Stop using `String` for error codes.

Error codes are integers, but `String` is used everywhere to represent
them. Gross!

This commit introduces `ErrCode`, an integral newtype for error codes,
replacing `String`. It also introduces a constant for every error code,
e.g. `E0123`, and removes the `error_code!` macro. The constants are
imported wherever used with `use rustc_errors::codes::*`.

With the old code, we have three different ways to specify an error code
at a use point:
```
error_code!(E0123)  // macro call

struct_span_code_err!(dcx, span, E0123, "msg");  // bare ident arg to macro call

\#[diag(name, code = "E0123")]  // string
struct Diag;
```

With the new code, they all use the `E0123` constant.
```
E0123  // constant

struct_span_code_err!(dcx, span, E0123, "msg");  // constant

\#[diag(name, code = E0123)]  // constant
struct Diag;
```

The commit also changes the structure of the error code definitions:
- `rustc_error_codes` now just defines a higher-order macro listing the
  used error codes and nothing else.
- Because that's now the only thing in the `rustc_error_codes` crate, I
  moved it into the `lib.rs` file and removed the `error_codes.rs` file.
- `rustc_errors` uses that macro to define everything, e.g. the error
  code constants and the `DIAGNOSTIC_TABLES`. This is in its new
  `codes.rs` file.

1 files changed, 669 insertions, 9 deletions

diff --git a/compiler/rustc_error_codes/src/lib.rs b/compiler/rustc_error_codes/src/lib.rs
index dd281811636..5b2766618fc 100644
--- a/compiler/rustc_error_codes/src/lib.rs
+++ b/compiler/rustc_error_codes/src/lib.rs
@@ -1,19 +1,679 @@
+//! This library is used to gather all error codes into one place, to make
+//! their maintenance easier.
+
 #![allow(internal_features)]
 #![feature(rustdoc_internals)]
 #![doc(rust_logo)]
 #![deny(rustdoc::invalid_codeblock_attributes)]
 #![deny(rustc::untranslatable_diagnostic)]
 #![deny(rustc::diagnostic_outside_of_impl)]
-//! This library is used to gather all error codes into one place,
-//! the goal being to make their maintenance easier.
 
