Avoid some unwraps.

By using `@` patterns more.

Also, use `Symbol` more in a couple of errors to avoid some unnecessary
conversions to strings. This even removes a lifetime.

Author: nnethercote

compiler/rustc_attr_parsing/src/attributes/repr.rs

@@ -96,9 +96,12 @@ fn parse_repr(cx: &AcceptContext<'_>, param: &MetaItemParser<'_>) -> Option<Repr
 
     // FIXME(jdonszelmann): invert the parsing here to match on the word first and then the
     // structure.
-    let ident = param.path_without_args().word();
-    let ident_span = ident.map_or(rustc_span::DUMMY_SP, |ident| ident.span);
-    let name = ident.map(|ident| ident.name);
+    let (name, ident_span) = if let Some(ident) = param.path_without_args().word() {
+        (Some(ident.name), ident.span)
+    } else {
+        (None, rustc_span::DUMMY_SP)
+    };
+
     let args = param.args();
 
     match (name, args) {
@@ -115,15 +118,15 @@ fn parse_repr(cx: &AcceptContext<'_>, param: &MetaItemParser<'_>) -> Option<Repr
             parse_repr_align(cx, l, param.span(), AlignKind::Packed)
         }
 
-        (Some(sym::align | sym::packed), ArgParser::NameValue(l)) => {
+        (Some(name @ sym::align | name @ sym::packed), ArgParser::NameValue(l)) => {
             cx.emit_err(session_diagnostics::IncorrectReprFormatGeneric {
                 span: param.span(),
                 // FIXME(jdonszelmann) can just be a string in the diag type
-                repr_arg: &ident.unwrap().to_string(),
+                repr_arg: name,
                 cause: IncorrectReprFormatGenericCause::from_lit_kind(
                     param.span(),
                     &l.value_as_lit().kind,
-                    ident.unwrap().as_str(),
+                    name,
                 ),
             });
             None
@@ -133,29 +136,35 @@ fn parse_repr(cx: &AcceptContext<'_>, param: &MetaItemParser<'_>) -> Option<Repr
         (Some(sym::C), ArgParser::NoArgs) => Some(ReprC),
         (Some(sym::simd), ArgParser::NoArgs) => Some(ReprSimd),
         (Some(sym::transparent), ArgParser::NoArgs) => Some(ReprTransparent),
-        (Some(i @ int_pat!()), ArgParser::NoArgs) => {
+        (Some(name @ int_pat!()), ArgParser::NoArgs) => {
             // int_pat!() should make sure it always parses
-            Some(ReprInt(int_type_of_word(i).unwrap()))
+            Some(ReprInt(int_type_of_word(name).unwrap()))
         }
 
         (
-            Some(sym::Rust | sym::C | sym::simd | sym::transparent | int_pat!()),
+            Some(
+                name @ sym::Rust
+                | name @ sym::C
+                | name @ sym::simd
+                | name @ sym::transparent
+                | name @ int_pat!(),
+            ),
             ArgParser::NameValue(_),
         ) => {
-            cx.emit_err(session_diagnostics::InvalidReprHintNoValue {
-                span: param.span(),
-                name: ident.unwrap().to_string(),
-            });
+            cx.emit_err(session_diagnostics::InvalidReprHintNoValue { span: param.span(), name });
             None
         }
         (
-            Some(sym::Rust | sym::C | sym::simd | sym::transparent | int_pat!()),
+            Some(
+                name @ sym::Rust
+                | name @ sym::C
+                | name @ sym::simd
+                | name @ sym::transparent
+                | name @ int_pat!(),
+            ),
             ArgParser::List(_),
         ) => {
-            cx.emit_err(session_diagnostics::InvalidReprHintNoParen {
-                span: param.span(),
-                name: ident.unwrap().to_string(),
-            });
+            cx.emit_err(session_diagnostics::InvalidReprHintNoParen { span: param.span(), name });
             None
         }
 

compiler/rustc_attr_parsing/src/session_diagnostics.rs

@@ -204,7 +204,7 @@ pub(crate) struct InvalidReprHintNoParen {
     #[primary_span]
     pub span: Span,
 
-    pub name: String,
+    pub name: Symbol,
 }
 
 #[derive(Diagnostic)]
@@ -213,7 +213,7 @@ pub(crate) struct InvalidReprHintNoValue {
     #[primary_span]
     pub span: Span,
 
-    pub name: String,
+    pub name: Symbol,
 }
 
 /// Error code: E0565
@@ -295,58 +295,58 @@ pub(crate) struct IncorrectReprFormatExpectInteger {
 
 #[derive(Diagnostic)]
 #[diag(attr_parsing_incorrect_repr_format_generic, code = E0693)]
-pub(crate) struct IncorrectReprFormatGeneric<'a> {
+pub(crate) struct IncorrectReprFormatGeneric {
     #[primary_span]
     pub span: Span,
 
-    pub repr_arg: &'a str,
+    pub repr_arg: Symbol,
 
     #[subdiagnostic]
-    pub cause: Option<IncorrectReprFormatGenericCause<'a>>,
+    pub cause: Option<IncorrectReprFormatGenericCause>,
 }
 
 #[derive(Subdiagnostic)]
-pub(crate) enum IncorrectReprFormatGenericCause<'a> {
+pub(crate) enum IncorrectReprFormatGenericCause {
     #[suggestion(
         attr_parsing_suggestion,
-        code = "{name}({int})",
+        code = "{name}({value})",
         applicability = "machine-applicable"
     )]
     Int {
         #[primary_span]
         span: Span,
 
         #[skip_arg]
-        name: &'a str,
+        name: Symbol,
 
         #[skip_arg]
-        int: u128,
+        value: u128,
     },
 
     #[suggestion(
         attr_parsing_suggestion,
-        code = "{name}({symbol})",
+        code = "{name}({value})",
         applicability = "machine-applicable"
     )]
     Symbol {
         #[primary_span]
         span: Span,
 
         #[skip_arg]
-        name: &'a str,
+        name: Symbol,
 
         #[skip_arg]
-        symbol: Symbol,
+        value: Symbol,
     },
 }
 
-impl<'a> IncorrectReprFormatGenericCause<'a> {
-    pub(crate) fn from_lit_kind(span: Span, kind: &ast::LitKind, name: &'a str) -> Option<Self> {
-        match kind {
-            ast::LitKind::Int(int, ast::LitIntType::Unsuffixed) => {
-                Some(Self::Int { span, name, int: int.get() })
+impl IncorrectReprFormatGenericCause {
+    pub(crate) fn from_lit_kind(span: Span, kind: &ast::LitKind, name: Symbol) -> Option<Self> {
+        match *kind {
+            ast::LitKind::Int(value, ast::LitIntType::Unsuffixed) => {
+                Some(Self::Int { span, name, value: value.get() })
             }
-            ast::LitKind::Str(symbol, _) => Some(Self::Symbol { span, name, symbol: *symbol }),
+            ast::LitKind::Str(value, _) => Some(Self::Symbol { span, name, value }),
             _ => None,
         }
     }