4 files changed, 594 insertions, 0 deletions

diff --git a/crates/ra_ide/src/completion.rs b/crates/ra_ide/src/completion.rs
index f0e02180b..4ca0fdf4f 100644
--- a/crates/ra_ide/src/completion.rs
+++ b/crates/ra_ide/src/completion.rs
@@ -5,6 +5,7 @@ mod completion_item;
 mod completion_context;
 mod presentation;
 
+mod complete_attribute;
 mod complete_dot;
 mod complete_record;
 mod complete_pattern;
@@ -78,6 +79,7 @@ pub(crate) fn completions(
     complete_postfix::complete_postfix(&mut acc, &ctx);
     complete_macro_in_item_position::complete_macro_in_item_position(&mut acc, &ctx);
     complete_trait_impl::complete_trait_impl(&mut acc, &ctx);
+    complete_attribute::complete_attribute(&mut acc, &ctx);
 
     Some(acc)
 }
diff --git a/crates/ra_ide/src/completion/complete_attribute.rs b/crates/ra_ide/src/completion/complete_attribute.rs
new file mode 100644
index 000000000..b405042e8
--- /dev/null
+++ b/crates/ra_ide/src/completion/complete_attribute.rs
@@ -0,0 +1,587 @@
+//! Completion for attributes
+//!
+//! This module uses a bit of static metadata to provide completions
+//! for built-in attributes.
+
+use super::completion_context::CompletionContext;
+use super::completion_item::{CompletionItem, CompletionItemKind, CompletionKind, Completions};
+use ra_syntax::{
+    ast::{Attr, AttrKind},
+    AstNode,
+};
+
+pub(super) fn complete_attribute(acc: &mut Completions, ctx: &CompletionContext) {
+    if !ctx.is_attribute {
+        return;
+    }
+
+    let is_inner = ctx
+        .original_token
+        .ancestors()
+        .find_map(Attr::cast)
+        .map(|attr| attr.kind() == AttrKind::Inner)
+        .unwrap_or(false);
+
+    for attr_completion in ATTRIBUTES {
+        let mut item = CompletionItem::new(
+            CompletionKind::Attribute,
+            ctx.source_range(),
+            attr_completion.label,
+        )
+        .kind(CompletionItemKind::Attribute);
+
+        match (attr_completion.snippet, ctx.config.snippet_cap) {
+            (Some(snippet), Some(cap)) => {
+                item = item.insert_snippet(cap, snippet);
+            }
+            _ => {}
+        }
+
+        if is_inner || !attr_completion.should_be_inner {
+            acc.add(item);
+        }
+    }
+}
+
+struct AttrCompletion {
+    label: &'static str,
+    snippet: Option<&'static str>,
+    should_be_inner: bool,
+}
+
+const ATTRIBUTES: &[AttrCompletion] = &[
+    AttrCompletion { label: "allow", snippet: Some("allow(${0:lint})"), should_be_inner: false },
+    AttrCompletion {
+        label: "cfg_attr",
+        snippet: Some("cfg_attr(${1:predicate}, ${0:attr})"),
+        should_be_inner: false,
+    },
+    AttrCompletion { label: "cfg", snippet: Some("cfg(${0:predicate})"), should_be_inner: false },
+    AttrCompletion { label: "deny", snippet: Some("deny(${0:lint})"), should_be_inner: false },
+    AttrCompletion {
+        label: "deprecated",
+        snippet: Some(r#"deprecated = "${0:reason}""#),
+        should_be_inner: false,
+    },
+    AttrCompletion {
+        label: "derive",
+        snippet: Some(r#"derive(${0:Debug})"#),
+        should_be_inner: false,
+    },
+    AttrCompletion { label: "doc", snippet: Some(r#"doc = "${0:docs}""#), should_be_inner: false },
+    AttrCompletion { label: "feature", snippet: Some("feature(${0:flag})"), should_be_inner: true },
+    AttrCompletion { label: "forbid", snippet: Some("forbid(${0:lint})"), should_be_inner: false },
+    // FIXME: resolve through macro resolution?
+    AttrCompletion { label: "global_allocator", snippet: None, should_be_inner: true },
+    AttrCompletion { label: "ignore", snippet: Some("ignore(${0:lint})"), should_be_inner: false },
+    AttrCompletion { label: "inline", snippet: Some("inline(${0:lint})"), should_be_inner: false },
+    AttrCompletion {
+        label: "link_name",
+        snippet: Some(r#"link_name = "${0:symbol_name}""#),
+        should_be_inner: false,
+    },
+    AttrCompletion { label: "link", snippet: None, should_be_inner: false },
+    AttrCompletion { label: "macro_export", snippet: None, should_be_inner: false },
+    AttrCompletion { label: "macro_use", snippet: None, should_be_inner: false },
+    AttrCompletion {
+        label: "must_use",
+        snippet: Some(r#"must_use = "${0:reason}""#),
+        should_be_inner: false,
+    },
+    AttrCompletion { label: "no_mangle", snippet: None, should_be_inner: false },
+    AttrCompletion { label: "no_std", snippet: None, should_be_inner: true },
+    AttrCompletion { label: "non_exhaustive", snippet: None, should_be_inner: false },
+    AttrCompletion { label: "panic_handler", snippet: None, should_be_inner: true },
+    AttrCompletion { label: "path", snippet: Some("path =\"${0:path}\""), should_be_inner: false },
+    AttrCompletion { label: "proc_macro", snippet: None, should_be_inner: false },
+    AttrCompletion { label: "proc_macro_attribute", snippet: None, should_be_inner: false },
+    AttrCompletion {
+        label: "proc_macro_derive",
+        snippet: Some("proc_macro_derive(${0:Trait})"),
+        should_be_inner: false,
+    },
+    AttrCompletion {
+        label: "recursion_limit",
+        snippet: Some("recursion_limit = ${0:128}"),
+        should_be_inner: true,
+    },
+    AttrCompletion { label: "repr", snippet: Some("repr(${0:C})"), should_be_inner: false },
+    AttrCompletion {
+        label: "should_panic",
+        snippet: Some(r#"expected = "${0:reason}""#),
+        should_be_inner: false,
+    },
+    AttrCompletion {
+        label: "target_feature",
+        snippet: Some("target_feature = \"${0:feature}\""),
+        should_be_inner: false,
+    },
+    AttrCompletion { label: "test", snippet: None, should_be_inner: false },
+    AttrCompletion { label: "used", snippet: None, should_be_inner: false },
+    AttrCompletion { label: "warn", snippet: Some("warn(${0:lint})"), should_be_inner: false },
+    AttrCompletion {
+        label: "windows_subsystem",
+        snippet: Some(r#"windows_subsystem = "${0:subsystem}""#),
+        should_be_inner: true,
+    },
+];
+
+#[cfg(test)]
+mod tests {
+    use crate::completion::{test_utils::do_completion, CompletionItem, CompletionKind};
+    use insta::assert_debug_snapshot;
