Avoid &format("...") calls in error message code.

Error message all end up passing into a function as an `impl
Into<{D,Subd}iagnosticMessage>`. If an error message is creatd as
`&format("...")` that means we allocate a string (in the `format!`
call), then take a reference, and then clone (allocating again) the
reference to produce the `{D,Subd}iagnosticMessage`, which is silly.

This commit removes the leading `&` from a lot of these cases. This
means the original `String` is moved into the
`{D,Subd}iagnosticMessage`, avoiding the double allocations. This
requires changing some function argument types from `&str` to `String`
(when all arguments are `String`) or `impl
Into<{D,Subd}iagnosticMessage>` (when some arguments are `String` and
some are `&str`).

compiler/rustc_builtin_macros/src/asm.rs

@@ -550,7 +550,7 @@ 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(InnerSpan::new(err.span.start, err.span.end));
-            let msg = &format!("invalid asm template string: {}", err.description);
+            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");
             if let Some(note) = err.note {
@@ -585,7 +585,7 @@ fn expand_preparsed_asm(ecx: &mut ExtCtxt<'_>, args: AsmArgs) -> Option<ast::Inl
                                 || args.reg_args.contains(idx)
                             {
                                 let msg = format!("invalid reference to argument at index {}", idx);
-                                let mut err = ecx.struct_span_err(span, &msg);
+                                let mut err = ecx.struct_span_err(span, msg);
                                 err.span_label(span, "from here");
 
                                 let positional_args = args.operands.len()
@@ -638,7 +638,7 @@ fn expand_preparsed_asm(ecx: &mut ExtCtxt<'_>, args: AsmArgs) -> Option<ast::Inl
                                     ecx.struct_span_err(
                                         template_span
                                             .from_inner(InnerSpan::new(span.start, span.end)),
-                                        &msg,
+                                        msg,
                                     )
                                     .emit();
                                     None

compiler/rustc_builtin_macros/src/deriving/clone.rs

@@ -145,7 +145,7 @@ fn cs_clone_simple(
             }
             _ => cx.span_bug(
                 trait_span,
-                &format!("unexpected substructure in simple `derive({})`", name),
+                format!("unexpected substructure in simple `derive({})`", name),
             ),
         }
     }
@@ -179,10 +179,10 @@ fn cs_clone(
             vdata = &variant.data;
         }
         EnumTag(..) | AllFieldlessEnum(..) => {
-            cx.span_bug(trait_span, &format!("enum tags in `derive({})`", name,))
+            cx.span_bug(trait_span, format!("enum tags in `derive({})`", name,))
         }
         StaticEnum(..) | StaticStruct(..) => {
-            cx.span_bug(trait_span, &format!("associated function in `derive({})`", name))
+            cx.span_bug(trait_span, format!("associated function in `derive({})`", name))
         }
     }
 
@@ -194,7 +194,7 @@ fn cs_clone(
                     let Some(ident) = field.name else {
                         cx.span_bug(
                             trait_span,
-                            &format!("unnamed field in normal struct in `derive({})`", name,),
+                            format!("unnamed field in normal struct in `derive({})`", name,),
                         );
                     };
                     let call = subcall(cx, field);

compiler/rustc_builtin_macros/src/deriving/generic/mod.rs

@@ -1591,7 +1591,7 @@ impl<'a> TraitDef<'a> {
                                 BYTE_SLICE_IN_PACKED_STRUCT_WITH_DERIVE,
                                 sp,
                                 ast::CRATE_NODE_ID,
-                                &format!(
+                                format!(
                                     "{} slice in a packed struct that derives a built-in trait",
                                     ty
                                 ),

compiler/rustc_builtin_macros/src/format.rs

@@ -814,7 +814,7 @@ fn report_invalid_references(
         };
         e = ecx.struct_span_err(
             span,
-            &format!("invalid reference to positional {} ({})", arg_list, num_args_desc),
+            format!("invalid reference to positional {} ({})", arg_list, num_args_desc),
         );
         e.note("positional arguments are zero-based");
     }

compiler/rustc_builtin_macros/src/source_util.rs

@@ -188,12 +188,12 @@ pub fn expand_include_str(
                 base::MacEager::expr(cx.expr_str(sp, interned_src))
             }
             Err(_) => {
-                cx.span_err(sp, &format!("{} wasn't a utf-8 file", file.display()));
+                cx.span_err(sp, format!("{} wasn't a utf-8 file", file.display()));
                 DummyResult::any(sp)
             }
         },
         Err(e) => {
-            cx.span_err(sp, &format!("couldn't read {}: {}", file.display(), e));
+            cx.span_err(sp, format!("couldn't read {}: {}", file.display(), e));
             DummyResult::any(sp)
         }
     }
@@ -221,7 +221,7 @@ pub fn expand_include_bytes(
             base::MacEager::expr(expr)
         }
         Err(e) => {
-            cx.span_err(sp, &format!("couldn't read {}: {}", file.display(), e));
+            cx.span_err(sp, format!("couldn't read {}: {}", file.display(), e));
             DummyResult::any(sp)
         }
     }