new pretty printer

3 files changed, 736 insertions, 405 deletions

diff --git a/src/comp/pretty/pp.rs b/src/comp/pretty/pp.rs
index 11c18edd88a..88d50e34083 100644
--- a/src/comp/pretty/pp.rs
+++ b/src/comp/pretty/pp.rs
@@ -2,267 +2,541 @@ import std::io;
 import std::vec;
 import std::str;
 
-tag boxtype {box_h; box_v; box_hv; box_align;}
-tag contexttype {cx_h; cx_v;}
-tag scantype {scan_hv; scan_h; scan_none;}
+/*
+ * This pretty-printer is a direct reimplementation of Philip Karlton's
+ * Mesa pretty-printer, as described in appendix A of
+ *
+ *     STAN-CS-79-770: "Pretty Printing", by Derek C. Oppen.
+ *     Stanford Department of Computer Science, 1979.
+ *
+ * The algorithm's aim is to break a stream into as few lines as possible
+ * while respecting the indentation-consistency requirements of the enclosing
+ * block, and avoiding breaking at silly places on block boundaries, for
+ * example, between "x" and ")" in "x)".
+ *
+ * I am implementing this algorithm because it comes with 20 pages of
+ * documentation explaining its theory, and because it addresses the set of
+ * concerns I've seen other pretty-printers fall down on. Weirdly. Even though
+ * it's 32 years old and not written in Haskell. What can I say?
+ *
+ * Despite some redundancies and quirks in the way it's implemented in that
+ * paper, I've opted to keep the implementation here as similar as I can,
+ * changing only what was blatantly wrong, a typo, or sufficiently
+ * non-idiomatic rust that it really stuck out.
+ *
+ * In particular you'll see a certain amount of churn related to INTEGER vs.
+ * CARDINAL in the Mesa implementation. Mesa apparently interconverts the two
+ * somewhat readily? In any case, I've used uint for indices-in-buffers and
+ * ints for character-sizes-and-indentation-offsets. This respects the need
+ * for ints to "go negative" while carrying a pending-calculation balance, and
+ * helps differentiate all the numbers flying around internally (slightly).
+ *
+ * I also inverted the indentation arithmetic used in the print stack, since
+ * the Mesa implementation (somewhat randomly) stores the offset on the print
+ * stack in terms of margin-col rather than col itself. I store col.
+ */
+
+tag breaks { consistent; inconsistent; }
+type break_t = rec(int offset, int blank_space);
+type begin_t = rec(int offset, breaks breaks);
 
 tag token {
-  brk(uint);
-  hardbrk;
-  word(str);
-  cword(str); // closing token
-  open(boxtype, uint);
-  close;
+    STRING(str);
+    BREAK(break_t);
+    BEGIN(begin_t);
+    END;
+    EOF;
 }
 
-type context = rec(contexttype tp, uint indent);
-
-type ps = @rec(mutable vec[context] context,
-               uint width,
-               io::writer out,
-               mutable uint col,
-               mutable uint spaces,
-               mutable vec[token] buffered,
-               mutable scantype scanning,
-               mutable vec[boxtype] scandepth,
-               mutable uint scancol,
-               mutable bool start_of_line,
-               mutable bool start_of_box,
-               mutable bool potential_brk);
-
-fn mkstate(io::writer out, uint width) -> ps {
-  let vec[context] stack = [rec(tp=cx_v, indent=0u)];
-  let vec[token] buff = [];
-  let vec[boxtype] sd = [];
-  ret @rec(mutable context=stack,
-           width=width,
-           out=out,
-           mutable col=0u,
-           mutable spaces=0u,
-           mutable buffered=buff,
-           mutable scanning=scan_none,
-           mutable scandepth=sd,
-           mutable scancol=0u,
-           mutable start_of_line=true,
-           mutable start_of_box=true,
-           mutable potential_brk=false);
-}
 
-fn write_spaces(ps p, uint i) {
-  while (i > 0u) {
-    i -= 1u;
-    p.out.write_str(" ");
-  }
+fn tok_str(token t) -> str {
+    alt (t) {
+        case (STRING(?s)) { ret "STR(" + s + ")"; }
+        case (BREAK(_)) { ret "BREAK"; }
+        case (BEGIN(_)) { ret "BEGIN"; }
+        case (END) { ret "END"; }
+        case (EOF) { ret "EOF"; }
+    }
 }
 
-fn push_context(ps p, contexttype tp, uint indent) {
-  before_print(p, false);
-  vec::push[context](p.context, rec(tp=tp, indent=indent));
-  p.start_of_box = true;
+fn buf_str(vec[token] toks, vec[int] szs,
+           uint left, uint right, uint lim) -> str {
+    auto n = vec::len(toks);
+    assert n == vec::len(szs);
+    auto i = left;
+    auto L = lim;
+    auto s = "[";
+    while (i != right && L != 0u) {
+        L -= 1u;
+        if (i != left) {
+            s += ", ";
+        }
+        s += #fmt("%d=%s", szs.(i), tok_str(toks.(i)));
+        i += 1u;
+        i %= n;
+    }
+    s += "]";
+    ret s;
 }
 
-fn pop_context(ps p) {
-  vec::pop[context](p.context);
-}
 
-fn add_token(ps p, token tok) {
-  if (p.width == 0u) {direct_token(p, tok);}
-  else if (p.scanning == scan_none) {do_token(p, tok);}
-  else {buffer_token(p, tok);}
-}
+tag print_stack_break { fits; broken(breaks); }
+type print_stack_elt = rec(int offset, print_stack_break pbreak);
 
-fn direct_token(ps p, token tok) {
-  alt (tok) {
-    case (brk(?sz)) {write_spaces(p, sz);}
-    case (word(?w)) {p.out.write_str(w);}
-    case (cword(?w)) {p.out.write_str(w);}
-    case (_) {}
-  }
-}
+const int size_infinity = 0xffff;
 
-fn buffer_token(ps p, token tok) {
-  p.buffered += [tok];
-  auto col = p.scancol;
-  p.scancol = col + token_size(tok);
-  if (p.scancol > p.width) {
-    finish_scan(p, false);
-  } else {
-    alt (tok) {
-      case (open(?tp,_)) {
-        vec::push[boxtype](p.scandepth, tp);
-        if (p.scanning == scan_h) {
-          if (tp == box_h) {
-            check_potential_brk(p);
-          }
-        }
-      }
-      case (close) {
-        vec::pop[boxtype](p.scandepth);
-        if (vec::len[boxtype](p.scandepth) == 0u) {
-          finish_scan(p, true);
-        }
-      }
-      case (brk(_)) {
-        if (p.scanning == scan_h) {
-          if (p.scandepth.(vec::len[boxtype](p.scandepth)-1u) == box_v) {
-            finish_scan(p, true);
-          }
-        }
-      }
-      case (_) {}
-    }
-  }
-}
+fn mk_printer(io::writer out, uint linewidth) -> printer {
 
-fn check_potential_brk(ps p) {
-  for (boxtype tp in p.scandepth) {
-    if (tp != box_h) {ret;}
-  }
-  p.potential_brk = true;
+    // Yes 3, it makes the ring buffers big enough to never
+    // fall behind.
+    let uint n = 3u * linewidth;
+
+    log #fmt("mk_printer %u", linewidth);
+
+    let vec[token] token = vec::init_elt[token](EOF, n);
+    let vec[int] size = vec::init_elt[int](0, n);
+    let vec[uint] scan_stack = vec::init_elt[uint](0u, n);
+    let vec[print_stack_elt] print_stack = [];
+
+    ret printer(out,
+                n,
+                linewidth as int, // margin
+                linewidth as int, // space
+                0u,               // left
+                0u,               // right
+                token,
+                size,
+                0,                // left_total
+                0,                // right_total
+                scan_stack,
+                true,             // scan_stack_empty
+                0u,               // top
+                0u,               // bottom
+                print_stack);
 }
 
