From: bjorn3 <bjorn3@users.noreply.github.com>
Date: Fri, 29 Apr 2022 16:48:58 +0000 (+0200)
Subject: Make rustc_parse_format compile on stable
X-Git-Url: https://git.lizzy.rs/?a=commitdiff_plain;h=d33140d2dc95c33bc8281b476048c923476c8b73;p=rust.git

Make rustc_parse_format compile on stable

This allows it to be used by lightweight formatting systems and may
allow it to be used by rust-analyzer.
---

diff --git a/Cargo.lock b/Cargo.lock
index ef4800a2261..94832a24409 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -4171,7 +4171,6 @@ name = "rustc_parse_format"
 version = "0.0.0"
 dependencies = [
  "rustc_lexer",
- "rustc_span",
 ]
 
 [[package]]
diff --git a/compiler/rustc_builtin_macros/src/asm.rs b/compiler/rustc_builtin_macros/src/asm.rs
index e9e3307ca95..c95d7147176 100644
--- a/compiler/rustc_builtin_macros/src/asm.rs
+++ b/compiler/rustc_builtin_macros/src/asm.rs
@@ -626,7 +626,7 @@ fn expand_preparsed_asm(ecx: &mut ExtCtxt<'_>, args: AsmArgs) -> Option<ast::Inl
 
         if !parser.errors.is_empty() {
             let err = parser.errors.remove(0);
-            let err_sp = template_span.from_inner(err.span);
+            let err_sp = template_span.from_inner(InnerSpan::new(err.span.start, err.span.end));
             let msg = &format!("invalid asm template string: {}", err.description);
             let mut e = ecx.struct_span_err(err_sp, msg);
             e.span_label(err_sp, err.label + " in asm template string");
@@ -634,7 +634,7 @@ fn expand_preparsed_asm(ecx: &mut ExtCtxt<'_>, args: AsmArgs) -> Option<ast::Inl
                 e.note(&note);
             }
             if let Some((label, span)) = err.secondary_label {
-                let err_sp = template_span.from_inner(span);
+                let err_sp = template_span.from_inner(InnerSpan::new(span.start, span.end));
                 e.span_label(err_sp, label);
             }
             e.emit();
@@ -643,7 +643,10 @@ fn expand_preparsed_asm(ecx: &mut ExtCtxt<'_>, args: AsmArgs) -> Option<ast::Inl
 
         curarg = parser.curarg;
 
-        let mut arg_spans = parser.arg_places.iter().map(|span| template_span.from_inner(*span));
+        let mut arg_spans = parser
+            .arg_places
+            .iter()
+            .map(|span| template_span.from_inner(InnerSpan::new(span.start, span.end)));
         for piece in unverified_pieces {
             match piece {
                 parse::Piece::String(s) => {
@@ -699,14 +702,21 @@ fn expand_preparsed_asm(ecx: &mut ExtCtxt<'_>, args: AsmArgs) -> Option<ast::Inl
                                 Some(idx)
                             }
                         }
-                        parse::ArgumentNamed(name, span) => match args.named_args.get(&name) {
-                            Some(&idx) => Some(idx),
-                            None => {
-                                let msg = format!("there is no argument named `{}`", name);
-                                ecx.struct_span_err(template_span.from_inner(span), &msg).emit();
-                                None
+                        parse::ArgumentNamed(name, span) => {
+                            match args.named_args.get(&Symbol::intern(name)) {
+                                Some(&idx) => Some(idx),
+                                None => {
+                                    let msg = format!("there is no argument named `{}`", name);
+                                    ecx.struct_span_err(
+                                        template_span
+                                            .from_inner(InnerSpan::new(span.start, span.end)),
+                                        &msg,
+                                    )
+                                    .emit();
+                                    None
+                                }
                             }
-                        },
+                        }
                     };
 
