1 files changed, 93 insertions, 0 deletions
diff --git a/src/tools/rust-analyzer/crates/ide-completion/src/completions/attribute/cfg.rs b/src/tools/rust-analyzer/crates/ide-completion/src/completions/attribute/cfg.rs
new file mode 100644
index 000000000..311060143
--- /dev/null
+++ b/src/tools/rust-analyzer/crates/ide-completion/src/completions/attribute/cfg.rs
@@ -0,0 +1,93 @@
+//! Completion for cfg
+
+use std::iter;
+
+use ide_db::SymbolKind;
+use itertools::Itertools;
+use syntax::SyntaxKind;
+
+use crate::{completions::Completions, context::CompletionContext, CompletionItem};
+
+pub(crate) fn complete_cfg(acc: &mut Completions, ctx: &CompletionContext<'_>) {
+    let add_completion = |item: &str| {
+        let mut completion = CompletionItem::new(SymbolKind::BuiltinAttr, ctx.source_range(), item);
+        completion.insert_text(format!(r#""{}""#, item));
+        acc.add(completion.build());
+    };
+
+    let previous = iter::successors(ctx.original_token.prev_token(), |t| {
+        (matches!(t.kind(), SyntaxKind::EQ) || t.kind().is_trivia())
+            .then(|| t.prev_token())
+            .flatten()
+    })
+    .find(|t| matches!(t.kind(), SyntaxKind::IDENT));
+
+    match previous.as_ref().map(|p| p.text()) {
+        Some("target_arch") => KNOWN_ARCH.iter().copied().for_each(add_completion),
+        Some("target_env") => KNOWN_ENV.iter().copied().for_each(add_completion),
+        Some("target_os") => KNOWN_OS.iter().copied().for_each(add_completion),
+        Some("target_vendor") => KNOWN_VENDOR.iter().copied().for_each(add_completion),
+        Some("target_endian") => ["little", "big"].into_iter().for_each(add_completion),
+        Some(name) => ctx.krate.potential_cfg(ctx.db).get_cfg_values(name).cloned().for_each(|s| {
+            let insert_text = format!(r#""{}""#, s);
+            let mut item = CompletionItem::new(SymbolKind::BuiltinAttr, ctx.source_range(), s);
+            item.insert_text(insert_text);
+
+            acc.add(item.build());
+        }),
+        None => ctx.krate.potential_cfg(ctx.db).get_cfg_keys().cloned().unique().for_each(|s| {
+            let item = CompletionItem::new(SymbolKind::BuiltinAttr, ctx.source_range(), s);
+            acc.add(item.build());
+        }),
+    };
+}
+
+const KNOWN_ARCH: [&str; 19] = [
+    "aarch64",
+    "arm",
+    "avr",
+    "hexagon",
+    "mips",
+    "mips64",
+    "msp430",
+    "nvptx64",
+    "powerpc",
+    "powerpc64",
+    "riscv32",
+    "riscv64",
+    "s390x",
+    "sparc",
+    "sparc64",
+    "wasm32",
+    "wasm64",
+    "x86",
+    "x86_64",
+];
+
+const KNOWN_ENV: [&str; 7] = ["eabihf", "gnu", "gnueabihf", "msvc", "relibc", "sgx", "uclibc"];
+
+const KNOWN_OS: [&str; 20] = [
+    "cuda",
+    "dragonfly",
+    "emscripten",
+    "freebsd",
+    "fuchsia",
+    "haiku",
+    "hermit",
+    "illumos",
+    "l4re",
+    "linux",
+    "netbsd",
+    "none",
+    "openbsd",
+    "psp",
+    "redox",
+    "solaris",
+    "uefi",
+    "unknown",
+    "vxworks",
+    "windows",
+];
+
+const KNOWN_VENDOR: [&str; 8] =
+    ["apple", "fortanix", "nvidia", "pc", "sony", "unknown", "wrs", "uwp"];