-fn finish_scan(ps p, bool fits) {
-  auto buf = p.buffered;
-  auto front = vec::shift[token](buf);
-  auto chosen_tp = cx_h;
-  if (!fits) {chosen_tp = cx_v;}
-  alt (front) {
-    case (open(box_hv, ?ind)) {
-      push_context(p, chosen_tp, base_indent(p) + ind);
+/*
+ * In case you do not have the paper, here is an explanation of what's going
+ * on.
+ *
+ * There is a stream of input tokens flowing through this printer.
+ *
+ * The printer buffers up to 3N tokens inside itself, where N is linewidth.
+ * Yes, linewidth is chars and tokens are multi-char, but in the worst
+ * case every token worth buffering is 1 char long, so it's ok.
+ *
+ * Tokens are STRING, BREAK, and BEGIN/END to delimit blocks.
+ *
+ * BEGIN tokens can carry an offset, saying "how far to indent when you break
+ * inside here", as well as a flag indicating "consistent" or "inconsistent"
+ * breaking. Consistent breaking means that after the first break, no attempt
+ * will be made to flow subsequent breaks together onto lines. Inconsistent
+ * is the opposite. Inconsistent breaking example would be, say:
+ *
+ *  foo(hello, there, good, friends)
+ *
+ * breaking inconsistently to become
+ *
+ *  foo(hello, there
+ *      good, friends);
+ *
+ * whereas a consistent breaking would yield:
+ *
+ *  foo(hello,
+ *      there
+ *      good,
+ *      friends);
+ *
+ * That is, in the consistent-break blocks we value vertical alignment
+ * more than the ability to cram stuff onto a line. But in all cases if it
+ * can make a block a one-liner, it'll do so.
+ *
+ * Carrying on with high-level logic:
+ *
+ * The buffered tokens go through a ring-buffer, 'tokens'. The 'left' and
+ * 'right' indices denote the active portion of the ring buffer as well as
+ * describing hypothetical points-in-the-infinite-stream at most 3N tokens
+ * apart (i.e. "not wrapped to ring-buffer boundaries"). The paper will switch
+ * between using 'left' and 'right' terms to denote the wrapepd-to-ring-buffer
+ * and point-in-infinite-stream senses freely.
+ *
+ * There is a parallel ring buffer, 'size', that holds the calculated size of
+ * each token. Why calculated? Because for BEGIN/END pairs, the "size"
+ * includes everything betwen the pair. That is, the "size" of BEGIN is
+ * actually the sum of the sizes of everything between BEGIN and the paired
+ * END that follows. Since that is arbitrarily far in the future, 'size' is
+ * being rewritten regularly while the printer runs; in fact most of the
+ * machinery is here to work out 'size' entries on the fly (and give up when
+ * they're so obviously over-long that "infinity" is a good enough
+ * approximation for purposes of line breaking).
+ *
+ * The "input side" of the printer is managed as an abstract process called
+ * SCAN, which uses 'scan_stack', 'scan_stack_empty', 'top' and 'bottom', to
+ * manage calculating 'size'. SCAN is, in other words, the process of
+ * calculating 'size' entries.
+ *
+ * The "output side" of the printer is managed by an abstract process called
+ * PRINT, which uses 'print_stack', 'margin' and 'space' to figure out what to
+ * do with each token/size pair it consumes as it goes. It's trying to consume
+ * the entire buffered window, but can't output anything until the size is >=
+ * 0 (sizes are set to negative while they're pending calculation).
+ *
+ * So SCAN takeks input and buffers tokens and pending calculations, while
+ * PRINT gobbles up completed calculations and tokens from the buffer. The
+ * theory is that the two can never get more than 3N tokens apart, because
+ * once there's "obviously" too much data to fit on a line, in a size
+ * calculation, SCAN will write "infinity" to the size and let PRINT consume
+ * it.
+ *
+ * In this implementation (following the paper, again) the SCAN process is
+ * the method called 'pretty_print', and the 'PRINT' process is the method
+ * called 'print'.
+ */
+
+obj printer(io::writer out,
+            uint buf_len,
+            mutable int margin,        // width of lines we're constrained to
+            mutable int space,         // number of spaces left on line
+
+            mutable uint left,         // index of left side of input stream
+            mutable uint right,        // index of right side of input stream
+            mutable vec[token] token,  // ring-buffer stream goes through
+            mutable vec[int] size,     // ring-buffer of calculated sizes
+            mutable int left_total,    // running size of stream "...left"
+            mutable int right_total,   // running size of stream "...right"
+
+            // pseudo-stack, really a ring too. Holds the primary-ring-buffers
+            // index of the BEGIN that started the current block, possibly
+            // with the most recent BREAK after that BEGIN (if there is any)
+            // on top of it. Stuff is flushed off the bottom as it becomes
+            // irrelevant due to the primary ring-buffer advancing.
+
+            mutable vec[uint] scan_stack,
+            mutable bool scan_stack_empty, // top==bottom disambiguator
+            mutable uint top,              // index of top of scan_stack
+            mutable uint bottom,           // index of bottom of scan_stack
+
+            // stack of blocks-in-progress being flushed by print
+            mutable vec[print_stack_elt] print_stack
+            ) {
+
+
+    fn pretty_print(token t) {
+
+        log #fmt("pp [%u,%u]", left, right);
+        alt (t) {
+
+            case (EOF) {
+                if (!scan_stack_empty) {
+                    self.check_stack(0);
+                    self.advance_left(token.(left), size.(left));
+                }
+                self.indent(0);
+            }
+
+            case (BEGIN(?b)) {
+                if (scan_stack_empty) {
+                    left_total = 1;
+                    right_total = 1;
+                    left = 0u;
+                    right = 0u;
+                } else {
+                    self.advance_right();
+                }
+                log #fmt("pp BEGIN/buffer [%u,%u]", left, right);
+                token.(right) = t;
+                size.(right) = -right_total;
+                self.scan_push(right);
+            }
+
+            case (END) {
+                if (scan_stack_empty) {
+                    log #fmt("pp END/print [%u,%u]", left, right);
+                    self.print(t, 0);
+                } else {
+                    log #fmt("pp END/buffer [%u,%u]", left, right);
+                    self.advance_right();
+                    token.(right) = t;
+                    size.(right) = -1;
+                    self.scan_push(right);
+                }
+            }
+
+            case (BREAK(?b)) {
+                if (scan_stack_empty) {
+                    left_total = 1;
+                    right_total = 1;
+                    left = 0u;
+                    right = 0u;
+                } else {
+                    self.advance_right();
+                }
+                log #fmt("pp BREAK/buffer [%u,%u]", left, right);
+                self.check_stack(0);
+                self.scan_push(right);
+                token.(right) = t;
+                size.(right) = -right_total;
+                right_total += b.blank_space;
+            }
+
+            case (STRING(?s)) {
+                auto len = str::char_len(s) as int;
+                if (scan_stack_empty) {
+                    log #fmt("pp STRING/print [%u,%u]", left, right);
+                    self.print(t, len);
+                } else {
+                    log #fmt("pp STRING/buffer [%u,%u]", left, right);
+                    self.advance_right();
+                    token.(right) = t;
+                    size.(right) = len;
+                    right_total += len;
+                    self.check_stream();
+                }
+            }
+        }
     }
-    case (open(box_align, _)) {
-      push_context(p, chosen_tp, p.col);
+
+    fn check_stream() {
+        log #fmt("check_stream [%u, %u] with left_total=%d, right_total=%d",
+                     left, right, left_total, right_total);;
+        if (right_total - left_total > space) {
+            log #fmt("scan window is %d, longer than space on line (%d)",
+                         right_total - left_total, space);
+            if (!scan_stack_empty) {
+                if (left == scan_stack.(bottom)) {
+                    log #fmt("setting %u to infinity and popping", left);
+                    size.(self.scan_pop_bottom()) = size_infinity;
+                }
+            }
+            self.advance_left(token.(left), size.(left));
+            if (left != right) {
+                self.check_stream();
+            }
+        }
     }
-    case (open(box_h, ?ind)) {
-      if (!fits && !p.start_of_box && !p.start_of_line && !p.potential_brk) {
-        line_break(p);
-      }
-      push_context(p, cx_h, base_indent(p) + ind);
+
+    fn scan_push(uint x) {
+        log #fmt("scan_push %u", x);
+        if (scan_stack_empty) {
+            scan_stack_empty = false;
+        } else {
+            top += 1u;
+            top %= buf_len;
+            assert top != bottom;
+        }
+        scan_stack.(top) = x;
     }
-  }
-  p.scandepth = [];
-  p.scanning = scan_none;
-  for (token t in buf) { add_token(p, t); }
-}
 