-macro_rules! register_diagnostics {
-    ($($ecode:ident: $message:expr,)*) => (
-        pub static DIAGNOSTICS: &[(&str, &str)] = &[
-            $( (stringify!($ecode), $message), )*
-        ];
+// This higher-order macro defines the error codes that are in use. It is used
+// in the `rustc_errors` crate. Removed error codes are listed in the comment
+// below.
+//
+// /!\ IMPORTANT /!\
+//
+// Error code explanation are defined in `error_codes/EXXXX.md` files. They must follow the RFC
+// 1567 available here:
+// https://rust-lang.github.io/rfcs/1567-long-error-codes-explanation-normalization.html
+//
+// Also, the contents of this macro is checked by tidy (in `check_error_codes_docs`). If you change
+// the macro syntax you will need to change tidy as well.
+//
+// Both columns are necessary because it's not possible in Rust to create a new identifier such as
+// `E0123` from an integer literal such as `0123`, unfortunately.
+#[macro_export]
+macro_rules! error_codes {
+    ($macro:path) => (
+        $macro!(
+E0001: 0001,
+E0002: 0002,
+E0004: 0004,
+E0005: 0005,
+E0007: 0007,
+E0009: 0009,
+E0010: 0010,
+E0013: 0013,
+E0014: 0014,
+E0015: 0015,
+E0023: 0023,
+E0025: 0025,
+E0026: 0026,
+E0027: 0027,
+E0029: 0029,
+E0030: 0030,
+E0033: 0033,
+E0034: 0034,
+E0038: 0038,
+E0040: 0040,
+E0044: 0044,
+E0045: 0045,
+E0046: 0046,
+E0049: 0049,
+E0050: 0050,
+E0053: 0053,
+E0054: 0054,
+E0055: 0055,
+E0057: 0057,
+E0059: 0059,
+E0060: 0060,
+E0061: 0061,
+E0062: 0062,
+E0063: 0063,
+E0067: 0067,
+E0069: 0069,
+E0070: 0070,
+E0071: 0071,
+E0072: 0072,
+E0073: 0073,
+E0074: 0074,
+E0075: 0075,
+E0076: 0076,
+E0077: 0077,
+E0080: 0080,
+E0081: 0081,
+E0084: 0084,
+E0087: 0087,
+E0088: 0088,
+E0089: 0089,
+E0090: 0090,
+E0091: 0091,
+E0092: 0092,
+E0093: 0093,
+E0094: 0094,
+E0106: 0106,
+E0107: 0107,
+E0109: 0109,
+E0110: 0110,
+E0116: 0116,
+E0117: 0117,
+E0118: 0118,
+E0119: 0119,
+E0120: 0120,
+E0121: 0121,
+E0124: 0124,
+E0128: 0128,
+E0130: 0130,
+E0131: 0131,
+E0132: 0132,
+E0133: 0133,
+E0136: 0136,
+E0137: 0137,
+E0138: 0138,
+E0139: 0139,
+E0152: 0152,
+E0154: 0154,
+E0158: 0158,
+E0161: 0161,
+E0162: 0162,
+E0164: 0164,
+E0165: 0165,
+E0170: 0170,
+E0178: 0178,
+E0183: 0183,
+E0184: 0184,
+E0185: 0185,
+E0186: 0186,
+E0191: 0191,
+E0192: 0192,
+E0193: 0193,
+E0195: 0195,
+E0197: 0197,
+E0198: 0198,
+E0199: 0199,
+E0200: 0200,
+E0201: 0201,
+E0203: 0203,
+E0204: 0204,
+E0205: 0205,
+E0206: 0206,
+E0207: 0207,
+E0208: 0208,
+E0210: 0210,
+E0211: 0211,
+E0212: 0212,
+E0214: 0214,
+E0220: 0220,
+E0221: 0221,
+E0222: 0222,
+E0223: 0223,
+E0224: 0224,
+E0225: 0225,
+E0226: 0226,
+E0227: 0227,
+E0228: 0228,
+E0229: 0229,
+E0230: 0230,
+E0231: 0231,
+E0232: 0232,
+E0243: 0243,
