Sema: Remove TypeCheckExprFlags::SkipMultiStmtClosures

Fold this into TypeCheckExprFlags::SubExpressionDiagnostics, which
is itself going away soon, hopefully!

Author: slavapestov

lib/Sema/CSApply.cpp

@@ -7208,7 +7208,7 @@ bool ConstraintSystem::applySolutionFixes(const Solution &solution) {
 Expr *ConstraintSystem::applySolution(Solution &solution, Expr *expr,
                                       Type convertType,
                                       bool discardedExpr,
-                                      bool skipClosures) {
+                                      bool performingDiagnostics) {
   // If any fixes needed to be applied to arrive at this solution, resolve
   // them to specific expressions.
   if (!solution.Fixes.empty()) {
@@ -7242,7 +7242,7 @@ Expr *ConstraintSystem::applySolution(Solution &solution, Expr *expr,
 
   // If we're re-typechecking an expression for diagnostics, don't
   // visit closures that have non-single expression bodies.
-  if (!skipClosures) {
+  if (!performingDiagnostics) {
     bool hadError = false;
     for (auto *closure : walker.getClosuresToTypeCheck())
       hadError |= TypeChecker::typeCheckClosureBody(closure);

lib/Sema/CSDiag.cpp

@@ -595,10 +595,6 @@ Expr *FailureDiagnosis::typeCheckChildIndependently(
   // to diagnose a problem.
   TCEOptions |= TypeCheckExprFlags::SubExpressionDiagnostics;
 
-  // Don't walk into non-single expression closure bodies, because
-  // ExprTypeSaver and TypeNullifier skip them too.
-  TCEOptions |= TypeCheckExprFlags::SkipMultiStmtClosures;
-
   // Claim that the result is discarded to preserve the lvalue type of
   // the expression.
   if (options.contains(TCC_AllowLValue))

lib/Sema/ConstraintSystem.h

@@ -3898,11 +3898,12 @@ class ConstraintSystem {
   /// expression should be converted, if any.
   /// \param discardedExpr if true, the result of the expression
   /// is contextually ignored.
-  /// \param skipClosures if true, don't descend into bodies of
-  /// non-single expression closures.
+  /// \param performingDiagnostics if true, don't descend into bodies of
+  /// non-single expression closures, or build curry thunks.
   Expr *applySolution(Solution &solution, Expr *expr,
-                      Type convertType, bool discardedExpr,
-                      bool skipClosures);
+                      Type convertType,
+                      bool discardedExpr,
+                      bool performingDiagnostics);
 
   /// Reorder the disjunctive clauses for a given expression to
   /// increase the likelihood that a favored constraint will be successfully

lib/Sema/TypeCheckConstraints.cpp

@@ -2259,7 +2259,7 @@ Type TypeChecker::typeCheckExpressionImpl(Expr *&expr, DeclContext *dc,
   result = cs.applySolution(
       solution, result, convertType.getType(),
       options.contains(TypeCheckExprFlags::IsDiscarded),
-      options.contains(TypeCheckExprFlags::SkipMultiStmtClosures));
+      options.contains(TypeCheckExprFlags::SubExpressionDiagnostics));
 
   if (!result) {
     listener.applySolutionFailed(solution, expr);

lib/Sema/TypeChecker.h

@@ -182,10 +182,6 @@ enum class TypeCheckExprFlags {
   /// not affect type checking itself.
   IsExprStmt = 0x20,
 
-  /// If set, this expression is being re-type checked as part of diagnostics,
-  /// and so we should not visit bodies of non-single expression closures.
-  SkipMultiStmtClosures = 0x40,
-
   /// This is an inout yield.
   IsInOutYield = 0x100,