+
+    fn do_attr_completion(code: &str) -> Vec<CompletionItem> {
+        do_completion(code, CompletionKind::Attribute)
+    }
+
+    #[test]
+    fn test_attribute_completion() {
+        assert_debug_snapshot!(
+        do_attr_completion(
+                r"
+                #[<|>]
+                ",
+        ),
+            @r###"
+        [
+            CompletionItem {
+                label: "allow",
+                source_range: [19; 19),
+                delete: [19; 19),
+                insert: "allow(${0:lint})",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "cfg",
+                source_range: [19; 19),
+                delete: [19; 19),
+                insert: "cfg(${0:predicate})",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "cfg_attr",
+                source_range: [19; 19),
+                delete: [19; 19),
+                insert: "cfg_attr(${1:predicate}, ${0:attr})",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "deny",
+                source_range: [19; 19),
+                delete: [19; 19),
+                insert: "deny(${0:lint})",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "deprecated",
+                source_range: [19; 19),
+                delete: [19; 19),
+                insert: "deprecated = \"${0:reason}\"",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "derive",
+                source_range: [19; 19),
+                delete: [19; 19),
+                insert: "derive(${0:Debug})",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "doc",
+                source_range: [19; 19),
+                delete: [19; 19),
+                insert: "doc = \"${0:docs}\"",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "forbid",
+                source_range: [19; 19),
+                delete: [19; 19),
+                insert: "forbid(${0:lint})",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "ignore",
+                source_range: [19; 19),
+                delete: [19; 19),
+                insert: "ignore(${0:lint})",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "inline",
+                source_range: [19; 19),
+                delete: [19; 19),
+                insert: "inline(${0:lint})",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "link",
+                source_range: [19; 19),
+                delete: [19; 19),
+                insert: "link",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "link_name",
+                source_range: [19; 19),
+                delete: [19; 19),
+                insert: "link_name = \"${0:symbol_name}\"",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "macro_export",
+                source_range: [19; 19),
+                delete: [19; 19),
+                insert: "macro_export",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "macro_use",
+                source_range: [19; 19),
+                delete: [19; 19),
+                insert: "macro_use",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "must_use",
+                source_range: [19; 19),
+                delete: [19; 19),
+                insert: "must_use = \"${0:reason}\"",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "no_mangle",
+                source_range: [19; 19),
+                delete: [19; 19),
+                insert: "no_mangle",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "non_exhaustive",
+                source_range: [19; 19),
+                delete: [19; 19),
+                insert: "non_exhaustive",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "path",
+                source_range: [19; 19),
+                delete: [19; 19),
+                insert: "path =\"${0:path}\"",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "proc_macro",
+                source_range: [19; 19),
+                delete: [19; 19),
+                insert: "proc_macro",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "proc_macro_attribute",
+                source_range: [19; 19),
+                delete: [19; 19),
+                insert: "proc_macro_attribute",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "proc_macro_derive",
+                source_range: [19; 19),
+                delete: [19; 19),
+                insert: "proc_macro_derive(${0:Trait})",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "repr",
+                source_range: [19; 19),
+                delete: [19; 19),
+                insert: "repr(${0:C})",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "should_panic",
+                source_range: [19; 19),
+                delete: [19; 19),
+                insert: "expected = \"${0:reason}\"",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "target_feature",
+                source_range: [19; 19),
+                delete: [19; 19),
+                insert: "target_feature = \"${0:feature}\"",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "test",
+                source_range: [19; 19),
+                delete: [19; 19),
+                insert: "test",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "used",
+                source_range: [19; 19),
+                delete: [19; 19),
+                insert: "used",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "warn",
+                source_range: [19; 19),
+                delete: [19; 19),
+                insert: "warn(${0:lint})",
+                kind: Attribute,
+            },
+        ]
+        "###
+        );
+    }
+
+    #[test]
+    fn test_inner_attribute_completion() {
+        assert_debug_snapshot!(
+        do_attr_completion(
+                r"
+                #![<|>]
+                ",
+        ),
+            @r###"
+        [
+            CompletionItem {
+                label: "allow",
+                source_range: [20; 20),
+                delete: [20; 20),
+                insert: "allow(${0:lint})",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "cfg",
+                source_range: [20; 20),
+                delete: [20; 20),
+                insert: "cfg(${0:predicate})",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "cfg_attr",
+                source_range: [20; 20),
+                delete: [20; 20),
