[clang] [NFC] Add const to a parameter that's not modified.

Reviewed as part of D119184.

Author: Arthur O'Dwyer

clang/include/clang/Sema/Sema.h

@@ -8701,7 +8701,7 @@ class Sema final {
 
   bool DeduceFunctionTypeFromReturnExpr(FunctionDecl *FD,
                                         SourceLocation ReturnLoc,
-                                        Expr *&RetExpr, AutoType *AT);
+                                        Expr *&RetExpr, const AutoType *AT);
 
   FunctionTemplateDecl *getMoreSpecializedTemplate(
       FunctionTemplateDecl *FT1, FunctionTemplateDecl *FT2, SourceLocation Loc,

clang/lib/Sema/SemaStmt.cpp

@@ -3762,8 +3762,8 @@ TypeLoc Sema::getReturnTypeLoc(FunctionDecl *FD) const {
 bool Sema::DeduceFunctionTypeFromReturnExpr(FunctionDecl *FD,
                                             SourceLocation ReturnLoc,
                                             Expr *&RetExpr,
-                                            AutoType *AT) {
-  // If this is the conversion function for a lambda, we choose to deduce it
+                                            const AutoType *AT) {
+  // If this is the conversion function for a lambda, we choose to deduce its
   // type from the corresponding call operator, not from the synthesized return
   // statement within it. See Sema::DeduceReturnType.
   if (isLambdaConversionOperator(FD))