Allow any pretty printed line to have at least 60 chars

compiler/rustc_ast_pretty/src/pp.rs

@@ -136,6 +136,7 @@ mod ring;
 
 use ring::RingBuffer;
 use std::borrow::Cow;
+use std::cmp;
 use std::collections::VecDeque;
 use std::iter;
 
@@ -199,10 +200,13 @@ enum PrintFrame {
 
 const SIZE_INFINITY: isize = 0xffff;
 
+/// Target line width.
+const MARGIN: isize = 78;
+/// Every line is allowed at least this much space, even if highly indented.
+const MIN_SPACE: isize = 60;
+
 pub struct Printer {
     out: String,
-    /// Width of lines we're constrained to
-    margin: isize,
     /// Number of spaces left on line
     space: isize,
     /// Ring-buffer of tokens and calculated sizes
@@ -237,11 +241,9 @@ struct BufEntry {
 
 impl Printer {
     pub fn new() -> Self {
-        let linewidth = 78;
         Printer {
             out: String::new(),
-            margin: linewidth as isize,
-            space: linewidth as isize,
+            space: MARGIN,
             buf: RingBuffer::new(),
             left_total: 0,
             right_total: 0,
@@ -395,7 +397,7 @@ impl Printer {
             self.print_stack.push(PrintFrame::Broken { indent: self.indent, breaks: token.breaks });
             self.indent = match token.indent {
                 IndentStyle::Block { offset } => (self.indent as isize + offset) as usize,
-                IndentStyle::Visual => (self.margin - self.space) as usize,
+                IndentStyle::Visual => (MARGIN - self.space) as usize,
             };
         } else {
             self.print_stack.push(PrintFrame::Fits);
@@ -421,7 +423,7 @@ impl Printer {
             self.out.push('\n');
             let indent = self.indent as isize + token.offset;
             self.pending_indentation = indent;
-            self.space = self.margin - indent;
+            self.space = cmp::max(MARGIN - indent, MIN_SPACE);
         }
     }
 

src/test/pretty/issue-4264.pp

@@ -35,8 +35,7 @@
                             for<'r> fn(Arguments<'r>) -> String {format})(((::core::fmt::Arguments::new_v1
                                 as
                                 fn(&[&'static str], &[ArgumentV1]) -> Arguments {Arguments::new_v1})((&([("test"
-                                            as &str)] as [&str; 1]) as
-                                &[&str; 1]),
+                                            as &str)] as [&str; 1]) as &[&str; 1]),
                             (&([] as [ArgumentV1; 0]) as &[ArgumentV1; 0])) as
                             Arguments)) as String);
                 (res as String)

src/test/ui/match/issue-82392.stdout

@@ -11,7 +11,6 @@ pub fn main() ({
                 ({ } as
                     ()) else if (let Some(a) =
                        ((Some as
-                               fn(i32) -> Option<i32> {Option::<i32>::Some})((3
-                               as i32)) as Option<i32>) as bool) ({ } as ())
-                   as ())
+                               fn(i32) -> Option<i32> {Option::<i32>::Some})((3 as i32)) as
+                           Option<i32>) as bool) ({ } as ()) as ())
                } as ())

src/test/ui/proc-macro/quote-debug.stdout

@@ -27,8 +27,7 @@ fn main() {
                         crate::TokenStream::from(crate::TokenTree::Literal({
                                     let mut iter =
                                         "\"world\"".parse::<crate::TokenStream>().unwrap().into_iter();
-                                    if let (Some(crate::TokenTree::Literal(mut lit)),
-                                                None) =
+                                    if let (Some(crate::TokenTree::Literal(mut lit)), None) =
                                                 (iter.next(), iter.next()) {
                                             lit.set_span(crate::Span::recover_proc_macro_span(2));
                                             lit