Auto merge of #18360 - roife:safe-kw-3, r=Veykril

feat: better completions for extern blcoks

This PR refactors `add_keywords` (making it much clearer!) and enhances completion for `extern` blocks.

It is recommended to reviewing the changes in order of the commits:

- The first commit (f3c4dde0a4917a2bac98605cc045eecfb4d69872) doesn’t change any logic but refactors parts of the `add_keywords` function and adds detailed comments.
- The second commit (5dcc1ab649bf8a49cadf006d620871b12f093a2f) improves completion for `extern` kw and extern blocks.

src/tools/rust-analyzer/crates/ide-completion/src/completions/item_list.rs

@@ -29,7 +29,9 @@ pub(crate) fn complete_item_list(
     kind: &ItemListKind,
 ) {
     let _p = tracing::info_span!("complete_item_list").entered();
-    if path_ctx.is_trivial_path() {
+
+    // We handle completions for trait-impls in [`item_list::trait_impl`]
+    if path_ctx.is_trivial_path() && !matches!(kind, ItemListKind::TraitImpl(_)) {
         add_keywords(acc, ctx, Some(kind));
     }
 
@@ -75,73 +77,95 @@ fn add_keywords(acc: &mut Completions, ctx: &CompletionContext<'_>, kind: Option
 
     let in_item_list = matches!(kind, Some(ItemListKind::SourceFile | ItemListKind::Module) | None);
     let in_assoc_non_trait_impl = matches!(kind, Some(ItemListKind::Impl | ItemListKind::Trait));
-    let in_extern_block = matches!(kind, Some(ItemListKind::ExternBlock));
+
+    let in_extern_block = matches!(kind, Some(ItemListKind::ExternBlock { .. }));
+    let in_unsafe_extern_block =
+        matches!(kind, Some(ItemListKind::ExternBlock { is_unsafe: true }));
+
     let in_trait = matches!(kind, Some(ItemListKind::Trait));
-    let in_trait_impl = matches!(kind, Some(ItemListKind::TraitImpl(_)));
     let in_inherent_impl = matches!(kind, Some(ItemListKind::Impl));
-    let no_vis_qualifiers = ctx.qualifier_ctx.vis_node.is_none();
     let in_block = kind.is_none();
 
-    let missing_qualifiers = [
-        ctx.qualifier_ctx.unsafe_tok.is_none().then_some(("unsafe", "unsafe $0")),
-        ctx.qualifier_ctx.async_tok.is_none().then_some(("async", "async $0")),
-    ];
-
-    if !in_trait_impl {
-        // handle qualifier tokens
-        if missing_qualifiers.iter().any(Option::is_none) {
-            // only complete missing qualifiers
-            missing_qualifiers.iter().filter_map(|x| *x).for_each(|(kw, snippet)| {
-                add_keyword(kw, snippet);
-            });
-
-            if in_item_list || in_assoc_non_trait_impl {
-                add_keyword("fn", "fn $1($2) {\n    $0\n}");
-            }
+    let no_vis_qualifiers = ctx.qualifier_ctx.vis_node.is_none();
+    let has_unsafe_kw = ctx.qualifier_ctx.unsafe_tok.is_some();
+    let has_async_kw = ctx.qualifier_ctx.async_tok.is_some();
+    let has_safe_kw = ctx.qualifier_ctx.safe_tok.is_some();
+
+    // Some keywords are invalid after non-vis qualifiers, so we handle them first.
+    if (has_unsafe_kw || has_safe_kw) && in_extern_block {
+        add_keyword("fn", "fn $1($2);");
+        add_keyword("static", "static $1: $2;");
+        return;
+    }
 
