Fix some clippy lints

compiler/rustc_expand/src/base.rs

@@ -235,12 +235,10 @@ impl Annotatable {
     pub fn derive_allowed(&self) -> bool {
         match *self {
             Annotatable::Stmt(ref stmt) => match stmt.kind {
-                ast::StmtKind::Item(ref item) => match item.kind {
+                ast::StmtKind::Item(ref item) => matches!(
-                    ast::ItemKind::Struct(..)
+                    item.kind,
-                    | ast::ItemKind::Enum(..)
+                    ast::ItemKind::Struct(..) | ast::ItemKind::Enum(..) | ast::ItemKind::Union(..)
-                    | ast::ItemKind::Union(..) => true,
+                ),
-                    _ => false,
-                },
                 _ => false,
             },
             Annotatable::Item(ref item) => match item.kind {

compiler/rustc_expand/src/expand.rs

@@ -1134,7 +1134,9 @@ impl<'a, 'b> MutVisitor for InvocationCollector<'a, 'b> {
             if let Some(attr) = self.take_first_attr_no_derive(&mut expr) {
                 // Collect the invoc regardless of whether or not attributes are permitted here
                 // expansion will eat the attribute so it won't error later.
-                attr.0.as_ref().map(|attr| self.cfg.maybe_emit_expr_attr_err(attr));
+                if let Some(attr) = attr.0.as_ref() {
+                    self.cfg.maybe_emit_expr_attr_err(attr)
+                }
 
                 // AstFragmentKind::Expr requires the macro to emit an expression.
                 return self
@@ -1231,7 +1233,9 @@ impl<'a, 'b> MutVisitor for InvocationCollector<'a, 'b> {
             self.cfg.configure_expr_kind(&mut expr.kind);
 
             if let Some(attr) = self.take_first_attr_no_derive(&mut expr) {
-                attr.0.as_ref().map(|attr| self.cfg.maybe_emit_expr_attr_err(attr));
+                if let Some(attr) = attr.0.as_ref() {
+                    self.cfg.maybe_emit_expr_attr_err(attr)
+                }
 
                 return self
                     .collect_attr(attr, Annotatable::Expr(P(expr)), AstFragmentKind::OptExpr)

compiler/rustc_hir/src/hir.rs

@@ -2401,7 +2401,7 @@ impl StructField<'_> {
     // Still necessary in couple of places
     pub fn is_positional(&self) -> bool {
         let first = self.ident.as_str().as_bytes()[0];
-        first >= b'0' && first <= b'9'
+        (b'0'..=b'9').contains(&first)
     }
 }
 

compiler/rustc_lexer/src/lib.rs

@@ -267,8 +267,8 @@ pub fn is_whitespace(c: char) -> bool {
 pub fn is_id_start(c: char) -> bool {
     // This is XID_Start OR '_' (which formally is not a XID_Start).
     // We also add fast-path for ascii idents
-    ('a' <= c && c <= 'z')
+    ('a'..='z').contains(&c)
-        || ('A' <= c && c <= 'Z')
+        || ('A'..='Z').contains(&c)
         || c == '_'
         || (c > '\x7f' && unicode_xid::UnicodeXID::is_xid_start(c))
 }
@@ -279,9 +279,9 @@ pub fn is_id_start(c: char) -> bool {
 pub fn is_id_continue(c: char) -> bool {
     // This is exactly XID_Continue.
     // We also add fast-path for ascii idents
-    ('a' <= c && c <= 'z')
+    ('a'..='z').contains(&c)
-        || ('A' <= c && c <= 'Z')
+        || ('A'..='Z').contains(&c)
-        || ('0' <= c && c <= '9')
+        || ('0'..='9').contains(&c)
         || c == '_'
         || (c > '\x7f' && unicode_xid::UnicodeXID::is_xid_continue(c))
 }

compiler/rustc_serialize/src/json.rs

@@ -1859,7 +1859,7 @@ impl<T: Iterator<Item = char>> Parser<T> {
                             }
 
