3 files changed, 131 insertions, 9 deletions

diff --git a/crates/ra_ide_api/src/completion/complete_macro_in_item_position.rs b/crates/ra_ide_api/src/completion/complete_macro_in_item_position.rs
index d808b2357..09f743c66 100644
--- a/crates/ra_ide_api/src/completion/complete_macro_in_item_position.rs
+++ b/crates/ra_ide_api/src/completion/complete_macro_in_item_position.rs
@@ -56,6 +56,16 @@ mod tests {
             do_reference_completion(
                 "
                 //- /main.rs
+                /// Creates a [`Vec`] containing the arguments.
+                ///
+                /// - Create a [`Vec`] containing a given list of elements:
+                ///
+                /// ```
+                /// let v = vec![1, 2, 3];
+                /// assert_eq!(v[0], 1);
+                /// assert_eq!(v[1], 2);
+                /// assert_eq!(v[2], 3);
+                /// ```
                 macro_rules! vec {
                     () => {}
                 }
@@ -68,13 +78,61 @@ mod tests {
             @r##"[
     CompletionItem {
         label: "vec!",
-        source_range: [46; 46),
-        delete: [46; 46),
+        source_range: [280; 280),
+        delete: [280; 280),
         insert: "vec![$0]",
         kind: Macro,
         detail: "macro_rules! vec",
+        documentation: Documentation(
+            "Creates a [`Vec`] containing the arguments.\n\n- Create a [`Vec`] containing a given list of elements:\n\n```\nlet v = vec![1, 2, 3];\nassert_eq!(v[0], 1);\nassert_eq!(v[1], 2);\nassert_eq!(v[2], 3);\n```",
+        ),
     },
 ]"##
         );
     }
+
+    #[test]
+    fn completes_macros_braces_guessing() {
+        assert_debug_snapshot!(
+            do_reference_completion(
+                "
+                //- /main.rs
+                /// Foo
+                ///
+                /// Not call `fooo!()` `fooo!()`, or `_foo![]` `_foo![]`.
+                /// Call as `let _=foo!  { hello world };`
+                macro_rules! foo {
+                    () => {}
+                }
+
+                fn main() {
+                    <|>
+                }
+                "
+            ),
+            @r###"[
+    CompletionItem {
+        label: "foo!",
+        source_range: [163; 163),
+        delete: [163; 163),
+        insert: "foo! {$0}",
+        kind: Macro,
+        detail: "macro_rules! foo",
+        documentation: Documentation(
+            "Foo\n\nNot call `fooo!()` `fooo!()`, or `_foo![]` `_foo![]`.\nCall as `let _=foo!  { hello world };`",
+        ),
+    },
+    CompletionItem {
+        label: "main()",
+        source_range: [163; 163),
+        delete: [163; 163),
+        insert: "main()$0",
+        kind: Function,
+        lookup: "main",
+        detail: "fn main()",
+    },
+]
+        "###
+        );
+    }
 }
diff --git a/crates/ra_ide_api/src/completion/presentation.rs b/crates/ra_ide_api/src/completion/presentation.rs
index 20242d293..aed4ce6d4 100644
--- a/crates/ra_ide_api/src/completion/presentation.rs
+++ b/crates/ra_ide_api/src/completion/presentation.rs
@@ -131,6 +131,33 @@ impl Completions {
         self.add_function_with_name(ctx, None, func)
     }
 
