Unit tests for flowgraph pretty printing.

Each test works by rendering the flowgraph for the last identified
block we see in expanded pretty-printed output, and comparing it (via
`diff`) against a checked in "foo.dot-expected.dot" file.

Each test post-processes the output to remove NodeIds ` (id=NUM)` so
that the expected output is somewhat stable (or at least independent
of how we assign NodeIds) and easier for a human to interpret when
looking at the expected output file itself.

----

Test writing style notes:

I usually tried to write the tests in a way that would avoid duplicate
labels in the output rendered flow graph, when possible.

The tests that have string literals "unreachable" in the program text
are deliberately written that way to remind the reader that the
unreachable nodes in the resulting graph are not an error in the
control flow computation, but rather a natural consequence of its
construction.

src/test/run-make/graphviz-flowgraph/Makefile

+-include ../tools.mk
+
+FILES=f00.rs f01.rs f02.rs f03.rs f04.rs f05.rs f06.rs f07.rs \
+      f08.rs f09.rs f10.rs f11.rs f12.rs f13.rs f14.rs f15.rs \
+      f16.rs f17.rs f18.rs f19.rs f20.rs f21.rs f22.rs
+
+
+# all: $(patsubst %.rs,$(TMPDIR)/%.dot,$(FILES)) $(patsubst %.rs,$(TMPDIR)/%.pp,$(FILES))
+all: $(patsubst %.rs,$(TMPDIR)/%.check,$(FILES))
+
+
+RUSTC_LIB=$(RUSTC) --crate-type=lib
+
+define FIND_LAST_BLOCK
+LASTBLOCKNUM_$(1) := $(shell $(RUSTC_LIB) --pretty=expanded,identified $(1) \
+			 | grep block
+			 | tail -1
+			 | sed -e 's@.*/\* block \([0-9]*\) \*/.*@\1@')
+endef
+
+ifeq ($(findstring rustc,$(RUSTC)),)
+$(error Must set RUSTC)
+endif
+
+$(TMPDIR)/%.pp: %.rs
+	$(RUSTC_LIB) --pretty=expanded,identified $< -o $@
+
+$(TMPDIR)/%.dot: %.rs
+	$(eval $(call FIND_LAST_BLOCK,$<))
+	$(RUSTC_LIB) --pretty flowgraph=$(LASTBLOCKNUM_$<) $< -o $@.tmp
+	cat $@.tmp | sed -e 's@ (id=[0-9]*)@@g' \
+                         -e 's@\[label=""\]@@' \
+                         -e 's@digraph [a-zA-Z0-9_]* @digraph block @' \
+                     > $@
+
+$(TMPDIR)/%.check: %.rs $(TMPDIR)/%.dot
+	diff -u $(patsubst %.rs,$(TMPDIR)/%.dot,$<) $(patsubst %.rs,%.dot-expected.dot,$<)

src/test/run-make/graphviz-flowgraph/f00.dot-expected.dot

+digraph block {
+    N0[label="entry"];
+    N1[label="exit"];
+    N2[label="block { }"];
+    N0 -> N2;
+    N2 -> N1;
+}

src/test/run-make/graphviz-flowgraph/f00.rs

+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+pub fn empty_0() {
+
+}

src/test/run-make/graphviz-flowgraph/f01.dot-expected.dot

+digraph block {
+    N0[label="entry"];
+    N1[label="exit"];
+    N2[label="expr 1"];
+    N3[label="block { 1; }"];
+    N0 -> N2;
+    N2 -> N3;
+    N3 -> N1;
+}

src/test/run-make/graphviz-flowgraph/f01.rs

+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+pub fn lit_1() {
+    1;
+}

src/test/run-make/graphviz-flowgraph/f02.dot-expected.dot

+digraph block {
+    N0[label="entry"];
+    N1[label="exit"];
+    N2[label="local _x"];
+    N3[label="block { let _x: int; }"];
+    N0 -> N2;
+    N2 -> N3;
+    N3 -> N1;
+}

src/test/run-make/graphviz-flowgraph/f02.rs

+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+pub fn decl_x_2() {
+    let _x : int;
+}

src/test/run-make/graphviz-flowgraph/f03.dot-expected.dot

+digraph block {
+    N0[label="entry"];
+    N1[label="exit"];
+    N2[label="expr 3"];
+    N3[label="expr 33"];
+    N4[label="expr 3 + 33"];
+    N5[label="block { 3 + 33; }"];
+    N0 -> N2;
+    N2 -> N3;
+    N3 -> N4;
+    N4 -> N5;
+    N5 -> N1;
+}

src/test/run-make/graphviz-flowgraph/f03.rs

+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+pub fn expr_add_3() {
+    3 + 33;
+}

src/test/run-make/graphviz-flowgraph/f04.dot-expected.dot

+digraph block {
+    N0[label="entry"];
+    N1[label="exit"];
+    N2[label="expr 4"];
+    N3[label="local _x"];
+    N4[label="block { let _x = 4; }"];
+    N0 -> N2;
+    N2 -> N3;
+    N3 -> N4;
+    N4 -> N1;
+}

