SSR: Match paths based on what they resolve to

Also render template paths appropriately for their context.

9 files changed, 482 insertions, 61 deletions

diff --git a/crates/ra_ide/src/ssr.rs b/crates/ra_ide/src/ssr.rs
index 3e2705d62..2f40bac08 100644
--- a/crates/ra_ide/src/ssr.rs
+++ b/crates/ra_ide/src/ssr.rs
@@ -11,6 +11,16 @@ use ra_ssr::{MatchFinder, SsrError, SsrRule};
 // A `$<name>` placeholder in the search pattern will match any AST node and `$<name>` will reference it in the replacement.
 // Within a macro call, a placeholder will match up until whatever token follows the placeholder.
 //
+// All paths in both the search pattern and the replacement template must resolve in the context
+// in which this command is invoked. Paths in the search pattern will then match the code if they
+// resolve to the same item, even if they're written differently. For example if we invoke the
+// command in the module `foo` with a pattern of `Bar`, then code in the parent module that refers
+// to `foo::Bar` will match.
+//
+// Paths in the replacement template will be rendered appropriately for the context in which the
+// replacement occurs. For example if our replacement template is `foo::Bar` and we match some
+// code in the `foo` module, we'll insert just `Bar`.
+//
 // Placeholders may be given constraints by writing them as `${<name>:<constraint1>:<constraint2>...}`.
 //
 // Supported constraints:
@@ -47,7 +57,7 @@ pub fn parse_search_replace(
 ) -> Result<Vec<SourceFileEdit>, SsrError> {
     let rule: SsrRule = rule.parse()?;
     let mut match_finder = MatchFinder::in_context(db, position);
-    match_finder.add_rule(rule);
+    match_finder.add_rule(rule)?;
     if parse_only {
         return Ok(Vec::new());
     }
diff --git a/crates/ra_ssr/src/lib.rs b/crates/ra_ssr/src/lib.rs
index a0a5c9762..286619f59 100644
--- a/crates/ra_ssr/src/lib.rs
+++ b/crates/ra_ssr/src/lib.rs
@@ -7,6 +7,7 @@ mod matching;
 mod nester;
 mod parsing;
 mod replacing;
+mod resolving;
 mod search;
 #[macro_use]
 mod errors;
@@ -21,6 +22,7 @@ use hir::Semantics;
 use ra_db::{FileId, FilePosition, FileRange};
 use ra_ide_db::source_change::SourceFileEdit;
 use ra_syntax::{ast, AstNode, SyntaxNode, TextRange};
+use resolving::ResolvedRule;
 use rustc_hash::FxHashMap;
 
 // A structured search replace rule. Create by calling `parse` on a str.
@@ -48,7 +50,9 @@ pub struct SsrMatches {
 pub struct MatchFinder<'db> {
     /// Our source of information about the user's code.
     sema: Semantics<'db, ra_ide_db::RootDatabase>,
-    rules: Vec<parsing::ParsedRule>,
+    rules: Vec<ResolvedRule>,
+    scope: hir::SemanticsScope<'db>,
+    hygiene: hir::Hygiene,
 }
 
 impl<'db> MatchFinder<'db> {
@@ -56,10 +60,24 @@ impl<'db> MatchFinder<'db> {
     /// `lookup_context`.
     pub fn in_context(
         db: &'db ra_ide_db::RootDatabase,
-        _lookup_context: FilePosition,
+        lookup_context: FilePosition,
     ) -> MatchFinder<'db> {
-        // FIXME: Use lookup_context
-        MatchFinder { sema: Semantics::new(db), rules: Vec::new() }
+        let sema = Semantics::new(db);
+        let file = sema.parse(lookup_context.file_id);
+        // Find a node at the requested position, falling back to the whole file.
+        let node = file
+            .syntax()
+            .token_at_offset(lookup_context.offset)
+            .left_biased()
+            .map(|token| token.parent())
+            .unwrap_or_else(|| file.syntax().clone());
+        let scope = sema.scope(&node);
+        MatchFinder {
+            sema: Semantics::new(db),
+            rules: Vec::new(),
+            scope,
+            hygiene: hir::Hygiene::new(db, lookup_context.file_id.into()),
+        }
     }
 
     /// Constructs an instance using the start of the first file in `db` as the lookup context.
@@ -84,8 +102,16 @@ impl<'db> MatchFinder<'db> {
     /// Adds a rule to be applied. The order in which rules are added matters. Earlier rules take
     /// precedence. If a node is matched by an earlier rule, then later rules won't be permitted to
     /// match to it.
-    pub fn add_rule(&mut self, rule: SsrRule) {
-        self.add_parsed_rules(rule.parsed_rules);
+    pub fn add_rule(&mut self, rule: SsrRule) -> Result<(), SsrError> {
+        for parsed_rule in rule.parsed_rules {
+            self.rules.push(ResolvedRule::new(
+                parsed_rule,
+                &self.scope,
+                &self.hygiene,
+                self.rules.len(),
+            )?);
+        }
+        Ok(())
     }
 
