Auto merge of #101558 - JhonnyBillM:session-diagnostic-to-diagnostic-handler-refactor, r=davidtwco

Move and rename `SessionDiagnostic` & `SessionSubdiagnostic` traits and macros

After PR #101434, we want to:
- [x] Move `SessionDiagnostic` to `rustc_errors`.
- [x] Add `emit_` methods that accept `impl SessionDiagnostic` to `Handler`.
- [x] _(optional)_ Rename trait `SessionDiagnostic` to `DiagnosticHandler`.
- [x] _(optional)_ Rename macro `SessionDiagnostic` to `DiagnosticHandler`.
- [x] Update Rustc Dev Guide and Docs to reflect these changes. rust-lang/rustc-dev-guide#1460

Now I am having build issues getting the compiler to build when trying to rename the macro.

<details>
  <summary>See diagnostics errors and context when building.</summary>

```
error: diagnostics should only be created in `SessionDiagnostic`/`AddSubdiagnostic` impls
  --> compiler/rustc_attr/src/session_diagnostics.rs:13:10
   |
13 |   #[derive(DiagnosticHandler)]
   |            ^^^^^^^^^^^^^^^^^ in this derive macro expansion
   |
  ::: /Users/jhonny/.cargo/registry/src/gb.xjqchip.workers.dev-1ecc6299db9ec823/synstructure-0.12.6/src/macros.rs:94:9
   |
94 | /         pub fn $derives(
95 | |             i: $crate::macros::TokenStream
96 | |         ) -> $crate::macros::TokenStream {
   | |________________________________________- in this expansion of `#[derive(DiagnosticHandler)]`
   |
note: the lint level is defined here
  --> compiler/rustc_attr/src/lib.rs:10:9
   |
10 | #![deny(rustc::diagnostic_outside_of_impl)]
   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

```

And also this one:

```
error: diagnostics should only be created in `SessionDiagnostic`/`AddSubdiagnostic` impls
   --> compiler/rustc_attr/src/session_diagnostics.rs:213:32
    |
213 |         let mut diag = handler.struct_span_err_with_code(
    |                                ^^^^^^^^^^^^^^^^^^^^^^^^^
```

> **Note**
> Can't find where this message is coming from, because you can see in [this experimental branch](https://github.com/JhonnyBillM/rust/tree/experimental/trying-to-rename-session-diagnostic-macro)  that I updated all errors and diags to say:
> error: diagnostics should only be created in **`DiagnosticHandler`**/`AddSubdiagnostic` impls
> and not:
> error: diagnostics should only be created in **`SessionDiagnostic`**/`AddSubdiagnostic` impls

</details>

I tried building the compiler in different ways (playing with the stages etc), but nothing worked.

## Question

**Do we need to build or do something different when renaming a macro and identifiers?**

For context, see experimental commit JhonnyBillM@f2193a9 where the macro and symbols are renamed, but it doesn't compile.

Author: bors

compiler/rustc_ast_lowering/src/errors.rs

@@ -1,8 +1,8 @@
-use rustc_errors::{fluent, AddSubdiagnostic, Applicability, Diagnostic, DiagnosticArgFromDisplay};
-use rustc_macros::{SessionDiagnostic, SessionSubdiagnostic};
+use rustc_errors::{fluent, AddToDiagnostic, Applicability, Diagnostic, DiagnosticArgFromDisplay};
+use rustc_macros::{Diagnostic, Subdiagnostic};
 use rustc_span::{symbol::Ident, Span, Symbol};
 
-#[derive(SessionDiagnostic, Clone, Copy)]
+#[derive(Diagnostic, Clone, Copy)]
 #[diag(ast_lowering::generic_type_with_parentheses, code = "E0214")]
 pub struct GenericTypeWithParentheses {
     #[primary_span]
@@ -18,7 +18,7 @@ pub struct UseAngleBrackets {
     pub close_param: Span,
 }
 