                             let n2 = self.decode_hex_escape()?;
-                            if n2 < 0xDC00 || n2 > 0xDFFF {
+                            if !(0xDC00..=0xDFFF).contains(&n2) {
                                 return self.error(LoneLeadingSurrogateInHexEscape);
                             }
                             let c =

compiler/rustc_span/src/analyze_source_file.rs

@@ -97,7 +97,7 @@ cfg_if::cfg_if! {
                 let ptr = src_bytes.as_ptr() as *const __m128i;
                 // We don't know if the pointer is aligned to 16 bytes, so we
                 // use `loadu`, which supports unaligned loading.
-                let chunk = _mm_loadu_si128(ptr.offset(chunk_index as isize));
+                let chunk = _mm_loadu_si128(ptr.add(chunk_index));
 
                 // For character in the chunk, see if its byte value is < 0, which
                 // indicates that it's part of a UTF-8 char.
@@ -253,7 +253,7 @@ fn analyze_source_file_generic(
             let pos = BytePos::from_usize(i) + output_offset;
 
             if char_len > 1 {
-                assert!(char_len >= 2 && char_len <= 4);
+                assert!((2..=4).contains(&char_len));
                 let mbc = MultiByteChar { pos, bytes: char_len as u8 };
                 multi_byte_chars.push(mbc);
             }

compiler/rustc_span/src/lib.rs

@@ -1015,10 +1015,7 @@ pub enum ExternalSourceKind {
 
 impl ExternalSource {
     pub fn is_absent(&self) -> bool {
-        match self {
+        !matches!(self, ExternalSource::Foreign { kind: ExternalSourceKind::Present(_), .. })
-            ExternalSource::Foreign { kind: ExternalSourceKind::Present(_), .. } => false,
-            _ => true,
-        }
     }
 
     pub fn get_source(&self) -> Option<&Lrc<String>> {

compiler/rustc_span/src/source_map.rs

@@ -623,7 +623,7 @@ impl SourceMap {
         self.span_to_source(sp, |src, start_index, end_index| {
             src.get(start_index..end_index)
                 .map(|s| s.to_string())
-                .ok_or_else(|| SpanSnippetError::IllFormedSpan(sp))
+                .ok_or(SpanSnippetError::IllFormedSpan(sp))
         })
     }
 
@@ -640,9 +640,7 @@ impl SourceMap {
     /// Returns the source snippet as `String` before the given `Span`.
     pub fn span_to_prev_source(&self, sp: Span) -> Result<String, SpanSnippetError> {
         self.span_to_source(sp, |src, start_index, _| {
-            src.get(..start_index)
+            src.get(..start_index).map(|s| s.to_string()).ok_or(SpanSnippetError::IllFormedSpan(sp))
-                .map(|s| s.to_string())
-                .ok_or_else(|| SpanSnippetError::IllFormedSpan(sp))
         })
     }
 

compiler/rustc_span/src/symbol.rs

@@ -1362,15 +1362,13 @@ impl fmt::Display for IdentPrinter {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         if self.is_raw {
             f.write_str("r#")?;
-        } else {
+        } else if self.symbol == kw::DollarCrate {
-            if self.symbol == kw::DollarCrate {
+            if let Some(span) = self.convert_dollar_crate {
-                if let Some(span) = self.convert_dollar_crate {
+                let converted = span.ctxt().dollar_crate_name();
-                    let converted = span.ctxt().dollar_crate_name();
+                if !converted.is_path_segment_keyword() {
-                    if !converted.is_path_segment_keyword() {
+                    f.write_str("::")?;
-                        f.write_str("::")?;
-                    }
-                    return fmt::Display::fmt(&converted, f);
                 }
+                return fmt::Display::fmt(&converted, f);
             }
         }
         fmt::Display::fmt(&self.symbol, f)