1 files changed, 688 insertions, 0 deletions

diff --git a/crates/assists/src/handlers/replace_qualified_name_with_use.rs b/crates/assists/src/handlers/replace_qualified_name_with_use.rs
new file mode 100644
index 000000000..011bf1106
--- /dev/null
+++ b/crates/assists/src/handlers/replace_qualified_name_with_use.rs
@@ -0,0 +1,688 @@
+use hir;
+use syntax::{algo::SyntaxRewriter, ast, match_ast, AstNode, SmolStr, SyntaxNode};
+
+use crate::{
+    utils::{find_insert_use_container, insert_use_statement},
+    AssistContext, AssistId, AssistKind, Assists,
+};
+
+// Assist: replace_qualified_name_with_use
+//
+// Adds a use statement for a given fully-qualified name.
+//
+// ```
+// fn process(map: std::collections::<|>HashMap<String, String>) {}
+// ```
+// ->
+// ```
+// use std::collections::HashMap;
+//
+// fn process(map: HashMap<String, String>) {}
+// ```
+pub(crate) fn replace_qualified_name_with_use(
+    acc: &mut Assists,
+    ctx: &AssistContext,
+) -> Option<()> {
+    let path: ast::Path = ctx.find_node_at_offset()?;
+    // We don't want to mess with use statements
+    if path.syntax().ancestors().find_map(ast::Use::cast).is_some() {
+        return None;
+    }
+
+    let hir_path = ctx.sema.lower_path(&path)?;
+    let segments = collect_hir_path_segments(&hir_path)?;
+    if segments.len() < 2 {
+        return None;
+    }
+
+    let target = path.syntax().text_range();
+    acc.add(
+        AssistId("replace_qualified_name_with_use", AssistKind::RefactorRewrite),
+        "Replace qualified path with use",
+        target,
+        |builder| {
+            let path_to_import = hir_path.mod_path().clone();
+            let container = match find_insert_use_container(path.syntax(), ctx) {
+                Some(c) => c,
+                None => return,
+            };
+            insert_use_statement(path.syntax(), &path_to_import, ctx, builder.text_edit_builder());
+
+            // Now that we've brought the name into scope, re-qualify all paths that could be
+            // affected (that is, all paths inside the node we added the `use` to).
+            let mut rewriter = SyntaxRewriter::default();
+            let syntax = container.either(|l| l.syntax().clone(), |r| r.syntax().clone());
+            shorten_paths(&mut rewriter, syntax, path);
+            builder.rewrite(rewriter);
+        },
+    )
+}
+
+fn collect_hir_path_segments(path: &hir::Path) -> Option<Vec<SmolStr>> {
+    let mut ps = Vec::<SmolStr>::with_capacity(10);
+    match path.kind() {
+        hir::PathKind::Abs => ps.push("".into()),
+        hir::PathKind::Crate => ps.push("crate".into()),
+        hir::PathKind::Plain => {}
+        hir::PathKind::Super(0) => ps.push("self".into()),
+        hir::PathKind::Super(lvl) => {
+            let mut chain = "super".to_string();
+            for _ in 0..*lvl {
+                chain += "::super";
+            }
+            ps.push(chain.into());
+        }
+        hir::PathKind::DollarCrate(_) => return None,
+    }
+    ps.extend(path.segments().iter().map(|it| it.name.to_string().into()));
+    Some(ps)
+}
+
+/// Adds replacements to `re` that shorten `path` in all descendants of `node`.
+fn shorten_paths(rewriter: &mut SyntaxRewriter<'static>, node: SyntaxNode, path: ast::Path) {
+    for child in node.children() {
+        match_ast! {
+            match child {
+                // Don't modify `use` items, as this can break the `use` item when injecting a new
+                // import into the use tree.
+                ast::Use(_it) => continue,
+                // Don't descend into submodules, they don't have the same `use` items in scope.
