Merge pull request #83036 from hamishknight/origami-6.2

[6.2] [Sema] Avoid folding sequences multiple times for completion

Author: hamishknight

lib/Sema/TypeCheckExpr.cpp

@@ -633,6 +633,14 @@ swift::DefaultTypeRequest::evaluate(Evaluator &evaluator,
 }
 
 Expr *TypeChecker::foldSequence(SequenceExpr *expr, DeclContext *dc) {
+  // We may end up running pre-checking multiple times for completion, just use
+  // the folded expression if we've already folded the sequence.
+  // FIXME: We ought to fix completion to not pre-check multiple times, strictly
+  // speaking it isn't idempotent (e.g for things like `markDirectCallee`).
+  if (dc->getASTContext().CompletionCallback) {
+    if (auto *folded = expr->getFoldedExpr())
+      return folded;
+  }
   // First resolve any unresolved decl references in operator positions.
   for (auto i : indices(expr->getElements())) {
     if (i % 2 == 0)

validation-test/IDE/issues_fixed/issue-75845.swift

@@ -0,0 +1,17 @@
+// RUN: %batch-code-completion
+
+// https://github.com/apple/swift/issues/75845
+// Make sure we don't crash.
+
+struct Foo {
+  init() {
+    do {
+    } catch {
+      #^A^#self#^B^# = #^C^#error#^D^#
+    }
+  }
+}
+// A: Decl[LocalVar]/Local: error[#any Error#]; name=error
+// B: Begin completions
+// C: Decl[LocalVar]/Local: error[#any Error#]; name=error
+// D: Begin completions