Auto merge of #83596 - jyn514:session-dead-code, r=oli-obk

Remove dead or useless code from Session

This is a more principled follow-up to https://github.com/rust-lang/rust/pull/83185#discussion_r601753839.

- Rename `Parser::span_fatal_err` -> `Parser::span_err`
- Remove some unnecessary uses of `struct_span_fatal`
- Make `Diagnostic::span_fatal` unconditionally raise an error
- Add `impl Deref<Target = Handler>` for Session and remove all functions that are exactly the same as their Handler counterparts
- Note why `Handler::fatal` is different from `Sesssion::fatal`
- Remove unused `opt_span_warn` function

r? `@oli-obk` or `@estebank`

5 files changed, 29 insertions, 53 deletions

diff --git a/compiler/rustc_parse/src/lexer/mod.rs b/compiler/rustc_parse/src/lexer/mod.rs
index bd8dfd678a9..1c2f9a9645f 100644
--- a/compiler/rustc_parse/src/lexer/mod.rs
+++ b/compiler/rustc_parse/src/lexer/mod.rs
@@ -148,15 +148,11 @@ impl<'a> StringReader<'a> {
                         None => "unterminated block comment",
                     };
                     let last_bpos = self.pos;
-                    self.sess
-                        .span_diagnostic
-                        .struct_span_fatal_with_code(
-                            self.mk_sp(start, last_bpos),
-                            msg,
-                            error_code!(E0758),
-                        )
-                        .emit();
-                    FatalError.raise();
+                    self.sess.span_diagnostic.span_fatal_with_code(
+                        self.mk_sp(start, last_bpos),
+                        msg,
+                        error_code!(E0758),
+                    );
                 }
 
                 // Skip non-doc comments
@@ -315,57 +311,41 @@ impl<'a> StringReader<'a> {
         let (lit_kind, mode, prefix_len, postfix_len) = match kind {
             rustc_lexer::LiteralKind::Char { terminated } => {
                 if !terminated {
-                    self.sess
-                        .span_diagnostic
-                        .struct_span_fatal_with_code(
-                            self.mk_sp(start, suffix_start),
-                            "unterminated character literal",
-                            error_code!(E0762),
-                        )
-                        .emit();
-                    FatalError.raise();
+                    self.sess.span_diagnostic.span_fatal_with_code(
+                        self.mk_sp(start, suffix_start),
+                        "unterminated character literal",
+                        error_code!(E0762),
+                    )
                 }
                 (token::Char, Mode::Char, 1, 1) // ' '
             }
             rustc_lexer::LiteralKind::Byte { terminated } => {
                 if !terminated {
-                    self.sess
-                        .span_diagnostic
-                        .struct_span_fatal_with_code(
-                            self.mk_sp(start + BytePos(1), suffix_start),
-                            "unterminated byte constant",
-                            error_code!(E0763),
-                        )
-                        .emit();
-                    FatalError.raise();
+                    self.sess.span_diagnostic.span_fatal_with_code(
+                        self.mk_sp(start + BytePos(1), suffix_start),
+                        "unterminated byte constant",
+                        error_code!(E0763),
+                    )
                 }
                 (token::Byte, Mode::Byte, 2, 1) // b' '
             }
             rustc_lexer::LiteralKind::Str { terminated } => {
                 if !terminated {
-                    self.sess
-                        .span_diagnostic
-                        .struct_span_fatal_with_code(
-                            self.mk_sp(start, suffix_start),
-                            "unterminated double quote string",
-                            error_code!(E0765),
-                        )
-                        .emit();
-                    FatalError.raise();
+                    self.sess.span_diagnostic.span_fatal_with_code(
+                        self.mk_sp(start, suffix_start),
+                        "unterminated double quote string",
+                        error_code!(E0765),
+                    )
                 }
                 (token::Str, Mode::Str, 1, 1) // " "
             }
             rustc_lexer::LiteralKind::ByteStr { terminated } => {
                 if !terminated {
-                    self.sess
-                        .span_diagnostic
-                        .struct_span_fatal_with_code(
-                            self.mk_sp(start + BytePos(1), suffix_start),
-                            "unterminated double quote byte string",
-                            error_code!(E0766),
-                        )
-                        .emit();
-                    FatalError.raise();
+                    self.sess.span_diagnostic.span_fatal_with_code(
+                        self.mk_sp(start + BytePos(1), suffix_start),
+                        "unterminated double quote byte string",
+                        error_code!(E0766),
+                    )
                 }
                 (token::ByteStr, Mode::ByteStr, 2, 1) // b" "
             }
diff --git a/compiler/rustc_parse/src/parser/diagnostics.rs b/compiler/rustc_parse/src/parser/diagnostics.rs
index 70a5ac6f15e..72fdc78c30c 100644
--- a/compiler/rustc_parse/src/parser/diagnostics.rs
+++ b/compiler/rustc_parse/src/parser/diagnostics.rs
@@ -144,11 +144,7 @@ impl AttemptLocalParseRecovery {
 }
 
