Remove LLVM_NODISCARD from StringRef.

This is a bit too aggressive of a warning, as it is forces
ANY function which returns a StringRef to have its return
value checked.  While useful on classes like llvm::Error which
are designed to require checking, this is not the case for
StringRef, and it is perfectly reasonable to have a function
return a StringRef for which the return value is not checked.

Move LLVM_NODISCARD to each of the individual member functions
where it makes sense instead.

llvm-svn: 287586

include/llvm/ADT/StringRef.h

@@ -44,7 +44,7 @@ namespace llvm {
   /// situations where the character data resides in some other buffer, whose
   /// lifetime extends past that of the StringRef. For this reason, it is not in
   /// general safe to store a StringRef.
-  class LLVM_NODISCARD StringRef {
+  class StringRef {
   public:
     typedef const char *iterator;
     typedef const char *const_iterator;
@@ -123,30 +123,36 @@ namespace llvm {
 
     /// data - Get a pointer to the start of the string (which may not be null
     /// terminated).
+    LLVM_NODISCARD
     LLVM_ATTRIBUTE_ALWAYS_INLINE
     const char *data() const { return Data; }
 
     /// empty - Check if the string is empty.
+    LLVM_NODISCARD
     LLVM_ATTRIBUTE_ALWAYS_INLINE
     bool empty() const { return Length == 0; }
 
     /// size - Get the string size.
+    LLVM_NODISCARD
     LLVM_ATTRIBUTE_ALWAYS_INLINE
     size_t size() const { return Length; }
 
     /// front - Get the first character in the string.
+    LLVM_NODISCARD
     char front() const {
       assert(!empty());
       return Data[0];
     }
 
     /// back - Get the last character in the string.
+    LLVM_NODISCARD
     char back() const {
       assert(!empty());
       return Data[Length-1];
     }
 
     // copy - Allocate copy in Allocator and return StringRef to it.
+    LLVM_NODISCARD
     template <typename Allocator> StringRef copy(Allocator &A) const {
       // Don't request a length 0 copy from the allocator.
       if (empty())
@@ -158,6 +164,7 @@ namespace llvm {
 
     /// equals - Check for string equality, this is more efficient than
     /// compare() when the relative ordering of inequal strings isn't needed.
+    LLVM_NODISCARD
     LLVM_ATTRIBUTE_ALWAYS_INLINE
     bool equals(StringRef RHS) const {
       return (Length == RHS.Length &&
@@ -165,12 +172,14 @@ namespace llvm {
     }
 
     /// equals_lower - Check for string equality, ignoring case.
+    LLVM_NODISCARD
     bool equals_lower(StringRef RHS) const {
       return Length == RHS.Length && compare_lower(RHS) == 0;
     }
 
     /// compare - Compare two strings; the result is -1, 0, or 1 if this string
     /// is lexicographically less than, equal to, or greater than the \p RHS.
+    LLVM_NODISCARD
     LLVM_ATTRIBUTE_ALWAYS_INLINE
     int compare(StringRef RHS) const {
       // Check the prefix for a mismatch.
@@ -184,10 +193,12 @@ namespace llvm {
     }
 
     /// compare_lower - Compare two strings, ignoring case.
+    LLVM_NODISCARD
     int compare_lower(StringRef RHS) const;
 
     /// compare_numeric - Compare two strings, treating sequences of digits as
     /// numbers.
+    LLVM_NODISCARD
     int compare_numeric(StringRef RHS) const;
 
     /// \brief Determine the edit distance between this string and another
@@ -208,10 +219,12 @@ namespace llvm {
     /// or (if \p AllowReplacements is \c true) replacements needed to
     /// transform one of the given strings into the other. If zero,
     /// the strings are identical.
+    LLVM_NODISCARD
     unsigned edit_distance(StringRef Other, bool AllowReplacements = true,
                            unsigned MaxEditDistance = 0) const;
 
     /// str - Get the contents as an std::string.
+    LLVM_NODISCARD
     std::string str() const {
       if (!Data) return std::string();
       return std::string(Data, Length);
@@ -221,6 +234,7 @@ namespace llvm {
     /// @name Operator Overloads
     /// @{
 
+    LLVM_NODISCARD
     char operator[](size_t Index) const {
       assert(Index < Length && "Invalid index!");
       return Data[Index];
@@ -248,6 +262,7 @@ namespace llvm {
     /// @{
 
     /// Check if this string starts with the given \p Prefix.
+    LLVM_NODISCARD
     LLVM_ATTRIBUTE_ALWAYS_INLINE
     bool startswith(StringRef Prefix) const {
       return Length >= Prefix.Length &&
@@ -255,16 +270,19 @@ namespace llvm {
     }
 
