Invert dependency between rustc_error_messages and rustc_ast*.

`rustc_error_messages` currently depends on
`rustc_ast`/`rustc_ast_pretty`. This is odd, because
`rustc_error_messages` feels like a very low-level module but
`rustc_ast`/`rustc_ast_pretty` do not.

The reason is that a few AST types impl `IntoDiagArg` via
pretty-printing. `rustc_error_messages` can define `IntoDiagArg` and
then impl it for the AST types. But if we invert the dependency we hit
a problem with the orphan rule: `rustc_ast` must impl `IntoDiagArg`
for the AST types, but that requires calling pretty-printing code which
is in `rustc_ast_pretty`, a downstream crate.

This commit avoids this problem by just removing the `IntoDiagArg` impls
for these AST types. There aren't that many of them, and we can just use
`String` in the relevant error structs and use the pretty printer in the
downstream crates that construct the error structs. There are plenty of
existing examples where `String` is used in error structs.

There is now no dependency between `rustc_ast*` and
`rustc_error_messages`.

Author: nnethercote

Cargo.lock

@@ -3853,8 +3853,6 @@ dependencies = [
  "icu_list",
  "icu_locale",
  "intl-memoizer",
- "rustc_ast",
- "rustc_ast_pretty",
  "rustc_baked_icu_data",
  "rustc_data_structures",
  "rustc_macros",

compiler/rustc_ast_passes/src/ast_validation.rs

@@ -1117,8 +1117,8 @@ fn validate_generic_param_order(dcx: DiagCtxtHandle<'_>, generics: &[GenericPara
             dcx.emit_err(errors::OutOfOrderParams {
                 spans: spans.clone(),
                 sugg_span: span,
-                param_ord,
-                max_param,
+                param_ord: param_ord.to_string(),
+                max_param: max_param.to_string(),
                 ordered_params: &ordered_params,
             });
         }

compiler/rustc_ast_passes/src/errors.rs

@@ -1,7 +1,6 @@
 //! Errors emitted by ast_passes.
 
 use rustc_abi::ExternAbi;
-use rustc_ast::ParamKindOrd;
 use rustc_errors::codes::*;
 use rustc_errors::{Applicability, Diag, EmissionGuarantee, Subdiagnostic};
 use rustc_macros::{Diagnostic, Subdiagnostic};
@@ -632,8 +631,8 @@ pub(crate) struct OutOfOrderParams<'a> {
         applicability = "machine-applicable"
     )]
     pub sugg_span: Span,
-    pub param_ord: &'a ParamKindOrd,
-    pub max_param: &'a ParamKindOrd,
+    pub param_ord: String,
+    pub max_param: String,
     pub ordered_params: &'a str,
 }
 

compiler/rustc_builtin_macros/src/env.rs

@@ -9,6 +9,7 @@ use std::env::VarError;
 use rustc_ast::token::{self, LitKind};
 use rustc_ast::tokenstream::TokenStream;
 use rustc_ast::{ExprKind, GenericArg, Mutability};
+use rustc_ast_pretty::pprust;
 use rustc_expand::base::{DummyResult, ExpandResult, ExtCtxt, MacEager, MacroExpanderResult};
 use rustc_span::edit_distance::edit_distance;
 use rustc_span::{Ident, Span, Symbol, kw, sym};
@@ -158,13 +159,13 @@ pub(crate) fn expand_env<'cx>(
                         cx.dcx().emit_err(errors::EnvNotDefined::CargoEnvVar {
                             span,
                             var: *symbol,
-                            var_expr: &var_expr,
+                            var_expr: pprust::expr_to_string(&var_expr),
                         })
                     } else {
                         cx.dcx().emit_err(errors::EnvNotDefined::CustomEnvVar {
                             span,
                             var: *symbol,
-                            var_expr: &var_expr,
+                            var_expr: pprust::expr_to_string(&var_expr),
                         })
                     }
                 }

compiler/rustc_builtin_macros/src/errors.rs

@@ -553,7 +553,7 @@ impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for EnvNotDefinedWithUserMessag
 }
 
 #[derive(Diagnostic)]
-pub(crate) enum EnvNotDefined<'a> {
+pub(crate) enum EnvNotDefined {
     #[diag("environment variable `{$var}` not defined at compile time")]
     #[help("`{$var}` may not be available for the current Cargo target")]
     #[help(
@@ -563,7 +563,7 @@ pub(crate) enum EnvNotDefined<'a> {
         #[primary_span]
         span: Span,
         var: Symbol,
-        var_expr: &'a rustc_ast::Expr,
+        var_expr: String,
     },
     #[diag("environment variable `{$var}` not defined at compile time")]
     #[help("there is a similar Cargo environment variable: `{$suggested_var}`")]
@@ -579,7 +579,7 @@ pub(crate) enum EnvNotDefined<'a> {
         #[primary_span]
         span: Span,
         var: Symbol,
-        var_expr: &'a rustc_ast::Expr,
+        var_expr: String,
     },
 }
 