-            if ctx.qualifier_ctx.unsafe_tok.is_some() && in_item_list {
-                add_keyword("trait", "trait $1 {\n    $0\n}");
-                if no_vis_qualifiers {
-                    add_keyword("impl", "impl $1 {\n    $0\n}");
-                }
-            }
+    if has_unsafe_kw || has_async_kw {
+        if !has_unsafe_kw {
+            add_keyword("unsafe", "unsafe $0");
+        }
+        if !has_async_kw {
+            add_keyword("async", "async $0");
+        }
 
-            return;
+        if in_item_list || in_assoc_non_trait_impl {
+            add_keyword("fn", "fn $1($2) {\n    $0\n}");
         }
 
-        if in_item_list {
-            add_keyword("enum", "enum $1 {\n    $0\n}");
-            add_keyword("mod", "mod $0");
-            add_keyword("static", "static $0");
-            add_keyword("struct", "struct $0");
+        if has_unsafe_kw && in_item_list {
             add_keyword("trait", "trait $1 {\n    $0\n}");
-            add_keyword("union", "union $1 {\n    $0\n}");
-            add_keyword("use", "use $0");
             if no_vis_qualifiers {
                 add_keyword("impl", "impl $1 {\n    $0\n}");
             }
         }
 
-        if !in_trait && !in_block && no_vis_qualifiers {
-            add_keyword("pub(crate)", "pub(crate) $0");
-            add_keyword("pub(super)", "pub(super) $0");
-            add_keyword("pub", "pub $0");
+        if !has_async_kw && no_vis_qualifiers && in_item_list {
+            add_keyword("extern", "extern $0");
         }
 
-        if in_extern_block {
-            add_keyword("fn", "fn $1($2);");
-        } else {
-            if !in_inherent_impl {
-                if !in_trait {
-                    add_keyword("extern", "extern $0");
-                }
-                add_keyword("type", "type $0");
-            }
+        return;
+    }
 
-            add_keyword("fn", "fn $1($2) {\n    $0\n}");
-            add_keyword("unsafe", "unsafe $0");
-            add_keyword("const", "const $0");
-            add_keyword("async", "async $0");
+    // ...and the rest deals with cases without any non-vis qualifiers.
+
+    // Visibility qualifiers
+    if !in_trait && !in_block && no_vis_qualifiers {
+        add_keyword("pub(crate)", "pub(crate) $0");
+        add_keyword("pub(super)", "pub(super) $0");
+        add_keyword("pub", "pub $0");
+    }
+
+    // Keywords that are valid in `item_list`
+    if in_item_list {
+        add_keyword("enum", "enum $1 {\n    $0\n}");
+        add_keyword("mod", "mod $0");
+        add_keyword("static", "static $0");
+        add_keyword("struct", "struct $0");
+        add_keyword("trait", "trait $1 {\n    $0\n}");
+        add_keyword("union", "union $1 {\n    $0\n}");
+        add_keyword("use", "use $0");
+        if no_vis_qualifiers {
+            add_keyword("impl", "impl $1 {\n    $0\n}");
+        }
+    }
+
+    if in_extern_block {
+        add_keyword("unsafe", "unsafe $0");
+        if in_unsafe_extern_block {
+            add_keyword("safe", "safe $0");
         }
+
+        add_keyword("fn", "fn $1($2);");
+        add_keyword("static", "static $1: $2;");
+    } else {
+        if !in_inherent_impl {
+            if !in_trait {
+                add_keyword("extern", "extern $0");
+            }
+            add_keyword("type", "type $0");
+        }
+
+        add_keyword("fn", "fn $1($2) {\n    $0\n}");
+        add_keyword("unsafe", "unsafe $0");
+        add_keyword("const", "const $0");
+        add_keyword("async", "async $0");
     }
 }

src/tools/rust-analyzer/crates/ide-completion/src/completions/keyword.rs

@@ -58,6 +58,7 @@ mod tests {
             r"fn my_fn() { unsafe $0 }",
             expect![[r#"
                 kw async
+                kw extern
                 kw fn
                 kw impl
                 kw trait