+E0244: 0244,
+E0251: 0251,
+E0252: 0252,
+E0253: 0253,
+E0254: 0254,
+E0255: 0255,
+E0256: 0256,
+E0259: 0259,
+E0260: 0260,
+E0261: 0261,
+E0262: 0262,
+E0263: 0263,
+E0264: 0264,
+E0267: 0267,
+E0268: 0268,
+E0271: 0271,
+E0275: 0275,
+E0276: 0276,
+E0277: 0277,
+E0281: 0281,
+E0282: 0282,
+E0283: 0283,
+E0284: 0284,
+E0297: 0297,
+E0301: 0301,
+E0302: 0302,
+E0303: 0303,
+E0307: 0307,
+E0308: 0308,
+E0309: 0309,
+E0310: 0310,
+E0311: 0311,
+E0312: 0312,
+E0316: 0316,
+E0317: 0317,
+E0320: 0320,
+E0321: 0321,
+E0322: 0322,
+E0323: 0323,
+E0324: 0324,
+E0325: 0325,
+E0326: 0326,
+E0328: 0328,
+E0329: 0329,
+E0364: 0364,
+E0365: 0365,
+E0366: 0366,
+E0367: 0367,
+E0368: 0368,
+E0369: 0369,
+E0370: 0370,
+E0371: 0371,
+E0373: 0373,
+E0374: 0374,
+E0375: 0375,
+E0376: 0376,
+E0377: 0377,
+E0378: 0378,
+E0379: 0379,
+E0380: 0380,
+E0381: 0381,
+E0382: 0382,
+E0383: 0383,
+E0384: 0384,
+E0386: 0386,
+E0387: 0387,
+E0388: 0388,
+E0389: 0389,
+E0390: 0390,
+E0391: 0391,
+E0392: 0392,
+E0393: 0393,
+E0398: 0398,
+E0399: 0399,
+E0401: 0401,
+E0403: 0403,
+E0404: 0404,
+E0405: 0405,
+E0407: 0407,
+E0408: 0408,
+E0409: 0409,
+E0411: 0411,
+E0412: 0412,
+E0415: 0415,
+E0416: 0416,
+E0422: 0422,
+E0423: 0423,
+E0424: 0424,
+E0425: 0425,
+E0426: 0426,
+E0428: 0428,
+E0429: 0429,
+E0430: 0430,
+E0431: 0431,
+E0432: 0432,
+E0433: 0433,
+E0434: 0434,
+E0435: 0435,
+E0436: 0436,
+E0437: 0437,
+E0438: 0438,
+E0439: 0439,
+E0445: 0445,
+E0446: 0446,
+E0447: 0447,
+E0448: 0448,
+E0449: 0449,
+E0451: 0451,
+E0452: 0452,
+E0453: 0453,
+E0454: 0454,
+E0455: 0455,
+E0457: 0457,
+E0458: 0458,
+E0459: 0459,
+E0460: 0460,
+E0461: 0461,
+E0462: 0462,
+E0463: 0463,
+E0464: 0464,
+E0466: 0466,
+E0468: 0468,
+E0469: 0469,
+E0472: 0472,
+E0476: 0476,
+E0477: 0477,
+E0478: 0478,
+E0482: 0482,
+E0491: 0491,
+E0492: 0492,
+E0493: 0493,
+E0495: 0495,
+E0496: 0496,
+E0497: 0497,
+E0498: 0498,
+E0499: 0499,
+E0500: 0500,
+E0501: 0501,
+E0502: 0502,
+E0503: 0503,
+E0504: 0504,
+E0505: 0505,
+E0506: 0506,
+E0507: 0507,
+E0508: 0508,
+E0509: 0509,
+E0510: 0510,
+E0511: 0511,
+E0512: 0512,
+E0514: 0514,
+E0515: 0515,
+E0516: 0516,
+E0517: 0517,
+E0518: 0518,
+E0519: 0519,
+E0520: 0520,
+E0521: 0521,
+E0522: 0522,
+E0523: 0523,
+E0524: 0524,
+E0525: 0525,
+E0527: 0527,
+E0528: 0528,
+E0529: 0529,
+E0530: 0530,
+E0531: 0531,
+E0532: 0532,
+E0533: 0533,
+E0534: 0534,
+E0535: 0535,
+E0536: 0536,
+E0537: 0537,
+E0538: 0538,
+E0539: 0539,
+E0541: 0541,
+E0542: 0542,
+E0543: 0543,
+E0544: 0544,
+E0545: 0545,
+E0546: 0546,
+E0547: 0547,
+E0549: 0549,
+E0550: 0550,
+E0551: 0551,
+E0552: 0552,
+E0554: 0554,
+E0556: 0556,
+E0557: 0557,
+E0559: 0559,
+E0560: 0560,
+E0561: 0561,
+E0562: 0562,
+E0565: 0565,
+E0566: 0566,
+E0567: 0567,
