Auto merge of #66314 - GuillaumeGomez:move-error-codes, r=Centril

Move error codes

Works towards #66210.

r? @Centril

Oh btw, for the ones interested, I used this python script to get all error codes content sorted into one final file:

<details>

```python
from os import listdir
from os.path import isdir, isfile, join

def get_error_codes(error_codes, f_path):
    with open(f_path) as f:
        short_mode = False
        lines = f.read().split("\n")
        i = 0
        while i < len(lines):
            line = lines[i]
            if not short_mode and line.startswith("E0") and line.endswith(": r##\""):
                error = line
                error += "\n"
                i += 1
                while i < len(lines):
                    line = lines[i]
                    error += line
                    if line.endswith("\"##,"):
                        break
                    error += "\n"
                    i += 1
                error_codes["long"].append(error)
            elif line == ';':
                short_mode = True
            elif short_mode is True and len(line) > 0 and line != "}":
                error_codes["short"].append(line)
                while i + 1 < len(lines):
                    line = lines[i + 1].strip()
                    if not line.startswith("//"):
                        break
                    parts = line.split("//")
                    if len(parts) < 2:
                        break
                    if parts[1].strip().startswith("E0"):
                        break
                    error_codes["short"][-1] += "\n"
                    error_codes["short"][-1] += lines[i + 1]
                    i += 1
            i += 1

def loop_dirs(error_codes, cur_dir):
    for entry in listdir(cur_dir):
        f = join(cur_dir, entry)
        if isfile(f) and entry == "error_codes.rs":
            get_error_codes(error_codes, f)
        elif isdir(f) and not entry.startswith("librustc_error_codes"):
            loop_dirs(error_codes, f)

def get_error_code(err):
    x = err.split(",")
    if len(x) < 2:
        return err
    x = x[0]
    if x.strip().startswith("//"):
        x = x.split("//")[1].strip()
    return x.strip()

def write_into_file(error_codes, f_path):
    with open(f_path, "w") as f:
        f.write("// Error messages for EXXXX errors.  Each message should start and end with a\n")
        f.write("// new line, and be wrapped to 80 characters.  In vim you can `:set tw=80` and\n")
        f.write("// use `gq` to wrap paragraphs. Use `:set tw=0` to disable.\n\n")
        f.write("syntax::register_diagnostics! {\n\n")
        error_codes["long"].sort()
        for i in error_codes["long"]:
            f.write(i)
            f.write("\n\n")
        f.write(";\n")
        error_codes["short"] = sorted(error_codes["short"], key=lambda err: get_error_code(err))
        for i in error_codes["short"]:
            f.write(i)
            f.write("\n")
        f.write("}\n")

error_codes = {
    "long": [],
    "short": []
}
loop_dirs(error_codes, "src")
write_into_file(error_codes, "src/librustc_error_codes/src/error_codes.rs")
```
</details>

And to move the error codes into their own files:

<details>

```python
import os

try:
    os.mkdir("src/librustc_error_codes/error_codes")
except OSError:
    print("Seems like folder already exist, moving on!")
data = ''
with open("src/librustc_error_codes/error_codes.rs") as f:
    x = f.read().split('\n')
    i = 0
    short_part = False
    while i < len(x):
        line = x[i]
        if short_part is False and line.startswith('E0') and line.endswith(': r##"'):
            err_code = line.split(':')[0]
            i += 1
            content = ''
            while i < len(x):
                if x[i] == '"##,':
                    break
                content += x[i]
                content += '\n'
                i += 1
            f_path = "src/librustc_error_codes/error_codes/{}.md".format(err_code)
            with open(f_path, "w") as ff:
                ff.write(content)
            data += '{}: include_str!("./error_codes/{}.md"),'.format(err_code, err_code)
        elif short_part is False and line == ';':
            short_part is True
            data += ';\n'
        else:
            data += line
            data += '\n'
        i += 1
with open("src/librustc_error_codes/error_codes.rs", "w") as f:
    f.write(data)
```
</details>