src/test/run-make/graphviz-flowgraph/f04.rs

+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+pub fn pat_id_4() {
+    let _x = 4;
+}

src/test/run-make/graphviz-flowgraph/f05.dot-expected.dot

+digraph block {
+    N0[label="entry"];
+    N1[label="exit"];
+    N2[label="expr 5"];
+    N3[label="expr 55"];
+    N4[label="expr (5, 55)"];
+    N5[label="local _x"];
+    N6[label="local _y"];
+    N7[label="pat (_x, _y)"];
+    N8[label="block { let (_x, _y) = (5, 55); }"];
+    N0 -> N2;
+    N2 -> N3;
+    N3 -> N4;
+    N4 -> N5;
+    N5 -> N6;
+    N6 -> N7;
+    N7 -> N8;
+    N8 -> N1;
+}

src/test/run-make/graphviz-flowgraph/f05.rs

+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+pub fn pat_tup_5() {
+    let (_x, _y) = (5, 55);
+}

src/test/run-make/graphviz-flowgraph/f06.dot-expected.dot

+digraph block {
+    N0[label="entry"];
+    N1[label="exit"];
+    N2[label="expr 6"];
+    N3[label="expr S6{val: 6,}"];
+    N4[label="local _x"];
+    N5[label="pat S6{val: _x}"];
+    N6[label="block { let S6{val: _x} = S6{val: 6,}; }"];
+    N0 -> N2;
+    N2 -> N3;
+    N3 -> N4;
+    N4 -> N5;
+    N5 -> N6;
+    N6 -> N1;
+}

src/test/run-make/graphviz-flowgraph/f06.rs

+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+struct S6 { val: int }
+pub fn pat_struct_6() {
+    let S6 { val: _x } = S6{ val: 6 };
+}

src/test/run-make/graphviz-flowgraph/f07.dot-expected.dot

+digraph block {
+    N0[label="entry"];
+    N1[label="exit"];
+    N2[label="expr 7"];
+    N3[label="expr 77"];
+    N4[label="expr 777"];
+    N5[label="expr 7777"];
+    N6[label="expr [7, 77, 777, 7777]"];
+    N7[label="expr match [7, 77, 777, 7777] { [x, y, ..] => x + y }"];
+    N8[label="local x"];
+    N9[label="local y"];
+    N10[label="pat .."];
+    N11[label="pat [x, y, ..]"];
+    N12[label="expr x"];
+    N13[label="expr y"];
+    N14[label="expr x + y"];
+    N15[label="block { match [7, 77, 777, 7777] { [x, y, ..] => x + y }; }"];
+    N0 -> N2;
+    N2 -> N3;
+    N3 -> N4;
+    N4 -> N5;
+    N5 -> N6;
+    N6 -> N8;
+    N8 -> N9;
+    N9 -> N10;
+    N10 -> N11;
+    N11 -> N12;
+    N12 -> N13;
+    N13 -> N14;
+    N14 -> N7;
+    N7 -> N15;
+    N15 -> N1;
+}

src/test/run-make/graphviz-flowgraph/f07.rs

+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+pub fn pat_vec_7() {
+    match [7, 77, 777, 7777] {
+        [x, y, ..] => x + y
+    };
+}

src/test/run-make/graphviz-flowgraph/f08.dot-expected.dot

+digraph block {
+    N0[label="entry"];
+    N1[label="exit"];
+    N2[label="expr 8"];
+    N3[label="local x"];
+    N4[label="local _y"];
+    N5[label="expr x"];
+    N6[label="expr 88"];
+    N7[label="expr x > 88"];
+    N8[label="expr 888"];
+    N9[label="expr _y"];
+    N10[label="expr _y = 888"];
+    N11[label="block { _y = 888; }"];
+    N12[label="expr if x > 88 { _y = 888; }"];
+    N13[label="block { let x = 8; let _y; if x > 88 { _y = 888; } }"];
+    N0 -> N2;
+    N2 -> N3;
+    N3 -> N4;
+    N4 -> N5;
+    N5 -> N6;
+    N6 -> N7;
+    N7 -> N8;
+    N8 -> N9;
+    N9 -> N10;
+    N10 -> N11;
+    N7 -> N12;
+    N11 -> N12;
+    N12 -> N13;
+    N13 -> N1;
+}

src/test/run-make/graphviz-flowgraph/f08.rs

+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+pub fn expr_if_onearm_8() {
+    let x = 8; let _y;
+    if x > 88 {
+        _y = 888;
+    }
+}