+                ast::Module(_it) => continue,
+
+                ast::Path(p) => {
+                    match maybe_replace_path(rewriter, p.clone(), path.clone()) {
+                        Some(()) => {},
+                        None => shorten_paths(rewriter, p.syntax().clone(), path.clone()),
+                    }
+                },
+                _ => shorten_paths(rewriter, child, path.clone()),
+            }
+        }
+    }
+}
+
+fn maybe_replace_path(
+    rewriter: &mut SyntaxRewriter<'static>,
+    path: ast::Path,
+    target: ast::Path,
+) -> Option<()> {
+    if !path_eq(path.clone(), target) {
+        return None;
+    }
+
+    // Shorten `path`, leaving only its last segment.
+    if let Some(parent) = path.qualifier() {
+        rewriter.delete(parent.syntax());
+    }
+    if let Some(double_colon) = path.coloncolon_token() {
+        rewriter.delete(&double_colon);
+    }
+
+    Some(())
+}
+
+fn path_eq(lhs: ast::Path, rhs: ast::Path) -> bool {
+    let mut lhs_curr = lhs;
+    let mut rhs_curr = rhs;
+    loop {
+        match (lhs_curr.segment(), rhs_curr.segment()) {
+            (Some(lhs), Some(rhs)) if lhs.syntax().text() == rhs.syntax().text() => (),
+            _ => return false,
+        }
+
+        match (lhs_curr.qualifier(), rhs_curr.qualifier()) {
+            (Some(lhs), Some(rhs)) => {
+                lhs_curr = lhs;
+                rhs_curr = rhs;
+            }
+            (None, None) => return true,
+            _ => return false,
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::tests::{check_assist, check_assist_not_applicable};
+
+    use super::*;
+
+    #[test]
+    fn test_replace_add_use_no_anchor() {
+        check_assist(
+            replace_qualified_name_with_use,
+            r"
+std::fmt::Debug<|>
+    ",
+            r"
+use std::fmt::Debug;
+
+Debug
+    ",
+        );
+    }
+    #[test]
+    fn test_replace_add_use_no_anchor_with_item_below() {
+        check_assist(
+            replace_qualified_name_with_use,
+            r"
+std::fmt::Debug<|>
+
+fn main() {
+}
+    ",
+            r"
+use std::fmt::Debug;
+
+Debug
+
+fn main() {
+}
+    ",
+        );
+    }
+
+    #[test]
+    fn test_replace_add_use_no_anchor_with_item_above() {
+        check_assist(
+            replace_qualified_name_with_use,
+            r"
+fn main() {
+}
+
+std::fmt::Debug<|>
+    ",
+            r"
+use std::fmt::Debug;
+
+fn main() {
+}
+
+Debug
+    ",
+        );
+    }
+
+    #[test]
+    fn test_replace_add_use_no_anchor_2seg() {
+        check_assist(
+            replace_qualified_name_with_use,
+            r"
+std::fmt<|>::Debug
+    ",
+            r"
+use std::fmt;
+
+fmt::Debug
+    ",
+        );
+    }
+
+    #[test]
+    fn test_replace_add_use() {
+        check_assist(
+            replace_qualified_name_with_use,
+            r"
+use stdx;
+
+impl std::fmt::Debug<|> for Foo {
+}
+    ",
+            r"
+use stdx;
+use std::fmt::Debug;
+
+impl Debug for Foo {
+}
+    ",
+        );
+    }
+
+    #[test]
+    fn test_replace_file_use_other_anchor() {
+        check_assist(
+            replace_qualified_name_with_use,
+            r"
+impl std::fmt::Debug<|> for Foo {
+}
+    ",
+            r"
+use std::fmt::Debug;
+
+impl Debug for Foo {
+}
+    ",
+        );
+    }
+
+    #[test]
+    fn test_replace_add_use_other_anchor_indent() {
+        check_assist(
+            replace_qualified_name_with_use,