+    fn guess_macro_braces(&self, macro_name: &str, docs: &str) -> &'static str {
+        let mut votes = [0, 0, 0];
+        for (idx, s) in docs.match_indices(&macro_name) {
+            let (before, after) = (&docs[..idx], &docs[idx + s.len()..]);
+            // Ensure to match the full word
+            if after.starts_with("!")
+                && before
+                    .chars()
+                    .rev()
+                    .next()
+                    .map_or(true, |c| c != '_' && !c.is_ascii_alphanumeric())
+            {
+                // It may have spaces before the braces like `foo! {}`
+                match after[1..].chars().find(|&c| !c.is_whitespace()) {
+                    Some('{') => votes[0] += 1,
+                    Some('[') => votes[1] += 1,
+                    Some('(') => votes[2] += 1,
+                    _ => {}
+                }
+            }
+        }
+
+        // Insert a space before `{}`.
+        // We prefer the last one when some votes equal.
+        *votes.iter().zip(&[" {$0}", "[$0]", "($0)"]).max_by_key(|&(&vote, _)| vote).unwrap().1
+    }
+
     pub(crate) fn add_macro(
         &mut self,
         ctx: &CompletionContext,
@@ -141,10 +168,9 @@ impl Completions {
         if let Some(name) = name {
             let detail = macro_label(&ast_node);
 
-            let macro_braces_to_insert = match name.as_str() {
-                "vec" => "[$0]",
-                _ => "($0)",
-            };
+            let docs = macro_.docs(ctx.db);
+            let macro_braces_to_insert =
+                self.guess_macro_braces(&name, docs.as_ref().map_or("", |s| s.as_str()));
             let macro_declaration = name + "!";
 
             let builder = CompletionItem::new(
@@ -153,7 +179,7 @@ impl Completions {
                 &macro_declaration,
             )
             .kind(CompletionItemKind::Macro)
-            .set_documentation(macro_.docs(ctx.db))
+            .set_documentation(docs)
             .detail(detail)
             .insert_snippet(macro_declaration + macro_braces_to_insert);
 
diff --git a/xtask/src/main.rs b/xtask/src/main.rs
index 623058436..c08915aac 100644
--- a/xtask/src/main.rs
+++ b/xtask/src/main.rs
@@ -8,9 +8,12 @@ use pico_args::Arguments;
 use std::{env, path::PathBuf};
 use xtask::{
     gen_tests, generate_boilerplate, install_format_hook, run, run_clippy, run_fuzzer, run_rustfmt,
-    Cmd, Overwrite, Result,
+    run_with_output, Cmd, Overwrite, Result,
 };
 
+// Latest stable, feel free to send a PR if this lags behind.
+const REQUIRED_RUST_VERSION: u32 = 38;
+
 struct InstallOpt {
     client: Option<ClientOpt>,
     server: Option<ServerOpt>,
@@ -210,9 +213,44 @@ fn install_client(ClientOpt::VsCode: ClientOpt) -> Result<()> {
 }
 
 fn install_server(opts: ServerOpt) -> Result<()> {
-    if opts.jemalloc {
+    let mut old_rust = false;
+    if let Ok(output) = run_with_output("cargo --version", ".") {
+        if let Ok(stdout) = String::from_utf8(output.stdout) {
+            if !check_version(&stdout, REQUIRED_RUST_VERSION) {
+                old_rust = true;
+            }
+        }
+    }
+
+    if old_rust {
+        eprintln!(
+            "\nWARNING: at least rust 1.{}.0 is required to compile rust-analyzer\n",
+            REQUIRED_RUST_VERSION
+        )
+    }
+
+    let res = if opts.jemalloc {
         run("cargo install --path crates/ra_lsp_server --locked --force --features jemalloc", ".")
     } else {
         run("cargo install --path crates/ra_lsp_server --locked --force", ".")
+    };
+
+    if res.is_err() && old_rust {
+        eprintln!(
+            "\nWARNING: at least rust 1.{}.0 is required to compile rust-analyzer\n",
+            REQUIRED_RUST_VERSION
+        )
+    }
+
+    res
+}
+
+fn check_version(version_output: &str, min_minor_version: u32) -> bool {
+    // Parse second the number out of
+    //      cargo 1.39.0-beta (1c6ec66d5 2019-09-30)
+    let minor: Option<u32> = version_output.split('.').nth(1).and_then(|it| it.parse().ok());
+    match minor {
+        None => true,
+        Some(minor) => minor >= min_minor_version,
     }
 }