Merge pull request #37858 from bnbarham/ignore-invalid-loc

[AST] Do not return invalid SourceLocs from Decl::getLoc

Author: bnbarham

lib/AST/Decl.cpp

@@ -636,9 +636,18 @@ const ExternalSourceLocs *Decl::getSerializedLocs() const {
     return &NullLocs;
   }
 
+  CharSourceRange BufferRange = SM.getRangeForBuffer(BufferID);
   auto ResolveLoc = [&](const ExternalSourceLocs::RawLoc &Raw) -> SourceLoc {
+    // If the underlying source has been updated and the swiftsourceinfo hasn't,
+    // make sure we don't produce invalid source locations. Ideally would check
+    // the file hasn't been modified.
+    if (Raw.Offset > BufferRange.getByteLength())
+      return SourceLoc();
+
     // If the decl had a presumed loc, create its virtual file so that
-    // getPresumedLineAndColForLoc works from serialized locations as well.
+    // getPresumedLineAndColForLoc works from serialized locations as well. No
+    // need to check the buffer range, the directive must be before the location
+    // itself.
     if (Raw.Directive.isValid()) {
       auto &LD = Raw.Directive;
       SourceLoc Loc = SM.getLocForOffset(BufferID, LD.Offset);

test/diagnostics/multi-module-diagnostics.swift

@@ -59,6 +59,14 @@ open class SubClass: ParentClass {
 // CHECK-OUTOFDATE-NOT: moda.ParentClass:{{.*}}: note:
 // CHECK-OUTOFDATE: moda.swift:{{.*}}: note:
 
+// Underlying file is empty, the locations are now completely invalid (ie. not
+// within the buffer). Make sure there's no crash and that we fallback to using
+// the generated source.
+// RUN: rm %t/moda.swift
+// RUN: touch %t/moda.swift
+// RUN: not %target-swift-frontend -typecheck -I %t/mods -D MODB %s 2>&1 | %FileCheck -check-prefix=CHECK-EMPTY %s
+// CHECK-EMPTY: moda.ParentClass:{{.*}}: note:
+
 // The file and line from a location directive should be used whether or not it
 // exists - the actual source still comes from the original file, so that's what
 // matters in terms of whether generated code is used or not