+                insert: "cfg_attr(${1:predicate}, ${0:attr})",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "deny",
+                source_range: [20; 20),
+                delete: [20; 20),
+                insert: "deny(${0:lint})",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "deprecated",
+                source_range: [20; 20),
+                delete: [20; 20),
+                insert: "deprecated = \"${0:reason}\"",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "derive",
+                source_range: [20; 20),
+                delete: [20; 20),
+                insert: "derive(${0:Debug})",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "doc",
+                source_range: [20; 20),
+                delete: [20; 20),
+                insert: "doc = \"${0:docs}\"",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "feature",
+                source_range: [20; 20),
+                delete: [20; 20),
+                insert: "feature(${0:flag})",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "forbid",
+                source_range: [20; 20),
+                delete: [20; 20),
+                insert: "forbid(${0:lint})",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "global_allocator",
+                source_range: [20; 20),
+                delete: [20; 20),
+                insert: "global_allocator",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "ignore",
+                source_range: [20; 20),
+                delete: [20; 20),
+                insert: "ignore(${0:lint})",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "inline",
+                source_range: [20; 20),
+                delete: [20; 20),
+                insert: "inline(${0:lint})",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "link",
+                source_range: [20; 20),
+                delete: [20; 20),
+                insert: "link",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "link_name",
+                source_range: [20; 20),
+                delete: [20; 20),
+                insert: "link_name = \"${0:symbol_name}\"",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "macro_export",
+                source_range: [20; 20),
+                delete: [20; 20),
+                insert: "macro_export",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "macro_use",
+                source_range: [20; 20),
+                delete: [20; 20),
+                insert: "macro_use",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "must_use",
+                source_range: [20; 20),
+                delete: [20; 20),
+                insert: "must_use = \"${0:reason}\"",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "no_mangle",
+                source_range: [20; 20),
+                delete: [20; 20),
+                insert: "no_mangle",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "no_std",
+                source_range: [20; 20),
+                delete: [20; 20),
+                insert: "no_std",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "non_exhaustive",
+                source_range: [20; 20),
+                delete: [20; 20),
+                insert: "non_exhaustive",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "panic_handler",
+                source_range: [20; 20),
+                delete: [20; 20),
+                insert: "panic_handler",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "path",
+                source_range: [20; 20),
+                delete: [20; 20),
+                insert: "path =\"${0:path}\"",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "proc_macro",
+                source_range: [20; 20),
+                delete: [20; 20),
+                insert: "proc_macro",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "proc_macro_attribute",
+                source_range: [20; 20),
+                delete: [20; 20),
+                insert: "proc_macro_attribute",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "proc_macro_derive",
+                source_range: [20; 20),
+                delete: [20; 20),
+                insert: "proc_macro_derive(${0:Trait})",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "recursion_limit",
+                source_range: [20; 20),
+                delete: [20; 20),
+                insert: "recursion_limit = ${0:128}",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "repr",
+                source_range: [20; 20),
+                delete: [20; 20),
+                insert: "repr(${0:C})",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "should_panic",
+                source_range: [20; 20),
+                delete: [20; 20),
+                insert: "expected = \"${0:reason}\"",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "target_feature",
+                source_range: [20; 20),
+                delete: [20; 20),
+                insert: "target_feature = \"${0:feature}\"",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "test",
+                source_range: [20; 20),
+                delete: [20; 20),
+                insert: "test",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "used",
+                source_range: [20; 20),
+                delete: [20; 20),
+                insert: "used",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "warn",
+                source_range: [20; 20),
+                delete: [20; 20),
+                insert: "warn(${0:lint})",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "windows_subsystem",
+                source_range: [20; 20),
+                delete: [20; 20),
+                insert: "windows_subsystem = \"${0:subsystem}\"",
+                kind: Attribute,
+            },
+        ]
+        "###
+        );
+    }
+}
diff --git a/crates/ra_ide/src/completion/completion_context.rs b/crates/ra_ide/src/completion/completion_context.rs
index a76d1ce45..37880448a 100644
--- a/crates/ra_ide/src/completion/completion_context.rs
+++ b/crates/ra_ide/src/completion/completion_context.rs
@@ -57,6 +57,7 @@ pub(crate) struct CompletionContext<'a> {
     pub(super) is_macro_call: bool,
     pub(super) is_path_type: bool,
     pub(super) has_type_args: bool,
+    pub(super) is_attribute: bool,
 }
 