1 files changed, 0 insertions, 379 deletions

diff --git a/src/libsyntax/error_codes.rs b/src/libsyntax/error_codes.rs
deleted file mode 100644
index 0e81de7d4a7..00000000000
--- a/src/libsyntax/error_codes.rs
+++ /dev/null
@@ -1,379 +0,0 @@
-// Error messages for EXXXX errors.
-// Each message should start and end with a new line, and be wrapped to 80
-// characters.  In vim you can `:set tw=80` and use `gq` to wrap paragraphs. Use
-// `:set tw=0` to disable.
-register_diagnostics! {
-
-E0536: r##"
-The `not` cfg-predicate was malformed.
-
-Erroneous code example:
-
-```compile_fail,E0536
-#[cfg(not())] // error: expected 1 cfg-pattern
-pub fn something() {}
-
-pub fn main() {}
-```
-
-The `not` predicate expects one cfg-pattern. Example:
-
-```
-#[cfg(not(target_os = "linux"))] // ok!
-pub fn something() {}
-
-pub fn main() {}
-```
-
-For more information about the cfg attribute, read:
-https://doc.rust-lang.org/reference.html#conditional-compilation
-"##,
-
-E0537: r##"
-An unknown predicate was used inside the `cfg` attribute.
-
-Erroneous code example:
-
-```compile_fail,E0537
-#[cfg(unknown())] // error: invalid predicate `unknown`
-pub fn something() {}
-
-pub fn main() {}
-```
-
-The `cfg` attribute supports only three kinds of predicates:
-
- * any
- * all
- * not
-
-Example:
-
-```
-#[cfg(not(target_os = "linux"))] // ok!
-pub fn something() {}
-
-pub fn main() {}
-```
-
-For more information about the cfg attribute, read:
-https://doc.rust-lang.org/reference.html#conditional-compilation
-"##,
-
-E0538: r##"
-Attribute contains same meta item more than once.
-
-Erroneous code example:
-
-```compile_fail,E0538
-#[deprecated(
-    since="1.0.0",
-    note="First deprecation note.",
-    note="Second deprecation note." // error: multiple same meta item
-)]
-fn deprecated_function() {}
-```
-
-Meta items are the key-value pairs inside of an attribute. Each key may only be
-used once in each attribute.
-
-To fix the problem, remove all but one of the meta items with the same key.
-
-Example:
-
-```
-#[deprecated(
-    since="1.0.0",
-    note="First deprecation note."
-)]
-fn deprecated_function() {}
-```
-"##,
-
-E0541: r##"
-An unknown meta item was used.
-
-Erroneous code example:
-
-```compile_fail,E0541
-#[deprecated(
-    since="1.0.0",
-    // error: unknown meta item
-    reason="Example invalid meta item. Should be 'note'")
-]
-fn deprecated_function() {}
-```
-
-Meta items are the key-value pairs inside of an attribute. The keys provided
-must be one of the valid keys for the specified attribute.
-
-To fix the problem, either remove the unknown meta item, or rename it if you
-provided the wrong name.
-
-In the erroneous code example above, the wrong name was provided, so changing
-to a correct one it will fix the error. Example:
-
-```
-#[deprecated(
-    since="1.0.0",
-    note="This is a valid meta item for the deprecated attribute."
-)]
-fn deprecated_function() {}
-```
-"##,
-
-E0550: r##"
-More than one `deprecated` attribute has been put on an item.
-
-Erroneous code example:
-
-```compile_fail,E0550
-#[deprecated(note = "because why not?")]
-#[deprecated(note = "right?")] // error!
-fn the_banished() {}
-```
-
-The `deprecated` attribute can only be present **once** on an item.
-
-```
-#[deprecated(note = "because why not, right?")]
-fn the_banished() {} // ok!
-```
-"##,
-
-E0551: r##"
-An invalid meta-item was used inside an attribute.
-
-Erroneous code example:
-
-```compile_fail,E0551
-#[deprecated(note)] // error!
-fn i_am_deprecated() {}
-```
-
-Meta items are the key-value pairs inside of an attribute. To fix this issue,
-you need to give a value to the `note` key. Example:
-
-```
-#[deprecated(note = "because")] // ok!
-fn i_am_deprecated() {}
-```
-"##,
-
-E0552: r##"
-A unrecognized representation attribute was used.
-
-Erroneous code example:
-
-```compile_fail,E0552
-#[repr(D)] // error: unrecognized representation hint
-struct MyStruct {
-    my_field: usize
-}
-```
-
-You can use a `repr` attribute to tell the compiler how you want a struct or
-enum to be laid out in memory.
-
-Make sure you're using one of the supported options:
-
-```
-#[repr(C)] // ok!
-struct MyStruct {
-    my_field: usize
-}
-```
-
-For more information about specifying representations, see the ["Alternative
-Representations" section] of the Rustonomicon.
-
-["Alternative Representations" section]: https://doc.rust-lang.org/nomicon/other-reprs.html
-"##,
-
-E0554: r##"
-Feature attributes are only allowed on the nightly release channel. Stable or
-beta compilers will not comply.
-
-Example of erroneous code (on a stable compiler):
-
-```ignore (depends on release channel)
-#![feature(non_ascii_idents)] // error: `#![feature]` may not be used on the