+E0568: 0568,
+E0569: 0569,
+E0570: 0570,
+E0571: 0571,
+E0572: 0572,
+E0573: 0573,
+E0574: 0574,
+E0575: 0575,
+E0576: 0576,
+E0577: 0577,
+E0578: 0578,
+E0579: 0579,
+E0580: 0580,
+E0581: 0581,
+E0582: 0582,
+E0583: 0583,
+E0584: 0584,
+E0585: 0585,
+E0586: 0586,
+E0587: 0587,
+E0588: 0588,
+E0589: 0589,
+E0590: 0590,
+E0591: 0591,
+E0592: 0592,
+E0593: 0593,
+E0594: 0594,
+E0595: 0595,
+E0596: 0596,
+E0597: 0597,
+E0599: 0599,
+E0600: 0600,
+E0601: 0601,
+E0602: 0602,
+E0603: 0603,
+E0604: 0604,
+E0605: 0605,
+E0606: 0606,
+E0607: 0607,
+E0608: 0608,
+E0609: 0609,
+E0610: 0610,
+E0614: 0614,
+E0615: 0615,
+E0616: 0616,
+E0617: 0617,
+E0618: 0618,
+E0619: 0619,
+E0620: 0620,
+E0621: 0621,
+E0622: 0622,
+E0623: 0623,
+E0624: 0624,
+E0625: 0625,
+E0626: 0626,
+E0627: 0627,
+E0628: 0628,
+E0631: 0631,
+E0632: 0632,
+E0633: 0633,
+E0634: 0634,
+E0635: 0635,
+E0636: 0636,
+E0637: 0637,
+E0638: 0638,
+E0639: 0639,
+E0640: 0640,
+E0641: 0641,
+E0642: 0642,
+E0643: 0643,
+E0644: 0644,
+E0646: 0646,
+E0647: 0647,
+E0648: 0648,
+E0657: 0657,
+E0658: 0658,
+E0659: 0659,
+E0660: 0660,
+E0661: 0661,
+E0662: 0662,
+E0663: 0663,
+E0664: 0664,
+E0665: 0665,
+E0666: 0666,
+E0667: 0667,
+E0668: 0668,
+E0669: 0669,
+E0670: 0670,
+E0671: 0671,
+E0687: 0687,
+E0688: 0688,
+E0689: 0689,
+E0690: 0690,
+E0691: 0691,
+E0692: 0692,
+E0693: 0693,
+E0695: 0695,
+E0696: 0696,
+E0697: 0697,
+E0698: 0698,
+E0699: 0699,
+E0700: 0700,
+E0701: 0701,
+E0703: 0703,
+E0704: 0704,
+E0705: 0705,
+E0706: 0706,
+E0708: 0708,
+E0710: 0710,
+E0712: 0712,
+E0713: 0713,
+E0714: 0714,
+E0715: 0715,
+E0716: 0716,
+E0711: 0711,
+E0717: 0717,
+E0718: 0718,
+E0719: 0719,
+E0720: 0720,
+E0722: 0722,
+E0724: 0724,
+E0725: 0725,
+E0726: 0726,
+E0727: 0727,
+E0728: 0728,
+E0729: 0729,
+E0730: 0730,
+E0731: 0731,
+E0732: 0732,
+E0733: 0733,
+E0734: 0734,
+E0735: 0735,
+E0736: 0736,
+E0737: 0737,
+E0739: 0739,
+E0740: 0740,
+E0741: 0741,
+E0742: 0742,
+E0743: 0743,
+E0744: 0744,
+E0745: 0745,
+E0746: 0746,
+E0747: 0747,
+E0748: 0748,
+E0749: 0749,
+E0750: 0750,
+E0751: 0751,
+E0752: 0752,
+E0753: 0753,
+E0754: 0754,
+E0755: 0755,
+E0756: 0756,
+E0757: 0757,
+E0758: 0758,
+E0759: 0759,
+E0760: 0760,
+E0761: 0761,
+E0762: 0762,
+E0763: 0763,
+E0764: 0764,
+E0765: 0765,
+E0766: 0766,
+E0767: 0767,
+E0768: 0768,
+E0769: 0769,
+E0770: 0770,
+E0771: 0771,
+E0772: 0772,
+E0773: 0773,
+E0774: 0774,
+E0775: 0775,
+E0776: 0776,
+E0777: 0777,
+E0778: 0778,
+E0779: 0779,
+E0780: 0780,
+E0781: 0781,
+E0782: 0782,
+E0783: 0783,
+E0784: 0784,
+E0785: 0785,
+E0786: 0786,
+E0787: 0787,
+E0788: 0788,
+E0789: 0789,
+E0790: 0790,
+E0791: 0791,
+E0792: 0792,
+E0793: 0793,
+E0794: 0794,
+E0795: 0795,
+E0796: 0796,
+E0797: 0797,
+        );
     )
 }
 