     /// Finds matches for all added rules and returns edits for all found matches.
@@ -110,8 +136,16 @@ impl<'db> MatchFinder<'db> {
 
     /// Adds a search pattern. For use if you intend to only call `find_matches_in_file`. If you
     /// intend to do replacement, use `add_rule` instead.
-    pub fn add_search_pattern(&mut self, pattern: SsrPattern) {
-        self.add_parsed_rules(pattern.parsed_rules);
+    pub fn add_search_pattern(&mut self, pattern: SsrPattern) -> Result<(), SsrError> {
+        for parsed_rule in pattern.parsed_rules {
+            self.rules.push(ResolvedRule::new(
+                parsed_rule,
+                &self.scope,
+                &self.hygiene,
+                self.rules.len(),
+            )?);
+        }
+        Ok(())
     }
 
     /// Returns matches for all added rules.
@@ -149,13 +183,6 @@ impl<'db> MatchFinder<'db> {
         res
     }
 
-    fn add_parsed_rules(&mut self, parsed_rules: Vec<parsing::ParsedRule>) {
-        for mut parsed_rule in parsed_rules {
-            parsed_rule.index = self.rules.len();
-            self.rules.push(parsed_rule);
-        }
-    }
-
     fn output_debug_for_nodes_at_range(
         &self,
         node: &SyntaxNode,
@@ -175,7 +202,7 @@ impl<'db> MatchFinder<'db> {
                     // we get lots of noise. If at some point we add support for restricting rules
                     // to a particular kind of thing (e.g. only match type references), then we can
                     // relax this.
-                    if rule.pattern.kind() != node.kind() {
+                    if rule.pattern.node.kind() != node.kind() {
                         continue;
                     }
                     out.push(MatchDebugInfo {
@@ -185,7 +212,7 @@ impl<'db> MatchFinder<'db> {
                                     "Match failed, but no reason was given".to_owned()
                                 }),
                             }),
-                        pattern: rule.pattern.clone(),
+                        pattern: rule.pattern.node.clone(),
                         node: node.clone(),
                     });
                 }
diff --git a/crates/ra_ssr/src/matching.rs b/crates/ra_ssr/src/matching.rs
index a43d57c34..f3cc60c29 100644
--- a/crates/ra_ssr/src/matching.rs
+++ b/crates/ra_ssr/src/matching.rs
@@ -2,7 +2,8 @@
 //! process of matching, placeholder values are recorded.
 
 use crate::{
-    parsing::{Constraint, NodeKind, ParsedRule, Placeholder},
+    parsing::{Constraint, NodeKind, Placeholder},
+    resolving::{ResolvedPattern, ResolvedRule},
     SsrMatches,
 };
 use hir::Semantics;
@@ -51,6 +52,8 @@ pub struct Match {
     pub(crate) rule_index: usize,
     /// The depth of matched_node.
     pub(crate) depth: usize,
+    // Each path in the template rendered for the module in which the match was found.
+    pub(crate) rendered_template_paths: FxHashMap<SyntaxNode, hir::ModPath>,
 }
 
 /// Represents a `$var` in an SSR query.
@@ -86,7 +89,7 @@ pub(crate) struct MatchFailed {
 /// parent module, we don't populate nested matches.
 pub(crate) fn get_match(
     debug_active: bool,
-    rule: &ParsedRule,
+    rule: &ResolvedRule,
     code: &SyntaxNode,
     restrict_range: &Option<FileRange>,
     sema: &Semantics<ra_ide_db::RootDatabase>,
@@ -102,7 +105,7 @@ struct Matcher<'db, 'sema> {
     /// If any placeholders come from anywhere outside of this range, then the match will be
     /// rejected.
     restrict_range: Option<FileRange>,
-    rule: &'sema ParsedRule,
+    rule: &'sema ResolvedRule,
 }
 
 /// Which phase of matching we're currently performing. We do two phases because most attempted
@@ -117,14 +120,14 @@ enum Phase<'a> {
 
