[AST] Remove AbstractFunctionDecl::getSingleExpressionBody

This is now unused.

Author: hamishknight

include/swift/AST/AnyFunctionRef.h

@@ -100,12 +100,6 @@ class AnyFunctionRef {
     return TheFunction.get<AbstractClosureExpr *>()->hasSingleExpressionBody();
   }
 
-  Expr *getSingleExpressionBody() const {
-    if (auto *AFD = TheFunction.dyn_cast<AbstractFunctionDecl *>())
-      return AFD->getSingleExpressionBody();
-    return TheFunction.get<AbstractClosureExpr *>()->getSingleExpressionBody();
-  }
-
   ParameterList *getParameters() const {
     if (auto *AFD = TheFunction.dyn_cast<AbstractFunctionDecl *>())
       return AFD->getParameters();

include/swift/AST/Decl.h

@@ -7219,8 +7219,6 @@ class AbstractFunctionDecl : public GenericContext, public ValueDecl {
     return Bits.AbstractFunctionDecl.HasSingleExpressionBody;
   }
 
-  Expr *getSingleExpressionBody() const;
-
   /// Returns the string for the base name, or "_" if this is unnamed.
   StringRef getNameStr() const {
     assert(!getName().isSpecial() && "Cannot get string for special names");

lib/AST/Decl.cpp

@@ -1010,25 +1010,6 @@ AbstractFunctionDecl::getEffectiveThrownErrorType() const {
   return llvm::None;
 }
 
-Expr *AbstractFunctionDecl::getSingleExpressionBody() const {
-  assert(hasSingleExpressionBody() && "Not a single-expression body");
-  auto braceStmt = getBody();
-  assert(braceStmt != nullptr && "No body currently available.");
-  auto body = getBody()->getLastElement();
-  if (auto *stmt = body.dyn_cast<Stmt *>()) {
-    if (auto *returnStmt = dyn_cast<ReturnStmt>(stmt)) {
-      return returnStmt->getResult();
-    } else if (isa<FailStmt>(stmt)) {
-      // We can only get to this point if we're a type-checked ConstructorDecl
-      // which was originally spelled init?(...) { nil }.  
-      //
-      // There no longer is a single-expression to return, so ignore null.
-      return nullptr;
-    }
-  }
-  return body.get<Expr *>();
-}
-
 bool AbstractStorageDecl::isCompileTimeConst() const {
   return getAttrs().hasAttribute<CompileTimeConstAttr>();
 }