Remove MacCall special cases from Parser::parse_full_stmt

It is impossible for expr here to be a braced macro call. Expr comes
from `parse_stmt_without_recovery`, in which macro calls are parsed by
`parse_stmt_mac`. See this part:

    let kind = if (style == MacStmtStyle::Braces
        && self.token != token::Dot
        && self.token != token::Question)
        || self.token == token::Semi
        || self.token == token::Eof
    {
        StmtKind::MacCall(P(MacCallStmt { mac, style, attrs, tokens: None }))
    } else {
        // Since none of the above applied, this is an expression statement macro.
        let e = self.mk_expr(lo.to(hi), ExprKind::MacCall(mac));
        let e = self.maybe_recover_from_bad_qpath(e)?;
        let e = self.parse_expr_dot_or_call_with(e, lo, attrs)?;
        let e = self.parse_expr_assoc_with(
            0,
            LhsExpr::AlreadyParsed { expr: e, starts_statement: false },
        )?;
        StmtKind::Expr(e)
    };

A braced macro call at the head of a statement is always either extended
into ExprKind::Field / MethodCall / Await / Try / Binary, or else
returned as StmtKind::MacCall. We can never get a StmtKind::Expr
containing ExprKind::MacCall containing brace delimiter.

compiler/rustc_parse/src/parser/stmt.rs

@@ -637,10 +637,8 @@ impl<'a> Parser<'a> {
         match &mut stmt.kind {
             // Expression without semicolon.
             StmtKind::Expr(expr)
-                if match expr.kind {
-                    ExprKind::MacCall(_) => true,
-                    _ => classify::expr_requires_semi_to_be_stmt(expr),
-                } && !expr.attrs.is_empty()
+                if classify::expr_requires_semi_to_be_stmt(expr)
+                    && !expr.attrs.is_empty()
                     && ![token::Eof, token::Semi, token::CloseDelim(Delimiter::Brace)]
                         .contains(&self.token.kind) =>
             {
@@ -653,11 +651,7 @@ impl<'a> Parser<'a> {
 
             // Expression without semicolon.
             StmtKind::Expr(expr)
-                if self.token != token::Eof
-                    && match expr.kind {
-                        ExprKind::MacCall(_) => true,
-                        _ => classify::expr_requires_semi_to_be_stmt(expr),
-                    } =>
+                if self.token != token::Eof && classify::expr_requires_semi_to_be_stmt(expr) =>
             {
                 // Just check for errors and recover; do not eat semicolon yet.
                 // `expect_one_of` returns PResult<'a, bool /* recovered */>