 impl<'a> CompletionContext<'a> {
@@ -113,6 +114,7 @@ impl<'a> CompletionContext<'a> {
             is_path_type: false,
             has_type_args: false,
             dot_receiver_is_ambiguous_float_literal: false,
+            is_attribute: false,
         };
 
         let mut original_file = original_file.syntax().clone();
@@ -306,6 +308,7 @@ impl<'a> CompletionContext<'a> {
                 .and_then(|it| it.syntax().parent().and_then(ast::CallExpr::cast))
                 .is_some();
             self.is_macro_call = path.syntax().parent().and_then(ast::MacroCall::cast).is_some();
+            self.is_attribute = path.syntax().parent().and_then(ast::Attr::cast).is_some();
 
             self.is_path_type = path.syntax().parent().and_then(ast::PathType::cast).is_some();
             self.has_type_args = segment.type_arg_list().is_some();
diff --git a/crates/ra_ide/src/completion/completion_item.rs b/crates/ra_ide/src/completion/completion_item.rs
index fb06cc125..5936fb8f7 100644
--- a/crates/ra_ide/src/completion/completion_item.rs
+++ b/crates/ra_ide/src/completion/completion_item.rs
@@ -121,6 +121,7 @@ pub enum CompletionItemKind {
     Method,
     TypeParam,
     Macro,
+    Attribute,
 }
 
 #[derive(Debug, PartialEq, Eq, Copy, Clone)]
@@ -134,6 +135,7 @@ pub(crate) enum CompletionKind {
     Snippet,
     Postfix,
     BuiltinType,
+    Attribute,
 }
 
 #[derive(Debug, PartialEq, Eq, Copy, Clone)]