[ASTScope] In the isBeforeInSource predicate, use the end location of the

original source location of a macro expansion when walking up the ancestor
list.

The original source range of a macro expansion buffer contains the entire
range of the code that is replaced by the expansion. In some cases, the
original code is type checked, so ASTScope needs to represent both the
original code and the macro-expanded code in the scope tree.

For accessor macros, the original code -- the initializer expression of
the property -- is type checked, but not before macro expansion, so
unqualified lookup must deal with the scope tree for the initializer and
the expanded accessors. The accessors are inserted in the tree after the
initializer scope, but the `isBeforeInSource` was using the start location
of the original source range for macro expansions, so the accessor scopes
were incorrectly considered to be ordered before a source location in the
initializer expression, which caused unqualified lookup of local variables
within the initializer to fail.

Author: hborla

lib/Basic/SourceLoc.cpp

@@ -797,11 +797,11 @@ static bool isBeforeInSource(
   SourceLoc firstLocInLCA = firstMismatch == firstAncestors.end()
       ? firstLoc
       : sourceMgr.getGeneratedSourceInfo(*firstMismatch)
-          ->originalSourceRange.getStart();
+          ->originalSourceRange.getEnd();
   SourceLoc secondLocInLCA = secondMismatch == secondAncestors.end()
       ? secondLoc
       : sourceMgr.getGeneratedSourceInfo(*secondMismatch)
-          ->originalSourceRange.getStart();
+          ->originalSourceRange.getEnd();
   return sourceMgr.isBeforeInBuffer(firstLocInLCA, secondLocInLCA) ||
     (allowEqual && firstLocInLCA == secondLocInLCA);
 }

test/stdlib/Observation/Observable.swift

@@ -215,6 +215,16 @@ class RecursiveOuter {
 class GuardedAvailability {
 }
 
+@Observable class TestASTScopeLCA {
+  // Make sure ASTScope unqualified lookup can find local variables
+  // inside initial values with closures when accessor macros are
+  // involved.
+  var state : Bool = {
+    let value = true
+    return value
+  }()
+}
+
 @main
 struct Validator {
   @MainActor