 impl<'db, 'sema> Matcher<'db, 'sema> {
     fn try_match(
-        rule: &ParsedRule,
+        rule: &ResolvedRule,
         code: &SyntaxNode,
         restrict_range: &Option<FileRange>,
         sema: &'sema Semantics<'db, ra_ide_db::RootDatabase>,
     ) -> Result<Match, MatchFailed> {
         let match_state = Matcher { sema, restrict_range: restrict_range.clone(), rule };
         // First pass at matching, where we check that node types and idents match.
-        match_state.attempt_match_node(&mut Phase::First, &rule.pattern, code)?;
+        match_state.attempt_match_node(&mut Phase::First, &rule.pattern.node, code)?;
         match_state.validate_range(&sema.original_range(code))?;
         let mut the_match = Match {
             range: sema.original_range(code),
@@ -133,11 +136,19 @@ impl<'db, 'sema> Matcher<'db, 'sema> {
             ignored_comments: Vec::new(),
             rule_index: rule.index,
             depth: 0,
+            rendered_template_paths: FxHashMap::default(),
         };
         // Second matching pass, where we record placeholder matches, ignored comments and maybe do
         // any other more expensive checks that we didn't want to do on the first pass.
-        match_state.attempt_match_node(&mut Phase::Second(&mut the_match), &rule.pattern, code)?;
+        match_state.attempt_match_node(
+            &mut Phase::Second(&mut the_match),
+            &rule.pattern.node,
+            code,
+        )?;
         the_match.depth = sema.ancestors_with_macros(the_match.matched_node.clone()).count();
+        if let Some(template) = &rule.template {
+            the_match.render_template_paths(template, sema)?;
+        }
         Ok(the_match)
     }
 
@@ -195,6 +206,7 @@ impl<'db, 'sema> Matcher<'db, 'sema> {
                 self.attempt_match_record_field_list(phase, pattern, code)
             }
             SyntaxKind::TOKEN_TREE => self.attempt_match_token_tree(phase, pattern, code),
+            SyntaxKind::PATH => self.attempt_match_path(phase, pattern, code),
             _ => self.attempt_match_node_children(phase, pattern, code),
         }
     }
@@ -311,6 +323,64 @@ impl<'db, 'sema> Matcher<'db, 'sema> {
         Ok(())
     }
 
+    /// Paths are matched based on whether they refer to the same thing, even if they're written
+    /// differently.
+    fn attempt_match_path(
+        &self,
+        phase: &mut Phase,
+        pattern: &SyntaxNode,
+        code: &SyntaxNode,
+    ) -> Result<(), MatchFailed> {
+        if let Some(pattern_resolved) = self.rule.pattern.resolved_paths.get(pattern) {
+            let pattern_path = ast::Path::cast(pattern.clone()).unwrap();
+            let code_path = ast::Path::cast(code.clone()).unwrap();
+            if let (Some(pattern_segment), Some(code_segment)) =
+                (pattern_path.segment(), code_path.segment())
+            {
+                // Match everything within the segment except for the name-ref, which is handled
+                // separately via comparing what the path resolves to below.
+                self.attempt_match_opt(
+                    phase,
+                    pattern_segment.type_arg_list(),
+                    code_segment.type_arg_list(),
+                )?;
+                self.attempt_match_opt(
+                    phase,
+                    pattern_segment.param_list(),
+                    code_segment.param_list(),
+                )?;
+            }
+            if matches!(phase, Phase::Second(_)) {
+                let resolution = self
+                    .sema
+                    .resolve_path(&code_path)
+                    .ok_or_else(|| match_error!("Failed to resolve path `{}`", code.text()))?;
+                if pattern_resolved.resolution != resolution {
+                    fail_match!("Pattern had path `{}` code had `{}`", pattern.text(), code.text());
+                }
+            }
+        } else {
+            return self.attempt_match_node_children(phase, pattern, code);
+        }
+        Ok(())
+    }
+
+    fn attempt_match_opt<T: AstNode>(
+        &self,
+        phase: &mut Phase,
+        pattern: Option<T>,
+        code: Option<T>,
+    ) -> Result<(), MatchFailed> {
+        match (pattern, code) {
+            (Some(p), Some(c)) => self.attempt_match_node(phase, &p.syntax(), &c.syntax()),
+            (None, None) => Ok(()),
+            (Some(p), None) => fail_match!("Pattern `{}` had nothing to match", p.syntax().text()),
+            (None, Some(c)) => {
+                fail_match!("Nothing in pattern to match code `{}`", c.syntax().text())
+            }
+        }
+    }
+
     /// We want to allow the records to match in any order, so we have special matching logic for
     /// them.
     fn attempt_match_record_field_list(
@@ -449,6 +519,28 @@ impl<'db, 'sema> Matcher<'db, 'sema> {
     }
 }
 