-fn start_scan(ps p, token tok, scantype tp) {
-  p.buffered = [];
-  p.scancol = p.col;
-  p.scanning = tp;
-  buffer_token(p, tok);
-  p.potential_brk = false;
-}
+    fn scan_pop() -> uint {
+        assert !scan_stack_empty;
+        auto x = scan_stack.(top);
+        if (top == bottom) {
+            scan_stack_empty = true;
+        } else {
+            top += (buf_len - 1u);
+            top %= buf_len;
+        }
+        ret x;
+    }
 
-fn cur_context(ps p) -> context {
-  ret p.context.(vec::len[context](p.context)-1u);
-}
-fn base_indent(ps p) -> uint {
-  auto i = vec::len[context](p.context);
-  while (i > 0u) {
-    i -= 1u;
-    auto cx = p.context.(i);
-    if (cx.tp == cx_v) {ret cx.indent;}
-  }
-  ret 0u;
-}
+    fn scan_top() -> uint {
+        assert !scan_stack_empty;
+        ret scan_stack.(top);
+    }
 
-fn cx_is(contexttype a, contexttype b) -> bool {
-  if (a == b) {ret true;}
-  else {ret false;}
-}
-fn box_is(boxtype a, boxtype b) -> bool {
-  if (a == b) {ret true;}
-  else {ret false;}
-}
+    fn scan_pop_bottom() -> uint {
+        assert !scan_stack_empty;
+        auto x = scan_stack.(bottom);
+        if (top == bottom) {
+            scan_stack_empty = true;
+        } else {
+            bottom += 1u;
+            bottom %= buf_len;
+        }
+        ret x;
+    }
 
-fn do_token(ps p, token tok) {
-  auto start_of_box = p.start_of_box;
-  p.start_of_box = false;
-  alt (tok) {
-    case (brk(?sz)) {
-      if (cx_is(cur_context(p).tp, cx_v) || sz + p.col > p.width) {
-        line_break(p);
-      }
-      else {
-        p.spaces += sz;
-      }
+    fn advance_right() {
+        right += 1u;
+        right %= buf_len;
+        assert right != left;
     }
-    case (hardbrk) {
-      line_break(p);
+
+    fn advance_left(token x, int L) {
+        log #fmt("advnce_left [%u,%u], sizeof(%u)=%d", left, right, left, L);
+        if (L >= 0) {
+            self.print(x, L);
+            alt (x) {
+                case (BREAK(?b)) {
+                    left_total += b.blank_space;
+                }
+                case (STRING(?s)) {
+                    // I think? paper says '1' here but 1 and L look same in
+                    // it.
+                    left_total += L;
+                }
+                case (_) {}
+            }
+            if (left != right) {
+                left += 1u;
+                left %= buf_len;
+                self.advance_left(token.(left), size.(left));
+            }
+        }
     }
-    case (word(?w)) {
-      auto len = str::char_len(w);
-      if (len + p.col + p.spaces > p.width && !start_of_box &&
-          !p.start_of_line) {
-        line_break(p);
-      }
-      before_print(p, false);
-      p.out.write_str(w);
-      p.col += len;
+
+    fn check_stack(int k) {
+        if (!scan_stack_empty) {
+            auto x = self.scan_top();
+            alt (token.(x)) {
+                case (BEGIN(?b)) {
+                    if (k > 0) {
+                        size.(self.scan_pop()) = size.(x) + right_total;
+                        self.check_stack(k - 1);
+                    }
+                }
+                case (END) {
+                    // paper says + not =, but that makes no sense.
+                    size.(self.scan_pop()) = 1;
+                    self.check_stack(k + 1);
+                }
+                case (_) {
+                    size.(self.scan_pop()) = size.(x) + right_total;
+                    if (k > 0) {
+                        self.check_stack(k);
+                    }
+                }
+            }
+        }
     }
-    case (cword(?w)) {
-      before_print(p, true);
-      p.out.write_str(w);
-      p.col += str::char_len(w);
+
+    fn print_newline(int amount) {
+        log #fmt("NEWLINE %d", amount);
+        out.write_str("\n");
+        self.indent(amount);
     }
-    case (open(?tp, ?indent)) {
-      if (tp == box_v) {
-        push_context(p, cx_v, base_indent(p) + indent);
-      } else if (box_is(tp, box_h) && cx_is(cur_context(p).tp, cx_v)) {
-        push_context(p, cx_h, base_indent(p) + indent);
-      } else if (tp == box_h) {
-        p.start_of_box = start_of_box;
-        start_scan(p, tok, scan_h);
-      } else {
-        p.start_of_box = start_of_box;
-        start_scan(p, tok, scan_hv);
-      }
+
+    fn indent(int amount) {
+        log #fmt("INDENT %d", amount);
+        auto u = 0;
+        while (u < amount) {
+            out.write_str(" ");
+            u += 1;
+        }
     }
-    case (close) {
-      pop_context(p);
+
+    fn print(token x, int L) {
+        log #fmt("print %s %d (remaining line space=%d)", tok_str(x), L, space);
+        log buf_str(token, size, left, right, 6u);
+        alt (x) {
+            case (BEGIN(?b)) {
+                if (L > space) {
+                    auto col = (margin - space) + b.offset;
+                    log #fmt("print BEGIN -> push broken block at col %d", col);
+                    vec::push(print_stack,
+                              rec(offset = col,
+                                  pbreak = broken(b.breaks)));
+                } else {
+                    log "print BEGIN -> push fitting block";
+                    vec::push(print_stack,
+                              rec(offset = 0,
+                                  pbreak = fits));
+                }
+            }
+
+            case (END) {
+                log "print END -> pop END";
+                assert vec::len(print_stack) != 0u;
+                vec::pop(print_stack);
+            }
+
+            case (BREAK(?b)) {
+
+                auto n = vec::len(print_stack);
+                let print_stack_elt top =
+                    rec(offset=0, pbreak=broken(inconsistent));;
+                if (n != 0u) {
+                    top = print_stack.(n - 1u);
+                }
+
+                alt (top.pbreak) {
+                    case (fits) {
+                        log "print BREAK in fitting block";
+                        space -= b.blank_space;
+                        self.indent(b.blank_space);
+                    }
+
+                    case (broken(consistent)) {
+                        log "print BREAK in consistent block";
+                        self.print_newline(top.offset + b.offset);
+                        space = margin - (top.offset + b.offset);
+                    }
+
+                    case (broken(inconsistent)) {
+                        if (L > space) {
+                            log "print BREAK w/ newline in inconsistent block";
+                            self.print_newline(top.offset + b.offset);
+                            space = margin - (top.offset + b.offset);
+                        } else {
+                            log "print BREAK w/o newline in inconsistent block";
+                            self.indent(b.blank_space);
+                            space -= b.blank_space;
+                        }
+                    }
+                }
+            }
+
+            case (STRING(?s)) {
+                log "print STRING";
+                assert L as uint == str::char_len(s);
+                // assert L <= space;
+                space -= L;
+                out.write_str(s);
+            }
+
+            case (EOF) {
+                // EOF should never get here.
+                fail;
+            }
+        }
     }
-  }
 }
 
-fn line_break(ps p) {
-  p.out.write_str("\n");
-  p.col = 0u;
-  p.spaces = cur_context(p).indent;
-  p.start_of_line = true;
+
+// Convenience functions to talk to the printer.
+
+fn ibox(printer p, uint indent) {
+    p.pretty_print(BEGIN(rec(offset = indent as int,
+                             breaks = inconsistent)));
 }
 
-fn before_print(ps p, bool closing) {
-  if (p.start_of_line) {
-    p.start_of_line = false;
-    if (closing) {p.spaces = base_indent(p);}
-    else {p.spaces = cur_context(p).indent;}
-  }
-  if (p.spaces > 0u) {
-    write_spaces(p, p.spaces);
-    p.col += p.spaces;
-    p.spaces = 0u;
-  }
+fn cbox(printer p, uint indent) {
+    p.pretty_print(BEGIN(rec(offset = indent as int,
+                             breaks = consistent)));
 }
 
