Explain source ranges

Author: David Ungar

include/swift/AST/ASTScope.h

@@ -169,7 +169,7 @@ class ASTScopeImpl {
 #pragma mark - source ranges
 
 public:
-  SourceRange getSourceRange(bool forDebugging = false) const;
+  SourceRange getSourceRange(bool omitAssertions = false) const;
 
 protected:
   SourceManager &getSourceManager() const;
@@ -186,7 +186,18 @@ class ASTScopeImpl {
   virtual NullablePtr<ClosureExpr> getClosureIfClosureScope() const;
 
 private:
-  SourceRange getUncachedSourceRange(bool forDebugging = false) const;
+  SourceRange getUncachedSourceRange(bool omitAssertions = false) const;
+  SourceRange widenSourceRangeForIgnoredASTNodes(SourceRange range) const;
+
+  /// If the scope refers to a Decl whose source range tells the whole story,
+  /// for example a NominalTypeScope, it is not necessary to widen the source
+  /// range by examining the children. In that case we could just return
+  /// the childlessRange here.
+  /// But, we have not marked such scopes yet. Doing so would be an
+  /// optimization.
+  SourceRange widenSourceRangeForChildren(SourceRange range,
+                                          bool omitAssertions) const;
+
 public: // for PatternEntryDeclScope::expandMe
   void cacheSourceRange();
 private:

lib/AST/ASTScopePrinting.cpp

@@ -123,8 +123,8 @@ void ASTScopeImpl::printRange(llvm::raw_ostream &out) const {
   if (!cachedSourceRange)
     out << "(uncached) ";
   SourceRange range = cachedSourceRange
-                          ? getSourceRange(/*forDebugging=*/true)
-                          : getUncachedSourceRange(/*forDebugging=*/true);
+                          ? getSourceRange(/*omitAssertions=*/true)
+                          : getUncachedSourceRange(/*omitAssertions=*/true);
   printSourceRange(out, range, getSourceManager());
 }
 

lib/AST/ASTScopeSourceRange.cpp

@@ -35,32 +35,55 @@ using namespace ast_scope;
 
 static SourceLoc getStartOfFirstParam(ClosureExpr *closure);
 
-SourceRange ASTScopeImpl::getSourceRange(bool forDebugging) const {
-  if (forDebugging && !cachedSourceRange)
+SourceRange ASTScopeImpl::getSourceRange(const bool omitAssertions) const {
+  if (omitAssertions && !cachedSourceRange)
     return SourceRange();
   assert(cachedSourceRange && "should have been cached after last expandMe");
   return *cachedSourceRange;
 }
 
-SourceRange ASTScopeImpl::getUncachedSourceRange(bool forDebugging) const {
-  auto childlessRange = getChildlessSourceRange();
+SourceRange
+ASTScopeImpl::getUncachedSourceRange(const bool omitAssertions) const {
+  const auto childlessRange = getChildlessSourceRange();
+  const auto rangeIncludingIgnoredNodes =
+      widenSourceRangeForIgnoredASTNodes(childlessRange);
+  return widenSourceRangeForChildren(rangeIncludingIgnoredNodes,
+                                     omitAssertions);
+}
+
+SourceRange ASTScopeImpl::widenSourceRangeForIgnoredASTNodes(
+    const SourceRange range) const {
+  if (range.isInvalid())
+    return sourceRangeOfIgnoredASTNodes;
+  auto r = range;
   if (sourceRangeOfIgnoredASTNodes.isValid())
-    childlessRange.widen(sourceRangeOfIgnoredASTNodes);
+    r.widen(sourceRangeOfIgnoredASTNodes);
+  return r;
+}
+
+SourceRange
+ASTScopeImpl::widenSourceRangeForChildren(const SourceRange range,
+                                          bool omitAssertions) const {
   if (getChildren().empty()) {
-    assert(childlessRange.Start.isValid());
-    return childlessRange;
+    assert(omitAssertions || range.Start.isValid());
+    return range;
   }
+  // If we change the caching to compute the source range lazily,
+  // the only children required here would be the first and last.
   for (auto *c: getChildren())
     c->cacheSourceRange();
+
   const auto childStart =
-      getChildren().front()->getSourceRange(forDebugging).Start;
-  assert(forDebugging || childStart.isValid());
-  const auto childEnd = getChildren().back()->getSourceRange(forDebugging).End;
+      getChildren().front()->getSourceRange(omitAssertions).Start;
+  const auto childEnd =
+      getChildren().back()->getSourceRange(omitAssertions).End;
   auto childRange = SourceRange(childStart, childEnd);
-  if (childlessRange.Start.isInvalid())
+  assert(omitAssertions || childRange.isValid());
+
+  if (range.isInvalid())
     return childRange;
-  auto r = childRange;
-  r.widen(childlessRange);
+  auto r = range;
+  r.widen(childRange);
   return r;
 }