src/test/run-make/graphviz-flowgraph/f09.dot-expected.dot

+digraph block {
+    N0[label="entry"];
+    N1[label="exit"];
+    N2[label="expr 91"];
+    N3[label="local x"];
+    N4[label="local _y"];
+    N5[label="expr x"];
+    N6[label="expr 92"];
+    N7[label="expr x > 92"];
+    N8[label="expr 93"];
+    N9[label="expr _y"];
+    N10[label="expr _y = 93"];
+    N11[label="block { _y = 93; }"];
+    N12[label="expr 94"];
+    N13[label="expr 95"];
+    N14[label="expr 94 + 95"];
+    N15[label="expr _y"];
+    N16[label="expr _y = 94 + 95"];
+    N17[label="block { _y = 94 + 95; }"];
+    N18[label="expr { _y = 94 + 95; }"];
+    N19[label="expr if x > 92 { _y = 93; } else { _y = 94 + 95; }"];
+    N20[label="block { let x = 91; let _y; if x > 92 { _y = 93; } else { _y = 94 + 95; } }"];
+    N0 -> N2;
+    N2 -> N3;
+    N3 -> N4;
+    N4 -> N5;
+    N5 -> N6;
+    N6 -> N7;
+    N7 -> N8;
+    N8 -> N9;
+    N9 -> N10;
+    N10 -> N11;
+    N7 -> N12;
+    N12 -> N13;
+    N13 -> N14;
+    N14 -> N15;
+    N15 -> N16;
+    N16 -> N17;
+    N17 -> N18;
+    N11 -> N19;
+    N18 -> N19;
+    N19 -> N20;
+    N20 -> N1;
+}

src/test/run-make/graphviz-flowgraph/f09.rs

+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+pub fn expr_if_twoarm_9() {
+    let x = 91; let _y;
+    if x > 92 {
+        _y = 93;
+    } else {
+        _y = 94+95;
+    }
+}

src/test/run-make/graphviz-flowgraph/f10.dot-expected.dot

+digraph block {
+    N0[label="entry"];
+    N1[label="exit"];
+    N2[label="expr 10"];
+    N3[label="local mut x"];
+    N4[label="(dummy_node)"];
+    N5[label="expr x"];
+    N6[label="expr 0"];
+    N7[label="expr x > 0"];
+    N8[label="expr while x > 0 { x -= 1; }"];
+    N9[label="expr 1"];
+    N10[label="expr x"];
+    N11[label="expr x -= 1"];
+    N12[label="block { x -= 1; }"];
+    N13[label="block { let mut x = 10; while x > 0 { x -= 1; } }"];
+    N0 -> N2;
+    N2 -> N3;
+    N3 -> N4;
+    N4 -> N5;
+    N5 -> N6;
+    N6 -> N7;
+    N7 -> N8;
+    N7 -> N9;
+    N9 -> N10;
+    N10 -> N11;
+    N11 -> N12;
+    N12 -> N4;
+    N8 -> N13;
+    N13 -> N1;
+}

src/test/run-make/graphviz-flowgraph/f10.rs

+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+pub fn expr_while_10() {
+    let mut x = 10;
+    while x > 0 {
+        x -= 1;
+    }
+}

src/test/run-make/graphviz-flowgraph/f11.dot-expected.dot

+digraph block {
+    N0[label="entry"];
+    N1[label="exit"];
+    N2[label="expr 11"];
+    N3[label="local mut _x"];
+    N4[label="(dummy_node)"];
+    N5[label="expr loop  { _x -= 1; }"];
+    N6[label="expr 1"];
+    N7[label="expr _x"];
+    N8[label="expr _x -= 1"];
+    N9[label="block { _x -= 1; }"];
+    N10[label="expr \"unreachable\""];
+    N11[label="block { let mut _x = 11; loop  { _x -= 1; } \"unreachable\"; }"];
+    N0 -> N2;
+    N2 -> N3;
+    N3 -> N4;
+    N4 -> N6;
+    N6 -> N7;
+    N7 -> N8;
+    N8 -> N9;
+    N9 -> N4;
+    N5 -> N10;
+    N10 -> N11;
+    N11 -> N1;
+}

src/test/run-make/graphviz-flowgraph/f11.rs

+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#[allow(unreachable_code)]
+pub fn expr_loop_11() {
+    let mut _x = 11;
+    loop {
+        _x -= 1;
+    }
+    "unreachable";
+}