-impl AddSubdiagnostic for UseAngleBrackets {
+impl AddToDiagnostic for UseAngleBrackets {
     fn add_to_diagnostic(self, diag: &mut Diagnostic) {
         diag.multipart_suggestion(
             fluent::ast_lowering::use_angle_brackets,
@@ -28,7 +28,7 @@ impl AddSubdiagnostic for UseAngleBrackets {
     }
 }
 
-#[derive(SessionDiagnostic)]
+#[derive(Diagnostic)]
 #[help]
 #[diag(ast_lowering::invalid_abi, code = "E0703")]
 pub struct InvalidAbi {
@@ -39,7 +39,7 @@ pub struct InvalidAbi {
     pub valid_abis: String,
 }
 
-#[derive(SessionDiagnostic, Clone, Copy)]
+#[derive(Diagnostic, Clone, Copy)]
 #[diag(ast_lowering::assoc_ty_parentheses)]
 pub struct AssocTyParentheses {
     #[primary_span]
@@ -54,7 +54,7 @@ pub enum AssocTyParenthesesSub {
     NotEmpty { open_param: Span, close_param: Span },
 }
 
-impl AddSubdiagnostic for AssocTyParenthesesSub {
+impl AddToDiagnostic for AssocTyParenthesesSub {
     fn add_to_diagnostic(self, diag: &mut Diagnostic) {
         match self {
             Self::Empty { parentheses_span } => diag.multipart_suggestion(
@@ -71,38 +71,38 @@ impl AddSubdiagnostic for AssocTyParenthesesSub {
     }
 }
 
-#[derive(SessionDiagnostic)]
+#[derive(Diagnostic)]
 #[diag(ast_lowering::misplaced_impl_trait, code = "E0562")]
 pub struct MisplacedImplTrait<'a> {
     #[primary_span]
     pub span: Span,
     pub position: DiagnosticArgFromDisplay<'a>,
 }
 
-#[derive(SessionDiagnostic, Clone, Copy)]
+#[derive(Diagnostic, Clone, Copy)]
 #[diag(ast_lowering::rustc_box_attribute_error)]
 pub struct RustcBoxAttributeError {
     #[primary_span]
     pub span: Span,
 }
 
-#[derive(SessionDiagnostic, Clone, Copy)]
+#[derive(Diagnostic, Clone, Copy)]
 #[diag(ast_lowering::underscore_expr_lhs_assign)]
 pub struct UnderscoreExprLhsAssign {
     #[primary_span]
     #[label]
     pub span: Span,
 }
 
-#[derive(SessionDiagnostic, Clone, Copy)]
+#[derive(Diagnostic, Clone, Copy)]
 #[diag(ast_lowering::base_expression_double_dot)]
 pub struct BaseExpressionDoubleDot {
     #[primary_span]
     #[label]
     pub span: Span,
 }
 
-#[derive(SessionDiagnostic, Clone, Copy)]
+#[derive(Diagnostic, Clone, Copy)]
 #[diag(ast_lowering::await_only_in_async_fn_and_blocks, code = "E0728")]
 pub struct AwaitOnlyInAsyncFnAndBlocks {
     #[primary_span]
@@ -112,58 +112,58 @@ pub struct AwaitOnlyInAsyncFnAndBlocks {
     pub item_span: Option<Span>,
 }
 
-#[derive(SessionDiagnostic, Clone, Copy)]
+#[derive(Diagnostic, Clone, Copy)]
 #[diag(ast_lowering::generator_too_many_parameters, code = "E0628")]
 pub struct GeneratorTooManyParameters {
     #[primary_span]
     pub fn_decl_span: Span,
 }
 
-#[derive(SessionDiagnostic, Clone, Copy)]
+#[derive(Diagnostic, Clone, Copy)]
 #[diag(ast_lowering::closure_cannot_be_static, code = "E0697")]
 pub struct ClosureCannotBeStatic {
     #[primary_span]
     pub fn_decl_span: Span,
 }
 
-#[derive(SessionDiagnostic, Clone, Copy)]
+#[derive(Diagnostic, Clone, Copy)]
 #[help]
 #[diag(ast_lowering::async_non_move_closure_not_supported, code = "E0708")]
 pub struct AsyncNonMoveClosureNotSupported {
     #[primary_span]
     pub fn_decl_span: Span,
 }
 