+impl Match {
+    fn render_template_paths(
+        &mut self,
+        template: &ResolvedPattern,
+        sema: &Semantics<ra_ide_db::RootDatabase>,
+    ) -> Result<(), MatchFailed> {
+        let module = sema
+            .scope(&self.matched_node)
+            .module()
+            .ok_or_else(|| match_error!("Matched node isn't in a module"))?;
+        for (path, resolved_path) in &template.resolved_paths {
+            if let hir::PathResolution::Def(module_def) = resolved_path.resolution {
+                let mod_path = module.find_use_path(sema.db, module_def).ok_or_else(|| {
+                    match_error!("Failed to render template path `{}` at match location")
+                })?;
+                self.rendered_template_paths.insert(path.clone(), mod_path);
+            }
+        }
+        Ok(())
+    }
+}
+
 impl Phase<'_> {
     fn next_non_trivial(&mut self, code_it: &mut SyntaxElementChildren) -> Option<SyntaxElement> {
         loop {
@@ -578,7 +670,7 @@ mod tests {
 
         let (db, position) = crate::tests::single_file(input);
         let mut match_finder = MatchFinder::in_context(&db, position);
-        match_finder.add_rule(rule);
+        match_finder.add_rule(rule).unwrap();
         let matches = match_finder.matches();
         assert_eq!(matches.matches.len(), 1);
         assert_eq!(matches.matches[0].matched_node.text(), "foo(1+2)");
diff --git a/crates/ra_ssr/src/parsing.rs b/crates/ra_ssr/src/parsing.rs
index cf7fb517f..2d6f4e514 100644
--- a/crates/ra_ssr/src/parsing.rs
+++ b/crates/ra_ssr/src/parsing.rs
@@ -7,7 +7,7 @@
 
 use crate::errors::bail;
 use crate::{SsrError, SsrPattern, SsrRule};
-use ra_syntax::{ast, AstNode, SmolStr, SyntaxKind, SyntaxNode, SyntaxToken, T};
+use ra_syntax::{ast, AstNode, SmolStr, SyntaxKind, SyntaxNode, T};
 use rustc_hash::{FxHashMap, FxHashSet};
 use std::str::FromStr;
 
@@ -16,7 +16,6 @@ pub(crate) struct ParsedRule {
     pub(crate) placeholders_by_stand_in: FxHashMap<SmolStr, Placeholder>,
     pub(crate) pattern: SyntaxNode,
     pub(crate) template: Option<SyntaxNode>,
-    pub(crate) index: usize,
 }
 
 #[derive(Debug)]
@@ -93,16 +92,11 @@ impl RuleBuilder {
                 placeholders_by_stand_in: self.placeholders_by_stand_in.clone(),
                 pattern: pattern.syntax().clone(),
                 template: Some(template.syntax().clone()),
-                // For now we give the rule an index of 0. It's given a proper index when the rule
-                // is added to the SsrMatcher. Using an Option<usize>, instead would be slightly
-                // more correct, but we delete this field from ParsedRule in a subsequent commit.
-                index: 0,
             }),
             (Ok(pattern), None) => self.rules.push(ParsedRule {
                 placeholders_by_stand_in: self.placeholders_by_stand_in.clone(),
                 pattern: pattern.syntax().clone(),
                 template: None,
-                index: 0,
             }),
             _ => {}
         }
@@ -171,15 +165,6 @@ impl RawPattern {
     }
 }
 
-impl ParsedRule {
-    pub(crate) fn get_placeholder(&self, token: &SyntaxToken) -> Option<&Placeholder> {
-        if token.kind() != SyntaxKind::IDENT {
-            return None;
-        }
-        self.placeholders_by_stand_in.get(token.text())
-    }
-}
-
 impl FromStr for SsrPattern {
     type Err = SsrError;
 
diff --git a/crates/ra_ssr/src/replacing.rs b/crates/ra_ssr/src/replacing.rs
index f1c5bdf14..4b3f5509c 100644
--- a/crates/ra_ssr/src/replacing.rs
+++ b/crates/ra_ssr/src/replacing.rs
@@ -1,9 +1,9 @@
 //! Code for applying replacement templates for matches that have previously been found.
 
 use crate::matching::Var;
-use crate::{parsing::ParsedRule, Match, SsrMatches};
-use ra_syntax::ast::AstToken;
-use ra_syntax::{SyntaxElement, SyntaxNode, SyntaxToken, TextSize};
+use crate::{resolving::ResolvedRule, Match, SsrMatches};
+use ra_syntax::ast::{self, AstToken};
+use ra_syntax::{SyntaxElement, SyntaxKind, SyntaxNode, SyntaxToken, TextSize};
 use ra_text_edit::TextEdit;
 
 /// Returns a text edit that will replace each match in `matches` with its corresponding replacement
@@ -12,7 +12,7 @@ use ra_text_edit::TextEdit;
 pub(crate) fn matches_to_edit(
     matches: &SsrMatches,
     file_src: &str,
-    rules: &[ParsedRule],
+    rules: &[ResolvedRule],
 ) -> TextEdit {
     matches_to_edit_at_offset(matches, file_src, 0.into(), rules)
 }
@@ -21,7 +21,7 @@ fn matches_to_edit_at_offset(
     matches: &SsrMatches,
     file_src: &str,
     relative_start: TextSize,
-    rules: &[ParsedRule],
+    rules: &[ResolvedRule],
 ) -> TextEdit {
     let mut edit_builder = ra_text_edit::TextEditBuilder::default();
     for m in &matches.matches {
@@ -36,11 +36,11 @@ fn matches_to_edit_at_offset(
 struct ReplacementRenderer<'a> {
     match_info: &'a Match,
     file_src: &'a str,
-    rules: &'a [ParsedRule],
-    rule: &'a ParsedRule,
+    rules: &'a [ResolvedRule],
+    rule: &'a ResolvedRule,
 }
 