 impl<'a> Parser<'a> {
-    pub(super) fn span_fatal_err<S: Into<MultiSpan>>(
-        &self,
-        sp: S,
-        err: Error,
-    ) -> DiagnosticBuilder<'a> {
+    pub(super) fn span_err<S: Into<MultiSpan>>(&self, sp: S, err: Error) -> DiagnosticBuilder<'a> {
         err.span_err(sp, self.diagnostic())
     }
 
diff --git a/compiler/rustc_parse/src/parser/item.rs b/compiler/rustc_parse/src/parser/item.rs
index 20e8b0f6425..553ffda814f 100644
--- a/compiler/rustc_parse/src/parser/item.rs
+++ b/compiler/rustc_parse/src/parser/item.rs
@@ -1326,7 +1326,7 @@ impl<'a> Parser<'a> {
             token::CloseDelim(token::Brace) => {}
             token::DocComment(..) => {
                 let previous_span = self.prev_token.span;
-                let mut err = self.span_fatal_err(self.token.span, Error::UselessDocComment);
+                let mut err = self.span_err(self.token.span, Error::UselessDocComment);
                 self.bump(); // consume the doc comment
                 let comma_after_doc_seen = self.eat(&token::Comma);
                 // `seen_comma` is always false, because we are inside doc block
diff --git a/compiler/rustc_parse/src/parser/mod.rs b/compiler/rustc_parse/src/parser/mod.rs
index 74481e236f3..ec11f2d3add 100644
--- a/compiler/rustc_parse/src/parser/mod.rs
+++ b/compiler/rustc_parse/src/parser/mod.rs
@@ -525,7 +525,7 @@ impl<'a> Parser<'a> {
     fn ident_or_err(&mut self) -> PResult<'a, (Ident, /* is_raw */ bool)> {
         self.token.ident().ok_or_else(|| match self.prev_token.kind {
             TokenKind::DocComment(..) => {
-                self.span_fatal_err(self.prev_token.span, Error::UselessDocComment)
+                self.span_err(self.prev_token.span, Error::UselessDocComment)
             }
             _ => self.expected_ident_found(),
         })
diff --git a/compiler/rustc_parse/src/parser/stmt.rs b/compiler/rustc_parse/src/parser/stmt.rs
index 592f64f4a39..b40eed8c5d1 100644
--- a/compiler/rustc_parse/src/parser/stmt.rs
+++ b/compiler/rustc_parse/src/parser/stmt.rs
@@ -168,7 +168,7 @@ impl<'a> Parser<'a> {
     fn error_outer_attrs(&self, attrs: &[Attribute]) {
         if let [.., last] = attrs {
             if last.is_doc_comment() {
-                self.span_fatal_err(last.span, Error::UselessDocComment).emit();
+                self.span_err(last.span, Error::UselessDocComment).emit();
             } else if attrs.iter().any(|a| a.style == AttrStyle::Outer) {
                 self.struct_span_err(last.span, "expected statement after outer attribute").emit();
             }