@@ -377,6 +377,8 @@ impl char {
377377     /// ``` 
378378     /// assert_eq!('❤'.escape_unicode().to_string(), "\\u{2764}"); 
379379     /// ``` 
380+      #[ must_use = "this returns the escaped char as an iterator, \   
381+                    without modifying the original"] 
380382    #[ stable( feature = "rust1" ,  since = "1.0.0" ) ]  
381383    #[ inline]  
382384    pub  fn  escape_unicode ( self )  -> EscapeUnicode  { 
@@ -453,6 +455,8 @@ impl char {
453455     /// ``` 
454456     /// assert_eq!('\n'.escape_debug().to_string(), "\\n"); 
455457     /// ``` 
458+      #[ must_use = "this returns the escaped char as an iterator, \   
459+                    without modifying the original"] 
456460    #[ stable( feature = "char_escape_debug" ,  since = "1.20.0" ) ]  
457461    #[ inline]  
458462    pub  fn  escape_debug ( self )  -> EscapeDebug  { 
@@ -507,6 +511,8 @@ impl char {
507511     /// ``` 
508512     /// assert_eq!('"'.escape_default().to_string(), "\\\""); 
509513     /// ``` 
514+      #[ must_use = "this returns the escaped char as an iterator, \   
515+                    without modifying the original"] 
510516    #[ stable( feature = "rust1" ,  since = "1.0.0" ) ]  
511517    #[ inline]  
512518    pub  fn  escape_default ( self )  -> EscapeDefault  { 
@@ -692,6 +698,7 @@ impl char {
692698     /// // love is many things, but it is not alphabetic 
693699     /// assert!(!c.is_alphabetic()); 
694700     /// ``` 
701+      #[ must_use]  
695702    #[ stable( feature = "rust1" ,  since = "1.0.0" ) ]  
696703    #[ inline]  
697704    pub  fn  is_alphabetic ( self )  -> bool  { 
@@ -724,6 +731,7 @@ impl char {
724731     /// assert!(!'中'.is_lowercase()); 
725732     /// assert!(!' '.is_lowercase()); 
726733     /// ``` 
734+      #[ must_use]  
727735    #[ stable( feature = "rust1" ,  since = "1.0.0" ) ]  
728736    #[ inline]  
729737    pub  fn  is_lowercase ( self )  -> bool  { 
@@ -756,6 +764,7 @@ impl char {
756764     /// assert!(!'中'.is_uppercase()); 
757765     /// assert!(!' '.is_uppercase()); 
758766     /// ``` 
767+      #[ must_use]  
759768    #[ stable( feature = "rust1" ,  since = "1.0.0" ) ]  
760769    #[ inline]  
761770    pub  fn  is_uppercase ( self )  -> bool  { 
@@ -784,6 +793,7 @@ impl char {
784793     /// 
785794     /// assert!(!'越'.is_whitespace()); 
786795     /// ``` 
796+      #[ must_use]  
787797    #[ stable( feature = "rust1" ,  since = "1.0.0" ) ]  
788798    #[ inline]  
789799    pub  fn  is_whitespace ( self )  -> bool  { 
@@ -812,6 +822,7 @@ impl char {
812822     /// assert!('و'.is_alphanumeric()); 
813823     /// assert!('藏'.is_alphanumeric()); 
814824     /// ``` 
825+      #[ must_use]  
815826    #[ stable( feature = "rust1" ,  since = "1.0.0" ) ]  
816827    #[ inline]  
817828    pub  fn  is_alphanumeric ( self )  -> bool  { 
@@ -837,6 +848,7 @@ impl char {
837848     /// assert!(''.is_control()); 
838849     /// assert!(!'q'.is_control()); 
839850     /// ``` 
851+      #[ must_use]  
840852    #[ stable( feature = "rust1" ,  since = "1.0.0" ) ]  
841853    #[ inline]  
842854    pub  fn  is_control ( self )  -> bool  { 
@@ -852,6 +864,7 @@ impl char {
852864     /// [uax29]: https://www.unicode.org/reports/tr29/ 
853865     /// [ucd]: https://www.unicode.org/reports/tr44/ 
854866     /// [`DerivedCoreProperties.txt`]: https://www.unicode.org/Public/UCD/latest/ucd/DerivedCoreProperties.txt 
867+      #[ must_use]  
855868    #[ inline]  
856869    pub ( crate )  fn  is_grapheme_extended ( self )  -> bool  { 
857870        unicode:: Grapheme_Extend ( self ) 
@@ -881,6 +894,7 @@ impl char {
881894     /// assert!(!'و'.is_numeric()); 
882895     /// assert!(!'藏'.is_numeric()); 
883896     /// ``` 
897+      #[ must_use]  
884898    #[ stable( feature = "rust1" ,  since = "1.0.0" ) ]  
885899    #[ inline]  
886900    pub  fn  is_numeric ( self )  -> bool  { 
@@ -1060,6 +1074,7 @@ impl char {
10601074     /// assert!(ascii.is_ascii()); 
10611075     /// assert!(!non_ascii.is_ascii()); 
10621076     /// ``` 
1077+      #[ must_use]  
10631078    #[ stable( feature = "ascii_methods_on_intrinsics" ,  since = "1.23.0" ) ]  
