feat(lsp): textDocument/implementation for interfaces (0.13)

Go-to-implementation resolves interface types to implementing types and
interface methods to extend Type for Iface method decls (Circle+Square).

Makefile

@@ -185,6 +185,9 @@ test-lsp: lsp
 	@echo "==> LSP path rename smoke"
 	@chmod +x tools/smoke_lsp_rename_path.sh
 	@tools/smoke_lsp_rename_path.sh
+	@echo "==> LSP implementation smoke"
+	@chmod +x tools/smoke_lsp_implementation.sh
+	@tools/smoke_lsp_implementation.sh
 
 .PHONY: test-registry
 test-registry: build

docs/QUALITY_PLAN.md

@@ -1,7 +1,7 @@
 # Bux — План към „добър“ език (v0.5 → v1.0)
 
 > **Дата:** 2026-07-19  
-> **Текущо:** v0.5.x — HirNode sourceFile, **optional selfhost-loop CI**, LSP 0.12, Nexus KA  
+> **Текущо:** v0.5.x — **LSP 0.13 implementation**, HirNode sourceFile, optional selfhost-loop CI  
 > **Цел:** Език, с който се пишат реални проекти комфортно, безопасно (по избор) и с надежден toolchain.
 
 ---
@@ -771,9 +771,24 @@ A (stdlib ergonomics)  →  B (compiler holes)  →  C (ownership depth)
 
 ---
 
+## Сесия 49 (LSP 0.13 textDocument/implementation)
+
+1. **`implementationProvider`** + `textDocument/implementation`
+2. **Interface type** under cursor → locations of implementing types
+   (`extend Type for Iface` / type decl)
+3. **Interface method** under cursor → implementor method decls
+   (reuses `collectImplementorFuncs` + `workspaceImpls`)
+4. Also: call-site / shared method name matching known iface methods;
+   implementor method → sibling implementors of same iface method
+5. Smoke: `tools/smoke_lsp_implementation.sh`
+   - Drawable → ≥2 types; Draw → ≥2 methods (Circle + Square)
+6. Version **bux-lsp 0.13.0**; `make test-lsp`
+
+---
+
 ## Следващи стъпки
 
-1. LSP find-implementations request (dedicated, beyond call hierarchy)
+1. Workspace-wide import path index without open documents (optional polish)
-2. Workspace-wide import path index without open documents (optional polish)
+2. Expr/Stmt-level sourceFile if macros / cross-file inlining land
-3. Expr/Stmt-level sourceFile if macros / cross-file inlining land
+3. Fix selfhost C backend so buxc2→buxc3 fixed-point is green
-4. Fix selfhost C backend so buxc2→buxc3 fixed-point is green
+4. Main PR CI workflow (`make test`) beyond optional selfhost-loop

tools/lsp_server.nim

@@ -14,6 +14,7 @@
 # v0.10.0: method rename + qualified path / extend Type rename edges.
 # v0.11.0: interface dispatch in call hierarchy (extend Type for Trait).
 # v0.12.0: module-path segment rename (import Std::Io / Std::Io::{…}).
+# v0.13.0: textDocument/implementation (interface → types / methods).
 