                     let mut chars = arg.format.ty.chars();
@@ -715,7 +725,7 @@ fn expand_preparsed_asm(ecx: &mut ExtCtxt<'_>, args: AsmArgs) -> Option<ast::Inl
                         let span = arg
                             .format
                             .ty_span
-                            .map(|sp| template_sp.from_inner(sp))
+                            .map(|sp| template_sp.from_inner(InnerSpan::new(sp.start, sp.end)))
                             .unwrap_or(template_sp);
                         ecx.struct_span_err(
                             span,
@@ -741,7 +751,12 @@ fn expand_preparsed_asm(ecx: &mut ExtCtxt<'_>, args: AsmArgs) -> Option<ast::Inl
             let template_num_lines = 1 + template_str.matches('\n').count();
             line_spans.extend(std::iter::repeat(template_sp).take(template_num_lines));
         } else {
-            line_spans.extend(parser.line_spans.iter().map(|span| template_span.from_inner(*span)));
+            line_spans.extend(
+                parser
+                    .line_spans
+                    .iter()
+                    .map(|span| template_span.from_inner(InnerSpan::new(span.start, span.end))),
+            );
         };
     }
 
diff --git a/compiler/rustc_builtin_macros/src/format.rs b/compiler/rustc_builtin_macros/src/format.rs
index 138e1fa0176..60b96399b5e 100644
--- a/compiler/rustc_builtin_macros/src/format.rs
+++ b/compiler/rustc_builtin_macros/src/format.rs
@@ -242,7 +242,7 @@ fn num_args(&self) -> usize {
     fn resolve_name_inplace(&self, p: &mut parse::Piece<'_>) {
         // NOTE: the `unwrap_or` branch is needed in case of invalid format
         // arguments, e.g., `format_args!("{foo}")`.
-        let lookup = |s: Symbol| *self.names.get(&s).unwrap_or(&0);
+        let lookup = |s: &str| *self.names.get(&Symbol::intern(s)).unwrap_or(&0);
 
         match *p {
             parse::String(_) => {}
@@ -276,7 +276,9 @@ fn verify_piece(&mut self, p: &parse::Piece<'_>) {
                 // it's written second, so it should come after width/precision.
                 let pos = match arg.position {
                     parse::ArgumentIs(i) | parse::ArgumentImplicitlyIs(i) => Exact(i),
-                    parse::ArgumentNamed(s, span) => Named(s, span),
+                    parse::ArgumentNamed(s, span) => {
+                        Named(Symbol::intern(s), InnerSpan::new(span.start, span.end))
+                    }
                 };
 
                 let ty = Placeholder(match arg.format.ty {
@@ -291,7 +293,10 @@ fn verify_piece(&mut self, p: &parse::Piece<'_>) {
                     "X" => "UpperHex",
                     _ => {
                         let fmtsp = self.fmtsp;
-                        let sp = arg.format.ty_span.map(|sp| fmtsp.from_inner(sp));
+                        let sp = arg
+                            .format
+                            .ty_span
+                            .map(|sp| fmtsp.from_inner(InnerSpan::new(sp.start, sp.end)));
                         let mut err = self.ecx.struct_span_err(
                             sp.unwrap_or(fmtsp),
                             &format!("unknown format trait `{}`", arg.format.ty),
@@ -340,14 +345,17 @@ fn verify_piece(&mut self, p: &parse::Piece<'_>) {
         }
     }
 
-    fn verify_count(&mut self, c: parse::Count) {
+    fn verify_count(&mut self, c: parse::Count<'_>) {
         match c {
             parse::CountImplied | parse::CountIs(..) => {}
             parse::CountIsParam(i) => {
                 self.verify_arg_type(Exact(i), Count);
             }
             parse::CountIsName(s, span) => {
-                self.verify_arg_type(Named(s, span), Count);
+                self.verify_arg_type(
+                    Named(Symbol::intern(s), InnerSpan::new(span.start, span.end)),
+                    Count,
+                );
             }
         }
     }
@@ -425,7 +433,7 @@ fn report_invalid_references(&self, numbered_position_args: bool) {
 
         for fmt in &self.arg_with_formatting {
             if let Some(span) = fmt.precision_span {
-                let span = self.fmtsp.from_inner(span);
+                let span = self.fmtsp.from_inner(InnerSpan::new(span.start, span.end));
                 match fmt.precision {
                     parse::CountIsParam(pos) if pos > self.num_args() => {
                         e.span_label(
@@ -471,7 +479,7 @@ fn report_invalid_references(&self, numbered_position_args: bool) {
                 }
             }
             if let Some(span) = fmt.width_span {
-                let span = self.fmtsp.from_inner(span);
+                let span = self.fmtsp.from_inner(InnerSpan::new(span.start, span.end));
                 match fmt.width {
                     parse::CountIsParam(pos) if pos > self.num_args() => {
                         e.span_label(
@@ -610,7 +618,7 @@ fn rtpath(ecx: &ExtCtxt<'_>, s: Symbol) -> Vec<Ident> {
         ecx.std_path(&[sym::fmt, sym::rt, sym::v1, s])
     }
 