-#[derive(SessionDiagnostic, Clone, Copy)]
+#[derive(Diagnostic, Clone, Copy)]
 #[diag(ast_lowering::functional_record_update_destructuring_assignment)]
 pub struct FunctionalRecordUpdateDestructuringAssignemnt {
     #[primary_span]
     #[suggestion(code = "", applicability = "machine-applicable")]
     pub span: Span,
 }
 
-#[derive(SessionDiagnostic, Clone, Copy)]
+#[derive(Diagnostic, Clone, Copy)]
 #[diag(ast_lowering::async_generators_not_supported, code = "E0727")]
 pub struct AsyncGeneratorsNotSupported {
     #[primary_span]
     pub span: Span,
 }
 
-#[derive(SessionDiagnostic, Clone, Copy)]
+#[derive(Diagnostic, Clone, Copy)]
 #[diag(ast_lowering::inline_asm_unsupported_target, code = "E0472")]
 pub struct InlineAsmUnsupportedTarget {
     #[primary_span]
     pub span: Span,
 }
 
-#[derive(SessionDiagnostic, Clone, Copy)]
+#[derive(Diagnostic, Clone, Copy)]
 #[diag(ast_lowering::att_syntax_only_x86)]
 pub struct AttSyntaxOnlyX86 {
     #[primary_span]
     pub span: Span,
 }
 
-#[derive(SessionDiagnostic, Clone, Copy)]
+#[derive(Diagnostic, Clone, Copy)]
 #[diag(ast_lowering::abi_specified_multiple_times)]
 pub struct AbiSpecifiedMultipleTimes {
     #[primary_span]
@@ -175,14 +175,14 @@ pub struct AbiSpecifiedMultipleTimes {
     pub equivalent: Option<()>,
 }
 
-#[derive(SessionDiagnostic, Clone, Copy)]
+#[derive(Diagnostic, Clone, Copy)]
 #[diag(ast_lowering::clobber_abi_not_supported)]
 pub struct ClobberAbiNotSupported {
     #[primary_span]
     pub abi_span: Span,
 }
 
-#[derive(SessionDiagnostic)]
+#[derive(Diagnostic)]
 #[note]
 #[diag(ast_lowering::invalid_abi_clobber_abi)]
 pub struct InvalidAbiClobberAbi {
@@ -191,7 +191,7 @@ pub struct InvalidAbiClobberAbi {
     pub supported_abis: String,
 }
 
-#[derive(SessionDiagnostic, Clone, Copy)]
+#[derive(Diagnostic, Clone, Copy)]
 #[diag(ast_lowering::invalid_register)]
 pub struct InvalidRegister<'a> {
     #[primary_span]
@@ -200,7 +200,7 @@ pub struct InvalidRegister<'a> {
     pub error: &'a str,
 }
 
-#[derive(SessionDiagnostic, Clone, Copy)]
+#[derive(Diagnostic, Clone, Copy)]
 #[diag(ast_lowering::invalid_register_class)]
 pub struct InvalidRegisterClass<'a> {
     #[primary_span]
@@ -209,7 +209,7 @@ pub struct InvalidRegisterClass<'a> {
     pub error: &'a str,
 }
 
-#[derive(SessionDiagnostic)]
+#[derive(Diagnostic)]
 #[diag(ast_lowering::invalid_asm_template_modifier_reg_class)]
 pub struct InvalidAsmTemplateModifierRegClass {
     #[primary_span]
@@ -221,15 +221,15 @@ pub struct InvalidAsmTemplateModifierRegClass {
     pub sub: InvalidAsmTemplateModifierRegClassSub,
 }
 
-#[derive(SessionSubdiagnostic)]
+#[derive(Subdiagnostic)]
 pub enum InvalidAsmTemplateModifierRegClassSub {
     #[note(ast_lowering::support_modifiers)]
     SupportModifier { class_name: Symbol, modifiers: String },
     #[note(ast_lowering::does_not_support_modifiers)]
     DoesNotSupportModifier { class_name: Symbol },
 }
 