-fn token_size(token tok) -> uint {
-  alt (tok) {
-    case (brk(?sz)) {ret sz;}
-    case (hardbrk) {ret 0xFFFFFFu;}
-    case (word(?w)) {ret str::char_len(w);}
-    case (cword(?w)) {ret str::char_len(w);}
-    case (open(_, _)) {ret 0u;}
-    case (close) {ret 0u;}
-  }
+
+fn break_offset(printer p, uint n, int off) {
+    p.pretty_print(BREAK(rec(offset = off,
+                             blank_space = n as int)));
 }
 
-fn box(ps p, uint indent) {add_token(p, open(box_hv, indent));}
-fn abox(ps p) {add_token(p, open(box_align, 0u));}
-fn vbox(ps p, uint indent) {add_token(p, open(box_v, indent));}
-fn hbox(ps p, uint indent) {add_token(p, open(box_h, indent));}
-fn end(ps p) {add_token(p, close);}
-fn wrd(ps p, str wrd) {add_token(p, word(wrd));}
-fn cwrd(ps p, str wrd) {add_token(p, cword(wrd));}
-fn space(ps p) {add_token(p, brk(1u));}
-fn spaces(ps p, uint n) {add_token(p, brk(n));}
-fn line(ps p) {add_token(p, brk(0u));}
-fn hardbreak(ps p) {add_token(p, hardbrk);}
+fn end(printer p) { p.pretty_print(END); }
+fn eof(printer p) { p.pretty_print(EOF); }
+fn wrd(printer p, str wrd) { p.pretty_print(STRING(wrd)); }
+fn spaces(printer p, uint n) { break_offset(p, n, 0); }
+fn space(printer p) { spaces(p, 1u); }
+fn hardbreak(printer p) { spaces(p, 0xffffu); }
+
+
+
+//
+// Local Variables:
+// mode: rust
+// fill-column: 78;
+// indent-tabs-mode: nil
+// c-basic-offset: 4
+// buffer-file-coding-system: utf-8-unix
+// compile-command: "make -k -C $RBUILD 2>&1 | sed -e 's/\\/x\\//x:\\//g'";
+// End:
+//
diff --git a/src/comp/pretty/pprust.rs b/src/comp/pretty/pprust.rs
index 30217230357..1684cb6f66e 100644
--- a/src/comp/pretty/pprust.rs
+++ b/src/comp/pretty/pprust.rs
@@ -7,7 +7,17 @@ import front::ast;
 import front::lexer;
 import middle::ty;
 import util::common;
-import pp::end; import pp::wrd; import pp::space; import pp::line;
+import pp;
+
+import pp::printer;
+import pp::break_offset;
+import pp::cbox;
+import pp::ibox;
+import pp::wrd;
+import pp::space;
+import pp::hardbreak;
+import pp::end;
+import pp::eof;
 
 const uint indent_unit = 4u;
 const uint default_columns = 78u;
@@ -17,7 +27,7 @@ tag mode {
     mo_typed(ty::ctxt);
 }
 
-type ps = @rec(pp::ps s,
+type ps = @rec(pp::printer s,
                option::t[vec[lexer::cmnt]] comments,
                mutable uint cur_cmnt,
                mode mode);
@@ -25,85 +35,102 @@ type ps = @rec(pp::ps s,
 fn print_file(session sess, ast::_mod _mod, str filename, io::writer out,
               mode mode) {
     auto cmnts = lexer::gather_comments(sess, filename);
-    auto s = @rec(s=pp::mkstate(out, default_columns),
+    auto s = @rec(s=pp::mk_printer(out, default_columns),
                   comments=option::some[vec[lexer::cmnt]](cmnts),
                   mutable cur_cmnt=0u,
                   mode=mode);
     print_mod(s, _mod);
+    eof(s.s);
 }
 
 fn ty_to_str(&@ast::ty ty) -> str {
     auto writer = io::string_writer();
-    auto s = @rec(s=pp::mkstate(writer.get_writer(), 0u),
+    auto s = @rec(s=pp::mk_printer(writer.get_writer(), default_columns),
                   comments=option::none[vec[lexer::cmnt]],
                   mutable cur_cmnt=0u,
                   mode=mo_untyped);
     print_type(s, ty);
+    eof(s.s);
     ret writer.get_str();
 }
 
 fn block_to_str(&ast::block blk) -> str {
     auto writer = io::string_writer();
-    auto s = @rec(s=pp::mkstate(writer.get_writer(), 78u),
+    auto s = @rec(s=pp::mk_printer(writer.get_writer(), default_columns),
                   comments=option::none[vec[lexer::cmnt]],
                   mutable cur_cmnt=0u,
                   mode=mo_untyped);
+    cbox(s.s, indent_unit); // containing cbox, will be closed by print-block at }
+    ibox(s.s, 0u); // head-ibox, will be closed by print-block after {
     print_block(s, blk);
+    eof(s.s);
     ret writer.get_str();
 }
 
 fn pat_to_str(&@ast::pat p) -> str {
     auto writer = io::string_writer();
-    auto s = @rec(s=pp::mkstate(writer.get_writer(), 78u),
+    auto s = @rec(s=pp::mk_printer(writer.get_writer(), default_columns),
                   comments=option::none[vec[lexer::cmnt]],
                   mutable cur_cmnt=0u,
                   mode=mo_untyped);
     print_pat(s, p);
+    eof(s.s);
     ret writer.get_str();
 }
 
-fn hbox(ps s) {
-    pp::hbox(s.s, indent_unit);
+fn word_nbsp(ps s, str word) {
+    wrd(s.s, word);
+    wrd(s.s, " ");
 }
-fn wrd1(ps s, str word) {
+
+fn word_space(ps s, str word) {
     wrd(s.s, word);
     space(s.s);
 }
+
 fn popen(ps s) {
     wrd(s.s, "(");
-    pp::abox(s.s);
-}
-fn popen_h(ps s) {
-    wrd(s.s, "(");
-    pp::hbox(s.s, 0u);
 }
+
 fn pclose(ps s) {
-    end(s.s);
     wrd(s.s, ")");
 }
+
+fn head(ps s, str word) {
+    // outer-box is consistent
+    cbox(s.s, indent_unit);
+    // head-box is inconsistent
+    ibox(s.s, str::char_len(word) + 1u);
+    // keyword that starts the head
+    word_nbsp(s, word);
+}
+
 fn bopen(ps s) {
     wrd(s.s, "{");
-    pp::vbox(s.s, indent_unit);
-    line(s.s);
-}
-fn bclose(ps s) {
-    end(s.s);
-    pp::cwrd(s.s, "}");
+    end(s.s); // close the head-box
 }
-fn bclose_c(ps s, common::span span) {
+
+fn bclose(ps s, common::span span) {
     maybe_print_comment(s, span.hi);
-    bclose(s);
+    break_offset(s.s, 1u, -(indent_unit as int));
+    wrd(s.s, "}");
+    end(s.s); // close the outer-box
 }
+
 fn commasep[IN](ps s, vec[IN] elts, fn(ps, &IN) op) {
+    ibox(s.s, 0u);
     auto first = true;
     for (IN elt in elts) {
         if (first) {first = false;}
-        else {wrd1(s, ",");}
+        else {word_space(s, ",");}
         op(s, elt);
     }
+    end(s.s);
 }
+
 fn commasep_cmnt[IN](ps s, vec[IN] elts, fn(ps, &IN) op,
-                            fn(&IN) -> common::span get_span) {
+                     fn(&IN) -> common::span get_span) {
+    ibox(s.s, 0u);
     auto len = vec::len[IN](elts);
     auto i = 0u;
     for (IN elt in elts) {
@@ -114,7 +141,9 @@ fn commasep_cmnt[IN](ps s, vec[IN] elts, fn(ps, &IN) op,
             if (!maybe_print_line_comment(s, get_span(elt))) {space(s.s);}
         }
     }
+    end(s.s);
 }
+
 fn commasep_exprs(ps s, vec[@ast::expr] exprs) {
     fn expr_span(&@ast::expr expr) -> common::span {ret expr.span;}
     auto f = print_expr;
@@ -126,14 +155,18 @@ fn print_mod(ps s, ast::_mod _mod) {
     for (@ast::view_item vitem in _mod.view_items) {
         print_view_item(s, vitem);
     }
-    line(s.s);
-    for (@ast::item item in _mod.items) {print_item(s, item);}
+    for (@ast::item item in _mod.items) {
+        // Mod-level item printing we're a little more space-y about.
+        hardbreak(s.s);
+        print_item(s, item);
+    }
     print_remaining_comments(s);
 }
 
