conditional-compilation/cfg-arg-invalid-8.rs b/src/test/ui/conditional-compilation/cfg-arg-invalid-8.rs
index 1d7fa788534..7c5531606fa 100644
--- a/src/test/ui/conditional-compilation/cfg-arg-invalid-8.rs
+++ b/src/test/ui/conditional-compilation/cfg-arg-invalid-8.rs
@@ -1,3 +1,3 @@
 // compile-flags: --cfg )
-// error-pattern: invalid `--cfg` argument: `)` (expected `key` or `key="value"`)
+// error-pattern: invalid `--cfg` argument: `)` (expected `key` or `key="value"`, ensure escaping is appropriate for your shell, try 'key="value"' or key=\"value\")
 fn main() {}
diff --git a/src/test/ui/conditional-compilation/cfg-arg-invalid-8.stderr b/src/test/ui/conditional-compilation/cfg-arg-invalid-8.stderr
index 7bb1814127b..16bb552f0d9 100644
--- a/src/test/ui/conditional-compilation/cfg-arg-invalid-8.stderr
+++ b/src/test/ui/conditional-compilation/cfg-arg-invalid-8.stderr
@@ -1,2 +1,2 @@
-error: invalid `--cfg` argument: `)` (expected `key` or `key="value"`)
+error: invalid `--cfg` argument: `)` (expected `key` or `key="value"`, ensure escaping is appropriate for your shell, try 'key="value"' or key=\"value\")
 
diff --git a/src/test/ui/conditional-compilation/cfg-empty-codemap.rs b/src/test/ui/conditional-compilation/cfg-empty-codemap.rs
index 9e34cacf74d..c23d2cee924 100644
--- a/src/test/ui/conditional-compilation/cfg-empty-codemap.rs
+++ b/src/test/ui/conditional-compilation/cfg-empty-codemap.rs
@@ -2,7 +2,7 @@
 
 // compile-flags: --cfg ""
 
-// error-pattern: invalid `--cfg` argument: `""` (expected `key` or `key="value"`)
+// error-pattern: invalid `--cfg` argument: `""` (expected `key` or `key="value"`, ensure escaping is appropriate for your shell, try 'key="value"' or key=\"value\")
 
 pub fn main() {
 }
diff --git a/src/test/ui/conditional-compilation/cfg-empty-codemap.stderr b/src/test/ui/conditional-compilation/cfg-empty-codemap.stderr
index 128e3cd7306..55e3dc131ae 100644
--- a/src/test/ui/conditional-compilation/cfg-empty-codemap.stderr
+++ b/src/test/ui/conditional-compilation/cfg-empty-codemap.stderr
@@ -1,2 +1,2 @@
-error: invalid `--cfg` argument: `""` (expected `key` or `key="value"`)
+error: invalid `--cfg` argument: `""` (expected `key` or `key="value"`, ensure escaping is appropriate for your shell, try 'key="value"' or key=\"value\")
 

From 32be3489a52271520e6bc6c6653ce7457292c48b Mon Sep 17 00:00:00 2001
From: Ivor Wanders <ivor@iwanders.net>
Date: Sun, 16 Jan 2022 11:04:11 -0500
Subject: [PATCH 3/5] Add unit test for cfg-arg without quotes.

---
 src/test/ui/conditional-compilation/cfg-arg-invalid-9.rs     | 3 +++
 src/test/ui/conditional-compilation/cfg-arg-invalid-9.stderr | 2 ++
 2 files changed, 5 insertions(+)
 create mode 100644 src/test/ui/conditional-compilation/cfg-arg-invalid-9.rs
 create mode 100644 src/test/ui/conditional-compilation/cfg-arg-invalid-9.stderr