-fn render_replace(match_info: &Match, file_src: &str, rules: &[ParsedRule]) -> String {
+fn render_replace(match_info: &Match, file_src: &str, rules: &[ResolvedRule]) -> String {
     let mut out = String::new();
     let rule = &rules[match_info.rule_index];
     let template = rule
@@ -48,7 +48,7 @@ fn render_replace(match_info: &Match, file_src: &str, rules: &[ParsedRule]) -> S
         .as_ref()
         .expect("You called MatchFinder::edits after calling MatchFinder::add_search_pattern");
     let renderer = ReplacementRenderer { match_info, file_src, rules, rule };
-    renderer.render_node_children(&template, &mut out);
+    renderer.render_node(&template.node, &mut out);
     for comment in &match_info.ignored_comments {
         out.push_str(&comment.syntax().to_string());
     }
@@ -68,11 +68,31 @@ impl ReplacementRenderer<'_> {
                 self.render_token(&token, out);
             }
             SyntaxElement::Node(child_node) => {
-                self.render_node_children(&child_node, out);
+                self.render_node(&child_node, out);
             }
         }
     }
 
+    fn render_node(&self, node: &SyntaxNode, out: &mut String) {
+        use ra_syntax::ast::AstNode;
+        if let Some(mod_path) = self.match_info.rendered_template_paths.get(&node) {
+            out.push_str(&mod_path.to_string());
+            // Emit everything except for the segment's name-ref, since we already effectively
+            // emitted that as part of `mod_path`.
+            if let Some(path) = ast::Path::cast(node.clone()) {
+                if let Some(segment) = path.segment() {
+                    for node_or_token in segment.syntax().children_with_tokens() {
+                        if node_or_token.kind() != SyntaxKind::NAME_REF {
+                            self.render_node_or_token(&node_or_token, out);
+                        }
+                    }
+                }
+            }
+        } else {
+            self.render_node_children(&node, out);
+        }
+    }
+
     fn render_token(&self, token: &SyntaxToken, out: &mut String) {
         if let Some(placeholder) = self.rule.get_placeholder(&token) {
             if let Some(placeholder_value) =
diff --git a/crates/ra_ssr/src/resolving.rs b/crates/ra_ssr/src/resolving.rs
new file mode 100644
index 000000000..e9d052111
--- /dev/null
+++ b/crates/ra_ssr/src/resolving.rs
@@ -0,0 +1,153 @@
+//! This module is responsible for resolving paths within rules.
+
+use crate::errors::error;
+use crate::{parsing, SsrError};
+use parsing::Placeholder;
+use ra_syntax::{ast, SmolStr, SyntaxKind, SyntaxNode, SyntaxToken};
+use rustc_hash::{FxHashMap, FxHashSet};
+use test_utils::mark;
+
+pub(crate) struct ResolvedRule {
+    pub(crate) pattern: ResolvedPattern,
+    pub(crate) template: Option<ResolvedPattern>,
+    pub(crate) index: usize,
+}
+
+pub(crate) struct ResolvedPattern {
+    pub(crate) placeholders_by_stand_in: FxHashMap<SmolStr, parsing::Placeholder>,
+    pub(crate) node: SyntaxNode,
+    // Paths in `node` that we've resolved.
+    pub(crate) resolved_paths: FxHashMap<SyntaxNode, ResolvedPath>,
+}
+
+pub(crate) struct ResolvedPath {
+    pub(crate) resolution: hir::PathResolution,
+}
+
+impl ResolvedRule {
+    pub(crate) fn new(
+        rule: parsing::ParsedRule,
+        scope: &hir::SemanticsScope,
+        hygiene: &hir::Hygiene,
+        index: usize,
+    ) -> Result<ResolvedRule, SsrError> {
+        let resolver =
+            Resolver { scope, hygiene, placeholders_by_stand_in: rule.placeholders_by_stand_in };
+        let resolved_template = if let Some(template) = rule.template {
+            Some(resolver.resolve_pattern_tree(template)?)
+        } else {
+            None
+        };
+        Ok(ResolvedRule {
+            pattern: resolver.resolve_pattern_tree(rule.pattern)?,
+            template: resolved_template,
+            index,
+        })
+    }
+
+    pub(crate) fn get_placeholder(&self, token: &SyntaxToken) -> Option<&Placeholder> {
+        if token.kind() != SyntaxKind::IDENT {
+            return None;
+        }
+        self.pattern.placeholders_by_stand_in.get(token.text())
+    }
+}
+
+struct Resolver<'a, 'db> {
