Don't expose hir::Path out of hir

Conjecture: it's impossible to use hir::Path *correctly* from an IDE.

I am not entirely sure about this, and we might need to add it back at
some point, but I have to arguments that convince me that we probably
won't:

* `hir::Path` has to know about hygiene, which an IDE can't set up
  properly.

* `hir::Path` lacks identity, but you actually have to know identity
  to resolve it correctly

5 files changed, 37 insertions, 47 deletions

diff --git a/crates/assists/src/handlers/auto_import.rs b/crates/assists/src/handlers/auto_import.rs
index cce789972..b9ec3f10b 100644
--- a/crates/assists/src/handlers/auto_import.rs
+++ b/crates/assists/src/handlers/auto_import.rs
@@ -53,7 +53,7 @@ pub(crate) fn auto_import(acc: &mut Assists, ctx: &AssistContext) -> Option<()>
             |builder| {
                 insert_use_statement(
                     &auto_import_assets.syntax_under_caret,
-                    &import,
+                    &import.to_string(),
                     ctx,
                     builder.text_edit_builder(),
                 );
diff --git a/crates/assists/src/handlers/expand_glob_import.rs b/crates/assists/src/handlers/expand_glob_import.rs
index f690ec343..81d0af2f3 100644
--- a/crates/assists/src/handlers/expand_glob_import.rs
+++ b/crates/assists/src/handlers/expand_glob_import.rs
@@ -1,3 +1,4 @@
+use either::Either;
 use hir::{AssocItem, MacroDef, ModuleDef, Name, PathResolution, ScopeDef, SemanticsScope};
 use ide_db::{
     defs::{classify_name_ref, Definition, NameRefClass},
@@ -10,8 +11,6 @@ use crate::{
     AssistId, AssistKind,
 };
 
-use either::Either;
-
 // Assist: expand_glob_import
 //
 // Expands glob imports.
@@ -40,11 +39,15 @@ use either::Either;
 pub(crate) fn expand_glob_import(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
     let star = ctx.find_token_at_offset(T![*])?;
     let mod_path = find_mod_path(&star)?;
+    let module = match ctx.sema.resolve_path(&mod_path)? {
+        PathResolution::Def(ModuleDef::Module(it)) => it,
+        _ => return None,
+    };
 
     let source_file = ctx.source_file();
     let scope = ctx.sema.scope_at_offset(source_file.syntax(), ctx.offset());
 
-    let defs_in_mod = find_defs_in_mod(ctx, scope, &mod_path)?;
+    let defs_in_mod = find_defs_in_mod(ctx, scope, module)?;
     let name_refs_in_source_file =
         source_file.syntax().descendants().filter_map(ast::NameRef::cast).collect();
     let used_names = find_used_names(ctx, defs_in_mod, name_refs_in_source_file);
@@ -82,17 +85,8 @@ impl Def {
 fn find_defs_in_mod(
     ctx: &AssistContext,
     from: SemanticsScope<'_>,
-    path: &ast::Path,
+    module: hir::Module,
 ) -> Option<Vec<Def>> {
-    let hir_path = ctx.sema.lower_path(&path)?;
-    let module = if let Some(PathResolution::Def(ModuleDef::Module(module))) =
-        from.resolve_hir_path_qualifier(&hir_path)
-    {
-        module
-    } else {
-        return None;
-    };
-
     let module_scope = module.scope(ctx.db(), from.module());
 
     let mut defs = vec![];
diff --git a/crates/assists/src/handlers/extract_struct_from_enum_variant.rs b/crates/assists/src/handlers/extract_struct_from_enum_variant.rs
index 4bcdae7ba..d62e06b4a 100644
--- a/crates/assists/src/handlers/extract_struct_from_enum_variant.rs
+++ b/crates/assists/src/handlers/extract_struct_from_enum_variant.rs
@@ -106,7 +106,12 @@ fn insert_import(
     if let Some(mut mod_path) = mod_path {
         mod_path.segments.pop();
         mod_path.segments.push(variant_hir_name.clone());
-        insert_use_statement(path.syntax(), &mod_path, ctx, builder.text_edit_builder());
+        insert_use_statement(
+            path.syntax(),
+            &mod_path.to_string(),
+            ctx,
+            builder.text_edit_builder(),
+        );
     }
     Some(())
 }
diff --git a/crates/assists/src/handlers/replace_qualified_name_with_use.rs b/crates/assists/src/handlers/replace_qualified_name_with_use.rs
index 011bf1106..470e5f8ff 100644
--- a/crates/assists/src/handlers/replace_qualified_name_with_use.rs
+++ b/crates/assists/src/handlers/replace_qualified_name_with_use.rs
@@ -1,5 +1,5 @@
-use hir;
-use syntax::{algo::SyntaxRewriter, ast, match_ast, AstNode, SmolStr, SyntaxNode};
+use syntax::{algo::SyntaxRewriter, ast, match_ast, AstNode, SyntaxNode, TextRange};
+use test_utils::mark;
 
 use crate::{
     utils::{find_insert_use_container, insert_use_statement},
@@ -28,12 +28,19 @@ pub(crate) fn replace_qualified_name_with_use(
     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 {
+    if path.qualifier().is_none() {
+        mark::hit!(dont_import_trivial_paths);
         return None;
     }
+    let path_to_import = path.to_string().clone();
+    let path_to_import = match path.segment()?.generic_arg_list() {
+        Some(generic_args) => {
+            let generic_args_start =
+                generic_args.syntax().text_range().start() - path.syntax().text_range().start();
+            &path_to_import[TextRange::up_to(generic_args_start)]
+        }
+        None => path_to_import.as_str(),
+    };
 
     let target = path.syntax().text_range();
     acc.add(
@@ -41,12 +48,16 @@ pub(crate) fn replace_qualified_name_with_use(
         "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());
+            insert_use_statement(
+                path.syntax(),
+                &path_to_import.to_string(),
+                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).
@@ -58,26 +69,6 @@ pub(crate) fn replace_qualified_name_with_use(
     )
 }
 
-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() {
@@ -467,7 +458,8 @@ impl Debug for Foo {
     }
 
     #[test]
-    fn test_replace_not_applicable_one_segment() {
+    fn dont_import_trivial_paths() {
+        mark::check!(dont_import_trivial_paths);
         check_assist_not_applicable(
             replace_qualified_name_with_use,
             r"
diff --git a/crates/assists/src/utils/insert_use.rs b/crates/assists/src/utils/insert_use.rs
index 50a62ee82..49096a67c 100644
--- a/crates/assists/src/utils/insert_use.rs
+++ b/crates/assists/src/utils/insert_use.rs
@@ -5,7 +5,6 @@
 use std::iter::successors;
 
 use either::Either;
-use hir::{self, ModPath};
 use syntax::{
     ast::{self, NameOwner, VisibilityOwner},
     AstNode, AstToken, Direction, SmolStr,
@@ -35,11 +34,11 @@ pub(crate) fn find_insert_use_container(
 pub(crate) fn insert_use_statement(
     // Ideally the position of the cursor, used to
     position: &SyntaxNode,
-    path_to_import: &ModPath,
+    path_to_import: &str,
     ctx: &AssistContext,
     builder: &mut TextEditBuilder,
 ) {
-    let target = path_to_import.to_string().split("::").map(SmolStr::new).collect::<Vec<_>>();
+    let target = path_to_import.split("::").map(SmolStr::new).collect::<Vec<_>>();
     let container = find_insert_use_container(position, ctx);
 
     if let Some(container) = container {