     /// Check if this string starts with the given \p Prefix, ignoring case.
+    LLVM_NODISCARD
     bool startswith_lower(StringRef Prefix) const;
 
     /// Check if this string ends with the given \p Suffix.
     LLVM_ATTRIBUTE_ALWAYS_INLINE
+    LLVM_NODISCARD
     bool endswith(StringRef Suffix) const {
       return Length >= Suffix.Length &&
         compareMemory(end() - Suffix.Length, Suffix.Data, Suffix.Length) == 0;
     }
 
     /// Check if this string ends with the given \p Suffix, ignoring case.
+    LLVM_NODISCARD
     bool endswith_lower(StringRef Suffix) const;
 
     /// @}
@@ -275,6 +293,7 @@ namespace llvm {
     ///
     /// \returns The index of the first occurrence of \p C, or npos if not
     /// found.
+    LLVM_NODISCARD
     LLVM_ATTRIBUTE_ALWAYS_INLINE
     size_t find(char C, size_t From = 0) const {
       size_t FindBegin = std::min(From, Length);
@@ -290,6 +309,7 @@ namespace llvm {
     ///
     /// \returns The index of the first occurrence of \p C, or npos if not
     /// found.
+    LLVM_NODISCARD
     size_t find_lower(char C, size_t From = 0) const;
 
     /// Search for the first character satisfying the predicate \p F
@@ -322,18 +342,21 @@ namespace llvm {
     ///
     /// \returns The index of the first occurrence of \p Str, or npos if not
     /// found.
+    LLVM_NODISCARD
     size_t find(StringRef Str, size_t From = 0) const;
 
     /// Search for the first string \p Str in the string, ignoring case.
     ///
     /// \returns The index of the first occurrence of \p Str, or npos if not
     /// found.
+    LLVM_NODISCARD
     size_t find_lower(StringRef Str, size_t From = 0) const;
 
     /// Search for the last character \p C in the string.
     ///
     /// \returns The index of the last occurrence of \p C, or npos if not
     /// found.
+    LLVM_NODISCARD
     size_t rfind(char C, size_t From = npos) const {
       From = std::min(From, Length);
       size_t i = From;
@@ -349,22 +372,26 @@ namespace llvm {
     ///
     /// \returns The index of the last occurrence of \p C, or npos if not
     /// found.
+    LLVM_NODISCARD
     size_t rfind_lower(char C, size_t From = npos) const;
 
     /// Search for the last string \p Str in the string.
     ///
     /// \returns The index of the last occurrence of \p Str, or npos if not
     /// found.
+    LLVM_NODISCARD
     size_t rfind(StringRef Str) const;
 
     /// Search for the last string \p Str in the string, ignoring case.
     ///
     /// \returns The index of the last occurrence of \p Str, or npos if not
     /// found.
+    LLVM_NODISCARD
     size_t rfind_lower(StringRef Str) const;
 
     /// Find the first character in the string that is \p C, or npos if not
     /// found. Same as find.
+    LLVM_NODISCARD
     size_t find_first_of(char C, size_t From = 0) const {
       return find(C, From);
     }
@@ -373,20 +400,24 @@ namespace llvm {
     /// not found.
     ///
     /// Complexity: O(size() + Chars.size())
+    LLVM_NODISCARD
     size_t find_first_of(StringRef Chars, size_t From = 0) const;
 
     /// Find the first character in the string that is not \p C or npos if not
     /// found.
+    LLVM_NODISCARD
     size_t find_first_not_of(char C, size_t From = 0) const;
 
     /// Find the first character in the string that is not in the string
     /// \p Chars, or npos if not found.
     ///
     /// Complexity: O(size() + Chars.size())
+    LLVM_NODISCARD
     size_t find_first_not_of(StringRef Chars, size_t From = 0) const;
 
     /// Find the last character in the string that is \p C, or npos if not
     /// found.
+    LLVM_NODISCARD
     size_t find_last_of(char C, size_t From = npos) const {
       return rfind(C, From);
     }
@@ -395,30 +426,36 @@ namespace llvm {
     /// found.
     ///
     /// Complexity: O(size() + Chars.size())
+    LLVM_NODISCARD
     size_t find_last_of(StringRef Chars, size_t From = npos) const;
 
     /// Find the last character in the string that is not \p C, or npos if not
     /// found.
+    LLVM_NODISCARD
     size_t find_last_not_of(char C, size_t From = npos) const;
 
     /// Find the last character in the string that is not in \p Chars, or
     /// npos if not found.
     ///
     /// Complexity: O(size() + Chars.size())
+    LLVM_NODISCARD
     size_t find_last_not_of(StringRef Chars, size_t From = npos) const;
 