src/test/run-make/graphviz-flowgraph/f12.dot-expected.dot

+digraph block {
+    N0[label="entry"];
+    N1[label="exit"];
+    N2[label="expr 12"];
+    N3[label="local mut x"];
+    N4[label="(dummy_node)"];
+    N5[label="expr loop  { x -= 1; if x == 2 { break ; \"unreachable\"; } }"];
+    N6[label="expr 1"];
+    N7[label="expr x"];
+    N8[label="expr x -= 1"];
+    N9[label="expr x"];
+    N10[label="expr 2"];
+    N11[label="expr x == 2"];
+    N12[label="expr break"];
+    N13[label="(dummy_node)"];
+    N14[label="expr \"unreachable\""];
+    N15[label="block { break ; \"unreachable\"; }"];
+    N16[label="expr if x == 2 { break ; \"unreachable\"; }"];
+    N17[label="block { x -= 1; if x == 2 { break ; \"unreachable\"; } }"];
+    N18[label="block { let mut x = 12; loop  { x -= 1; if x == 2 { break ; \"unreachable\"; } } }"];
+    N0 -> N2;
+    N2 -> N3;
+    N3 -> N4;
+    N4 -> N6;
+    N6 -> N7;
+    N7 -> N8;
+    N8 -> N9;
+    N9 -> N10;
+    N10 -> N11;
+    N11 -> N12;
+    N12 -> N5[label="exiting scope_0 expr break,\lexiting scope_1 stmt break ;,\lexiting scope_2 block { break ; \"unreachable\"; },\lexiting scope_3 expr if x == 2 { break ; \"unreachable\"; },\lexiting scope_4 block { x -= 1; if x == 2 { break ; \"unreachable\"; } }"];
+    N13 -> N14;
+    N14 -> N15;
+    N11 -> N16;
+    N15 -> N16;
+    N16 -> N17;
+    N17 -> N4;
+    N5 -> N18;
+    N18 -> N1;
+}

src/test/run-make/graphviz-flowgraph/f12.rs

+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#[allow(unreachable_code)]
+pub fn expr_loop_12() {
+    let mut x = 12;
+    loop {
+        x -= 1;
+        if x == 2 { break; "unreachable"; }
+    }
+}

src/test/run-make/graphviz-flowgraph/f13.dot-expected.dot

+digraph block {
+    N0[label="entry"];
+    N1[label="exit"];
+    N2[label="expr E13b"];
+    N3[label="expr 13"];
+    N4[label="expr E13b(13)"];
+    N5[label="local x"];
+    N6[label="local _y"];
+    N7[label="expr x"];
+    N8[label="expr match x { E13a => _y = 1, E13b(v) => _y = v + 1 }"];
+    N9[label="local E13a"];
+    N10[label="expr 1"];
+    N11[label="expr _y"];
+    N12[label="expr _y = 1"];
+    N13[label="local v"];
+    N14[label="pat E13b(v)"];
+    N15[label="expr v"];
+    N16[label="expr 1"];
+    N17[label="expr v + 1"];
+    N18[label="expr _y"];
+    N19[label="expr _y = v + 1"];
+    N20[label="block {\l    let x = E13b(13);\l    let _y;\l    match x { E13a => _y = 1, E13b(v) => _y = v + 1 }\l}\l"];
+    N0 -> N2;
+    N2 -> N3;
+    N3 -> N4;
+    N4 -> N5;
+    N5 -> N6;
+    N6 -> N7;
+    N7 -> N9;
+    N9 -> N10;
+    N10 -> N11;
+    N11 -> N12;
+    N12 -> N8;
+    N7 -> N13;
+    N13 -> N14;
+    N14 -> N15;
+    N15 -> N16;
+    N16 -> N17;
+    N17 -> N18;
+    N18 -> N19;
+    N19 -> N8;
+    N8 -> N20;
+    N20 -> N1;
+}

src/test/run-make/graphviz-flowgraph/f13.rs

+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+enum E13 { E13a, E13b(int) }
+pub fn expr_match_13() {
+    let x = E13b(13); let _y;
+    match x {
+        E13a => _y = 1,
+        E13b(v) => _y = v + 1,
+    }
+}

src/test/run-make/graphviz-flowgraph/f14.dot-expected.dot

+digraph block {
+    N0[label="entry"];
+    N1[label="exit"];
+    N2[label="expr 14"];
+    N3[label="local x"];
+    N4[label="expr x"];
+    N5[label="expr 1"];
+    N6[label="expr x > 1"];
+    N7[label="expr return"];
+    N8[label="(dummy_node)"];
+    N9[label="expr \"unreachable\""];
+    N10[label="block { return; \"unreachable\"; }"];
+    N11[label="expr if x > 1 { return; \"unreachable\"; }"];
+    N12[label="block { let x = 14; if x > 1 { return; \"unreachable\"; } }"];
+    N0 -> N2;
+    N2 -> N3;
+    N3 -> N4;
+    N4 -> N5;
+    N5 -> N6;
+    N6 -> N7;
+    N7 -> N1;
+    N8 -> N9;
+    N9 -> N10;
+    N6 -> N11;
+    N10 -> N11;
+    N11 -> N12;
+    N12 -> N1;
+}

src/test/run-make/graphviz-flowgraph/f14.rs

+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#[allow(unreachable_code)]
+pub fn expr_ret_14() {
+    let x = 14;
+    if x > 1 {
+        return;
+        "unreachable";
+    }
+}