-    fn build_count(&self, c: parse::Count) -> P<ast::Expr> {
+    fn build_count(&self, c: parse::Count<'_>) -> P<ast::Expr> {
         let sp = self.macsp;
         let count = |c, arg| {
             let mut path = Context::rtpath(self.ecx, sym::Count);
@@ -1033,7 +1041,7 @@ pub fn expand_preparsed_format_args(
     if !parser.errors.is_empty() {
         let err = parser.errors.remove(0);
         let sp = if efmt_kind_is_lit {
-            fmt_span.from_inner(err.span)
+            fmt_span.from_inner(InnerSpan::new(err.span.start, err.span.end))
         } else {
             // The format string could be another macro invocation, e.g.:
             //     format!(concat!("abc", "{}"), 4);
@@ -1052,14 +1060,18 @@ pub fn expand_preparsed_format_args(
         }
         if let Some((label, span)) = err.secondary_label {
             if efmt_kind_is_lit {
-                e.span_label(fmt_span.from_inner(span), label);
+                e.span_label(fmt_span.from_inner(InnerSpan::new(span.start, span.end)), label);
             }
         }
         e.emit();
         return DummyResult::raw_expr(sp, true);
     }
 
-    let arg_spans = parser.arg_places.iter().map(|span| fmt_span.from_inner(*span)).collect();
+    let arg_spans = parser
+        .arg_places
+        .iter()
+        .map(|span| fmt_span.from_inner(InnerSpan::new(span.start, span.end)))
+        .collect();
 
     let named_pos: FxHashSet<usize> = names.values().cloned().collect();
 
diff --git a/compiler/rustc_lint/src/non_fmt_panic.rs b/compiler/rustc_lint/src/non_fmt_panic.rs
index 71769fceec1..4e7aeca9ce1 100644
--- a/compiler/rustc_lint/src/non_fmt_panic.rs
+++ b/compiler/rustc_lint/src/non_fmt_panic.rs
@@ -254,7 +254,10 @@ fn check_panic_str<'tcx>(
     if n_arguments > 0 && fmt_parser.errors.is_empty() {
         let arg_spans: Vec<_> = match &fmt_parser.arg_places[..] {
             [] => vec![fmt_span],
-            v => v.iter().map(|span| fmt_span.from_inner(*span)).collect(),
+            v => v
+                .iter()
+                .map(|span| fmt_span.from_inner(InnerSpan::new(span.start, span.end)))
+                .collect(),
         };
         cx.struct_span_lint(NON_FMT_PANICS, arg_spans, |lint| {
             let mut l = lint.build(match n_arguments {
diff --git a/compiler/rustc_parse_format/Cargo.toml b/compiler/rustc_parse_format/Cargo.toml
index aa1714e820f..fcc68b3a219 100644
--- a/compiler/rustc_parse_format/Cargo.toml
+++ b/compiler/rustc_parse_format/Cargo.toml
@@ -4,5 +4,4 @@ version = "0.0.0"
 edition = "2021"
 
 [dependencies]
-rustc_span = { path = "../rustc_span" }
 rustc_lexer = { path = "../rustc_lexer" }
diff --git a/compiler/rustc_parse_format/src/lib.rs b/compiler/rustc_parse_format/src/lib.rs
index 00bac26a16a..f6fa19030ac 100644
--- a/compiler/rustc_parse_format/src/lib.rs
+++ b/compiler/rustc_parse_format/src/lib.rs
@@ -9,8 +9,8 @@
     html_playground_url = "https://play.rust-lang.org/",
     test(attr(deny(warnings)))
 )]
-#![feature(nll)]
-#![feature(bool_to_option)]
+// We want to be able to build this crate with a stable compiler, so no
+// `#![feature]` attributes should be added.
 
 pub use Alignment::*;
 pub use Count::*;
@@ -22,7 +22,19 @@
 use std::str;
 use std::string;
 
