1 files changed, 146 insertions, 0 deletions
diff --git a/third_party/rust/cargo-platform/src/lib.rs b/third_party/rust/cargo-platform/src/lib.rs
new file mode 100644
index 0000000000..0a3dcf1af1
--- /dev/null
+++ b/third_party/rust/cargo-platform/src/lib.rs
@@ -0,0 +1,146 @@
+//! Platform definition used by Cargo.
+//!
+//! This defines a [`Platform`] type which is used in Cargo to specify a target platform.
+//! There are two kinds, a named target like `x86_64-apple-darwin`, and a "cfg expression"
+//! like `cfg(any(target_os = "macos", target_os = "ios"))`.
+//!
+//! See `examples/matches.rs` for an example of how to match against a `Platform`.
+//!
+//! [`Platform`]: enum.Platform.html
+
+use std::fmt;
+use std::str::FromStr;
+
+mod cfg;
+mod error;
+
+pub use cfg::{Cfg, CfgExpr};
+pub use error::{ParseError, ParseErrorKind};
+
+/// Platform definition.
+#[derive(Eq, PartialEq, Hash, Ord, PartialOrd, Clone, Debug)]
+pub enum Platform {
+    /// A named platform, like `x86_64-apple-darwin`.
+    Name(String),
+    /// A cfg expression, like `cfg(windows)`.
+    Cfg(CfgExpr),
+}
+
+impl Platform {
+    /// Returns whether the Platform matches the given target and cfg.
+    ///
+    /// The named target and cfg values should be obtained from `rustc`.
+    pub fn matches(&self, name: &str, cfg: &[Cfg]) -> bool {
+        match *self {
+            Platform::Name(ref p) => p == name,
+            Platform::Cfg(ref p) => p.matches(cfg),
+        }
+    }
+
+    fn validate_named_platform(name: &str) -> Result<(), ParseError> {
+        if let Some(ch) = name
+            .chars()
+            .find(|&c| !(c.is_alphanumeric() || c == '_' || c == '-' || c == '.'))
+        {
+            if name.chars().any(|c| c == '(') {
+                return Err(ParseError::new(
+                    name,
+                    ParseErrorKind::InvalidTarget(
+                        "unexpected `(` character, cfg expressions must start with `cfg(`"
+                            .to_string(),
+                    ),
+                ));
+            }
+            return Err(ParseError::new(
+                name,
+                ParseErrorKind::InvalidTarget(format!(
+                    "unexpected character {} in target name",
+                    ch
+                )),
+            ));
+        }
+        Ok(())
+    }
+
+    pub fn check_cfg_attributes(&self, warnings: &mut Vec<String>) {
+        fn check_cfg_expr(expr: &CfgExpr, warnings: &mut Vec<String>) {
+            match *expr {
+                CfgExpr::Not(ref e) => check_cfg_expr(e, warnings),
+                CfgExpr::All(ref e) | CfgExpr::Any(ref e) => {
+                    for e in e {
+                        check_cfg_expr(e, warnings);
+                    }
+                }
+                CfgExpr::Value(ref e) => match e {
+                    Cfg::Name(name) => match name.as_str() {
+                        "test" | "debug_assertions" | "proc_macro" =>
+                            warnings.push(format!(
+                                "Found `{}` in `target.'cfg(...)'.dependencies`. \
+                                 This value is not supported for selecting dependencies \
+                                 and will not work as expected. \
+                                 To learn more visit \
+                                 https://doc.rust-lang.org/cargo/reference/specifying-dependencies.html#platform-specific-dependencies",
+                                 name
+                            )),
+                        _ => (),
+                    },
+                    Cfg::KeyPair(name, _) => if name.as_str() == "feature" {
+                        warnings.push(String::from(
+                            "Found `feature = ...` in `target.'cfg(...)'.dependencies`. \
+                             This key is not supported for selecting dependencies \
+                             and will not work as expected. \
+                             Use the [features] section instead: \
+                             https://doc.rust-lang.org/cargo/reference/features.html"
+                        ))
+                    },
+                }
+            }
+        }
+
+        if let Platform::Cfg(cfg) = self {
+            check_cfg_expr(cfg, warnings);
+        }
+    }
+}
+
+impl serde::Serialize for Platform {
+    fn serialize<S>(&self, s: S) -> Result<S::Ok, S::Error>
+    where
+        S: serde::Serializer,
+    {
+        self.to_string().serialize(s)
+    }
+}
+
+impl<'de> serde::Deserialize<'de> for Platform {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: serde::Deserializer<'de>,
+    {
+        let s = String::deserialize(deserializer)?;
+        FromStr::from_str(&s).map_err(serde::de::Error::custom)
+    }
+}
+
+impl FromStr for Platform {
+    type Err = ParseError;
+
+    fn from_str(s: &str) -> Result<Platform, ParseError> {
+        if s.starts_with("cfg(") && s.ends_with(')') {
+            let s = &s[4..s.len() - 1];
+            s.parse().map(Platform::Cfg)
+        } else {
+            Platform::validate_named_platform(s)?;
+            Ok(Platform::Name(s.to_string()))
+        }
+    }
+}
+
+impl fmt::Display for Platform {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match *self {
+            Platform::Name(ref n) => n.fmt(f),
+            Platform::Cfg(ref e) => write!(f, "cfg({})", e),
+        }
+    }
+}