diff --git a/src/test/ui/conditional-compilation/cfg-arg-invalid-9.rs b/src/test/ui/conditional-compilation/cfg-arg-invalid-9.rs
new file mode 100644
index 00000000000..51d8c4b885c
--- /dev/null
+++ b/src/test/ui/conditional-compilation/cfg-arg-invalid-9.rs
@@ -0,0 +1,3 @@
+// compile-flags: --cfg key=value
+// error-pattern: invalid `--cfg` argument: `key=value` (expected `key` or `key="value"`, ensure escaping is appropriate for your shell, try 'key="value"' or key=\"value\")
+fn main() {}
diff --git a/src/test/ui/conditional-compilation/cfg-arg-invalid-9.stderr b/src/test/ui/conditional-compilation/cfg-arg-invalid-9.stderr
new file mode 100644
index 00000000000..985b5252258
--- /dev/null
+++ b/src/test/ui/conditional-compilation/cfg-arg-invalid-9.stderr
@@ -0,0 +1,2 @@
+error: invalid `--cfg` argument: `key=value` (expected `key` or `key="value"`, ensure escaping is appropriate for your shell, try 'key="value"' or key=\"value\")
+

From 1531d26fa3896869818b40d6771d8b3cdaf2f6eb Mon Sep 17 00:00:00 2001
From: Ivor Wanders <ivor@iwanders.net>
Date: Sun, 16 Jan 2022 11:43:16 -0500
Subject: [PATCH 4/5] Limit scope of the hint about escaping.

---
 compiler/rustc_interface/src/interface.rs | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/compiler/rustc_interface/src/interface.rs b/compiler/rustc_interface/src/interface.rs
index 8fa1e18df3c..26343561959 100644
--- a/compiler/rustc_interface/src/interface.rs
+++ b/compiler/rustc_interface/src/interface.rs
@@ -124,10 +124,16 @@ macro_rules! error {
                     Err(errs) => errs.into_iter().for_each(|mut err| err.cancel()),
                 }
 
-                error!(concat!(
-                    r#"expected `key` or `key="value"`, ensure escaping is appropriate"#,
-                    r#" for your shell, try 'key="value"' or key=\"value\""#
-                ));
+                // If the user tried to use a key="value" flag, but is missing the quotes, provide
+                // a hint about how to resolve this.
+                if s.contains("=") && !s.contains("=\"") && !s.ends_with("\"") {
+                    error!(concat!(
+                        r#"expected `key` or `key="value"`, ensure escaping is appropriate"#,
+                        r#" for your shell, try 'key="value"' or key=\"value\""#
+                    ));
+                } else {
+                    error!(r#"expected `key` or `key="value"`"#);
+                }
             })
             .collect::<CrateConfig>();
         cfg.into_iter().map(|(a, b)| (a.to_string(), b.map(|b| b.to_string()))).collect()

From af87248037a8c86f580c469ce7d2a10c0b12f2fd Mon Sep 17 00:00:00 2001
From: Ivor Wanders <ivor@iwanders.net>
Date: Sun, 16 Jan 2022 11:44:10 -0500
Subject: [PATCH 5/5] Update unit tests to match more limited hint about
 escaping.