     /// Return true if the given string is a substring of *this, and false
     /// otherwise.
+    LLVM_NODISCARD
     LLVM_ATTRIBUTE_ALWAYS_INLINE
     bool contains(StringRef Other) const { return find(Other) != npos; }
 
     /// Return true if the given character is contained in *this, and false
     /// otherwise.
+    LLVM_NODISCARD
     LLVM_ATTRIBUTE_ALWAYS_INLINE
     bool contains(char C) const { return find_first_of(C) != npos; }
 
     /// Return true if the given string is a substring of *this, and false
     /// otherwise.
+    LLVM_NODISCARD
     LLVM_ATTRIBUTE_ALWAYS_INLINE
     bool contains_lower(StringRef Other) const {
       return find_lower(Other) != npos;
@@ -426,6 +463,7 @@ namespace llvm {
 
     /// Return true if the given character is contained in *this, and false
     /// otherwise.
+    LLVM_NODISCARD
     LLVM_ATTRIBUTE_ALWAYS_INLINE
     bool contains_lower(char C) const { return find_lower(C) != npos; }
 
@@ -434,6 +472,7 @@ namespace llvm {
     /// @{
 
     /// Return the number of occurrences of \p C in the string.
+    LLVM_NODISCARD
     size_t count(char C) const {
       size_t Count = 0;
       for (size_t i = 0, e = Length; i != e; ++i)
@@ -453,6 +492,7 @@ namespace llvm {
     /// If the string is invalid or if only a subset of the string is valid,
     /// this returns true to signify the error.  The string is considered
     /// erroneous if empty or if it overflows T.
+    LLVM_NODISCARD
     template <typename T>
     typename std::enable_if<std::numeric_limits<T>::is_signed, bool>::type
     getAsInteger(unsigned Radix, T &Result) const {
@@ -464,6 +504,7 @@ namespace llvm {
       return false;
     }
 
+    LLVM_NODISCARD
     template <typename T>
     typename std::enable_if<!std::numeric_limits<T>::is_signed, bool>::type
     getAsInteger(unsigned Radix, T &Result) const {
@@ -519,6 +560,7 @@ namespace llvm {
     ///
     /// APInt::fromString is superficially similar but assumes the
     /// string is well-formed in the given radix.
+    LLVM_NODISCARD
     bool getAsInteger(unsigned Radix, APInt &Result) const;
 
     /// @}
@@ -526,9 +568,11 @@ namespace llvm {
     /// @{
 
     // Convert the given ASCII string to lowercase.
+    LLVM_NODISCARD
     std::string lower() const;
 
     /// Convert the given ASCII string to uppercase.
+    LLVM_NODISCARD
     std::string upper() const;
 
     /// @}
@@ -544,6 +588,7 @@ namespace llvm {
     /// \param N The number of characters to included in the substring. If N
     /// exceeds the number of characters remaining in the string, the string
     /// suffix (starting with \p Start) will be returned.
+    LLVM_NODISCARD
     LLVM_ATTRIBUTE_ALWAYS_INLINE
     StringRef substr(size_t Start, size_t N = npos) const {
       Start = std::min(Start, Length);
@@ -553,6 +598,7 @@ namespace llvm {
     /// Return a StringRef equal to 'this' but with only the first \p N
     /// elements remaining.  If \p N is greater than the length of the
     /// string, the entire string is returned.
+    LLVM_NODISCARD
     LLVM_ATTRIBUTE_ALWAYS_INLINE
     StringRef take_front(size_t N = 1) const {
       if (N >= size())
@@ -563,6 +609,7 @@ namespace llvm {
     /// Return a StringRef equal to 'this' but with only the first \p N
     /// elements remaining.  If \p N is greater than the length of the
     /// string, the entire string is returned.
+    LLVM_NODISCARD
     LLVM_ATTRIBUTE_ALWAYS_INLINE
     StringRef take_back(size_t N = 1) const {
       if (N >= size())
@@ -572,6 +619,7 @@ namespace llvm {
 
     /// Return the longest prefix of 'this' such that every character
     /// in the prefix satisfies the given predicate.
+    LLVM_NODISCARD
     LLVM_ATTRIBUTE_ALWAYS_INLINE
     StringRef take_while(function_ref<bool(char)> F) const {
       return substr(0, find_if_not(F));
@@ -579,6 +627,7 @@ namespace llvm {
 
     /// Return the longest prefix of 'this' such that no character in
     /// the prefix satisfies the given predicate.
+    LLVM_NODISCARD
     LLVM_ATTRIBUTE_ALWAYS_INLINE
     StringRef take_until(function_ref<bool(char)> F) const {
       return substr(0, find_if(F));
@@ -586,6 +635,7 @@ namespace llvm {
 
