Give `DiagnosticBuilder` a default type.

`IntoDiagnostic` defaults to `ErrorGuaranteed`, because errors are the
most common diagnostic level. It makes sense to do likewise for the
closely-related (and much more widely used) `DiagnosticBuilder` type,
letting us write `DiagnosticBuilder<'a, ErrorGuaranteed>` as just
`DiagnosticBuilder<'a>`. This cuts over 200 lines of code due to many
multi-line things becoming single line things.

2 files changed, 8 insertions, 14 deletions

diff --git a/compiler/rustc_errors/src/diagnostic_builder.rs b/compiler/rustc_errors/src/diagnostic_builder.rs
index 828560ec452..e8cad62f393 100644
--- a/compiler/rustc_errors/src/diagnostic_builder.rs
+++ b/compiler/rustc_errors/src/diagnostic_builder.rs
@@ -43,7 +43,7 @@ where
 /// extending `DiagCtxtFlags`.
 #[must_use]
 #[derive(Clone)]
-pub struct DiagnosticBuilder<'a, G: EmissionGuarantee> {
+pub struct DiagnosticBuilder<'a, G: EmissionGuarantee = ErrorGuaranteed> {
     inner: DiagnosticBuilderInner<'a>,
     _marker: PhantomData<G>,
 }
@@ -128,7 +128,7 @@ impl<'a, G: EmissionGuarantee> DiagnosticBuilder<'a, G> {
     }
 }
 
-impl<'a> DiagnosticBuilder<'a, ErrorGuaranteed> {
+impl<'a> DiagnosticBuilder<'a> {
     /// Discard the guarantee `.emit()` would return, in favor of having the
     /// type `DiagnosticBuilder<'a, ()>`. This may be necessary whenever there
     /// is a common codepath handling both errors and warnings.
diff --git a/compiler/rustc_errors/src/lib.rs b/compiler/rustc_errors/src/lib.rs
index dafb67932a0..c48fe1ca8c2 100644
--- a/compiler/rustc_errors/src/lib.rs
+++ b/compiler/rustc_errors/src/lib.rs
@@ -91,7 +91,7 @@ mod styled_buffer;
 mod tests;
 pub mod translation;
 
-pub type PErr<'a> = DiagnosticBuilder<'a, ErrorGuaranteed>;
+pub type PErr<'a> = DiagnosticBuilder<'a>;
 pub type PResult<'a, T> = Result<T, PErr<'a>>;
 
 rustc_fluent_macro::fluent_messages! { "../messages.ftl" }
@@ -788,7 +788,7 @@ impl DiagCtxt {
         &self,
         span: impl Into<MultiSpan>,
         msg: impl Into<DiagnosticMessage>,
-    ) -> DiagnosticBuilder<'_, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'_> {
         let mut result = self.struct_err(msg);
         result.set_span(span);
         result
@@ -802,7 +802,7 @@ impl DiagCtxt {
         span: impl Into<MultiSpan>,
         msg: impl Into<DiagnosticMessage>,
         code: DiagnosticId,
-    ) -> DiagnosticBuilder<'_, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'_> {
         let mut result = self.struct_span_err(span, msg);
         result.code(code);
         result
@@ -812,10 +812,7 @@ impl DiagCtxt {
     // FIXME: This method should be removed (every error should have an associated error code).
     #[rustc_lint_diagnostics]
     #[track_caller]
-    pub fn struct_err(
-        &self,
-        msg: impl Into<DiagnosticMessage>,
-    ) -> DiagnosticBuilder<'_, ErrorGuaranteed> {
+    pub fn struct_err(&self, msg: impl Into<DiagnosticMessage>) -> DiagnosticBuilder<'_> {
         DiagnosticBuilder::new(self, Level::Error { lint: false }, msg)
     }
 
@@ -826,7 +823,7 @@ impl DiagCtxt {
         &self,
         msg: impl Into<DiagnosticMessage>,
         code: DiagnosticId,
-    ) -> DiagnosticBuilder<'_, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'_> {
         let mut result = self.struct_err(msg);
         result.code(code);
         result
@@ -1221,10 +1218,7 @@ impl DiagCtxt {
     }
 
     #[track_caller]
-    pub fn create_err<'a>(
-        &'a self,
-        err: impl IntoDiagnostic<'a>,
-    ) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
+    pub fn create_err<'a>(&'a self, err: impl IntoDiagnostic<'a>) -> DiagnosticBuilder<'a> {
         err.into_diagnostic(self, Level::Error { lint: false })
     }