 fn print_type(ps s, &@ast::ty ty) {
+
     maybe_print_comment(s, ty.span.lo);
-    hbox(s);
+    ibox(s.s, 0u);
     alt (ty.node) {
         case (ast::ty_nil) {wrd(s.s, "()");}
         case (ast::ty_bool) {wrd(s.s, "bool");}
@@ -166,7 +199,7 @@ fn print_type(ps s, &@ast::ty ty) {
             wrd(s.s, "rec");
             popen(s);
             fn print_field(ps s, &ast::ty_field f) {
-                hbox(s);
+                cbox(s.s, indent_unit);
                 print_mt(s, f.mt);
                 space(s.s);
                 wrd(s.s, f.ident);
@@ -184,17 +217,16 @@ fn print_type(ps s, &@ast::ty ty) {
             pclose(s);
         }
         case (ast::ty_obj(?methods)) {
-            wrd1(s, "obj");
+            head(s, "obj");
             bopen(s);
             for (ast::ty_method m in methods) {
-                hbox(s);
+                cbox(s.s, indent_unit);
                 print_ty_fn(s, m.proto, option::some[str](m.ident),
                             m.inputs, m.output, m.cf);
                 wrd(s.s, ";");
                 end(s.s);
-                line(s.s);
             }
-            bclose_c(s, ty.span);
+            bclose(s, ty.span);
         }
         case (ast::ty_fn(?proto,?inputs,?output,?cf)) {
             print_ty_fn(s, proto, option::none[str], inputs, output, cf);
@@ -207,53 +239,56 @@ fn print_type(ps s, &@ast::ty ty) {
 }
 
 fn print_item(ps s, @ast::item item) {
+
+    hardbreak(s.s);
     maybe_print_comment(s, item.span.lo);
-    hbox(s);
     alt (item.node) {
         case (ast::item_const(?id, ?ty, ?expr, _, _)) {
-            wrd1(s, "const");
+            head(s, "const");
             print_type(s, ty);
             space(s.s);
-            wrd1(s, id);
-            wrd1(s, "=");
+            word_space(s, id);
+            end(s.s); // end the head-ibox
+            word_space(s, "=");
             print_expr(s, expr);
             wrd(s.s, ";");
+            end(s.s); // end the outer cbox
         }
         case (ast::item_fn(?name,?_fn,?typarams,_,_)) {
             print_fn(s, _fn.decl, name, typarams);
-            space(s.s);
+            wrd(s.s, " ");
             print_block(s, _fn.body);
         }
         case (ast::item_mod(?id,?_mod,_)) {
-            wrd1(s, "mod");
-            wrd1(s, id);
+            head(s, "mod");
             bopen(s);
             for (@ast::item itm in _mod.items) {print_item(s, itm);}
-            bclose_c(s, item.span);
+            bclose(s, item.span);
         }
         case (ast::item_native_mod(?id,?nmod,_)) {
-            wrd1(s, "native");
+            head(s, "native");
             alt (nmod.abi) {
-                case (ast::native_abi_rust) {wrd1(s, "\"rust\"");}
-                case (ast::native_abi_cdecl) {wrd1(s, "\"cdecl\"");}
+                case (ast::native_abi_rust) {word_nbsp(s, "\"rust\"");}
+                case (ast::native_abi_cdecl) {word_nbsp(s, "\"cdecl\"");}
                 case (ast::native_abi_rust_intrinsic) {
-                    wrd1(s, "\"rust-intrinsic\"");
+                    word_nbsp(s, "\"rust-intrinsic\"");
                 }
             }
-            wrd1(s, "mod");
-            wrd1(s, id);
+            word_nbsp(s, "mod");
+            word_nbsp(s, id);
             bopen(s);
             for (@ast::native_item item in nmod.items) {
-                hbox(s);
+                ibox(s.s, indent_unit);
                 maybe_print_comment(s, item.span.lo);
                 alt (item.node) {
                     case (ast::native_item_ty(?id,_)) {
-                        wrd1(s, "type");
+                        word_nbsp(s, "type");
                         wrd(s.s, id);
                     }
                     case (ast::native_item_fn(?id,?lname,?decl,
                                              ?typarams,_,_)) {
                         print_fn(s, decl, id, typarams);
+                        end(s.s); // end head-ibox
                         alt (lname) {
                             case (option::none[str]) {}
                             case (option::some[str](?ss)) {
@@ -265,24 +300,30 @@ fn print_item(ps s, @ast::item item) {
                 wrd(s.s, ";");
                 end(s.s);
             }
-            bclose_c(s, item.span);
+            bclose(s, item.span);
         }
         case (ast::item_ty(?id,?ty,?params,_,_)) {
-            wrd1(s, "type");
+            ibox(s.s, indent_unit);
+            ibox(s.s, 0u);
+            word_nbsp(s, "type");
             wrd(s.s, id);
             print_type_params(s, params);
+            end(s.s); // end the inner ibox
             space(s.s);
-            wrd1(s, "=");
+            word_space(s, "=");
             print_type(s, ty);
             wrd(s.s, ";");
+            end(s.s); // end the outer ibox
+            break_offset(s.s, 0u, 0);
         }
         case (ast::item_tag(?id,?variants,?params,_,_)) {
-            wrd1(s, "tag");
+            head(s, "tag");
             wrd(s.s, id);
             print_type_params(s, params);
             space(s.s);
             bopen(s);
             for (ast::variant v in variants) {
+                space(s.s);
                 maybe_print_comment(s, v.span.lo);
                 wrd(s.s, v.node.name);
                 if (vec::len[ast::variant_arg](v.node.args) > 0u) {
@@ -295,17 +336,17 @@ fn print_item(ps s, @ast::item item) {
                     pclose(s);
                 }
                 wrd(s.s, ";");
-                if (!maybe_print_line_comment(s, v.span)) {line(s.s);}
+                maybe_print_line_comment(s, v.span);
             }
-            bclose_c(s, item.span);
+            bclose(s, item.span);
         }
         case (ast::item_obj(?id,?_obj,?params,_,_)) {
-            wrd1(s, "obj");
+            head(s, "obj");
             wrd(s.s, id);
             print_type_params(s, params);
             popen(s);
             fn print_field(ps s, &ast::obj_field field) {
-                hbox(s);
+                ibox(s.s, indent_unit);
                 print_type(s, field.ty);
                 space(s.s);
                 wrd(s.s, field.ident);
@@ -319,53 +360,52 @@ fn print_item(ps s, @ast::item item) {
             space(s.s);
             bopen(s);
             for (@ast::method meth in _obj.methods) {
-                hbox(s);
                 let vec[ast::ty_param] typarams = [];
+                hardbreak(s.s);
                 maybe_print_comment(s, meth.span.lo);
                 print_fn(s, meth.node.meth.decl, meth.node.ident, typarams);
-                space(s.s);
+                wrd(s.s, " ");
                 print_block(s, meth.node.meth.body);
-                end(s.s);
-                line(s.s);
             }
             alt (_obj.dtor) {
                 case (option::some[@ast::method](?dtor)) {
-                    hbox(s);
-                    wrd1(s, "close");
+                    head(s, "drop");
                     print_block(s, dtor.node.meth.body);
-                    end(s.s);
-                    line(s.s);
                 }
                 case (_) {}
             }
-            bclose_c(s, item.span);
+            bclose(s, item.span);
         }
     }
-    end(s.s);
-    line(s.s);
-    line(s.s);
 }
 