 import std/[json, os, strutils, streams, tables, osproc, sequtils, sets]
 import lexer, parser, ast, sema, types, scope, source_location
@@ -2579,6 +2580,147 @@ proc collectImplementorFuncs(iface, meth: string): seq[FuncSym] =
           if seen.contains(key): continue
           seen.incl(key)
           result.add(FuncSym(name: meth, uri: uri, info: info))
+  # Closed-file index from workspace scan
+  let wkey = iface & "." & meth
+  if workspaceImpls.hasKey(wkey):
+    for impl in workspaceImpls[wkey]:
+      let key = impl.uri & "#" & impl.typeName & "." & meth
+      if seen.contains(key): continue
+      seen.incl(key)
+      if documents.hasKey(impl.uri):
+        let doc = documents[impl.uri]
+        ensureAnalyzed(doc)
+        if doc.symbols.hasKey(meth) and doc.symbols[meth].kind == "method" and
+           doc.symbols[meth].container == impl.typeName:
+          result.add(FuncSym(name: meth, uri: impl.uri, info: doc.symbols[meth]))
+          continue
+      if workspaceSymbols.hasKey(meth) and workspaceSymbols[meth].uri == impl.uri:
+        var info = workspaceSymbols[meth].info
+        info.container = impl.typeName
+        result.add(FuncSym(name: meth, uri: impl.uri, info: info))
+      else:
+        result.add(FuncSym(
+          name: meth, uri: impl.uri,
+          info: SymbolInfo(line: 0, col: 0, kind: "method",
+            detail: impl.typeName & "." & meth, container: impl.typeName)))
+
+proc collectTypeImplementorLocs(iface: string): seq[JsonNode] =
+  ## Locations of types that `extend Type for iface`.
+  result = @[]
+  var seen = initHashSet[string]()
+  for uri, doc in documents.pairs:
+    ensureAnalyzed(doc)
+    for impl in doc.impls:
+      if impl.iface != iface: continue
+      let key = uri & "#" & impl.typeName
+      if seen.contains(key): continue
+      seen.incl(key)
+      if doc.symbols.hasKey(impl.typeName):
+        let info = doc.symbols[impl.typeName]
+        result.add(locationJson(uri, info.line, info.col, impl.typeName.len))
+      else:
+        # Fall back to the `extend` line
+        result.add(locationJson(uri, impl.line, 0, max(1, impl.typeName.len)))
+  # Derive types from workspaceImpls (Iface.Method → typeName)
+  for wkey, impls in workspaceImpls.pairs:
+    if not wkey.startsWith(iface & "."): continue
+    for impl in impls:
+      let key = impl.uri & "#" & impl.typeName
+      if seen.contains(key): continue
+      seen.incl(key)
+      if documents.hasKey(impl.uri):
+        let doc = documents[impl.uri]
+        ensureAnalyzed(doc)
+        if doc.symbols.hasKey(impl.typeName):
+          let info = doc.symbols[impl.typeName]
+          result.add(locationJson(impl.uri, info.line, info.col, impl.typeName.len))
+          continue
+      if workspaceSymbols.hasKey(impl.typeName):
+        let ws = workspaceSymbols[impl.typeName]
+        result.add(locationJson(ws.uri, ws.info.line, ws.info.col, impl.typeName.len))
+      else:
+        result.add(locationJson(impl.uri, 0, 0, max(1, impl.typeName.len)))
+
+proc handleImplementation(stream: FileStream, id: JsonNode, paramsNode: JsonNode) =