src/test/run-make/graphviz-flowgraph/f15.dot-expected.dot

+digraph block {
+    N0[label="entry"];
+    N1[label="exit"];
+    N2[label="expr 15"];
+    N3[label="local mut x"];
+    N4[label="expr 151"];
+    N5[label="local mut y"];
+    N6[label="(dummy_node)"];
+    N7[label="expr \'outer:\l    loop  {\l        \'inner:\l            loop  {\l                if x == 1 { break \'outer ; \"unreachable\" }\l                if y >= 2 { break ; \"unreachable\" }\l                y -= 3;\l            }\l        y -= 4;\l        x -= 5;\l    }\l"];
+    N8[label="(dummy_node)"];
+    N9[label="expr \'inner:\l    loop  {\l        if x == 1 { break \'outer ; \"unreachable\" }\l        if y >= 2 { break ; \"unreachable\" }\l        y -= 3;\l    }\l"];
+    N10[label="expr x"];
+    N11[label="expr 1"];
+    N12[label="expr x == 1"];
+    N13[label="expr break \'outer"];
+    N14[label="(dummy_node)"];
+    N15[label="expr \"unreachable\""];
+    N16[label="block { break \'outer ; \"unreachable\" }"];
+    N17[label="expr if x == 1 { break \'outer ; \"unreachable\" }"];
+    N18[label="expr y"];
+    N19[label="expr 2"];
+    N20[label="expr y >= 2"];
+    N21[label="expr break"];
+    N22[label="(dummy_node)"];
+    N23[label="expr \"unreachable\""];
+    N24[label="block { break ; \"unreachable\" }"];
+    N25[label="expr if y >= 2 { break ; \"unreachable\" }"];
+    N26[label="expr 3"];
+    N27[label="expr y"];
+    N28[label="expr y -= 3"];
+    N29[label="block {\l    if x == 1 { break \'outer ; \"unreachable\" }\l    if y >= 2 { break ; \"unreachable\" }\l    y -= 3;\l}\l"];
+    N30[label="expr 4"];
+    N31[label="expr y"];
+    N32[label="expr y -= 4"];
+    N33[label="expr 5"];
+    N34[label="expr x"];
+    N35[label="expr x -= 5"];
+    N36[label="block {\l    \'inner:\l        loop  {\l            if x == 1 { break \'outer ; \"unreachable\" }\l            if y >= 2 { break ; \"unreachable\" }\l            y -= 3;\l        }\l    y -= 4;\l    x -= 5;\l}\l"];
+    N37[label="block {\l    let mut x = 15;\l    let mut y = 151;\l    \'outer:\l        loop  {\l            \'inner:\l                loop  {\l                    if x == 1 { break \'outer ; \"unreachable\" }\l                    if y >= 2 { break ; \"unreachable\" }\l                    y -= 3;\l                }\l            y -= 4;\l            x -= 5;\l        }\l}\l"];
+    N0 -> N2;
+    N2 -> N3;
+    N3 -> N4;
+    N4 -> N5;
+    N5 -> N6;
+    N6 -> N8;
+    N8 -> N10;
+    N10 -> N11;
+    N11 -> N12;
+    N12 -> N13;
+    N13 -> N7[label="exiting scope_0 expr break \'outer,\lexiting scope_1 stmt break \'outer ;,\lexiting scope_2 block { break \'outer ; \"unreachable\" },\lexiting scope_3 expr if x == 1 { break \'outer ; \"unreachable\" },\lexiting scope_4 stmt if x == 1 { break \'outer ; \"unreachable\" },\lexiting scope_5 block {\l    if x == 1 { break \'outer ; \"unreachable\" }\l    if y >= 2 { break ; \"unreachable\" }\l    y -= 3;\l}\l,\lexiting scope_6 expr \'inner:\l    loop  {\l        if x == 1 { break \'outer ; \"unreachable\" }\l        if y >= 2 { break ; \"unreachable\" }\l        y -= 3;\l    }\l,\lexiting scope_7 stmt \'inner:\l    loop  {\l        if x == 1 { break \'outer ; \"unreachable\" }\l        if y >= 2 { break ; \"unreachable\" }\l        y -= 3;\l    }\l,\lexiting scope_8 block {\l    \'inner:\l        loop  {\l            if x == 1 { break \'outer ; \"unreachable\" }\l            if y >= 2 { break ; \"unreachable\" }\l            y -= 3;\l        }\l    y -= 4;\l    x -= 5;\l}\l"];
+    N14 -> N15;
+    N15 -> N16;
+    N12 -> N17;
+    N16 -> N17;
+    N17 -> N18;
+    N18 -> N19;
+    N19 -> N20;
+    N20 -> N21;
+    N21 -> N9[label="exiting scope_0 expr break,\lexiting scope_1 stmt break ;,\lexiting scope_2 block { break ; \"unreachable\" },\lexiting scope_3 expr if y >= 2 { break ; \"unreachable\" },\lexiting scope_4 stmt if y >= 2 { break ; \"unreachable\" },\lexiting scope_5 block {\l    if x == 1 { break \'outer ; \"unreachable\" }\l    if y >= 2 { break ; \"unreachable\" }\l    y -= 3;\l}\l"];
+    N22 -> N23;
+    N23 -> N24;
+    N20 -> N25;
+    N24 -> N25;
+    N25 -> N26;
+    N26 -> N27;
+    N27 -> N28;
+    N28 -> N29;
+    N29 -> N8;
+    N9 -> N30;
+    N30 -> N31;
+    N31 -> N32;
+    N32 -> N33;
+    N33 -> N34;
+    N34 -> N35;
+    N35 -> N36;
+    N36 -> N6;
+    N7 -> N37;
+    N37 -> N1;
+}