compiler/rustc_codegen_gcc/src/intrinsic/simd.rs

@@ -828,7 +828,7 @@ pub fn generic_simd_intrinsic<'a, 'gcc, 'tcx>(
                 return_error!(InvalidMonomorphization::FloatingPointVector {
                     span,
                     name,
-                    f_ty: *f,
+                    f_ty: f.name_str().to_string(),
                     in_ty
                 });
             }

compiler/rustc_codegen_ssa/src/errors.rs

@@ -13,8 +13,8 @@ use rustc_errors::{
     Level, msg,
 };
 use rustc_macros::{Diagnostic, Subdiagnostic};
+use rustc_middle::ty::Ty;
 use rustc_middle::ty::layout::LayoutError;
-use rustc_middle::ty::{FloatTy, Ty};
 use rustc_span::{Span, Symbol};
 
 use crate::assert_module_sources::CguReuse;
@@ -748,7 +748,7 @@ pub enum InvalidMonomorphization<'tcx> {
         #[primary_span]
         span: Span,
         name: Symbol,
-        f_ty: FloatTy,
+        f_ty: String,
         in_ty: Ty<'tcx>,
     },
 

compiler/rustc_error_messages/Cargo.toml

@@ -9,8 +9,6 @@ fluent-bundle = "0.16"
 icu_list = { version = "2.0", default-features = false, features = ["alloc"] }
 icu_locale = { version = "2.0", default-features = false }
 intl-memoizer = "0.5.1"
-rustc_ast = { path = "../rustc_ast" }
-rustc_ast_pretty = { path = "../rustc_ast_pretty" }
 rustc_baked_icu_data = { path = "../rustc_baked_icu_data" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_macros = { path = "../rustc_macros" }

compiler/rustc_error_messages/src/diagnostic_impls.rs

@@ -5,8 +5,6 @@ use std::num::ParseIntError;
 use std::path::{Path, PathBuf};
 use std::process::ExitStatus;
 
-use rustc_ast as ast;
-use rustc_ast_pretty::pprust;
 use rustc_span::edition::Edition;
 
 use crate::{DiagArgValue, IntoDiagArg};
@@ -69,7 +67,6 @@ macro_rules! into_diag_arg_for_number {
 }
 
 into_diag_arg_using_display!(
-    ast::ParamKindOrd,
     std::io::Error,
     Box<dyn std::error::Error>,
     std::num::NonZero<u32>,
@@ -142,30 +139,6 @@ impl IntoDiagArg for PathBuf {
     }
 }
 
-impl IntoDiagArg for ast::Expr {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(Cow::Owned(pprust::expr_to_string(&self)))
-    }
-}
-
-impl IntoDiagArg for ast::Path {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(Cow::Owned(pprust::path_to_string(&self)))
-    }
-}
-
-impl IntoDiagArg for ast::token::Token {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(pprust::token_to_string(&self))
-    }
-}
-
-impl IntoDiagArg for ast::token::TokenKind {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(pprust::token_kind_to_string(&self))
-    }
-}
-
 impl IntoDiagArg for std::ffi::CString {
     fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
         DiagArgValue::Str(Cow::Owned(self.to_string_lossy().into_owned()))
@@ -178,28 +151,8 @@ impl IntoDiagArg for rustc_data_structures::small_c_str::SmallCStr {
     }
 }
 
-impl IntoDiagArg for ast::Visibility {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        let s = pprust::vis_to_string(&self);
-        let s = s.trim_end().to_string();
-        DiagArgValue::Str(Cow::Owned(s))
-    }
-}
-
 impl IntoDiagArg for Backtrace {
     fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
         DiagArgValue::Str(Cow::from(self.to_string()))
     }
 }
-
-impl IntoDiagArg for ast::util::parser::ExprPrecedence {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Number(self as i32)
-    }
-}
-
-impl IntoDiagArg for ast::FloatTy {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(Cow::Borrowed(self.name_str()))
-    }
-}

compiler/rustc_expand/src/errors.rs

@@ -1,6 +1,5 @@
 use std::borrow::Cow;
 
-use rustc_ast::ast;
 use rustc_errors::codes::*;
 use rustc_hir::limit::Limit;
 use rustc_macros::{Diagnostic, Subdiagnostic};
@@ -230,7 +229,7 @@ pub(crate) struct WrongFragmentKind<'a> {
     #[primary_span]
     pub span: Span,
     pub kind: &'a str,
-    pub name: &'a ast::Path,
+    pub name: String,
 }
 
 #[derive(Diagnostic)]
@@ -249,7 +248,7 @@ pub(crate) struct IncompleteParse<'a> {
     pub descr: String,
     #[label("caused by the macro expansion here")]
     pub label_span: Span,
-    pub macro_path: &'a ast::Path,
+    pub macro_path: String,
     pub kind_name: &'a str,
     #[note("macros cannot expand to match arms")]
     pub expands_to_match_arm: bool,