+    scope: &'a hir::SemanticsScope<'db>,
+    hygiene: &'a hir::Hygiene,
+    placeholders_by_stand_in: FxHashMap<SmolStr, parsing::Placeholder>,
+}
+
+impl Resolver<'_, '_> {
+    fn resolve_pattern_tree(&self, pattern: SyntaxNode) -> Result<ResolvedPattern, SsrError> {
+        let mut resolved_paths = FxHashMap::default();
+        self.resolve(pattern.clone(), &mut resolved_paths)?;
+        Ok(ResolvedPattern {
+            node: pattern,
+            resolved_paths,
+            placeholders_by_stand_in: self.placeholders_by_stand_in.clone(),
+        })
+    }
+
+    fn resolve(
+        &self,
+        node: SyntaxNode,
+        resolved_paths: &mut FxHashMap<SyntaxNode, ResolvedPath>,
+    ) -> Result<(), SsrError> {
+        use ra_syntax::ast::AstNode;
+        if let Some(path) = ast::Path::cast(node.clone()) {
+            // Check if this is an appropriate place in the path to resolve. If the path is
+            // something like `a::B::<i32>::c` then we want to resolve `a::B`. If the path contains
+            // a placeholder. e.g. `a::$b::c` then we want to resolve `a`.
+            if !path_contains_type_arguments(path.qualifier())
+                && !self.path_contains_placeholder(&path)
+            {
+                let resolution = self
+                    .resolve_path(&path)
+                    .ok_or_else(|| error!("Failed to resolve path `{}`", node.text()))?;
+                resolved_paths.insert(node, ResolvedPath { resolution });
+                return Ok(());
+            }
+        }
+        for node in node.children() {
+            self.resolve(node, resolved_paths)?;
+        }
+        Ok(())
+    }
+
+    /// Returns whether `path` contains a placeholder, but ignores any placeholders within type
+    /// arguments.
+    fn path_contains_placeholder(&self, path: &ast::Path) -> bool {
+        if let Some(segment) = path.segment() {
+            if let Some(name_ref) = segment.name_ref() {
+                if self.placeholders_by_stand_in.contains_key(name_ref.text()) {
+                    return true;
+                }
+            }
+        }
+        if let Some(qualifier) = path.qualifier() {
+            return self.path_contains_placeholder(&qualifier);
+        }
+        false
+    }
+
+    fn resolve_path(&self, path: &ast::Path) -> Option<hir::PathResolution> {
+        let hir_path = hir::Path::from_src(path.clone(), self.hygiene)?;
+        // First try resolving the whole path. This will work for things like
+        // `std::collections::HashMap`, but will fail for things like
+        // `std::collections::HashMap::new`.
+        if let Some(resolution) = self.scope.resolve_hir_path(&hir_path) {
+            return Some(resolution);
+        }
+        // Resolution failed, try resolving the qualifier (e.g. `std::collections::HashMap` and if
+        // that succeeds, then iterate through the candidates on the resolved type with the provided
+        // name.
+        let resolved_qualifier = self.scope.resolve_hir_path_qualifier(&hir_path.qualifier()?)?;
+        if let hir::PathResolution::Def(hir::ModuleDef::Adt(adt)) = resolved_qualifier {
+            adt.ty(self.scope.db).iterate_path_candidates(
+                self.scope.db,
+                self.scope.module()?.krate(),
+                &FxHashSet::default(),
+                Some(hir_path.segments().last()?.name),
+                |_ty, assoc_item| Some(hir::PathResolution::AssocItem(assoc_item)),
+            )
+        } else {
+            None
+        }
+    }
+}
+
+/// Returns whether `path` or any of its qualifiers contains type arguments.
+fn path_contains_type_arguments(path: Option<ast::Path>) -> bool {
+    if let Some(path) = path {
+        if let Some(segment) = path.segment() {
+            if segment.type_arg_list().is_some() {
+                mark::hit!(type_arguments_within_path);
+                return true;
+            }
+        }
+        return path_contains_type_arguments(path.qualifier());
+    }
+    false
+}
diff --git a/crates/ra_ssr/src/search.rs b/crates/ra_ssr/src/search.rs
index a28e9f341..ccc2d544a 100644
--- a/crates/ra_ssr/src/search.rs
+++ b/crates/ra_ssr/src/search.rs
@@ -1,6 +1,6 @@
 //! Searching for matches.
 