src/test/run-make/graphviz-flowgraph/f15.rs

+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#[allow(unreachable_code)]
+pub fn expr_break_label_15() {
+    let mut x = 15;
+    let mut y = 151;
+    'outer: loop {
+        'inner: loop {
+            if x == 1 {
+                break 'outer;
+                "unreachable"
+            }
+            if y >= 2 {
+                break;
+                "unreachable"
+            }
+            y -= 3;
+        }
+        y -= 4;
+        x -= 5;
+    }
+}

src/test/run-make/graphviz-flowgraph/f16.dot-expected.dot

+digraph block {
+    N0[label="entry"];
+    N1[label="exit"];
+    N2[label="expr 16"];
+    N3[label="local mut x"];
+    N4[label="expr 16"];
+    N5[label="local mut y"];
+    N6[label="(dummy_node)"];
+    N7[label="expr \'outer:\l    loop  {\l        \'inner:\l            loop  {\l                if x == 1 { continue \'outer ; \"unreachable\" }\l                if y >= 1 { break ; \"unreachable\" }\l                y -= 1;\l            }\l        y -= 1;\l        x -= 1;\l    }\l"];
+    N8[label="(dummy_node)"];
+    N9[label="expr \'inner:\l    loop  {\l        if x == 1 { continue \'outer ; \"unreachable\" }\l        if y >= 1 { break ; \"unreachable\" }\l        y -= 1;\l    }\l"];
+    N10[label="expr x"];
+    N11[label="expr 1"];
+    N12[label="expr x == 1"];
+    N13[label="expr continue \'outer"];
+    N14[label="(dummy_node)"];
+    N15[label="expr \"unreachable\""];
+    N16[label="block { continue \'outer ; \"unreachable\" }"];
+    N17[label="expr if x == 1 { continue \'outer ; \"unreachable\" }"];
+    N18[label="expr y"];
+    N19[label="expr 1"];
+    N20[label="expr y >= 1"];
+    N21[label="expr break"];
+    N22[label="(dummy_node)"];
+    N23[label="expr \"unreachable\""];
+    N24[label="block { break ; \"unreachable\" }"];
+    N25[label="expr if y >= 1 { break ; \"unreachable\" }"];
+    N26[label="expr 1"];
+    N27[label="expr y"];
+    N28[label="expr y -= 1"];
+    N29[label="block {\l    if x == 1 { continue \'outer ; \"unreachable\" }\l    if y >= 1 { break ; \"unreachable\" }\l    y -= 1;\l}\l"];
+    N30[label="expr 1"];
+    N31[label="expr y"];
+    N32[label="expr y -= 1"];
+    N33[label="expr 1"];
+    N34[label="expr x"];
+    N35[label="expr x -= 1"];
+    N36[label="block {\l    \'inner:\l        loop  {\l            if x == 1 { continue \'outer ; \"unreachable\" }\l            if y >= 1 { break ; \"unreachable\" }\l            y -= 1;\l        }\l    y -= 1;\l    x -= 1;\l}\l"];
+    N37[label="expr \"unreachable\""];
+    N38[label="block {\l    let mut x = 16;\l    let mut y = 16;\l    \'outer:\l        loop  {\l            \'inner:\l                loop  {\l                    if x == 1 { continue \'outer ; \"unreachable\" }\l                    if y >= 1 { break ; \"unreachable\" }\l                    y -= 1;\l                }\l            y -= 1;\l            x -= 1;\l        }\l    \"unreachable\";\l}\l"];
+    N0 -> N2;
+    N2 -> N3;
+    N3 -> N4;
+    N4 -> N5;
+    N5 -> N6;
+    N6 -> N8;
+    N8 -> N10;
+    N10 -> N11;
+    N11 -> N12;
+    N12 -> N13;
+    N13 -> N6[label="exiting scope_0 expr continue \'outer,\lexiting scope_1 stmt continue \'outer ;,\lexiting scope_2 block { continue \'outer ; \"unreachable\" },\lexiting scope_3 expr if x == 1 { continue \'outer ; \"unreachable\" },\lexiting scope_4 stmt if x == 1 { continue \'outer ; \"unreachable\" },\lexiting scope_5 block {\l    if x == 1 { continue \'outer ; \"unreachable\" }\l    if y >= 1 { break ; \"unreachable\" }\l    y -= 1;\l}\l,\lexiting scope_6 expr \'inner:\l    loop  {\l        if x == 1 { continue \'outer ; \"unreachable\" }\l        if y >= 1 { break ; \"unreachable\" }\l        y -= 1;\l    }\l,\lexiting scope_7 stmt \'inner:\l    loop  {\l        if x == 1 { continue \'outer ; \"unreachable\" }\l        if y >= 1 { break ; \"unreachable\" }\l        y -= 1;\l    }\l,\lexiting scope_8 block {\l    \'inner:\l        loop  {\l            if x == 1 { continue \'outer ; \"unreachable\" }\l            if y >= 1 { break ; \"unreachable\" }\l            y -= 1;\l        }\l    y -= 1;\l    x -= 1;\l}\l"];
+    N14 -> N15;
+    N15 -> N16;
+    N12 -> N17;
+    N16 -> N17;
+    N17 -> N18;
+    N18 -> N19;
+    N19 -> N20;
+    N20 -> N21;
+    N21 -> N9[label="exiting scope_0 expr break,\lexiting scope_1 stmt break ;,\lexiting scope_2 block { break ; \"unreachable\" },\lexiting scope_3 expr if y >= 1 { break ; \"unreachable\" },\lexiting scope_4 stmt if y >= 1 { break ; \"unreachable\" },\lexiting scope_5 block {\l    if x == 1 { continue \'outer ; \"unreachable\" }\l    if y >= 1 { break ; \"unreachable\" }\l    y -= 1;\l}\l"];
+    N22 -> N23;
+    N23 -> N24;
+    N20 -> N25;
+    N24 -> N25;
+    N25 -> N26;
+    N26 -> N27;
+    N27 -> N28;
+    N28 -> N29;
+    N29 -> N8;
+    N9 -> N30;
+    N30 -> N31;
+    N31 -> N32;
+    N32 -> N33;
+    N33 -> N34;
+    N34 -> N35;
+    N35 -> N36;
+    N36 -> N6;
+    N7 -> N37;
+    N37 -> N38;
+    N38 -> N1;
+}