 fn print_block(ps s, ast::block blk) {
     maybe_print_comment(s, blk.span.lo);
     bopen(s);
+    auto first = true;
     for (@ast::stmt st in blk.node.stmts) {
         maybe_print_comment(s, st.span.lo);
         alt (st.node) {
-          case (ast::stmt_decl(?decl,_)) {print_decl(s, decl);}
-          case (ast::stmt_expr(?expr,_)) {print_expr(s, expr);}
+          case (ast::stmt_decl(?decl,_)) {
+              print_decl(s, decl);
+          }
+          case (ast::stmt_expr(?expr,_)) {
+              space(s.s);
+              print_expr(s, expr);
+          }
         }
         if (front::parser::stmt_ends_with_semi(st)) {wrd(s.s, ";");}
-        if (!maybe_print_line_comment(s, st.span)) {line(s.s);}
+        maybe_print_line_comment(s, st.span);
     }
     alt (blk.node.expr) {
         case (option::some[@ast::expr](?expr)) {
+            space(s.s);
             print_expr(s, expr);
-            if (!maybe_print_line_comment(s, expr.span)) {line(s.s);}
+            maybe_print_line_comment(s, expr.span);
         }
         case (_) {}
     }
-    bclose_c(s, blk.span);
+    bclose(s, blk.span);
 }
 
 fn print_literal(ps s, @ast::lit lit) {
@@ -403,7 +443,7 @@ fn print_literal(ps s, @ast::lit lit) {
 
 fn print_expr(ps s, &@ast::expr expr) {
     maybe_print_comment(s, expr.span.lo);
-    hbox(s);
+    ibox(s.s, indent_unit);
 
     alt (s.mode) {
         case (mo_untyped) { /* no-op */ }
@@ -413,18 +453,18 @@ fn print_expr(ps s, &@ast::expr expr) {
     alt (expr.node) {
         case (ast::expr_vec(?exprs,?mut,_)) {
             if (mut == ast::mut) {
-                wrd1(s, "mutable");
+                word_nbsp(s, "mutable");
             }
+            ibox(s.s, indent_unit);
             wrd(s.s, "[");
-            pp::abox(s.s);
             commasep_exprs(s, exprs);
-            end(s.s);
             wrd(s.s, "]");
+            end(s.s);
         }
         case (ast::expr_tup(?exprs,_)) {
             fn printElt(ps s, &ast::elt elt) {
-                hbox(s);
-                if (elt.mut == ast::mut) {wrd1(s, "mutable");}
+                ibox(s.s, indent_unit);
+                if (elt.mut == ast::mut) {word_nbsp(s, "mutable");}
                 print_expr(s, elt.expr);
                 end(s.s);
             }
@@ -438,8 +478,8 @@ fn print_expr(ps s, &@ast::expr expr) {
         }
         case (ast::expr_rec(?fields,?wth,_)) {
             fn print_field(ps s, &ast::field field) {
-                hbox(s);
-                if (field.mut == ast::mut) {wrd1(s, "mutable");}
+                ibox(s.s, indent_unit);
+                if (field.mut == ast::mut) {word_nbsp(s, "mutable");}
                 wrd(s.s, field.ident);
                 wrd(s.s, "=");
                 print_expr(s, field.expr);
@@ -456,8 +496,8 @@ fn print_expr(ps s, &@ast::expr expr) {
             alt (wth) {
                 case (option::some[@ast::expr](?expr)) {
                     if (vec::len[ast::field](fields) > 0u) {space(s.s);}
-                    hbox(s);
-                    wrd1(s, "with");
+                    ibox(s.s, indent_unit);
+                    word_space(s, "with");
                     print_expr(s, expr);
                     end(s.s);
                 }
@@ -484,7 +524,7 @@ fn print_expr(ps s, &@ast::expr expr) {
                     case (_) {wrd(s.s, "_");}
                 }
             }
-            wrd1(s, "bind");
+            word_nbsp(s, "bind");
             print_expr(s, func);
             popen(s);
             auto f = print_opt;
@@ -492,7 +532,7 @@ fn print_expr(ps s, &@ast::expr expr) {
             pclose(s);
         }
     case (ast::expr_spawn(_,_,?e,?es,_)) {
-          wrd1(s, "spawn");
+          word_nbsp(s, "spawn");
           print_expr(s, e);
           popen(s);
           commasep_exprs(s, es);
@@ -502,7 +542,7 @@ fn print_expr(ps s, &@ast::expr expr) {
             auto prec = operator_prec(op);
             print_maybe_parens(s, lhs, prec);
             space(s.s);
-            wrd1(s, ast::binop_to_str(op));
+            word_space(s, ast::binop_to_str(op));
             print_maybe_parens(s, rhs, prec + 1);
         }
         case (ast::expr_unary(?op,?expr,_)) {
@@ -515,111 +555,119 @@ fn print_expr(ps s, &@ast::expr expr) {
         case (ast::expr_cast(?expr,?ty,_)) {
             print_maybe_parens(s, expr, front::parser::as_prec);
             space(s.s);
-            wrd1(s, "as");
+            word_space(s, "as");
             print_type(s, ty);
         }
         case (ast::expr_if(?test,?block,?elseopt,_)) {
-            wrd1(s, "if");
-            popen_h(s);
+            head(s, "if");
+            popen(s);
             print_expr(s, test);
             pclose(s);
             space(s.s);
             print_block(s, block);
             alt (elseopt) {
                 case (option::some[@ast::expr](?_else)) {
-                    space(s.s);
-                    wrd1(s, "else");
-                    print_expr(s, _else);
+                    // NB: we can't use 'head' here since
+                    // it builds a block that starts in the
+                    // wrong column.
+                    cbox(s.s, indent_unit-1u);
+                    ibox(s.s, 0u);
+                    wrd(s.s, " else ");
+                    alt (_else.node) {
+                        case (ast::expr_block(?b, _)) {
+                            print_block(s, block);
+                        }
+                    }
                 }
                 case (_) { /* fall through */ }
             }
         }
         case (ast::expr_while(?test,?block,_)) {
-            wrd1(s, "while");
-            popen_h(s);
+            head(s, "while");
+            popen(s);
             print_expr(s, test);
             pclose(s);
             space(s.s);
             print_block(s, block);
         }
         case (ast::expr_for(?decl,?expr,?block,_)) {
-            wrd1(s, "for");
-            popen_h(s);
+            head(s, "for");
+            popen(s);
             print_for_decl(s, decl);
             space(s.s);
-            wrd1(s, "in");
+            word_space(s, "in");
             print_expr(s, expr);
             pclose(s);
             space(s.s);
             print_block(s, block);
         }
         case (ast::expr_for_each(?decl,?expr,?block,_)) {
-            wrd1(s, "for each");
-            popen_h(s);
+            head(s, "for each");
+            popen(s);
             print_for_decl(s, decl);
             space(s.s);
-            wrd1(s, "in");
+            word_space(s, "in");
             print_expr(s, expr);
             pclose(s);
             space(s.s);
             print_block(s, block);
         }
         case (ast::expr_do_while(?block,?expr,_)) {
-            wrd1(s, "do");
+            head(s, "do");
             space(s.s);
             print_block(s, block);
             space(s.s);
-            wrd1(s, "while");
-            popen_h(s);
+            word_space(s, "while");
+            popen(s);
             print_expr(s, expr);
             pclose(s);
         }
         case (ast::expr_alt(?expr,?arms,_)) {
-            wrd1(s, "alt");
-            popen_h(s);
+            head(s, "alt");
+            popen(s);
             print_expr(s, expr);
             pclose(s);
             space(s.s);
             bopen(s);
             for (ast::arm arm in arms) {
-                hbox(s);
-                wrd1(s, "case");
-                popen_h(s);
+                space(s.s);
+                head(s, "case");
+                popen(s);
                 print_pat(s, arm.pat);
                 pclose(s);
                 space(s.s);
                 print_block(s, arm.block);
-                end(s.s);
-                line(s.s);
             }
-            bclose_c(s, expr.span);
+            bclose(s, expr.span);
         }
         case (ast::expr_block(?block,_)) {
+            cbox(s.s, indent_unit); // containing cbox, will be closed by print-block at }
+            ibox(s.s, 0u); // head-box, will be closed by print-block after {
             print_block(s, block);
         }
         case (ast::expr_assign(?lhs,?rhs,_)) {
             print_expr(s, lhs);
             space(s.s);
-            wrd1(s, "=");
+            word_space(s, "=");
             print_expr(s, rhs);
         }
         case (ast::expr_assign_op(?op,?lhs,?rhs,_)) {
             print_expr(s, lhs);
             space(s.s);
             wrd(s.s, ast::binop_to_str(op));
-            wrd1(s, "=");
+            word_space(s, "=");
             print_expr(s, rhs);
         }
         case (ast::expr_send(?lhs, ?rhs, _)) {
             print_expr(s, lhs);
             space(s.s);
-            wrd1(s, "<|");
+            word_space(s, "<|");
             print_expr(s, rhs);
         }
         case (ast::expr_recv(?lhs, ?rhs, _)) {
             print_expr(s, rhs);
             space(s.s);
-            wrd1(s, "|>");
+            word_space(s, "|>");
             print_expr(s, lhs);
         }
         case (ast::expr_field(?expr,?id,_)) {
@@ -630,7 +678,7 @@ fn print_expr(ps s, &@ast::expr expr) {
         case (ast::expr_index(?expr,?index,_)) {
             print_expr(s, expr);
             wrd(s.s, ".");
-            popen_h(s);
+            popen(s);
             print_expr(s, index);
             pclose(s);
         }
@@ -650,7 +698,7 @@ fn print_expr(ps s, &@ast::expr expr) {
             wrd(s.s, "ret");
             alt (result) {
                 case (option::some[@ast::expr](?expr)) {
-                    space(s.s);
+                    wrd(s.s, " ");
                     print_expr(s, expr);
                 }
                 case (_) {}
@@ -660,32 +708,32 @@ fn print_expr(ps s, &@ast::expr expr) {
             wrd(s.s, "put");
             alt (result) {
                 case (option::some[@ast::expr](?expr)) {
-                    space(s.s);
+                    wrd(s.s, " ");
                     print_expr(s, expr);
                 }
                 case (_) {}
             }
         }
         case (ast::expr_be(?result,_)) {
-            wrd1(s, "be");
+            word_nbsp(s, "be");
             print_expr(s, result);
         }
         case (ast::expr_log(?lvl,?expr,_)) {
             alt (lvl) {
-                case (1) {wrd1(s, "log");}
-                case (0) {wrd1(s, "log_err");}
+                case (1) {word_nbsp(s, "log");}
+                case (0) {word_nbsp(s, "log_err");}
             }
             print_expr(s, expr);
         }
         case (ast::expr_check(?expr,_)) {
-            wrd1(s, "check");
-            popen_h(s);
+            word_nbsp(s, "check");
+            popen(s);
             print_expr(s, expr);
             pclose(s);
         }
         case (ast::expr_assert(?expr,_)) {
-            wrd1(s, "assert");
-            popen_h(s);
+            word_nbsp(s, "assert");
+            popen(s);
             print_expr(s, expr);
             pclose(s);
         }
@@ -701,12 +749,12 @@ fn print_expr(ps s, &@ast::expr expr) {
         }
         case (ast::expr_port(_)) {
             wrd(s.s, "port");
-            popen_h(s);
+            popen(s);
             pclose(s);
         }
         case (ast::expr_chan(?expr, _)) {
             wrd(s.s, "chan");
-            popen_h(s);
+            popen(s);
             print_expr(s, expr);
             pclose(s);
         }
@@ -722,7 +770,8 @@ fn print_expr(ps s, &@ast::expr expr) {
         case (mo_untyped) { /* no-op */ }
         case (mo_typed(?tcx)) {
             space(s.s);
-            wrd1(s, "as");
+            wrd(s.s, "as");
+            space(s.s);
             wrd(s.s, ty::ty_to_str(tcx, ty::expr_ty(tcx, expr)));
             pclose(s);
         }
@@ -733,17 +782,18 @@ fn print_expr(ps s, &@ast::expr expr) {
 
