[TypeChecker] Consolidate StmtChecker constructors

Author: rintaro

lib/Sema/TypeCheckStmt.cpp

@@ -364,18 +364,15 @@ class StmtChecker : public StmtVisitor<StmtChecker, Stmt*> {
     }
   };
 
-  StmtChecker(AbstractFunctionDecl *AFD)
-      : Ctx(AFD->getASTContext()), TheFunc(AFD), DC(AFD),
-        IsBraceStmtFromTopLevelDecl(false) {}
-
-  StmtChecker(ClosureExpr *TheClosure)
-      : Ctx(TheClosure->getASTContext()), TheFunc(TheClosure),
-        DC(TheClosure), IsBraceStmtFromTopLevelDecl(false) {}
-
   StmtChecker(DeclContext *DC)
       : Ctx(DC->getASTContext()), TheFunc(), DC(DC),
         IsBraceStmtFromTopLevelDecl(false) {
-    IsBraceStmtFromTopLevelDecl = isa<TopLevelCodeDecl>(DC);
+    if (auto *AFD = dyn_cast<AbstractFunctionDecl>(DC))
+      TheFunc = AFD;
+    else if (auto *CE = dyn_cast<ClosureExpr>(DC))
+      TheFunc = CE;
+    else if (isa<TopLevelCodeDecl>(DC))
+      IsBraceStmtFromTopLevelDecl = true;
   }
 
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