src/test/run-make/graphviz-flowgraph/f16.rs

+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#[allow(unreachable_code)]
+pub fn expr_continue_label_16() {
+    let mut x = 16;
+    let mut y = 16;
+    'outer: loop {
+        'inner: loop {
+            if x == 1 {
+                continue 'outer;
+                "unreachable"
+            }
+            if y >= 1 {
+                break;
+                "unreachable"
+            }
+            y -= 1;
+        }
+        y -= 1;
+        x -= 1;
+    }
+    "unreachable";
+}

src/test/run-make/graphviz-flowgraph/f17.dot-expected.dot

+digraph block {
+    N0[label="entry"];
+    N1[label="exit"];
+    N2[label="expr 1"];
+    N3[label="expr 7"];
+    N4[label="expr 17"];
+    N5[label="expr [1, 7, 17]"];
+    N6[label="local _v"];
+    N7[label="block { let _v = [1, 7, 17]; }"];
+    N0 -> N2;
+    N2 -> N3;
+    N3 -> N4;
+    N4 -> N5;
+    N5 -> N6;
+    N6 -> N7;
+    N7 -> N1;
+}

src/test/run-make/graphviz-flowgraph/f17.rs

+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+pub fn expr_vec_17() {
+    let _v = [1, 7, 17];
+}

src/test/run-make/graphviz-flowgraph/f18.dot-expected.dot

+digraph block {
+    N0[label="entry"];
+    N1[label="exit"];
+    N2[label="expr inner"];
+    N3[label="expr inner"];
+    N4[label="expr 18"];
+    N5[label="expr inner(18)"];
+    N6[label="expr inner(inner(18))"];
+    N7[label="block {\l    fn inner(x: int) -> int { x + x }\l    inner(inner(18));\l}\l"];
+    N0 -> N2;
+    N2 -> N3;
+    N3 -> N4;
+    N4 -> N5;
+    N5 -> N6;
+    N6 -> N7;
+    N7 -> N1;
+}

src/test/run-make/graphviz-flowgraph/f18.rs

+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+pub fn expr_call_18() {
+    fn inner(x:int) -> int { x + x }
+    inner(inner(18));
+}

src/test/run-make/graphviz-flowgraph/f19.dot-expected.dot

+digraph block {
+    N0[label="entry"];
+    N1[label="exit"];
+    N2[label="expr 19"];
+    N3[label="expr S19{x: 19,}"];
+    N4[label="local s"];
+    N5[label="expr s"];
+    N6[label="expr s.inner()"];
+    N7[label="expr s.inner().inner()"];
+    N8[label="block {\l    struct S19 {\l        x: int,\l    }\l    impl S19 {\l        fn inner(self) -> S19 { S19{x: self.x + self.x,} }\l    }\l    let s = S19{x: 19,};\l    s.inner().inner();\l}\l"];
+    N0 -> N2;
+    N2 -> N3;
+    N3 -> N4;
+    N4 -> N5;
+    N5 -> N6;
+    N6 -> N7;
+    N7 -> N8;
+    N8 -> N1;
+}