-mod error_codes;
-pub use error_codes::DIAGNOSTICS;
+// Undocumented removed error codes. Note that many removed error codes are kept in the list above
+// and marked as no-longer emitted with a note in the markdown file (see E0001 for an example).
+//  E0006, // merged with E0005
+//  E0008, // cannot bind by-move into a pattern guard
+//  E0019, // merged into E0015
+//  E0035, // merged into E0087/E0089
+//  E0036, // merged into E0087/E0089
+//  E0068,
+//  E0085,
+//  E0086,
+//  E0101, // replaced with E0282
+//  E0102, // replaced with E0282
+//  E0103,
+//  E0104,
+//  E0122, // bounds in type aliases are ignored, turned into proper lint
+//  E0123,
+//  E0127,
+//  E0129,
+//  E0134,
+//  E0135,
+//  E0141,
+//  E0153, // unused error code
+//  E0157, // unused error code
+//  E0159, // use of trait `{}` as struct constructor
+//  E0163, // merged into E0071
+//  E0167,
+//  E0168,
+//  E0172, // non-trait found in a type sum, moved to resolve
+//  E0173, // manual implementations of unboxed closure traits are experimental
+//  E0174,
+//  E0182, // merged into E0229
+//  E0187, // cannot infer the kind of the closure
+//  E0188, // can not cast an immutable reference to a mutable pointer
+//  E0189, // deprecated: can only cast a boxed pointer to a boxed object
+//  E0190, // deprecated: can only cast a &-pointer to an &-object
+//  E0194, // merged into E0403
+//  E0196, // cannot determine a type for this closure
+//  E0209, // builtin traits can only be implemented on structs or enums
+//  E0213, // associated types are not accepted in this context
+//  E0215, // angle-bracket notation is not stable with `Fn`
+//  E0216, // parenthetical notation is only stable with `Fn`
+//  E0217, // ambiguous associated type, defined in multiple supertraits
+//  E0218, // no associated type defined
+//  E0219, // associated type defined in higher-ranked supertrait
+//  E0233,
+//  E0234,
+//  E0235, // structure constructor specifies a structure of type but
+//  E0236, // no lang item for range syntax
+//  E0237, // no lang item for range syntax
+//  E0238, // parenthesized parameters may only be used with a trait
+//  E0239, // `next` method of `Iterator` trait has unexpected type
+//  E0240,
+//  E0241,
+//  E0242,
+//  E0245, // not a trait
+//  E0246, // invalid recursive type
+//  E0247,
+//  E0248, // value used as a type, now reported earlier during resolution
+//         // as E0412
+//  E0249,
+//  E0257,
+//  E0258,
+//  E0272, // on_unimplemented #0
+//  E0273, // on_unimplemented #1
+//  E0274, // on_unimplemented #2
+//  E0278, // requirement is not satisfied
+//  E0279,
+//  E0280, // changed to ICE
+//  E0285, // overflow evaluation builtin bounds
+//  E0296, // replaced with a generic attribute input check
+//  E0298, // cannot compare constants
+//  E0299, // mismatched types between arms
+//  E0300, // unexpanded macro
+//  E0304, // expected signed integer constant
+//  E0305, // expected constant
+//  E0313, // removed: found unreachable
+//  E0314, // closure outlives stack frame
+//  E0315, // cannot invoke closure outside of its lifetime
+//  E0319, // trait impls for defaulted traits allowed just for structs/enums
+//  E0372, // coherence not object safe
+//  E0385, // {} in an aliasable location
+//  E0402, // cannot use an outer type parameter in this context
+//  E0406, // merged into 420
+//  E0410, // merged into 408
+//  E0413, // merged into 530
+//  E0414, // merged into 530
+//  E0417, // merged into 532
+//  E0418, // merged into 532
+//  E0419, // merged into 531
+//  E0420, // merged into 532
+//  E0421, // merged into 531
+//  E0427, // merged into 530
+//  E0445, // merged into 446 and type privacy lints
+//  E0456, // plugin `..` is not available for triple `..`
+//  E0465, // removed: merged with E0464
+//  E0467, // removed
+//  E0470, // removed
+//  E0471, // constant evaluation error (in pattern)
+//  E0473, // dereference of reference outside its lifetime
+//  E0474, // captured variable `..` does not outlive the enclosing closure
+//  E0475, // index of slice outside its lifetime
+//  E0479, // the type `..` (provided as the value of a type parameter) is...
+//  E0480, // lifetime of method receiver does not outlive the method call
+//  E0481, // lifetime of function argument does not outlive the function call
+//  E0483, // lifetime of operand does not outlive the operation
+//  E0484, // reference is not valid at the time of borrow
+//  E0485, // automatically reference is not valid at the time of borrow
+//  E0486, // type of expression contains references that are not valid during..
+//  E0487, // unsafe use of destructor: destructor might be called while...
+//  E0488, // lifetime of variable does not enclose its declaration
+//  E0489, // type/lifetime parameter not in scope here
+//  E0490, // removed: unreachable
+//  E0526, // shuffle indices are not constant
+//  E0540, // multiple rustc_deprecated attributes
+//  E0548, // replaced with a generic attribute input check
+//  E0553, // multiple rustc_const_unstable attributes
+//  E0555, // replaced with a generic attribute input check
+//  E0558, // replaced with a generic attribute input check
+//  E0563, // cannot determine a type for this `impl Trait` removed in 6383de15
+//  E0564, // only named lifetimes are allowed in `impl Trait`,
+//         // but `{}` was found in the type `{}`
+//  E0598, // lifetime of {} is too short to guarantee its contents can be...
+//  E0611, // merged into E0616
+//  E0612, // merged into E0609
+//  E0613, // Removed (merged with E0609)
+//  E0629, // missing 'feature' (rustc_const_unstable)
+//  E0630, // rustc_const_unstable attribute must be paired with stable/unstable
+//         // attribute
+//  E0645, // trait aliases not finished
+//  E0694, // an unknown tool name found in scoped attributes
+//  E0702, // replaced with a generic attribute input check
+//  E0707, // multiple elided lifetimes used in arguments of `async fn`
+//  E0709, // multiple different lifetimes used in arguments of `async fn`
+//  E0721, // `await` keyword
+//  E0723, // unstable feature in `const` context
+//  E0738, // Removed; errored on `#[track_caller] fn`s in `extern "Rust" { ... }`.
+//  E0744, // merged into E0728