From d7958fa9761bd17c9db7edf442d479e2bc948cd7 Mon Sep 17 00:00:00 2001
From: Robert Widmann <devteam.codafi@gmail.com>
Date: Fri, 10 Dec 2021 14:44:39 -0800
Subject: [PATCH] Fully Check Decls in Result Builders

In particular, this turns redeclaration checking on for variables in
pattern bindings.

rdar://85784090
---
 lib/Sema/BuilderTransform.cpp               |  9 ++++++++-
 test/Constraints/result_builder_diags.swift | 11 +++++++++++
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/lib/Sema/BuilderTransform.cpp b/lib/Sema/BuilderTransform.cpp
index 5b6260ed84d08..82a4a8b9ef92e 100644
--- a/lib/Sema/BuilderTransform.cpp
+++ b/lib/Sema/BuilderTransform.cpp
@@ -1122,10 +1122,15 @@ class BuilderClosureRewriter
       if (!resultTarget)
         continue;
 
+      // FIXME: It's unfortunate that we're duplicating code from CSApply here.
+      // If there were a request for the fully-typechecked initializer of a
+      // pattern binding we may be able to eliminate the duplication here.
       patternBinding->setPattern(
           index, resultTarget->getInitializationPattern(),
-          resultTarget->getDeclContext());
+          resultTarget->getDeclContext(),
+          /*isFullyValidated=*/true);
       patternBinding->setInit(index, resultTarget->getAsExpr());
+      patternBinding->setInitializerChecked(index);
     }
   }
 
@@ -1226,6 +1231,7 @@ class BuilderClosureRewriter
       // Skip variable declarations; they're always part of a pattern
       // binding.
       if (isa<VarDecl>(decl)) {
+        TypeChecker::typeCheckDecl(decl);
         newElements.push_back(decl);
         continue;
       }
@@ -1233,6 +1239,7 @@ class BuilderClosureRewriter
       // Handle pattern bindings.
       if (auto patternBinding = dyn_cast<PatternBindingDecl>(decl)) {
         finishPatternBindingDecl(patternBinding);
+        TypeChecker::typeCheckDecl(decl);
         newElements.push_back(decl);
         continue;
       }
diff --git a/test/Constraints/result_builder_diags.swift b/test/Constraints/result_builder_diags.swift
index 396047f1a0c58..6be029e292806 100644
--- a/test/Constraints/result_builder_diags.swift
+++ b/test/Constraints/result_builder_diags.swift
@@ -815,3 +815,14 @@ func test_missing_member_in_optional_context() {
     }
   }
 }
+
+func test_redeclations() {
+  tuplify(true) { c in
+    let foo = 0 // expected-note {{'foo' previously declared here}}
+    let foo = foo // expected-error {{invalid redeclaration of 'foo'}}
+  }
+
+  tuplify(true) { c in
+    let (foo, foo) = (5, 6) // expected-error {{invalid redeclaration of 'foo'}} expected-note {{'foo' previously declared here}}
+  }
+}