-use crate::{matching, parsing::ParsedRule, Match, MatchFinder};
+use crate::{matching, resolving::ResolvedRule, Match, MatchFinder};
 use ra_db::FileRange;
 use ra_syntax::{ast, AstNode, SyntaxNode};
 
@@ -8,13 +8,13 @@ impl<'db> MatchFinder<'db> {
     /// Adds all matches for `rule` to `matches_out`. Matches may overlap in ways that make
     /// replacement impossible, so further processing is required in order to properly nest matches
     /// and remove overlapping matches. This is done in the `nesting` module.
-    pub(crate) fn find_matches_for_rule(&self, rule: &ParsedRule, matches_out: &mut Vec<Match>) {
+    pub(crate) fn find_matches_for_rule(&self, rule: &ResolvedRule, matches_out: &mut Vec<Match>) {
         // FIXME: Use resolved paths in the pattern to find places to search instead of always
         // scanning every node.
         self.slow_scan(rule, matches_out);
     }
 
-    fn slow_scan(&self, rule: &ParsedRule, matches_out: &mut Vec<Match>) {
+    fn slow_scan(&self, rule: &ResolvedRule, matches_out: &mut Vec<Match>) {
         use ra_db::SourceDatabaseExt;
         use ra_ide_db::symbol_index::SymbolsDatabase;
         for &root in self.sema.db.local_roots().iter() {
@@ -30,7 +30,7 @@ impl<'db> MatchFinder<'db> {
     fn slow_scan_node(
         &self,
         code: &SyntaxNode,
-        rule: &ParsedRule,
+        rule: &ResolvedRule,
         restrict_range: &Option<FileRange>,
         matches_out: &mut Vec<Match>,
     ) {
diff --git a/crates/ra_ssr/src/tests.rs b/crates/ra_ssr/src/tests.rs
index 63d527894..33742dc8e 100644
--- a/crates/ra_ssr/src/tests.rs
+++ b/crates/ra_ssr/src/tests.rs
@@ -85,7 +85,7 @@ fn assert_ssr_transforms(rules: &[&str], input: &str, expected: Expect) {
     let mut match_finder = MatchFinder::in_context(&db, position);
     for rule in rules {
         let rule: SsrRule = rule.parse().unwrap();
-        match_finder.add_rule(rule);
+        match_finder.add_rule(rule).unwrap();
     }
     let edits = match_finder.edits();
     if edits.is_empty() {
@@ -114,7 +114,7 @@ fn print_match_debug_info(match_finder: &MatchFinder, file_id: FileId, snippet:
 fn assert_matches(pattern: &str, code: &str, expected: &[&str]) {
     let (db, position) = single_file(code);
     let mut match_finder = MatchFinder::in_context(&db, position);
-    match_finder.add_search_pattern(pattern.parse().unwrap());
+    match_finder.add_search_pattern(pattern.parse().unwrap()).unwrap();
     let matched_strings: Vec<String> =
         match_finder.matches().flattened().matches.iter().map(|m| m.matched_text()).collect();
     if matched_strings != expected && !expected.is_empty() {
@@ -126,7 +126,7 @@ fn assert_matches(pattern: &str, code: &str, expected: &[&str]) {
 fn assert_no_match(pattern: &str, code: &str) {
     let (db, position) = single_file(code);
     let mut match_finder = MatchFinder::in_context(&db, position);
-    match_finder.add_search_pattern(pattern.parse().unwrap());
+    match_finder.add_search_pattern(pattern.parse().unwrap()).unwrap();
     let matches = match_finder.matches().flattened().matches;
     if !matches.is_empty() {
         print_match_debug_info(&match_finder, position.file_id, &matches[0].matched_text());
@@ -137,7 +137,7 @@ fn assert_no_match(pattern: &str, code: &str) {
 fn assert_match_failure_reason(pattern: &str, code: &str, snippet: &str, expected_reason: &str) {
     let (db, position) = single_file(code);
     let mut match_finder = MatchFinder::in_context(&db, position);
-    match_finder.add_search_pattern(pattern.parse().unwrap());
+    match_finder.add_search_pattern(pattern.parse().unwrap()).unwrap();
     let mut reasons = Vec::new();
     for d in match_finder.debug_where_text_equal(position.file_id, snippet) {
         if let Some(reason) = d.match_failure_reason() {
@@ -350,6 +350,60 @@ fn match_pattern() {
     assert_matches("Some($a)", "struct Some(); fn f() {if let Some(x) = foo() {}}", &["Some(x)"]);
 }
 