 fn print_decl(ps s, @ast::decl decl) {
     maybe_print_comment(s, decl.span.lo);
-    hbox(s);
     alt (decl.node) {
         case (ast::decl_local(?loc)) {
+            space(s.s);
+            ibox(s.s, indent_unit);
             alt (loc.ty) {
                 case (option::some[@ast::ty](?ty)) {
-                    wrd1(s, "let");
+                    word_nbsp(s, "let");
                     print_type(s, ty);
                     space(s.s);
                 }
                 case (_) {
-                    wrd1(s, "auto");
+                    word_nbsp(s, "auto");
 
                     // Print the type if necessary.
                     alt (s.mode) {
@@ -751,7 +801,7 @@ fn print_decl(ps s, @ast::decl decl) {
                         case (mo_typed(?tcx)) {
                             auto lty =
                                 ty::ann_to_type(tcx.node_types, loc.ann);
-                            wrd1(s, ty::ty_to_str(tcx, lty));
+                            word_space(s, ty::ty_to_str(tcx, lty));
                         }
                     }
                 }
@@ -762,22 +812,22 @@ fn print_decl(ps s, @ast::decl decl) {
                     space(s.s);
                     alt (init.op) {
                         case (ast::init_assign) {
-                            wrd1(s, "=");
+                            word_space(s, "=");
                         }
                         case (ast::init_recv) {
-                            wrd1(s, "<-");
+                            word_space(s, "<-");
                         }
                     }
                     print_expr(s, init.expr);
                 }
                 case (_) {}
             }
+            end(s.s);
         }
         case (ast::decl_item(?item)) {
             print_item(s, item);
         }
     }
-    end(s.s);
 }
 
 fn print_ident(ps s, ast::ident ident) {
@@ -819,7 +869,7 @@ fn print_pat(ps s, &@ast::pat pat) {
         case (ast::pat_tag(?path,?args,_)) {
             print_path(s, path);
             if (vec::len[@ast::pat](args) > 0u) {
-                popen_h(s);
+                popen(s);
                 auto f = print_pat;
                 commasep[@ast::pat](s, args, f);
                 pclose(s);
@@ -832,17 +882,17 @@ fn print_fn(ps s, ast::fn_decl decl, str name,
                    vec[ast::ty_param] typarams) {
     alt (decl.purity) {
         case (ast::impure_fn) {
-            wrd1(s, "fn");
+            head(s, "fn");
         }
         case (_) {
-            wrd1(s, "pred");
+            head(s, "pred");
         }
     }
     wrd(s.s, name);
     print_type_params(s, typarams);
     popen(s);
     fn print_arg(ps s, &ast::arg x) {
-        hbox(s);
+        ibox(s.s, indent_unit);
         if (x.mode == ast::alias) {wrd(s.s, "&");}
         print_type(s, x.ty);
         space(s.s);
@@ -855,10 +905,8 @@ fn print_fn(ps s, ast::fn_decl decl, str name,
     maybe_print_comment(s, decl.output.span.lo);
     if (decl.output.node != ast::ty_nil) {
         space(s.s);
-        hbox(s);
-        wrd1(s, "->");
+        word_space(s, "->");
         print_type(s, decl.output);
-        end(s.s);
     }
 }
 