-                              //        stable release channel
-```
-
-If you need the feature, make sure to use a nightly release of the compiler
-(but be warned that the feature may be removed or altered in the future).
-"##,
-
-E0556: r##"
-The `feature` attribute was badly formed.
-
-Erroneous code example:
-
-```compile_fail,E0556
-#![feature(foo_bar_baz, foo(bar), foo = "baz", foo)] // error!
-#![feature] // error!
-#![feature = "foo"] // error!
-```
-
-The `feature` attribute only accept a "feature flag" and can only be used on
-nightly. Example:
-
-```ignore (only works in nightly)
-#![feature(flag)]
-```
-"##,
-
-E0557: r##"
-A feature attribute named a feature that has been removed.
-
-Erroneous code example:
-
-```compile_fail,E0557
-#![feature(managed_boxes)] // error: feature has been removed
-```
-
-Delete the offending feature attribute.
-"##,
-
-E0565: r##"
-A literal was used in a built-in attribute that doesn't support literals.
-
-Erroneous code example:
-
-```ignore (compile_fail not working here; see Issue #43707)
-#[inline("always")] // error: unsupported literal
-pub fn something() {}
-```
-
-Literals in attributes are new and largely unsupported in built-in attributes.
-Work to support literals where appropriate is ongoing. Try using an unquoted
-name instead:
-
-```
-#[inline(always)]
-pub fn something() {}
-```
-"##,
-
-E0589: r##"
-The value of `N` that was specified for `repr(align(N))` was not a power
-of two, or was greater than 2^29.
-
-```compile_fail,E0589
-#[repr(align(15))] // error: invalid `repr(align)` attribute: not a power of two
-enum Foo {
-    Bar(u64),
-}
-```
-"##,
-
-E0658: r##"
-An unstable feature was used.
-
-Erroneous code example:
-
-```compile_fail,E658
-#[repr(u128)] // error: use of unstable library feature 'repr128'
-enum Foo {
-    Bar(u64),
-}
-```
-
-If you're using a stable or a beta version of rustc, you won't be able to use
-any unstable features. In order to do so, please switch to a nightly version of
-rustc (by using rustup).
-
-If you're using a nightly version of rustc, just add the corresponding feature
-to be able to use it:
-
-```
-#![feature(repr128)]
-
-#[repr(u128)] // ok!
-enum Foo {
-    Bar(u64),
-}
-```
-"##,
-
-E0633: r##"
-The `unwind` attribute was malformed.
-
-Erroneous code example:
-
-```ignore (compile_fail not working here; see Issue #43707)
-#[unwind()] // error: expected one argument
-pub extern fn something() {}
-
-fn main() {}
-```
-
-The `#[unwind]` attribute should be used as follows:
-
-- `#[unwind(aborts)]` -- specifies that if a non-Rust ABI function
-  should abort the process if it attempts to unwind. This is the safer
-  and preferred option.
-
-- `#[unwind(allowed)]` -- specifies that a non-Rust ABI function
-  should be allowed to unwind. This can easily result in Undefined
-  Behavior (UB), so be careful.
-
-NB. The default behavior here is "allowed", but this is unspecified
-and likely to change in the future.
-
-"##,
-
-E0705: r##"
-A `#![feature]` attribute was declared for a feature that is stable in
-the current edition, but not in all editions.
-
-Erroneous code example:
-
-```ignore (limited to a warning during 2018 edition development)
-#![feature(rust_2018_preview)]
-#![feature(test_2018_feature)] // error: the feature
-                               // `test_2018_feature` is
-                               // included in the Rust 2018 edition
-```
-"##,
-
-E0725: r##"
-A feature attribute named a feature that was disallowed in the compiler
-command line flags.
-
-Erroneous code example:
-
-```ignore (can't specify compiler flags from doctests)
-#![feature(never_type)] // error: the feature `never_type` is not in
-                        // the list of allowed features
-```
-
-Delete the offending feature attribute, or add it to the list of allowed
-features in the `-Z allow_features` flag.
-"##,
-
-;
-
-    E0539, // incorrect meta item
-    E0540, // multiple rustc_deprecated attributes
-    E0542, // missing 'since'
-    E0543, // missing 'reason'
-    E0544, // multiple stability levels
-    E0545, // incorrect 'issue'
-    E0546, // missing 'feature'
-    E0547, // missing 'issue'
-//  E0548, // replaced with a generic attribute input check
-    // rustc_deprecated attribute must be paired with either stable or unstable
-    // attribute
-    E0549,
-    E0553, // multiple rustc_const_unstable attributes
-//  E0555, // replaced with a generic attribute input check
-    E0629, // missing 'feature' (rustc_const_unstable)
-    // rustc_const_unstable attribute must be paired with stable/unstable
-    // attribute
-    E0630,
-    E0693, // incorrect `repr(align)` attribute format
-//  E0694, // an unknown tool name found in scoped attributes
-    E0717, // rustc_promotable without stability attribute
-}