-use rustc_span::{InnerSpan, Symbol};
+// Note: copied from rustc_span
+/// Range inside of a `Span` used for diagnostics when we only have access to relative positions.
+#[derive(Copy, Clone, PartialEq, Eq, Debug)]
+pub struct InnerSpan {
+    pub start: usize,
+    pub end: usize,
+}
+
+impl InnerSpan {
+    pub fn new(start: usize, end: usize) -> InnerSpan {
+        InnerSpan { start, end }
+    }
+}
 
 /// The type of format string that we are parsing.
 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
@@ -57,7 +69,7 @@ pub enum Piece<'a> {
 #[derive(Copy, Clone, Debug, PartialEq)]
 pub struct Argument<'a> {
     /// Where to find this argument
-    pub position: Position,
+    pub position: Position<'a>,
     /// How to format the argument
     pub format: FormatSpec<'a>,
 }
@@ -72,11 +84,11 @@ pub struct FormatSpec<'a> {
     /// Packed version of various flags provided.
     pub flags: u32,
     /// The integer precision to use.
-    pub precision: Count,
+    pub precision: Count<'a>,
     /// The span of the precision formatting flag (for diagnostics).
     pub precision_span: Option<InnerSpan>,
     /// The string width requested for the resulting format.
-    pub width: Count,
+    pub width: Count<'a>,
     /// The span of the width formatting flag (for diagnostics).
     pub width_span: Option<InnerSpan>,
     /// The descriptor string representing the name of the format desired for
@@ -89,16 +101,16 @@ pub struct FormatSpec<'a> {
 
 /// Enum describing where an argument for a format can be located.
 #[derive(Copy, Clone, Debug, PartialEq)]
-pub enum Position {
+pub enum Position<'a> {
     /// The argument is implied to be located at an index
     ArgumentImplicitlyIs(usize),
     /// The argument is located at a specific index given in the format
     ArgumentIs(usize),
     /// The argument has a name.
-    ArgumentNamed(Symbol, InnerSpan),
+    ArgumentNamed(&'a str, InnerSpan),
 }
 
-impl Position {
+impl Position<'_> {
     pub fn index(&self) -> Option<usize> {
         match self {
             ArgumentIs(i) | ArgumentImplicitlyIs(i) => Some(*i),
@@ -143,11 +155,11 @@ pub enum Flag {
 /// A count is used for the precision and width parameters of an integer, and
 /// can reference either an argument or a literal integer.
 #[derive(Copy, Clone, Debug, PartialEq)]
-pub enum Count {
+pub enum Count<'a> {
     /// The count is specified explicitly.
     CountIs(usize),
     /// The count is specified by the argument with the given name.
-    CountIsName(Symbol, InnerSpan),
+    CountIsName(&'a str, InnerSpan),
     /// The count is specified by the argument at the given index.
     CountIsParam(usize),
     /// The count is implied and cannot be explicitly specified.
@@ -489,7 +501,7 @@ fn argument(&mut self) -> Argument<'a> {
     /// integer index of an argument, a named argument, or a blank string.
     /// Returns `Some(parsed_position)` if the position is not implicitly
     /// consuming a macro argument, `None` if it's the case.
-    fn position(&mut self) -> Option<Position> {
+    fn position(&mut self) -> Option<Position<'a>> {
         if let Some(i) = self.integer() {
             Some(ArgumentIs(i))
         } else {
@@ -498,7 +510,7 @@ fn position(&mut self) -> Option<Position> {
                     let word = self.word();
                     let end = start + word.len();
                     let span = self.to_span_index(start).to(self.to_span_index(end));
-                    Some(ArgumentNamed(Symbol::intern(word), span))
+                    Some(ArgumentNamed(word, span))
                 }
 
                 // This is an `ArgumentNext`.
@@ -651,7 +663,7 @@ fn inline_asm(&mut self) -> FormatSpec<'a> {
     /// Parses a `Count` parameter at the current position. This does not check
     /// for 'CountIsNextParam' because that is only used in precision, not
     /// width.
-    fn count(&mut self, start: usize) -> (Count, Option<InnerSpan>) {
+    fn count(&mut self, start: usize) -> (Count<'a>, Option<InnerSpan>) {
         if let Some(i) = self.integer() {
             if let Some(end) = self.consume_pos('$') {
                 let span = self.to_span_index(start).to(self.to_span_index(end + 1));
@@ -667,7 +679,7 @@ fn count(&mut self, start: usize) -> (Count, Option<InnerSpan>) {
                 (CountImplied, None)
             } else if let Some(end) = self.consume_pos('$') {
                 let span = self.to_span_index(start + 1).to(self.to_span_index(end));
-                (CountIsName(Symbol::intern(word), span), None)
+                (CountIsName(word, span), None)
             } else {
                 self.cur = tmp;
                 (CountImplied, None)
@@ -723,7 +735,7 @@ fn integer(&mut self) -> Option<usize> {
                 break;
             }
         }
-        found.then_some(cur)
+        if found { Some(cur) } else { None }
     }
 }
 