@@ -875,18 +923,18 @@ fn print_type_params(ps s, vec[ast::ty_param] params) {
 }
 
 fn print_view_item(ps s, @ast::view_item item) {
+    hardbreak(s.s);
     maybe_print_comment(s, item.span.lo);
-    hbox(s);
     alt (item.node) {
         case (ast::view_item_use(?id,?mta,_,_)) {
-            wrd1(s, "use");
+            head(s, "use");
             wrd(s.s, id);
             if (vec::len[@ast::meta_item](mta) > 0u) {
                 popen(s);
                 fn print_meta(ps s, &@ast::meta_item item) {
-                    hbox(s);
-                    wrd1(s, item.node.name);
-                    wrd1(s, "=");
+                    ibox(s.s, indent_unit);
+                    word_space(s, item.node.name);
+                    word_space(s, "=");
                     print_string(s, item.node.value);
                     end(s.s);
                 }
@@ -896,10 +944,10 @@ fn print_view_item(ps s, @ast::view_item item) {
             }
         }
         case (ast::view_item_import(?id,?ids,_)) {
-            wrd1(s, "import");
+            head(s, "import");
             if (!str::eq(id, ids.(vec::len[str](ids)-1u))) {
-                wrd1(s, id);
-                wrd1(s, "=");
+                word_space(s, id);
+                word_space(s, "=");
             }
             auto first = true;
             for (str elt in ids) {
@@ -909,13 +957,13 @@ fn print_view_item(ps s, @ast::view_item item) {
             }
         }
         case (ast::view_item_export(?id)) {
-            wrd1(s, "export");
+            head(s, "export");
             wrd(s.s, id);
         }
     }
-    end(s.s);
     wrd(s.s, ";");
-    line(s.s);
+    end(s.s); // end inner head-block
+    end(s.s); // end outer head-block
 }
 
 // FIXME: The fact that this builds up the table anew for every call is
@@ -968,8 +1016,8 @@ fn escape_str(str st, char to_escape) -> str {
 
 fn print_mt(ps s, &ast::mt mt) {
     alt (mt.mut) {
-        case (ast::mut)       { wrd1(s, "mutable");  }
-        case (ast::maybe_mut) { wrd1(s, "mutable?"); }
+        case (ast::mut)       { word_nbsp(s, "mutable");  }
+        case (ast::maybe_mut) { word_nbsp(s, "mutable?"); }
         case (ast::imm)       { /* nothing */        }
     }
     print_type(s, mt.ty);
@@ -988,7 +1036,7 @@ fn print_ty_fn(ps s, ast::proto proto, option::t[str] id,
         case (option::some[str](?id)) {space(s.s); wrd(s.s, id);}
         case (_) {}
     }
-    popen_h(s);
+    popen(s);
     fn print_arg(ps s, &ast::ty_arg input) {
         if (input.mode == ast::alias) {wrd(s.s, "&");}
         print_type(s, input.ty);
@@ -999,14 +1047,14 @@ fn print_ty_fn(ps s, ast::proto proto, option::t[str] id,
     maybe_print_comment(s, output.span.lo);
     if (output.node != ast::ty_nil) {
         space(s.s);
-        hbox(s);
-        wrd1(s, "->");
+        ibox(s.s, indent_unit);
+        word_space(s, "->");
         alt (cf) {
             case (ast::return) {
                 print_type(s, output);
             }
             case (ast::noreturn) {
-                wrd1(s, "!");
+                word_nbsp(s, "!");
             }
         }
         end(s.s);
@@ -1025,12 +1073,16 @@ fn next_comment(ps s) -> option::t[lexer::cmnt] {
 }
 
 fn maybe_print_comment(ps s, uint pos) {
+    auto first = true;
     while (true) {
         alt (next_comment(s)) {
             case (option::some[lexer::cmnt](?cmnt)) {
                 if (cmnt.pos < pos) {
+                    if (first) {
+                        first = false;
+                        break_offset(s.s, 0u, 0);
+                    }
                     print_comment(s, cmnt.val);
-                    if (cmnt.space_after) {line(s.s);}
                     s.cur_cmnt += 1u;
                 } else { break; }
             }
@@ -1055,11 +1107,15 @@ fn maybe_print_line_comment(ps s, common::span span) -> bool {
 }
 
 fn print_remaining_comments(ps s) {
+    auto first = true;
     while (true) {
         alt (next_comment(s)) {
             case (option::some[lexer::cmnt](?cmnt)) {
+                if (first) {
+                    first = false;
+                    break_offset(s.s, 0u, 0);
+                }
                 print_comment(s, cmnt.val);
-                if (cmnt.space_after) {line(s.s);}
                 s.cur_cmnt += 1u;
             }
             case (_) {break;}
@@ -1071,22 +1127,23 @@ fn print_comment(ps s, lexer::cmnt_ cmnt) {
     alt (cmnt) {
         case (lexer::cmnt_line(?val)) {
             wrd(s.s, "// " + val);
-            pp::hardbreak(s.s);
+            hardbreak(s.s);
         }
         case (lexer::cmnt_block(?lines)) {
-            pp::abox(s.s);
-            wrd(s.s, "/* ");
-            pp::abox(s.s);
+            cbox(s.s, 1u);
+            wrd(s.s, "/*");
             auto first = true;
             for (str ln in lines) {
-                if (first) {first = false;}
-                else {pp::hardbreak(s.s);}
+                if (first) {
+                    first = false;
+                } else {
+                    hardbreak(s.s);
+                }
                 wrd(s.s, ln);
             }
-            end(s.s);
             wrd(s.s, "*/");
             end(s.s);
-            line(s.s);
+            hardbreak(s.s);
         }
     }
 }
diff --git a/src/comp/util/common.rs b/src/comp/util/common.rs
index 070324dd9e8..119fcce806c 100644
--- a/src/comp/util/common.rs
+++ b/src/comp/util/common.rs
@@ -20,7 +20,7 @@ import pretty::pprust::print_decl;
 import pretty::pprust::print_fn;
 import pretty::pprust::print_type;
 import pretty::pprust::mo_untyped;
-import pretty::pp::mkstate;
+import pretty::pp::mk_printer;
 
 type filename = str;
 type span = rec(uint lo, uint hi);
@@ -127,7 +127,7 @@ fn field_exprs(vec[ast::field] fields) -> vec [@ast::expr] {
 
 fn expr_to_str(&@ast::expr e) -> str {
   let str_writer s = string_writer();
-  auto out_ = mkstate(s.get_writer(), 80u);
+  auto out_ = mk_printer(s.get_writer(), 80u);
   auto out = @rec(s=out_,
                   comments=none[vec[front::lexer::cmnt]],
                   mutable cur_cmnt=0u,
@@ -138,7 +138,7 @@ fn expr_to_str(&@ast::expr e) -> str {
 
 fn ty_to_str(&ty t) -> str {
   let str_writer s = string_writer();
-  auto out_ = mkstate(s.get_writer(), 80u);
+  auto out_ = mk_printer(s.get_writer(), 80u);
   auto out = @rec(s=out_,
                   comments=none[vec[front::lexer::cmnt]],
                   mutable cur_cmnt=0u,
@@ -165,7 +165,7 @@ fn log_pat_err(&@pat p) -> () {
 
 fn block_to_str(&ast::block b) -> str {
   let str_writer s = string_writer();
-  auto out_ = mkstate(s.get_writer(), 80u);
+  auto out_ = mk_printer(s.get_writer(), 80u);
   auto out = @rec(s=out_,
                   comments=none[vec[front::lexer::cmnt]],
                   mutable cur_cmnt=0u,
@@ -177,7 +177,7 @@ fn block_to_str(&ast::block b) -> str {
 
 fn item_to_str(&@ast::item i) -> str {
   let str_writer s = string_writer();
-  auto out_ = mkstate(s.get_writer(), 80u);
+  auto out_ = mk_printer(s.get_writer(), 80u);
   auto out = @rec(s=out_,
                   comments=none[vec[front::lexer::cmnt]],
                   mutable cur_cmnt=0u,
@@ -200,7 +200,7 @@ fn log_item_err(&@ast::item i) -> () {
 
 fn fun_to_str(&ast::_fn f, str name, vec[ast::ty_param] params) -> str {
  let str_writer s = string_writer();
-  auto out_ = mkstate(s.get_writer(), 80u);
+  auto out_ = mk_printer(s.get_writer(), 80u);
   auto out = @rec(s=out_,
                   comments=none[vec[front::lexer::cmnt]],
                   mutable cur_cmnt=0u,
@@ -220,7 +220,7 @@ fn log_fn_err(&ast::_fn f, str name, vec[ast::ty_param] params) -> () {
 
 fn stmt_to_str(&ast::stmt st) -> str {
   let str_writer s = string_writer();
-  auto out_ = mkstate(s.get_writer(), 80u);
+  auto out_ = mk_printer(s.get_writer(), 80u);
   auto out = @rec(s=out_,
                   comments=none[vec[front::lexer::cmnt]],
                   mutable cur_cmnt=0u,