From 21d2cebcf1a417bce72da98aa638a20235c050db Mon Sep 17 00:00:00 2001
From: David Lattimore <dml@google.com>
Date: Sat, 1 Aug 2020 12:43:10 +1000
Subject: SSR: Matching trait associated constants, types and functions

This fixes matching of things like `HashMap::default()` by resolving
`HashMap` instead of `default` (which resolves to `Default::default`).

Same for associated constants and types that are part of a trait
implementation.

However, we still don't support matching calls to trait methods.
---
 crates/ra_ssr/src/resolving.rs | 31 +++++++++++++++++++++++++++----
 1 file changed, 27 insertions(+), 4 deletions(-)

(limited to 'crates/ra_ssr/src/resolving.rs')

diff --git a/crates/ra_ssr/src/resolving.rs b/crates/ra_ssr/src/resolving.rs
index 6f62000f4..d5b65eaac 100644
--- a/crates/ra_ssr/src/resolving.rs
+++ b/crates/ra_ssr/src/resolving.rs
@@ -5,7 +5,7 @@ use crate::{parsing, SsrError};
 use parsing::Placeholder;
 use ra_db::FilePosition;
 use ra_syntax::{ast, SmolStr, SyntaxKind, SyntaxNode, SyntaxToken};
-use rustc_hash::{FxHashMap, FxHashSet};
+use rustc_hash::FxHashMap;
 use test_utils::mark;
 
 pub(crate) struct ResolutionScope<'db> {
@@ -111,8 +111,10 @@ impl Resolver<'_, '_> {
                     .resolution_scope
                     .resolve_path(&path)
                     .ok_or_else(|| error!("Failed to resolve path `{}`", node.text()))?;
-                resolved_paths.insert(node, ResolvedPath { resolution, depth });
-                return Ok(());
+                if self.ok_to_use_path_resolution(&resolution) {
+                    resolved_paths.insert(node, ResolvedPath { resolution, depth });
+                    return Ok(());
+                }
             }
         }
         for node in node.children() {
@@ -136,6 +138,27 @@ impl Resolver<'_, '_> {
         }
         false
     }
+
+    fn ok_to_use_path_resolution(&self, resolution: &hir::PathResolution) -> bool {
+        match resolution {
+            hir::PathResolution::AssocItem(hir::AssocItem::Function(function)) => {
+                if function.has_self_param(self.resolution_scope.scope.db) {
+                    // If we don't use this path resolution, then we won't be able to match method
+                    // calls. e.g. `Foo::bar($s)` should match `x.bar()`.
+                    true
+                } else {
+                    mark::hit!(replace_associated_trait_default_function_call);
+                    false
+                }
+            }
+            hir::PathResolution::AssocItem(_) => {
+                // Not a function. Could be a constant or an associated type.
+                mark::hit!(replace_associated_trait_constant);
+                false
+            }
+            _ => true,
+        }
+    }
 }
 
 impl<'db> ResolutionScope<'db> {
@@ -176,7 +199,7 @@ impl<'db> ResolutionScope<'db> {
             adt.ty(self.scope.db).iterate_path_candidates(
                 self.scope.db,
                 self.scope.module()?.krate(),
-                &FxHashSet::default(),
+                &self.scope.traits_in_scope(),
                 Some(hir_path.segments().last()?.name),
                 |_ty, assoc_item| Some(hir::PathResolution::AssocItem(assoc_item)),
             )
-- 
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