diff --git a/compiler/rustc_parse_format/src/tests.rs b/compiler/rustc_parse_format/src/tests.rs
index 6c960fdc72b..c9667922ee7 100644
--- a/compiler/rustc_parse_format/src/tests.rs
+++ b/compiler/rustc_parse_format/src/tests.rs
@@ -144,93 +144,91 @@ fn format_align_fill() {
 }
 #[test]
 fn format_counts() {
-    rustc_span::create_default_session_globals_then(|| {
-        same(
-            "{:10x}",
-            &[NextArgument(Argument {
-                position: ArgumentImplicitlyIs(0),
-                format: FormatSpec {
-                    fill: None,
-                    align: AlignUnknown,
-                    flags: 0,
-                    precision: CountImplied,
-                    width: CountIs(10),
-                    precision_span: None,
-                    width_span: None,
-                    ty: "x",
-                    ty_span: None,
-                },
-            })],
-        );
-        same(
-            "{:10$.10x}",
-            &[NextArgument(Argument {
-                position: ArgumentImplicitlyIs(0),
-                format: FormatSpec {
-                    fill: None,
-                    align: AlignUnknown,
-                    flags: 0,
-                    precision: CountIs(10),
-                    width: CountIsParam(10),
-                    precision_span: None,
-                    width_span: Some(InnerSpan::new(3, 6)),
-                    ty: "x",
-                    ty_span: None,
-                },
-            })],
-        );
-        same(
-            "{:.*x}",
-            &[NextArgument(Argument {
-                position: ArgumentImplicitlyIs(1),
-                format: FormatSpec {
-                    fill: None,
-                    align: AlignUnknown,
-                    flags: 0,
-                    precision: CountIsParam(0),
-                    width: CountImplied,
-                    precision_span: Some(InnerSpan::new(3, 5)),
-                    width_span: None,
-                    ty: "x",
-                    ty_span: None,
-                },
-            })],
-        );
-        same(
-            "{:.10$x}",
-            &[NextArgument(Argument {
-                position: ArgumentImplicitlyIs(0),
-                format: FormatSpec {
-                    fill: None,
-                    align: AlignUnknown,
-                    flags: 0,
-                    precision: CountIsParam(10),
-                    width: CountImplied,
-                    precision_span: Some(InnerSpan::new(3, 7)),
-                    width_span: None,
-                    ty: "x",
-                    ty_span: None,
-                },
-            })],
-        );
-        same(
-            "{:a$.b$?}",
-            &[NextArgument(Argument {
-                position: ArgumentImplicitlyIs(0),
-                format: FormatSpec {
-                    fill: None,
-                    align: AlignUnknown,
-                    flags: 0,
-                    precision: CountIsName(Symbol::intern("b"), InnerSpan::new(6, 7)),
-                    width: CountIsName(Symbol::intern("a"), InnerSpan::new(4, 4)),
-                    precision_span: None,
-                    width_span: None,
-                    ty: "?",
-                    ty_span: None,
-                },
-            })],
-        );
-    });
+    same(
+        "{:10x}",
+        &[NextArgument(Argument {
+            position: ArgumentImplicitlyIs(0),
+            format: FormatSpec {
+                fill: None,
+                align: AlignUnknown,
+                flags: 0,
+                precision: CountImplied,
+                width: CountIs(10),
+                precision_span: None,
+                width_span: None,
+                ty: "x",
+                ty_span: None,
+            },
+        })],
+    );
+    same(
+        "{:10$.10x}",
+        &[NextArgument(Argument {
+            position: ArgumentImplicitlyIs(0),
+            format: FormatSpec {
+                fill: None,
+                align: AlignUnknown,
+                flags: 0,
+                precision: CountIs(10),
+                width: CountIsParam(10),
+                precision_span: None,
+                width_span: Some(InnerSpan::new(3, 6)),
+                ty: "x",
+                ty_span: None,
+            },
+        })],
+    );
+    same(
+        "{:.*x}",
+        &[NextArgument(Argument {
+            position: ArgumentImplicitlyIs(1),
+            format: FormatSpec {
+                fill: None,
+                align: AlignUnknown,
+                flags: 0,
+                precision: CountIsParam(0),
+                width: CountImplied,
+                precision_span: Some(InnerSpan::new(3, 5)),
+                width_span: None,
+                ty: "x",
+                ty_span: None,
+            },
+        })],
+    );
+    same(
+        "{:.10$x}",
+        &[NextArgument(Argument {
+            position: ArgumentImplicitlyIs(0),
+            format: FormatSpec {
+                fill: None,
+                align: AlignUnknown,