-#[derive(SessionDiagnostic, Clone, Copy)]
+#[derive(Diagnostic, Clone, Copy)]
 #[diag(ast_lowering::invalid_asm_template_modifier_const)]
 pub struct InvalidAsmTemplateModifierConst {
     #[primary_span]
@@ -239,7 +239,7 @@ pub struct InvalidAsmTemplateModifierConst {
     pub op_span: Span,
 }
 
-#[derive(SessionDiagnostic, Clone, Copy)]
+#[derive(Diagnostic, Clone, Copy)]
 #[diag(ast_lowering::invalid_asm_template_modifier_sym)]
 pub struct InvalidAsmTemplateModifierSym {
     #[primary_span]
@@ -249,15 +249,15 @@ pub struct InvalidAsmTemplateModifierSym {
     pub op_span: Span,
 }
 
-#[derive(SessionDiagnostic, Clone, Copy)]
+#[derive(Diagnostic, Clone, Copy)]
 #[diag(ast_lowering::register_class_only_clobber)]
 pub struct RegisterClassOnlyClobber {
     #[primary_span]
     pub op_span: Span,
     pub reg_class_name: Symbol,
 }
 
-#[derive(SessionDiagnostic, Clone, Copy)]
+#[derive(Diagnostic, Clone, Copy)]
 #[diag(ast_lowering::register_conflict)]
 pub struct RegisterConflict<'a> {
     #[primary_span]
@@ -271,7 +271,7 @@ pub struct RegisterConflict<'a> {
     pub in_out: Option<Span>,
 }
 
-#[derive(SessionDiagnostic, Clone, Copy)]
+#[derive(Diagnostic, Clone, Copy)]
 #[help]
 #[diag(ast_lowering::sub_tuple_binding)]
 pub struct SubTupleBinding<'a> {
@@ -288,7 +288,7 @@ pub struct SubTupleBinding<'a> {
     pub ctx: &'a str,
 }
 
-#[derive(SessionDiagnostic, Clone, Copy)]
+#[derive(Diagnostic, Clone, Copy)]
 #[diag(ast_lowering::extra_double_dot)]
 pub struct ExtraDoubleDot<'a> {
     #[primary_span]
@@ -299,43 +299,43 @@ pub struct ExtraDoubleDot<'a> {
     pub ctx: &'a str,
 }
 
-#[derive(SessionDiagnostic, Clone, Copy)]
+#[derive(Diagnostic, Clone, Copy)]
 #[note]
 #[diag(ast_lowering::misplaced_double_dot)]
 pub struct MisplacedDoubleDot {
     #[primary_span]
     pub span: Span,
 }
 
-#[derive(SessionDiagnostic, Clone, Copy)]
+#[derive(Diagnostic, Clone, Copy)]
 #[diag(ast_lowering::misplaced_relax_trait_bound)]
 pub struct MisplacedRelaxTraitBound {
     #[primary_span]
     pub span: Span,
 }
 
-#[derive(SessionDiagnostic, Clone, Copy)]
+#[derive(Diagnostic, Clone, Copy)]
 #[diag(ast_lowering::not_supported_for_lifetime_binder_async_closure)]
 pub struct NotSupportedForLifetimeBinderAsyncClosure {
     #[primary_span]
     pub span: Span,
 }
 
-#[derive(SessionDiagnostic, Clone, Copy)]
+#[derive(Diagnostic, Clone, Copy)]
 #[diag(ast_lowering::arbitrary_expression_in_pattern)]
 pub struct ArbitraryExpressionInPattern {
     #[primary_span]
     pub span: Span,
 }
 
-#[derive(SessionDiagnostic, Clone, Copy)]
+#[derive(Diagnostic, Clone, Copy)]
 #[diag(ast_lowering::inclusive_range_with_no_end)]
 pub struct InclusiveRangeWithNoEnd {
     #[primary_span]
     pub span: Span,
 }
 
-#[derive(SessionDiagnostic, Clone, Copy)]
+#[derive(Diagnostic, Clone, Copy)]
 #[diag(ast_lowering::trait_fn_async, code = "E0706")]
 #[note]
 #[note(ast_lowering::note2)]