+  ## textDocument/implementation — go to implementors of interface / iface method.
+  let uri = paramsNode["textDocument"]["uri"].getStr()
+  let position = paramsNode["position"]
+  let lineNum = position["line"].getInt()
+  let col = position["character"].getInt()
+  let doc = getDoc(uri)
+  if doc.content == "":
+    sendResponse(stream, id, %*[])
+    return
+  ensureAnalyzed(doc)
+  let word = findWordAt(doc.content, lineNum, col)
+  if word.len == 0:
+    sendResponse(stream, id, %*[])
+    return
+
+  var arr = newJArray()
+
+  # 1) Interface method under cursor → implementor methods
+  let (iok, im) = findIfaceMethodAt(doc, word, lineNum, col)
+  if iok:
+    for fs in collectImplementorFuncs(im.parent, im.name):
+      arr.add(locationJson(fs.uri, fs.info.line, fs.info.col, fs.name.len))
+    sendResponse(stream, id, arr)
+    return
+
+  # 2) Interface type name → implementing types (extend Type for Iface)
+  var isIface = false
+  if doc.symbols.hasKey(word) and doc.symbols[word].kind == "interface":
+    isIface = true
+  elif workspaceSymbols.hasKey(word) and workspaceSymbols[word].info.kind == "interface":
+    isIface = true
+  if isIface:
+    for loc in collectTypeImplementorLocs(word):
+      arr.add(loc)
+    sendResponse(stream, id, arr)
+    return
+
+  # 3) Call site / method name that matches a known iface method
+  #    (e.g. cursor on Draw in c.Draw() or on implementor name shared with iface)
+  for m in doc.ifaceMethods:
+    if m.name != word: continue
+    for fs in collectImplementorFuncs(m.parent, m.name):
+      arr.add(locationJson(fs.uri, fs.info.line, fs.info.col, fs.name.len))
+    if arr.len > 0:
+      sendResponse(stream, id, arr)
+      return
+
+  # 4) Method registered as implementor of some interface — still list siblings?
+  #    Prefer: if word is method on a type that implements I, and I has that method,
+  #    return all implementors of I.Method (including self).
+  if doc.symbols.hasKey(word) and doc.symbols[word].kind == "method":
+    let container = doc.symbols[word].container
+    for impl in doc.impls:
+      if impl.typeName != container: continue
+      # This type implements impl.iface; if method is an iface method, list all
+      for m in doc.ifaceMethods:
+        if m.parent == impl.iface and m.name == word:
+          for fs in collectImplementorFuncs(impl.iface, word):
+            arr.add(locationJson(fs.uri, fs.info.line, fs.info.col, fs.name.len))
+          if arr.len > 0:
+            sendResponse(stream, id, arr)
+            return
+    # workspaceImpls reverse lookup
+    for wkey, impls in workspaceImpls.pairs:
+      if not wkey.endsWith("." & word): continue
+      let iface = wkey[0 ..< wkey.len - word.len - 1]
+      var onType = false
+      for impl in impls:
+        if impl.typeName == container or impl.uri == uri:
+          onType = true
+          break
+      if onType:
+        for fs in collectImplementorFuncs(iface, word):
+          arr.add(locationJson(fs.uri, fs.info.line, fs.info.col, fs.name.len))
+        if arr.len > 0:
+          sendResponse(stream, id, arr)
+          return
+
+  sendResponse(stream, id, arr)
 