     /// Return a StringRef equal to 'this' but with the first \p N elements
     /// dropped.
+    LLVM_NODISCARD
     LLVM_ATTRIBUTE_ALWAYS_INLINE
     StringRef drop_front(size_t N = 1) const {
       assert(size() >= N && "Dropping more elements than exist");
@@ -594,6 +644,7 @@ namespace llvm {
 
     /// Return a StringRef equal to 'this' but with the last \p N elements
     /// dropped.
+    LLVM_NODISCARD
     LLVM_ATTRIBUTE_ALWAYS_INLINE
     StringRef drop_back(size_t N = 1) const {
       assert(size() >= N && "Dropping more elements than exist");
@@ -602,6 +653,7 @@ namespace llvm {
 
     /// Return a StringRef equal to 'this', but with all characters satisfying
     /// the given predicate dropped from the beginning of the string.
+    LLVM_NODISCARD
     LLVM_ATTRIBUTE_ALWAYS_INLINE
     StringRef drop_while(function_ref<bool(char)> F) const {
       return substr(find_if_not(F));
@@ -609,6 +661,7 @@ namespace llvm {
 
     /// Return a StringRef equal to 'this', but with all characters not
     /// satisfying the given predicate dropped from the beginning of the string.
+    LLVM_NODISCARD
     LLVM_ATTRIBUTE_ALWAYS_INLINE
     StringRef drop_until(function_ref<bool(char)> F) const {
       return substr(find_if(F));
@@ -649,6 +702,7 @@ namespace llvm {
     /// remaining in the string, the string suffix (starting with \p Start)
     /// will be returned. If this is less than \p Start, an empty string will
     /// be returned.
+    LLVM_NODISCARD
     LLVM_ATTRIBUTE_ALWAYS_INLINE
     StringRef slice(size_t Start, size_t End) const {
       Start = std::min(Start, Length);
@@ -666,6 +720,7 @@ namespace llvm {
     ///
     /// \param Separator The character to split on.
     /// \returns The split substrings.
+    LLVM_NODISCARD
     std::pair<StringRef, StringRef> split(char Separator) const {
       size_t Idx = find(Separator);
       if (Idx == npos)
@@ -683,6 +738,7 @@ namespace llvm {
     ///
     /// \param Separator - The string to split on.
     /// \return - The split substrings.
+    LLVM_NODISCARD
     std::pair<StringRef, StringRef> split(StringRef Separator) const {
       size_t Idx = find(Separator);
       if (Idx == npos)
@@ -735,6 +791,7 @@ namespace llvm {
     ///
     /// \param Separator - The character to split on.
     /// \return - The split substrings.
+    LLVM_NODISCARD
     std::pair<StringRef, StringRef> rsplit(char Separator) const {
       size_t Idx = rfind(Separator);
       if (Idx == npos)
@@ -744,36 +801,42 @@ namespace llvm {
 
     /// Return string with consecutive \p Char characters starting from the
     /// the left removed.
+    LLVM_NODISCARD
     StringRef ltrim(char Char) const {
       return drop_front(std::min(Length, find_first_not_of(Char)));
     }
 
     /// Return string with consecutive characters in \p Chars starting from
     /// the left removed.
+    LLVM_NODISCARD
     StringRef ltrim(StringRef Chars = " \t\n\v\f\r") const {
       return drop_front(std::min(Length, find_first_not_of(Chars)));
     }
 
     /// Return string with consecutive \p Char characters starting from the
     /// right removed.
+    LLVM_NODISCARD
     StringRef rtrim(char Char) const {
       return drop_back(Length - std::min(Length, find_last_not_of(Char) + 1));
     }
 
     /// Return string with consecutive characters in \p Chars starting from
     /// the right removed.
+    LLVM_NODISCARD
     StringRef rtrim(StringRef Chars = " \t\n\v\f\r") const {
       return drop_back(Length - std::min(Length, find_last_not_of(Chars) + 1));
     }
 
     /// Return string with consecutive \p Char characters starting from the
     /// left and right removed.
+    LLVM_NODISCARD
     StringRef trim(char Char) const {
       return ltrim(Char).rtrim(Char);
     }
 
     /// Return string with consecutive characters in \p Chars starting from
     /// the left and right removed.
+    LLVM_NODISCARD
     StringRef trim(StringRef Chars = " \t\n\v\f\r") const {
       return ltrim(Chars).rtrim(Chars);
     }
@@ -817,6 +880,7 @@ namespace llvm {
   /// @}
 
   /// \brief Compute a hash_code for a StringRef.
+  LLVM_NODISCARD
   hash_code hash_value(StringRef S);
 
   // StringRefs can be treated like a POD type.