+                flags: 0,
+                precision: CountIsParam(10),
+                width: CountImplied,
+                precision_span: Some(InnerSpan::new(3, 7)),
+                width_span: None,
+                ty: "x",
+                ty_span: None,
+            },
+        })],
+    );
+    same(
+        "{:a$.b$?}",
+        &[NextArgument(Argument {
+            position: ArgumentImplicitlyIs(0),
+            format: FormatSpec {
+                fill: None,
+                align: AlignUnknown,
+                flags: 0,
+                precision: CountIsName("b", InnerSpan::new(6, 7)),
+                width: CountIsName("a", InnerSpan::new(4, 4)),
+                precision_span: None,
+                width_span: None,
+                ty: "?",
+                ty_span: None,
+            },
+        })],
+    );
 }
 #[test]
 fn format_flags() {
diff --git a/compiler/rustc_trait_selection/src/traits/on_unimplemented.rs b/compiler/rustc_trait_selection/src/traits/on_unimplemented.rs
index ce0e0a21ff5..c266eec25aa 100644
--- a/compiler/rustc_trait_selection/src/traits/on_unimplemented.rs
+++ b/compiler/rustc_trait_selection/src/traits/on_unimplemented.rs
@@ -304,42 +304,40 @@ fn verify(
             match token {
                 Piece::String(_) => (), // Normal string, no need to check it
                 Piece::NextArgument(a) => match a.position {
-                    // `{Self}` is allowed
-                    Position::ArgumentNamed(s, _) if s == kw::SelfUpper => (),
-                    // `{ThisTraitsName}` is allowed
-                    Position::ArgumentNamed(s, _) if s == trait_name => (),
-                    // `{from_method}` is allowed
-                    Position::ArgumentNamed(s, _) if s == sym::from_method => (),
-                    // `{from_desugaring}` is allowed
-                    Position::ArgumentNamed(s, _) if s == sym::from_desugaring => (),
-                    // `{ItemContext}` is allowed
-                    Position::ArgumentNamed(s, _) if s == sym::ItemContext => (),
-                    // `{integral}` and `{integer}` and `{float}` are allowed
-                    Position::ArgumentNamed(s, _)
-                        if s == sym::integral || s == sym::integer_ || s == sym::float =>
-                    {
-                        ()
-                    }
-                    // So is `{A}` if A is a type parameter
                     Position::ArgumentNamed(s, _) => {
-                        match generics.params.iter().find(|param| param.name == s) {
-                            Some(_) => (),
-                            None => {
-                                let reported = struct_span_err!(
-                                    tcx.sess,
-                                    span,
-                                    E0230,
-                                    "there is no parameter `{}` on {}",
-                                    s,
-                                    if trait_def_id == item_def_id {
-                                        format!("trait `{}`", trait_name)
-                                    } else {
-                                        "impl".to_string()
-                                    }
-                                )
-                                .emit();
-                                result = Err(reported);
-                            }
+                        match Symbol::intern(s) {
+                            // `{Self}` is allowed
+                            kw::SelfUpper => (),
+                            // `{ThisTraitsName}` is allowed
+                            s if s == trait_name => (),
+                            // `{from_method}` is allowed
+                            sym::from_method => (),
+                            // `{from_desugaring}` is allowed
+                            sym::from_desugaring => (),
+                            // `{ItemContext}` is allowed
+                            sym::ItemContext => (),
+                            // `{integral}` and `{integer}` and `{float}` are allowed
+                            sym::integral | sym::integer_ | sym::float => (),
+                            // So is `{A}` if A is a type parameter
+                            s => match generics.params.iter().find(|param| param.name == s) {
+                                Some(_) => (),
+                                None => {
+                                    let reported = struct_span_err!(
+                                        tcx.sess,
+                                        span,
+                                        E0230,
+                                        "there is no parameter `{}` on {}",
+                                        s,
+                                        if trait_def_id == item_def_id {
+                                            format!("trait `{}`", trait_name)
+                                        } else {
+                                            "impl".to_string()
