AST: Add Evaluator::getInnermostSourceLoc()

Author: slavapestov

include/swift/AST/AnyRequest.h

@@ -58,6 +58,9 @@ struct AnyRequestVTable {
     static void noteCycleStep(const void *ptr, DiagnosticEngine &diags) {
       static_cast<const Request *>(ptr)->noteCycleStep(diags);
     }
+    static SourceLoc getNearestLoc(const void *ptr) {
+      return static_cast<const Request *>(ptr)->getNearestLoc();
+    }
   };
 
   const uint64_t typeID;
@@ -66,6 +69,7 @@ struct AnyRequestVTable {
   const std::function<void(const void *, llvm::raw_ostream &)> simpleDisplay;
   const std::function<void(const void *, DiagnosticEngine &)> diagnoseCycle;
   const std::function<void(const void *, DiagnosticEngine &)> noteCycleStep;
+  const std::function<SourceLoc(const void *)> getNearestLoc;
 
   template <typename Request>
   static const AnyRequestVTable *get() {
@@ -75,7 +79,8 @@ struct AnyRequestVTable {
         &Impl<Request>::isEqual,
         &Impl<Request>::simpleDisplay,
         &Impl<Request>::diagnoseCycle,
-        &Impl<Request>::noteCycleStep
+        &Impl<Request>::noteCycleStep,
+        &Impl<Request>::getNearestLoc
     };
     return &vtable;
   }
@@ -173,6 +178,11 @@ class AnyRequestBase {
     getVTable()->noteCycleStep(getRawStorage(), diags);
   }
 
+  /// Get the best source location describing the parameters to this request.
+  SourceLoc getNearestLoc() const {
+    return getVTable()->getNearestLoc(getRawStorage());
+  }
+
   /// Compare two instances for equality.
   friend bool operator==(const AnyRequestBase<Derived> &lhs,
                          const AnyRequestBase<Derived> &rhs) {
@@ -224,6 +234,8 @@ class AnyRequestBase {
 ///   - Cycle diagnostics operations:
 ///       void diagnoseCycle(DiagnosticEngine &diags) const;
 ///       void noteCycleStep(DiagnosticEngine &diags) const;
+///   - Source location information:
+///       SourceLoc getNearestLoc() const;
 ///
 class ActiveRequest final : public AnyRequestBase<ActiveRequest> {
   template <typename T>

include/swift/AST/Evaluator.h

@@ -229,6 +229,11 @@ class Evaluator {
   /// diagnostics through the given diagnostics engine.
   Evaluator(DiagnosticEngine &diags, const LangOptions &opts);
 
+  /// For last-ditch diagnostics, get a good approximate source location for
+  /// the thing we're currently type checking by searching for a request whose
+  /// source location matches the predicate.
+  SourceLoc getInnermostSourceLoc(llvm::function_ref<bool(SourceLoc)> fn);
+
   /// Emit GraphViz output visualizing the request graph.
   void emitRequestEvaluatorGraphViz(llvm::StringRef graphVizPath);
 

include/swift/AST/Expr.h

@@ -6403,6 +6403,8 @@ void simple_display(llvm::raw_ostream &out, const DefaultArgumentExpr *expr);
 void simple_display(llvm::raw_ostream &out, const Expr *expr);
 
 SourceLoc extractNearestSourceLoc(const DefaultArgumentExpr *expr);
+SourceLoc extractNearestSourceLoc(const MacroExpansionExpr *expr);
+SourceLoc extractNearestSourceLoc(const ClosureExpr *expr);
 
 } // end namespace swift
 

lib/AST/Evaluator.cpp

@@ -60,6 +60,17 @@ Evaluator::Evaluator(DiagnosticEngine &diags, const LangOptions &opts)
       debugDumpCycles(opts.DebugDumpCycles),
       recorder(opts.RecordRequestReferences) {}
 
+SourceLoc Evaluator::getInnermostSourceLoc(
+    llvm::function_ref<bool(SourceLoc)> fn) {
+  for (auto request : llvm::reverse(activeRequests)) {
+    SourceLoc loc = request.getNearestLoc();
+    if (fn(loc))
+      return loc;
+  }
+
+  return SourceLoc();
+}
+
 bool Evaluator::checkDependency(const ActiveRequest &request) {
   // Record this as an active request.
   if (activeRequests.insert(request)) {

lib/AST/Expr.cpp

@@ -2835,10 +2835,18 @@ void swift::simple_display(llvm::raw_ostream &out,
   out << "expression";
 }
 
+SourceLoc swift::extractNearestSourceLoc(const ClosureExpr *expr) {
+  return expr->getLoc();
+}
+
 SourceLoc swift::extractNearestSourceLoc(const DefaultArgumentExpr *expr) {
   return expr->getLoc();
 }
 
+SourceLoc swift::extractNearestSourceLoc(const MacroExpansionExpr *expr) {
+  return expr->getLoc();
+}
+
 // See swift/Basic/Statistic.h for declaration: this enables tracing Exprs, is
 // defined here to avoid too much layering violation / circular linkage
 // dependency.