1 files changed, 91 insertions, 0 deletions
diff --git a/compiler/rustc_builtin_macros/src/env.rs b/compiler/rustc_builtin_macros/src/env.rs
new file mode 100644
index 000000000..b8828fa67
--- /dev/null
+++ b/compiler/rustc_builtin_macros/src/env.rs
@@ -0,0 +1,91 @@
+// The compiler code necessary to support the env! extension.  Eventually this
+// should all get sucked into either the compiler syntax extension plugin
+// interface.
+//
+
+use rustc_ast::tokenstream::TokenStream;
+use rustc_ast::{self as ast, GenericArg};
+use rustc_expand::base::{self, *};
+use rustc_span::symbol::{kw, sym, Ident, Symbol};
+use rustc_span::Span;
+
+use std::env;
+
+pub fn expand_option_env<'cx>(
+    cx: &'cx mut ExtCtxt<'_>,
+    sp: Span,
+    tts: TokenStream,
+) -> Box<dyn base::MacResult + 'cx> {
+    let Some(var) = get_single_str_from_tts(cx, sp, tts, "option_env!") else {
+        return DummyResult::any(sp);
+    };
+
+    let sp = cx.with_def_site_ctxt(sp);
+    let value = env::var(var.as_str()).ok().as_deref().map(Symbol::intern);
+    cx.sess.parse_sess.env_depinfo.borrow_mut().insert((var, value));
+    let e = match value {
+        None => {
+            let lt = cx.lifetime(sp, Ident::new(kw::StaticLifetime, sp));
+            cx.expr_path(cx.path_all(
+                sp,
+                true,
+                cx.std_path(&[sym::option, sym::Option, sym::None]),
+                vec![GenericArg::Type(cx.ty_rptr(
+                    sp,
+                    cx.ty_ident(sp, Ident::new(sym::str, sp)),
+                    Some(lt),
+                    ast::Mutability::Not,
+                ))],
+            ))
+        }
+        Some(value) => cx.expr_call_global(
+            sp,
+            cx.std_path(&[sym::option, sym::Option, sym::Some]),
+            vec![cx.expr_str(sp, value)],
+        ),
+    };
+    MacEager::expr(e)
+}
+
+pub fn expand_env<'cx>(
+    cx: &'cx mut ExtCtxt<'_>,
+    sp: Span,
+    tts: TokenStream,
+) -> Box<dyn base::MacResult + 'cx> {
+    let mut exprs = match get_exprs_from_tts(cx, sp, tts) {
+        Some(ref exprs) if exprs.is_empty() => {
+            cx.span_err(sp, "env! takes 1 or 2 arguments");
+            return DummyResult::any(sp);
+        }
+        None => return DummyResult::any(sp),
+        Some(exprs) => exprs.into_iter(),
+    };
+
+    let Some((var, _style)) = expr_to_string(cx, exprs.next().unwrap(), "expected string literal") else {
+        return DummyResult::any(sp);
+    };
+    let msg = match exprs.next() {
+        None => Symbol::intern(&format!("environment variable `{}` not defined", var)),
+        Some(second) => match expr_to_string(cx, second, "expected string literal") {
+            None => return DummyResult::any(sp),
+            Some((s, _style)) => s,
+        },
+    };
+
+    if exprs.next().is_some() {
+        cx.span_err(sp, "env! takes 1 or 2 arguments");
+        return DummyResult::any(sp);
+    }
+
+    let sp = cx.with_def_site_ctxt(sp);
+    let value = env::var(var.as_str()).ok().as_deref().map(Symbol::intern);
+    cx.sess.parse_sess.env_depinfo.borrow_mut().insert((var, value));
+    let e = match value {
+        None => {
+            cx.span_err(sp, msg.as_str());
+            return DummyResult::any(sp);
+        }
+        Some(value) => cx.expr_str(sp, value),
+    };
+    MacEager::expr(e)
+}