 proc handlePrepareCallHierarchy(stream: FileStream, id: JsonNode, paramsNode: JsonNode) =
   let uri = paramsNode["textDocument"]["uri"].getStr()
@@ -2769,9 +2911,10 @@ proc handleMessage(stream: FileStream, msg: JsonNode) =
         "referencesProvider": true,
         "renameProvider": {"prepareProvider": true},
         "workspaceSymbolProvider": true,
-        "callHierarchyProvider": true
+        "callHierarchyProvider": true,
+        "implementationProvider": true
       },
-      "serverInfo": {"name": "bux-lsp", "version": "0.12.0"}
+      "serverInfo": {"name": "bux-lsp", "version": "0.13.0"}
     })
     if paramsNode.hasKey("rootPath") and paramsNode["rootPath"].kind != JNull:
       rootPath = paramsNode["rootPath"].getStr()
@@ -2871,6 +3014,9 @@ proc handleMessage(stream: FileStream, msg: JsonNode) =
   of "callHierarchy/outgoingCalls":
     handleOutgoingCalls(stream, id, paramsNode)
 
+  of "textDocument/implementation":
+    handleImplementation(stream, id, paramsNode)
+
   else:
     if id != nil:
       sendError(stream, id, -32601, "method not found: " & methodName)

tools/smoke_lsp_implementation.sh

@@ -0,0 +1,112 @@
+#!/usr/bin/env bash
+# Smoke: textDocument/implementation (bux-lsp 0.13)
+set -euo pipefail
+ROOT="$(cd "$(dirname "$0")/.." && pwd)"
+LSP="$ROOT/tools/bux-lsp"
+TMP=$(mktemp -d)
+trap 'rm -rf "$TMP"' EXIT
+
+if [[ ! -x "$LSP" ]]; then
+  (cd "$ROOT" && make lsp >/dev/null)
+fi
+
+cat > "$TMP/Main.bux" <<'EOF'
+interface Drawable {
+    func Draw(self: &Self);
+}
+struct Circle {
+    radius: int;
+}
+struct Square {
+    side: int;
+}
+extend Circle for Drawable {
+    func Draw(self: &Circle) {
+        let r: int = self.radius;
+    }
+}
+extend Square for Drawable {
+    func Draw(self: &Square) {
+        let s: int = self.side;
+    }
+}
+func Render(c: Circle) {
+    c.Draw();
+}
+func Main() -> int {
+    return 0;
+}
+EOF
+
+rpc() {
+  local body="$1"
+  local len
+  len=$(printf '%s' "$body" | wc -c)
+  printf 'Content-Length: %s\r\n\r\n%s' "$len" "$body"
+}
+
+CONTENT_JSON=$(python3 -c 'import json,sys; print(json.dumps(open(sys.argv[1]).read()))' "$TMP/Main.bux")
+URI="file://$TMP/Main.bux"
+
+# Drawable interface name ~ line 0 character 10
+# Draw iface method ~ line 1 character 9
+# c.Draw() call ~ line 22 character 6 (approx)
+{
+  rpc '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"capabilities":{},"rootUri":"file://'"$TMP"'"}}'
+  rpc '{"jsonrpc":"2.0","method":"initialized","params":{}}'
+  rpc '{"jsonrpc":"2.0","method":"textDocument/didOpen","params":{"textDocument":{"uri":"'"$URI"'","languageId":"bux","version":1,"text":'"$CONTENT_JSON"'}}}'
+  # implementation on interface type Drawable
+  rpc '{"jsonrpc":"2.0","id":2,"method":"textDocument/implementation","params":{"textDocument":{"uri":"'"$URI"'"},"position":{"line":0,"character":10}}}'
+  # implementation on iface method Draw
+  rpc '{"jsonrpc":"2.0","id":3,"method":"textDocument/implementation","params":{"textDocument":{"uri":"'"$URI"'"},"position":{"line":1,"character":9}}}'
+  rpc '{"jsonrpc":"2.0","id":4,"method":"shutdown","params":null}'
+  rpc '{"jsonrpc":"2.0","method":"exit","params":null}'
+} | "$LSP" 2>/dev/null | tr '\r' '\n' > "$TMP/out.txt"
+
+if ! grep -q '0.13.0' "$TMP/out.txt"; then
+  echo "WARN: version not 0.13.0"
+fi
+
+if ! grep -q 'implementationProvider' "$TMP/out.txt"; then
+  echo "FAIL: missing implementationProvider capability"
+  cat "$TMP/out.txt"
+  exit 1
+fi
+
+# id 2: interface → Circle + Square type locations
+# Count locations in response for id 2 roughly via line ranges mentioning Circle/Square
+# Parse with python for robustness
+python3 - <<'PY' "$TMP/out.txt"
+import json, sys, re
+raw = open(sys.argv[1]).read()
+# Split Content-Length messages into JSON bodies
+bodies = []
+for m in re.finditer(r'Content-Length:\s*(\d+)\s*\n\s*\n', raw):
+    pass
+# Simpler: find all JSON objects with "id"
+parts = re.split(r'Content-Length:\s*\d+\s*', raw)
+for p in parts:
+    p = p.strip()
+    if not p.startswith('{'):
+        continue
+    try:
+        j = json.loads(p)
+    except Exception:
+        continue
+    if j.get('id') == 2:
+        r = j.get('result') or []
+        if len(r) < 2:
+            print(f"FAIL: interface Drawable expected ≥2 implementor types, got {len(r)}")
+            print(json.dumps(j, indent=2)[:800])
+            sys.exit(1)
+        print(f"  interface Drawable → {len(r)} type location(s)")
+    if j.get('id') == 3:
+        r = j.get('result') or []
+        if len(r) < 2:
+            print(f"FAIL: iface method Draw expected ≥2 implementors, got {len(r)}")
+            print(json.dumps(j, indent=2)[:800])
+            sys.exit(1)
+        # Expect two method sites (Circle.Draw + Square.Draw)
+        print(f"  iface Draw → {len(r)} method location(s)")
+print("PASS: LSP textDocument/implementation (0.13)")
+PY