don't use .into() to convert types into identical types.

example:
    let s: String = format!("hello").into();

5 files changed, 11 insertions, 17 deletions

diff --git a/src/librustc_parse/lexer/mod.rs b/src/librustc_parse/lexer/mod.rs
index e60f1138ddc..66280638a2d 100644
--- a/src/librustc_parse/lexer/mod.rs
+++ b/src/librustc_parse/lexer/mod.rs
@@ -327,8 +327,7 @@ impl<'a> StringReader<'a> {
         match kind {
             rustc_lexer::LiteralKind::Char { terminated } => {
                 if !terminated {
-                    self.fatal_span_(start, suffix_start, "unterminated character literal".into())
-                        .raise()
+                    self.fatal_span_(start, suffix_start, "unterminated character literal").raise()
                 }
                 let content_start = start + BytePos(1);
                 let content_end = suffix_start - BytePos(1);
@@ -338,12 +337,8 @@ impl<'a> StringReader<'a> {
             }
             rustc_lexer::LiteralKind::Byte { terminated } => {
                 if !terminated {
-                    self.fatal_span_(
-                        start + BytePos(1),
-                        suffix_start,
-                        "unterminated byte constant".into(),
-                    )
-                    .raise()
+                    self.fatal_span_(start + BytePos(1), suffix_start, "unterminated byte constant")
+                        .raise()
                 }
                 let content_start = start + BytePos(2);
                 let content_end = suffix_start - BytePos(1);
@@ -353,7 +348,7 @@ impl<'a> StringReader<'a> {
             }
             rustc_lexer::LiteralKind::Str { terminated } => {
                 if !terminated {
-                    self.fatal_span_(start, suffix_start, "unterminated double quote string".into())
+                    self.fatal_span_(start, suffix_start, "unterminated double quote string")
                         .raise()
                 }
                 let content_start = start + BytePos(1);
@@ -367,7 +362,7 @@ impl<'a> StringReader<'a> {
                     self.fatal_span_(
                         start + BytePos(1),
                         suffix_start,
-                        "unterminated double quote byte string".into(),
+                        "unterminated double quote byte string",
                     )
                     .raise()
                 }
diff --git a/src/librustc_parse/lexer/tokentrees.rs b/src/librustc_parse/lexer/tokentrees.rs
index c28b59a7908..4f0276225fb 100644
--- a/src/librustc_parse/lexer/tokentrees.rs
+++ b/src/librustc_parse/lexer/tokentrees.rs
@@ -212,7 +212,7 @@ impl<'a> TokenTreesReader<'a> {
                     _ => {}
                 }
 
-                Ok(TokenTree::Delimited(delim_span, delim, tts.into()).into())
+                Ok(TokenTree::Delimited(delim_span, delim, tts).into())
             }
             token::CloseDelim(delim) => {
                 // An unexpected closing delimiter (i.e., there is no
diff --git a/src/librustc_parse/lib.rs b/src/librustc_parse/lib.rs
index bd0b189d4fd..4cf9e4c3059 100644
--- a/src/librustc_parse/lib.rs
+++ b/src/librustc_parse/lib.rs
@@ -420,7 +420,7 @@ fn prepend_attrs(
         builder.push(tokenstream::TokenTree::Delimited(
             delim_span,
             token::DelimToken::Bracket,
-            brackets.build().into(),
+            brackets.build(),
         ));
     }
     builder.push(tokens.clone());
diff --git a/src/librustc_parse/parser/mod.rs b/src/librustc_parse/parser/mod.rs
index 75d4b3750f1..7b8642b0151 100644
--- a/src/librustc_parse/parser/mod.rs
+++ b/src/librustc_parse/parser/mod.rs
@@ -263,8 +263,7 @@ impl TokenCursor {
             ]
             .iter()
             .cloned()
-            .collect::<TokenStream>()
-            .into(),
+            .collect::<TokenStream>(),
         );
 
         self.stack.push(mem::replace(
@@ -389,7 +388,7 @@ impl<'a> Parser<'a> {
             root_module_name: None,
             expected_tokens: Vec::new(),
             token_cursor: TokenCursor {
-                frame: TokenCursorFrame::new(DelimSpan::dummy(), token::NoDelim, &tokens.into()),
+                frame: TokenCursorFrame::new(DelimSpan::dummy(), token::NoDelim, &tokens),
                 stack: Vec::new(),
             },
             desugar_doc_comments,
@@ -1006,7 +1005,7 @@ impl<'a> Parser<'a> {
                 );
                 self.set_token(Token::new(TokenKind::CloseDelim(frame.delim), frame.span.close));
                 self.bump();
-                TokenTree::Delimited(frame.span, frame.delim, frame.tree_cursor.stream.into())
+                TokenTree::Delimited(frame.span, frame.delim, frame.tree_cursor.stream)
             }
             token::CloseDelim(_) | token::Eof => unreachable!(),
             _ => {
diff --git a/src/librustc_parse/parser/stmt.rs b/src/librustc_parse/parser/stmt.rs
index d2a6f0b7fcf..257292ae072 100644
--- a/src/librustc_parse/parser/stmt.rs
+++ b/src/librustc_parse/parser/stmt.rs
@@ -169,7 +169,7 @@ impl<'a> Parser<'a> {
     }
 
     fn parse_local_mk(&mut self, lo: Span, attrs: AttrVec) -> PResult<'a, Stmt> {
-        let local = self.parse_local(attrs.into())?;
+        let local = self.parse_local(attrs)?;
         Ok(self.mk_stmt(lo.to(self.prev_span), StmtKind::Local(local)))
     }