AST: Compute actor isolation when expanding semantic attributes.

Declarations may have semantic actor isolation requirements that were not
written in source. For example, the default implementation of a protocol
requirement must be `@MainActor` isolated if the protocol declaration itself is
`@MainActor` isolated. When computing the semantic attributes of a declaration
lazily, we must compute the actor isolation of the declaration to ensure that
any global actor constraint attributes are added.

Also, avoid request cycles and recursive diagnostic printing by only triggering
the computation of semantic attributes when printing for swiftinterfaces.

Resolves rdar://118277555

Author: tshortli

lib/AST/ASTPrinter.cpp

@@ -146,7 +146,7 @@ static bool isInObjCImpl(const ValueDecl *VD) {
 /// be complete (for example, when printing a .swiftinterface). In other
 /// contexts, though, triggering type checking could cause re-entrancy and
 /// should be avoided.
-static bool shouldTypeCheck(const PrintOptions &options) {
+static bool shouldPrintAllSemanticDetails(const PrintOptions &options) {
   if (options.IsForSwiftInterface)
     return true;
 
@@ -1150,7 +1150,11 @@ void PrintAST::printAttributes(const Decl *D) {
   if (Options.SkipAttributes)
     return;
 
-  auto attrs = D->getSemanticAttrs();
+  // Force semantic attrs to be computed if appropriate.
+  if (shouldPrintAllSemanticDetails(Options))
+    (void)D->getSemanticAttrs();
+
+  auto attrs = D->getAttrs();
 
   // Save the current number of exclude attrs to restore once we're done.
   unsigned originalExcludeAttrCount = Options.ExcludeAttrList.size();
@@ -2259,7 +2263,7 @@ void PrintAST::printAccessors(const AbstractStorageDecl *ASD) {
   }
 
   // Force implicit accessors to be created if they haven't been already.
-  if (shouldTypeCheck(Options)) {
+  if (shouldPrintAllSemanticDetails(Options)) {
     ASD->visitEmittedAccessors([](AccessorDecl *accessor) {
       (void)accessor;
     });
@@ -3900,7 +3904,7 @@ void PrintAST::visitPatternBindingDecl(PatternBindingDecl *decl) {
     auto *pattern = decl->getPattern(idx);
 
     // Force the entry to be typechecked before attempting to print.
-    if (shouldTypeCheck(Options) && !pattern->hasType())
+    if (shouldPrintAllSemanticDetails(Options) && !pattern->hasType())
       (void)decl->getCheckedPatternBindingEntry(idx);
 
     if (!shouldPrintPattern(pattern))

lib/AST/TypeCheckRequests.cpp

@@ -2050,7 +2050,8 @@ DeclAttributes SemanticDeclAttrsRequest::evaluate(Evaluator &evaluator,
                           {});
 
   // Trigger requests that cause additional semantic attributes to be added.
-  if (auto vd = dyn_cast<ValueDecl>(decl)) {
+  if (auto vd = dyn_cast<ValueDecl>(mutableDecl)) {
+    (void)getActorIsolation(vd);
     (void)vd->isDynamic();
     (void)vd->isFinal();
   }

test/Inputs/lazy_typecheck.swift

@@ -115,6 +115,12 @@ public protocol PublicProtoWithAssociatedType {
   func req() throws -> Int
 }
 
+extension MainActorProtocol {
+  public func req() throws -> Int {
+    return 1
+  }
+}
+
 protocol InternalProtoWithAssociatedType {
   associatedtype A
   func internalReq() -> A