+            r"
+    impl std::fmt::Debug<|> for Foo {
+    }
+    ",
+            r"
+    use std::fmt::Debug;
+
+    impl Debug for Foo {
+    }
+    ",
+        );
+    }
+
+    #[test]
+    fn test_replace_split_different() {
+        check_assist(
+            replace_qualified_name_with_use,
+            r"
+use std::fmt;
+
+impl std::io<|> for Foo {
+}
+    ",
+            r"
+use std::{io, fmt};
+
+impl io for Foo {
+}
+    ",
+        );
+    }
+
+    #[test]
+    fn test_replace_split_self_for_use() {
+        check_assist(
+            replace_qualified_name_with_use,
+            r"
+use std::fmt;
+
+impl std::fmt::Debug<|> for Foo {
+}
+    ",
+            r"
+use std::fmt::{self, Debug, };
+
+impl Debug for Foo {
+}
+    ",
+        );
+    }
+
+    #[test]
+    fn test_replace_split_self_for_target() {
+        check_assist(
+            replace_qualified_name_with_use,
+            r"
+use std::fmt::Debug;
+
+impl std::fmt<|> for Foo {
+}
+    ",
+            r"
+use std::fmt::{self, Debug};
+
+impl fmt for Foo {
+}
+    ",
+        );
+    }
+
+    #[test]
+    fn test_replace_add_to_nested_self_nested() {
+        check_assist(
+            replace_qualified_name_with_use,
+            r"
+use std::fmt::{Debug, nested::{Display}};
+
+impl std::fmt::nested<|> for Foo {
+}
+",
+            r"
+use std::fmt::{Debug, nested::{Display, self}};
+
+impl nested for Foo {
+}
+",
+        );
+    }
+
+    #[test]
+    fn test_replace_add_to_nested_self_already_included() {
+        check_assist(
+            replace_qualified_name_with_use,
+            r"
+use std::fmt::{Debug, nested::{self, Display}};
+
+impl std::fmt::nested<|> for Foo {
+}
+",
+            r"
+use std::fmt::{Debug, nested::{self, Display}};
+
+impl nested for Foo {
+}
+",
+        );
+    }
+
+    #[test]
+    fn test_replace_add_to_nested_nested() {
+        check_assist(
+            replace_qualified_name_with_use,
+            r"
+use std::fmt::{Debug, nested::{Display}};
+
+impl std::fmt::nested::Debug<|> for Foo {
+}
+",
+            r"
+use std::fmt::{Debug, nested::{Display, Debug}};
+
+impl Debug for Foo {
+}
+",
+        );
+    }
+
+    #[test]
+    fn test_replace_split_common_target_longer() {
+        check_assist(
+            replace_qualified_name_with_use,
+            r"
+use std::fmt::Debug;
+
+impl std::fmt::nested::Display<|> for Foo {
+}
+",
+            r"
+use std::fmt::{nested::Display, Debug};
+
+impl Display for Foo {
+}
+",
+        );
+    }
+
+    #[test]
+    fn test_replace_split_common_use_longer() {
+        check_assist(
+            replace_qualified_name_with_use,
+            r"
+use std::fmt::nested::Debug;
+
+impl std::fmt::Display<|> for Foo {
+}
+",
+            r"
+use std::fmt::{Display, nested::Debug};
+
+impl Display for Foo {
+}
+",
+        );
+    }
+
+    #[test]
+    fn test_replace_use_nested_import() {
+        check_assist(
+            replace_qualified_name_with_use,
+            r"
+use crate::{
+    ty::{Substs, Ty},
+    AssocItem,
+};
+
+fn foo() { crate::ty::lower<|>::trait_env() }
+",
+            r"
+use crate::{
+    ty::{Substs, Ty, lower},
+    AssocItem,
+};
+
+fn foo() { lower::trait_env() }
+",
+        );
+    }
+
+    #[test]
+    fn test_replace_alias() {
+        check_assist(
+            replace_qualified_name_with_use,
+            r"
+use std::fmt as foo;
+
+impl foo::Debug<|> for Foo {
+}
+",
+            r"
+use std::fmt as foo;