src/tools/rust-analyzer/crates/ide-completion/src/context.rs

@@ -48,12 +48,16 @@ pub(crate) struct QualifierCtx {
     // TODO: Add try_tok and default_tok
     pub(crate) async_tok: Option<SyntaxToken>,
     pub(crate) unsafe_tok: Option<SyntaxToken>,
+    pub(crate) safe_tok: Option<SyntaxToken>,
     pub(crate) vis_node: Option<ast::Visibility>,
 }
 
 impl QualifierCtx {
     pub(crate) fn none(&self) -> bool {
-        self.async_tok.is_none() && self.unsafe_tok.is_none() && self.vis_node.is_none()
+        self.async_tok.is_none()
+            && self.unsafe_tok.is_none()
+            && self.safe_tok.is_none()
+            && self.vis_node.is_none()
     }
 }
 
@@ -229,7 +233,7 @@ pub(crate) enum ItemListKind {
     Impl,
     TraitImpl(Option<ast::Impl>),
     Trait,
-    ExternBlock,
+    ExternBlock { is_unsafe: bool },
 }
 
 #[derive(Debug)]

src/tools/rust-analyzer/crates/ide-completion/src/context/analysis.rs

@@ -1108,7 +1108,14 @@ fn classify_name_ref(
                     },
                     None => return None,
                 } },
-                ast::ExternItemList(_) => PathKind::Item { kind: ItemListKind::ExternBlock },
+                ast::ExternItemList(it) => {
+                    let exn_blk = it.syntax().parent().and_then(ast::ExternBlock::cast);
+                    PathKind::Item {
+                        kind: ItemListKind::ExternBlock {
+                            is_unsafe: exn_blk.and_then(|it| it.unsafe_token()).is_some(),
+                        }
+                    }
+                },
                 ast::SourceFile(_) => PathKind::Item { kind: ItemListKind::SourceFile },
                 _ => return None,
             }
@@ -1310,6 +1317,7 @@ fn classify_name_ref(
                         match token.kind() {
                             SyntaxKind::UNSAFE_KW => qualifier_ctx.unsafe_tok = Some(token),
                             SyntaxKind::ASYNC_KW => qualifier_ctx.async_tok = Some(token),
+                            SyntaxKind::SAFE_KW => qualifier_ctx.safe_tok = Some(token),
                             _ => {}
                         }
                     }

src/tools/rust-analyzer/crates/ide-completion/src/tests/item_list.rs

@@ -124,6 +124,7 @@ fn after_unsafe_token() {
         r#"unsafe $0"#,
         expect![[r#"
             kw async
+            kw extern
             kw fn
             kw impl
             kw trait
@@ -495,3 +496,57 @@ type O = $0;
 ",
     )
 }
+
+#[test]
+fn inside_extern_blocks() {
+    // Should suggest `fn`, `static`, `unsafe`
+    check(
+        r#"extern { $0 }"#,
+        expect![[r#"
+            ma makro!(…)  macro_rules! makro
+            md module
+            kw crate::
+            kw fn
+            kw pub
+            kw pub(crate)
+            kw pub(super)
+            kw self::
+            kw static
+            kw unsafe
+        "#]],
+    );
+
+    // Should suggest `fn`, `static`, `safe`, `unsafe`
+    check(
+        r#"unsafe extern { $0 }"#,
+        expect![[r#"
+            ma makro!(…)  macro_rules! makro
+            md module
+            kw crate::
+            kw fn
+            kw pub
+            kw pub(crate)
+            kw pub(super)
+            kw safe
+            kw self::
+            kw static
+            kw unsafe
+        "#]],
+    );
+
+    check(
+        r#"unsafe extern { pub safe $0 }"#,
+        expect![[r#"
+            kw fn
+            kw static
+        "#]],
+    );
+
+    check(
+        r#"unsafe extern { pub unsafe $0 }"#,
+        expect![[r#"
+            kw fn
+            kw static
+        "#]],
+    )
+}