10641079    #[ rustc_const_stable( feature = "const_ascii_methods_on_intrinsics" ,  since = "1.32.0" ) ]  
10651080    #[ inline]  
@@ -1237,6 +1252,7 @@ impl char {
12371252     /// assert!(!lf.is_ascii_alphabetic()); 
12381253     /// assert!(!esc.is_ascii_alphabetic()); 
12391254     /// ``` 
1255+      #[ must_use]  
12401256    #[ stable( feature = "ascii_ctype_on_intrinsics" ,  since = "1.24.0" ) ]  
12411257    #[ rustc_const_stable( feature = "const_ascii_ctype_on_intrinsics" ,  since = "1.47.0" ) ]  
12421258    #[ inline]  
@@ -1270,6 +1286,7 @@ impl char {
12701286     /// assert!(!lf.is_ascii_uppercase()); 
12711287     /// assert!(!esc.is_ascii_uppercase()); 
12721288     /// ``` 
1289+      #[ must_use]  
12731290    #[ stable( feature = "ascii_ctype_on_intrinsics" ,  since = "1.24.0" ) ]  
12741291    #[ rustc_const_stable( feature = "const_ascii_ctype_on_intrinsics" ,  since = "1.47.0" ) ]  
12751292    #[ inline]  
@@ -1303,6 +1320,7 @@ impl char {
13031320     /// assert!(!lf.is_ascii_lowercase()); 
13041321     /// assert!(!esc.is_ascii_lowercase()); 
13051322     /// ``` 
1323+      #[ must_use]  
13061324    #[ stable( feature = "ascii_ctype_on_intrinsics" ,  since = "1.24.0" ) ]  
13071325    #[ rustc_const_stable( feature = "const_ascii_ctype_on_intrinsics" ,  since = "1.47.0" ) ]  
13081326    #[ inline]  
@@ -1339,6 +1357,7 @@ impl char {
13391357     /// assert!(!lf.is_ascii_alphanumeric()); 
13401358     /// assert!(!esc.is_ascii_alphanumeric()); 
13411359     /// ``` 
1360+      #[ must_use]  
13421361    #[ stable( feature = "ascii_ctype_on_intrinsics" ,  since = "1.24.0" ) ]  
13431362    #[ rustc_const_stable( feature = "const_ascii_ctype_on_intrinsics" ,  since = "1.47.0" ) ]  
13441363    #[ inline]  
@@ -1372,6 +1391,7 @@ impl char {
13721391     /// assert!(!lf.is_ascii_digit()); 
13731392     /// assert!(!esc.is_ascii_digit()); 
13741393     /// ``` 
1394+      #[ must_use]  
13751395    #[ stable( feature = "ascii_ctype_on_intrinsics" ,  since = "1.24.0" ) ]  
13761396    #[ rustc_const_stable( feature = "const_ascii_ctype_on_intrinsics" ,  since = "1.47.0" ) ]  
13771397    #[ inline]  
@@ -1408,6 +1428,7 @@ impl char {
14081428     /// assert!(!lf.is_ascii_hexdigit()); 
14091429     /// assert!(!esc.is_ascii_hexdigit()); 
14101430     /// ``` 
1431+      #[ must_use]  
14111432    #[ stable( feature = "ascii_ctype_on_intrinsics" ,  since = "1.24.0" ) ]  
14121433    #[ rustc_const_stable( feature = "const_ascii_ctype_on_intrinsics" ,  since = "1.47.0" ) ]  
14131434    #[ inline]  
@@ -1445,6 +1466,7 @@ impl char {
14451466     /// assert!(!lf.is_ascii_punctuation()); 
14461467     /// assert!(!esc.is_ascii_punctuation()); 
14471468     /// ``` 
1469+      #[ must_use]  
14481470    #[ stable( feature = "ascii_ctype_on_intrinsics" ,  since = "1.24.0" ) ]  
14491471    #[ rustc_const_stable( feature = "const_ascii_ctype_on_intrinsics" ,  since = "1.47.0" ) ]  
14501472    #[ inline]  
@@ -1478,6 +1500,7 @@ impl char {
14781500     /// assert!(!lf.is_ascii_graphic()); 
14791501     /// assert!(!esc.is_ascii_graphic()); 
14801502     /// ``` 
1503+      #[ must_use]  
14811504    #[ stable( feature = "ascii_ctype_on_intrinsics" ,  since = "1.24.0" ) ]  
14821505    #[ rustc_const_stable( feature = "const_ascii_ctype_on_intrinsics" ,  since = "1.47.0" ) ]  
14831506    #[ inline]  
@@ -1528,6 +1551,7 @@ impl char {
15281551     /// assert!(lf.is_ascii_whitespace()); 
15291552     /// assert!(!esc.is_ascii_whitespace()); 
15301553     /// ``` 
1554+      #[ must_use]  
15311555    #[ stable( feature = "ascii_ctype_on_intrinsics" ,  since = "1.24.0" ) ]  
15321556    #[ rustc_const_stable( feature = "const_ascii_ctype_on_intrinsics" ,  since = "1.47.0" ) ]  
15331557    #[ inline]  
@@ -1563,6 +1587,7 @@ impl char {
15631587     /// assert!(lf.is_ascii_control()); 
15641588     /// assert!(esc.is_ascii_control()); 
15651589     /// ``` 
1590+      #[ must_use]  
15661591    #[ stable( feature = "ascii_ctype_on_intrinsics" ,  since = "1.24.0" ) ]  
15671592    #[ rustc_const_stable( feature = "const_ascii_ctype_on_intrinsics" ,  since = "1.47.0" ) ]  
15681593    #[ inline]  
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