Add missing docs and remove dead code

Author: rylev

compiler/rustc_errors/src/lib.rs

@@ -521,14 +521,18 @@ impl Handler {
     }
 
     /// Construct a builder at the `Warning` level at the given `span` and with the `msg`.
-    /// Cancel the builder if warnings cannot be emitted
+    ///
+    /// The builder will be canceled if warnings cannot be emitted.
     pub fn struct_span_warn(&self, span: impl Into<MultiSpan>, msg: &str) -> DiagnosticBuilder<'_> {
         let mut result = self.struct_warn(msg);
         result.set_span(span);
         result
     }
 
     /// Construct a builder at the `Warning` level at the given `span` and with the `msg`.
+    ///
+    /// This will "force" the warning meaning it will not be canceled even
+    /// if warnings cannot be emitted.
     pub fn struct_span_force_warn(
         &self,
         span: impl Into<MultiSpan>,
@@ -564,7 +568,8 @@ impl Handler {
     }
 
     /// Construct a builder at the `Warning` level with the `msg`.
-    /// Cancel the builder if warnings cannot be emitted
+    ///
+    /// The builder will be canceled if warnings cannot be emitted.
     pub fn struct_warn(&self, msg: &str) -> DiagnosticBuilder<'_> {
         let mut result = DiagnosticBuilder::new(self, Level::Warning, msg);
         if !self.flags.can_emit_warnings {
@@ -574,6 +579,9 @@ impl Handler {
     }
 
     /// Construct a builder at the `Warning` level with the `msg`.
+    ///
+    /// This will "force" a warning meaning it will not be canceled even
+    /// if warnings cannot be emitted.
     pub fn struct_force_warn(&self, msg: &str) -> DiagnosticBuilder<'_> {
         DiagnosticBuilder::new(self, Level::Warning, msg)
     }

compiler/rustc_middle/src/lint.rs

@@ -251,9 +251,6 @@ pub fn struct_lint_level<'s, 'd>(
         let has_future_breakage =
             future_incompatible.map_or(false, |incompat| incompat.future_breakage.is_some());
 
-        let is_force_warn = matches!(level, Level::ForceWarn)
-            || matches!(src, LintLevelSource::CommandLine(_, Level::ForceWarn));
-
         let mut err = match (level, span) {
             (Level::Allow, span) => {
                 if has_future_breakage {
@@ -359,6 +356,7 @@ pub fn struct_lint_level<'s, 'd>(
             }
         }
 
+        let is_force_warn = matches!(level, Level::ForceWarn);
         err.code(DiagnosticId::Lint { name, has_future_breakage, is_force_warn });
 
         if let Some(future_incompatible) = future_incompatible {