+                                        }
+                                    )
+                                    .emit();
+                                    result = Err(reported);
+                                }
+                            },
                         }
                     }
                     // `{:1}` and `{}` are not to be used
@@ -392,34 +390,37 @@ pub fn format(
             .map(|p| match p {
                 Piece::String(s) => s,
                 Piece::NextArgument(a) => match a.position {
-                    Position::ArgumentNamed(s, _) => match generic_map.get(&s) {
-                        Some(val) => val,
-                        None if s == name => &trait_str,
-                        None => {
-                            if let Some(val) = options.get(&s) {
-                                val
-                            } else if s == sym::from_desugaring || s == sym::from_method {
-                                // don't break messages using these two arguments incorrectly
-                                &empty_string
-                            } else if s == sym::ItemContext {
-                                &item_context
-                            } else if s == sym::integral {
-                                "{integral}"
-                            } else if s == sym::integer_ {
-                                "{integer}"
-                            } else if s == sym::float {
-                                "{float}"
-                            } else {
-                                bug!(
-                                    "broken on_unimplemented {:?} for {:?}: \
+                    Position::ArgumentNamed(s, _) => {
+                        let s = Symbol::intern(s);
+                        match generic_map.get(&s) {
+                            Some(val) => val,
+                            None if s == name => &trait_str,
+                            None => {
+                                if let Some(val) = options.get(&s) {
+                                    val
+                                } else if s == sym::from_desugaring || s == sym::from_method {
+                                    // don't break messages using these two arguments incorrectly
+                                    &empty_string
+                                } else if s == sym::ItemContext {
+                                    &item_context
+                                } else if s == sym::integral {
+                                    "{integral}"
+                                } else if s == sym::integer_ {
+                                    "{integer}"
+                                } else if s == sym::float {
+                                    "{float}"
+                                } else {
+                                    bug!(
+                                        "broken on_unimplemented {:?} for {:?}: \
                                       no argument matching {:?}",
-                                    self.0,
-                                    trait_ref,
-                                    s
-                                )
+                                        self.0,
+                                        trait_ref,
+                                        s
+                                    )
+                                }
                             }
                         }
-                    },
+                    }
                     _ => bug!("broken on_unimplemented {:?} - bad format arg", self.0),
                 },
             })
diff --git a/src/tools/clippy/clippy_lints/src/write.rs b/src/tools/clippy/clippy_lints/src/write.rs
index f3d818cc348..54b93a20a05 100644
--- a/src/tools/clippy/clippy_lints/src/write.rs
+++ b/src/tools/clippy/clippy_lints/src/write.rs
@@ -13,7 +13,7 @@
 use rustc_parse::parser;
 use rustc_session::{declare_tool_lint, impl_lint_pass};
 use rustc_span::symbol::{kw, Symbol};
-use rustc_span::{sym, BytePos, Span, DUMMY_SP};
+use rustc_span::{sym, BytePos, InnerSpan, Span, DUMMY_SP};
 
 declare_clippy_lint! {
     /// ### What it does
@@ -454,6 +454,7 @@ fn push(&mut self, arg: rustc_parse_format::Argument<'_>, span: Span) {
                 }
             },
             ArgumentNamed(n, _) => {
+                let n = Symbol::intern(n);
                 if let Some(x) = self.named.iter_mut().find(|x| x.0 == n) {
                     match x.1.as_slice() {
                         // A non-empty format string has been seen already.
@@ -495,7 +496,7 @@ fn parse_fmt_string(&self, cx: &EarlyContext<'_>, str_lit: &StrLit) -> Option<Si
             let span = parser
                 .arg_places
                 .last()
-                .map_or(DUMMY_SP, |&x| str_lit.span.from_inner(x));
+                .map_or(DUMMY_SP, |&x| str_lit.span.from_inner(InnerSpan::new(x.start, x.end)));
 
             if !self.in_debug_impl && arg.format.ty == "?" {
                 // FIXME: modify rustc's fmt string parser to give us the current span