+
+impl Debug for Foo {
+}
+",
+        );
+    }
+
+    #[test]
+    fn test_replace_not_applicable_one_segment() {
+        check_assist_not_applicable(
+            replace_qualified_name_with_use,
+            r"
+impl foo<|> for Foo {
+}
+",
+        );
+    }
+
+    #[test]
+    fn test_replace_not_applicable_in_use() {
+        check_assist_not_applicable(
+            replace_qualified_name_with_use,
+            r"
+use std::fmt<|>;
+",
+        );
+    }
+
+    #[test]
+    fn test_replace_add_use_no_anchor_in_mod_mod() {
+        check_assist(
+            replace_qualified_name_with_use,
+            r"
+mod foo {
+    mod bar {
+        std::fmt::Debug<|>
+    }
+}
+    ",
+            r"
+mod foo {
+    mod bar {
+        use std::fmt::Debug;
+
+        Debug
+    }
+}
+    ",
+        );
+    }
+
+    #[test]
+    fn inserts_imports_after_inner_attributes() {
+        check_assist(
+            replace_qualified_name_with_use,
+            r"
+#![allow(dead_code)]
+
+fn main() {
+    std::fmt::Debug<|>
+}
+    ",
+            r"
+#![allow(dead_code)]
+use std::fmt::Debug;
+
+fn main() {
+    Debug
+}
+    ",
+        );
+    }
+
+    #[test]
+    fn replaces_all_affected_paths() {
+        check_assist(
+            replace_qualified_name_with_use,
+            r"
+fn main() {
+    std::fmt::Debug<|>;
+    let x: std::fmt::Debug = std::fmt::Debug;
+}
+    ",
+            r"
+use std::fmt::Debug;
+
+fn main() {
+    Debug;
+    let x: Debug = Debug;
+}
+    ",
+        );
+    }
+
+    #[test]
+    fn replaces_all_affected_paths_mod() {
+        check_assist(
+            replace_qualified_name_with_use,
+            r"
+mod m {
+    fn f() {
+        std::fmt::Debug<|>;
+        let x: std::fmt::Debug = std::fmt::Debug;
+    }
+    fn g() {
+        std::fmt::Debug;
+    }
+}
+
+fn f() {
+    std::fmt::Debug;
+}
+    ",
+            r"
+mod m {
+    use std::fmt::Debug;
+
+    fn f() {
+        Debug;
+        let x: Debug = Debug;
+    }
+    fn g() {
+        Debug;
+    }
+}
+
+fn f() {
+    std::fmt::Debug;
+}
+    ",
+        );
+    }
+
+    #[test]
+    fn does_not_replace_in_submodules() {
+        check_assist(
+            replace_qualified_name_with_use,
+            r"
+fn main() {
+    std::fmt::Debug<|>;
+}
+
+mod sub {
+    fn f() {
+        std::fmt::Debug;
+    }
+}
+    ",
+            r"
+use std::fmt::Debug;
+
+fn main() {
+    Debug;
+}
+
+mod sub {
+    fn f() {
+        std::fmt::Debug;
+    }
+}
+    ",
+        );
+    }
+
+    #[test]
+    fn does_not_replace_in_use() {
+        check_assist(
+            replace_qualified_name_with_use,
+            r"
+use std::fmt::Display;
+
+fn main() {
+    std::fmt<|>;
+}
+    ",
+            r"
+use std::fmt::{self, Display};
+
+fn main() {
+    fmt;
+}
+    ",
+        );
+    }
+
+    #[test]
+    fn does_not_replace_pub_use() {
+        check_assist(
+            replace_qualified_name_with_use,
+            r"
+pub use std::fmt;
+
+impl std::io<|> for Foo {
+}
+    ",
+            r"
+use std::io;
+
+pub use std::fmt;
+
+impl io for Foo {
+}
+    ",
+        );
+    }
+
+    #[test]
+    fn does_not_replace_pub_crate_use() {
+        check_assist(
+            replace_qualified_name_with_use,
+            r"
+pub(crate) use std::fmt;
+
+impl std::io<|> for Foo {
+}
+    ",
+            r"
+use std::io;
+
+pub(crate) use std::fmt;
+
+impl io for Foo {
+}
+    ",
+        );
+    }
+}