+// If our pattern has a full path, e.g. a::b::c() and the code has c(), but c resolves to
+// a::b::c, then we should match.
+#[test]
+fn match_fully_qualified_fn_path() {
+    let code = r#"
+        mod a {
+            pub mod b {
+                pub fn c(_: i32) {}
+            }
+        }
+        use a::b::c;
+        fn f1() {
+            c(42);
+        }
+        "#;
+    assert_matches("a::b::c($a)", code, &["c(42)"]);
+}
+
+#[test]
+fn match_resolved_type_name() {
+    let code = r#"
+        mod m1 {
+            pub mod m2 {
+                pub trait Foo<T> {}
+            }
+        }
+        mod m3 {
+            trait Foo<T> {}
+            fn f1(f: Option<&dyn Foo<bool>>) {}
+        }
+        mod m4 {
+            use crate::m1::m2::Foo;
+            fn f1(f: Option<&dyn Foo<i32>>) {}
+        }
+        "#;
+    assert_matches("m1::m2::Foo<$t>", code, &["Foo<i32>"]);
+}
+
+#[test]
+fn type_arguments_within_path() {
+    mark::check!(type_arguments_within_path);
+    let code = r#"
+        mod foo {
+            pub struct Bar<T> {t: T}
+            impl<T> Bar<T> {
+                pub fn baz() {}
+            }
+        }
+        fn f1() {foo::Bar::<i32>::baz();}
+        "#;
+    assert_no_match("foo::Bar::<i64>::baz()", code);
+    assert_matches("foo::Bar::<i32>::baz()", code, &["foo::Bar::<i32>::baz()"]);
+}
+
 #[test]
 fn literal_constraint() {
     mark::check!(literal_constraint);
@@ -483,6 +537,86 @@ fn replace_associated_function_call() {
 }
 
 #[test]
+fn replace_path_in_different_contexts() {
+    // Note the <|> inside module a::b which marks the point where the rule is interpreted. We
+    // replace foo with bar, but both need different path qualifiers in different contexts. In f4,
+    // foo is unqualified because of a use statement, however the replacement needs to be fully
+    // qualified.
+    assert_ssr_transform(
+        "c::foo() ==>> c::bar()",
+        r#"
+            mod a {
+                pub mod b {<|>
+                    pub mod c {
+                        pub fn foo() {}
+                        pub fn bar() {}
+                        fn f1() { foo() }
+                    }
+                    fn f2() { c::foo() }
+                }
+                fn f3() { b::c::foo() }
+            }
+            use a::b::c::foo;
+            fn f4() { foo() }
+            "#,
+        expect![[r#"
+            mod a {
+                pub mod b {
+                    pub mod c {
+                        pub fn foo() {}
+                        pub fn bar() {}
+                        fn f1() { bar() }
+                    }
+                    fn f2() { c::bar() }
+                }
+                fn f3() { b::c::bar() }
+            }
+            use a::b::c::foo;
+            fn f4() { a::b::c::bar() }
+            "#]],
+    );
+}
+
+#[test]
+fn replace_associated_function_with_generics() {
+    assert_ssr_transform(
+        "c::Foo::<$a>::new() ==>> d::Bar::<$a>::default()",
+        r#"
+            mod c {
+                pub struct Foo<T> {v: T}
+                impl<T> Foo<T> { pub fn new() {} }
+                fn f1() {
+                    Foo::<i32>::new();
+                }
+            }
+            mod d {
+                pub struct Bar<T> {v: T}
+                impl<T> Bar<T> { pub fn default() {} }
+                fn f1() {
+                    super::c::Foo::<i32>::new();
+                }
+            }
+            "#,
+        expect![[r#"
+            mod c {
+                pub struct Foo<T> {v: T}
+                impl<T> Foo<T> { pub fn new() {} }
+                fn f1() {
+                    crate::d::Bar::<i32>::default();
+                }
+            }
+            mod d {
+                pub struct Bar<T> {v: T}
+                impl<T> Bar<T> { pub fn default() {} }
+                fn f1() {
+                    Bar::<i32>::default();
+                }
+            }
+            "#]],
+    );
+}
+
+#[test]
 fn replace_type() {
     assert_ssr_transform(
         "Result<(), $a> ==>> Option<$a>",
diff --git a/crates/rust-analyzer/src/cli/ssr.rs b/crates/rust-analyzer/src/cli/ssr.rs
index 22f5b4be0..194bec008 100644
--- a/crates/rust-analyzer/src/cli/ssr.rs
+++ b/crates/rust-analyzer/src/cli/ssr.rs
@@ -9,7 +9,7 @@ pub fn apply_ssr_rules(rules: Vec<SsrRule>) -> Result<()> {
     let db = host.raw_database();
     let mut match_finder = MatchFinder::at_first_file(db)?;
     for rule in rules {
-        match_finder.add_rule(rule);
+        match_finder.add_rule(rule)?;
     }
     let edits = match_finder.edits();
     for edit in edits {
@@ -32,7 +32,7 @@ pub fn search_for_patterns(patterns: Vec<SsrPattern>, debug_snippet: Option<Stri
     let db = host.raw_database();
     let mut match_finder = MatchFinder::at_first_file(db)?;
     for pattern in patterns {
-        match_finder.add_search_pattern(pattern);
+        match_finder.add_search_pattern(pattern)?;
     }
     if let Some(debug_snippet) = &debug_snippet {
         for &root in db.local_roots().iter() {