---
 src/test/ui/conditional-compilation/cfg-arg-invalid-2.rs     | 2 +-
 src/test/ui/conditional-compilation/cfg-arg-invalid-2.stderr | 2 +-
 src/test/ui/conditional-compilation/cfg-arg-invalid-4.rs     | 2 +-
 src/test/ui/conditional-compilation/cfg-arg-invalid-4.stderr | 2 +-
 src/test/ui/conditional-compilation/cfg-arg-invalid-6.rs     | 2 +-
 src/test/ui/conditional-compilation/cfg-arg-invalid-6.stderr | 2 +-
 src/test/ui/conditional-compilation/cfg-arg-invalid-8.rs     | 2 +-
 src/test/ui/conditional-compilation/cfg-arg-invalid-8.stderr | 2 +-
 src/test/ui/conditional-compilation/cfg-arg-invalid-9.rs     | 1 +
 src/test/ui/conditional-compilation/cfg-empty-codemap.rs     | 2 +-
 src/test/ui/conditional-compilation/cfg-empty-codemap.stderr | 2 +-
 11 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/src/test/ui/conditional-compilation/cfg-arg-invalid-2.rs b/src/test/ui/conditional-compilation/cfg-arg-invalid-2.rs
index 660d5d1b1ea..48d656a4a28 100644
--- a/src/test/ui/conditional-compilation/cfg-arg-invalid-2.rs
+++ b/src/test/ui/conditional-compilation/cfg-arg-invalid-2.rs
@@ -1,3 +1,3 @@
 // compile-flags: --cfg a{b}
-// error-pattern: invalid `--cfg` argument: `a{b}` (expected `key` or `key="value"`, ensure escaping is appropriate for your shell, try 'key="value"' or key=\"value\")
+// error-pattern: invalid `--cfg` argument: `a{b}` (expected `key` or `key="value"`)
 fn main() {}
diff --git a/src/test/ui/conditional-compilation/cfg-arg-invalid-2.stderr b/src/test/ui/conditional-compilation/cfg-arg-invalid-2.stderr
index 2e141137129..b92e1fd3d97 100644
--- a/src/test/ui/conditional-compilation/cfg-arg-invalid-2.stderr
+++ b/src/test/ui/conditional-compilation/cfg-arg-invalid-2.stderr
@@ -1,2 +1,2 @@
-error: invalid `--cfg` argument: `a{b}` (expected `key` or `key="value"`, ensure escaping is appropriate for your shell, try 'key="value"' or key=\"value\")
+error: invalid `--cfg` argument: `a{b}` (expected `key` or `key="value"`)
 
diff --git a/src/test/ui/conditional-compilation/cfg-arg-invalid-4.rs b/src/test/ui/conditional-compilation/cfg-arg-invalid-4.rs
index d8b3c0284cc..e7dfa17b4b6 100644
--- a/src/test/ui/conditional-compilation/cfg-arg-invalid-4.rs
+++ b/src/test/ui/conditional-compilation/cfg-arg-invalid-4.rs
@@ -1,3 +1,3 @@
 // compile-flags: --cfg a(b)
-// error-pattern: invalid `--cfg` argument: `a(b)` (expected `key` or `key="value"`, ensure escaping is appropriate for your shell, try 'key="value"' or key=\"value\")
+// error-pattern: invalid `--cfg` argument: `a(b)` (expected `key` or `key="value"`)
 fn main() {}
diff --git a/src/test/ui/conditional-compilation/cfg-arg-invalid-4.stderr b/src/test/ui/conditional-compilation/cfg-arg-invalid-4.stderr
index 52685d7b4a2..6853a69b9eb 100644
--- a/src/test/ui/conditional-compilation/cfg-arg-invalid-4.stderr
+++ b/src/test/ui/conditional-compilation/cfg-arg-invalid-4.stderr
@@ -1,2 +1,2 @@
-error: invalid `--cfg` argument: `a(b)` (expected `key` or `key="value"`, ensure escaping is appropriate for your shell, try 'key="value"' or key=\"value\")
+error: invalid `--cfg` argument: `a(b)` (expected `key` or `key="value"`)
 
diff --git a/src/test/ui/conditional-compilation/cfg-arg-invalid-6.rs b/src/test/ui/conditional-compilation/cfg-arg-invalid-6.rs
index 4a0d116e644..9fa726f93e3 100644
--- a/src/test/ui/conditional-compilation/cfg-arg-invalid-6.rs
+++ b/src/test/ui/conditional-compilation/cfg-arg-invalid-6.rs
@@ -1,3 +1,3 @@
 // compile-flags: --cfg a{
-// error-pattern: invalid `--cfg` argument: `a{` (expected `key` or `key="value"`, ensure escaping is appropriate for your shell, try 'key="value"' or key=\"value\")
+// error-pattern: invalid `--cfg` argument: `a{` (expected `key` or `key="value"`)
 fn main() {}
diff --git a/src/test/ui/conditional-compilation/cfg-arg-invalid-6.stderr b/src/test/ui/conditional-compilation/cfg-arg-invalid-6.stderr
index 618d12aba68..7d2087b4b71 100644
--- a/src/test/ui/conditional-compilation/cfg-arg-invalid-6.stderr
+++ b/src/test/ui/conditional-compilation/cfg-arg-invalid-6.stderr
@@ -1,2 +1,2 @@
-error: invalid `--cfg` argument: `a{` (expected `key` or `key="value"`, ensure escaping is appropriate for your shell, try 'key="value"' or key=\"value\")
+error: invalid `--cfg` argument: `a{` (expected `key` or `key="value"`)
 
diff --git a/src/test/ui/conditional-compilation/cfg-arg-invalid-8.rs b/src/test/ui/conditional-compilation/cfg-arg-invalid-8.rs
index 7c5531606fa..1d7fa788534 100644
--- a/src/test/ui/conditional-compilation/cfg-arg-invalid-8.rs
+++ b/src/test/ui/conditional-compilation/cfg-arg-invalid-8.rs
@@ -1,3 +1,3 @@
 // compile-flags: --cfg )
-// error-pattern: invalid `--cfg` argument: `)` (expected `key` or `key="value"`, ensure escaping is appropriate for your shell, try 'key="value"' or key=\"value\")
+// error-pattern: invalid `--cfg` argument: `)` (expected `key` or `key="value"`)
 fn main() {}
diff --git a/src/test/ui/conditional-compilation/cfg-arg-invalid-8.stderr b/src/test/ui/conditional-compilation/cfg-arg-invalid-8.stderr
index 16bb552f0d9..7bb1814127b 100644
--- a/src/test/ui/conditional-compilation/cfg-arg-invalid-8.stderr
+++ b/src/test/ui/conditional-compilation/cfg-arg-invalid-8.stderr
@@ -1,2 +1,2 @@
-error: invalid `--cfg` argument: `)` (expected `key` or `key="value"`, ensure escaping is appropriate for your shell, try 'key="value"' or key=\"value\")
+error: invalid `--cfg` argument: `)` (expected `key` or `key="value"`)
 
diff --git a/src/test/ui/conditional-compilation/cfg-arg-invalid-9.rs b/src/test/ui/conditional-compilation/cfg-arg-invalid-9.rs
index 51d8c4b885c..628b335c873 100644
--- a/src/test/ui/conditional-compilation/cfg-arg-invalid-9.rs
+++ b/src/test/ui/conditional-compilation/cfg-arg-invalid-9.rs
@@ -1,3 +1,4 @@
+// Test for missing quotes around value, issue #66450.
 // compile-flags: --cfg key=value
 // error-pattern: invalid `--cfg` argument: `key=value` (expected `key` or `key="value"`, ensure escaping is appropriate for your shell, try 'key="value"' or key=\"value\")
 fn main() {}
diff --git a/src/test/ui/conditional-compilation/cfg-empty-codemap.rs b/src/test/ui/conditional-compilation/cfg-empty-codemap.rs
index c23d2cee924..9e34cacf74d 100644
--- a/src/test/ui/conditional-compilation/cfg-empty-codemap.rs
+++ b/src/test/ui/conditional-compilation/cfg-empty-codemap.rs
@@ -2,7 +2,7 @@
 
 // compile-flags: --cfg ""
 
-// error-pattern: invalid `--cfg` argument: `""` (expected `key` or `key="value"`, ensure escaping is appropriate for your shell, try 'key="value"' or key=\"value\")
+// error-pattern: invalid `--cfg` argument: `""` (expected `key` or `key="value"`)
 
 pub fn main() {
 }
diff --git a/src/test/ui/conditional-compilation/cfg-empty-codemap.stderr b/src/test/ui/conditional-compilation/cfg-empty-codemap.stderr
index 55e3dc131ae..128e3cd7306 100644
--- a/src/test/ui/conditional-compilation/cfg-empty-codemap.stderr
+++ b/src/test/ui/conditional-compilation/cfg-empty-codemap.stderr
@@ -1,2 +1,2 @@
-error: invalid `--cfg` argument: `""` (expected `key` or `key="value"`, ensure escaping is appropriate for your shell, try 'key="value"' or key=\"value\")
+error: invalid `--cfg` argument: `""` (expected `key` or `key="value"`)