src/test/run-make/graphviz-flowgraph/f19.rs

+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+pub fn expr_method_call_19() {
+    struct S19 { x: int }
+    impl S19 { fn inner(self) -> S19 { S19 { x: self.x + self.x } } }
+    let s = S19 { x: 19 };
+    s.inner().inner();
+}

src/test/run-make/graphviz-flowgraph/f20.dot-expected.dot

+digraph block {
+    N0[label="entry"];
+    N1[label="exit"];
+    N2[label="expr 2"];
+    N3[label="expr 0"];
+    N4[label="expr 20"];
+    N5[label="expr [2, 0, 20]"];
+    N6[label="local v"];
+    N7[label="expr v"];
+    N8[label="expr 20"];
+    N9[label="expr v[20]"];
+    N10[label="block { let v = [2, 0, 20]; v[20]; }"];
+    N0 -> N2;
+    N2 -> N3;
+    N3 -> N4;
+    N4 -> N5;
+    N5 -> N6;
+    N6 -> N7;
+    N7 -> N8;
+    N8 -> N9;
+    N9 -> N10;
+    N10 -> N1;
+}

src/test/run-make/graphviz-flowgraph/f20.rs

+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+pub fn expr_index_20() {
+    let v = [2, 0, 20];
+    v[20];
+}

src/test/run-make/graphviz-flowgraph/f21.dot-expected.dot

+digraph block {
+    N0[label="entry"];
+    N1[label="exit"];
+    N2[label="expr 15"];
+    N3[label="local mut x"];
+    N4[label="expr 151"];
+    N5[label="local mut y"];
+    N6[label="(dummy_node)"];
+    N7[label="expr \'outer:\l    loop  {\l        \'inner:\l            loop  {\l                if x == 1 { break \'outer ; \"unreachable\"; }\l                if y >= 2 { return; \"unreachable\"; }\l                y -= 3;\l                x -= 5;\l            }\l        \"unreachable\";\l    }\l"];
+    N8[label="(dummy_node)"];
+    N9[label="expr \'inner:\l    loop  {\l        if x == 1 { break \'outer ; \"unreachable\"; }\l        if y >= 2 { return; \"unreachable\"; }\l        y -= 3;\l        x -= 5;\l    }\l"];
+    N10[label="expr x"];
+    N11[label="expr 1"];
+    N12[label="expr x == 1"];
+    N13[label="expr break \'outer"];
+    N14[label="(dummy_node)"];
+    N15[label="expr \"unreachable\""];
+    N16[label="block { break \'outer ; \"unreachable\"; }"];
+    N17[label="expr if x == 1 { break \'outer ; \"unreachable\"; }"];
+    N18[label="expr y"];
+    N19[label="expr 2"];
+    N20[label="expr y >= 2"];
+    N21[label="expr return"];
+    N22[label="(dummy_node)"];
+    N23[label="expr \"unreachable\""];
+    N24[label="block { return; \"unreachable\"; }"];
+    N25[label="expr if y >= 2 { return; \"unreachable\"; }"];
+    N26[label="expr 3"];
+    N27[label="expr y"];
+    N28[label="expr y -= 3"];
+    N29[label="expr 5"];
+    N30[label="expr x"];
+    N31[label="expr x -= 5"];
+    N32[label="block {\l    if x == 1 { break \'outer ; \"unreachable\"; }\l    if y >= 2 { return; \"unreachable\"; }\l    y -= 3;\l    x -= 5;\l}\l"];
+    N33[label="expr \"unreachable\""];
+    N34[label="block {\l    \'inner:\l        loop  {\l            if x == 1 { break \'outer ; \"unreachable\"; }\l            if y >= 2 { return; \"unreachable\"; }\l            y -= 3;\l            x -= 5;\l        }\l    \"unreachable\";\l}\l"];
+    N35[label="block {\l    let mut x = 15;\l    let mut y = 151;\l    \'outer:\l        loop  {\l            \'inner:\l                loop  {\l                    if x == 1 { break \'outer ; \"unreachable\"; }\l                    if y >= 2 { return; \"unreachable\"; }\l                    y -= 3;\l                    x -= 5;\l                }\l            \"unreachable\";\l        }\l}\l"];
+    N0 -> N2;
+    N2 -> N3;
+    N3 -> N4;
+    N4 -> N5;
+    N5 -> N6;
+    N6 -> N8;
+    N8 -> N10;
+    N10 -> N11;
+    N11 -> N12;
+    N12 -> N13;
+    N13 -> N7[label="exiting scope_0 expr break \'outer,\lexiting scope_1 stmt break \'outer ;,\lexiting scope_2 block { break \'outer ; \"unreachable\"; },\lexiting scope_3 expr if x == 1 { break \'outer ; \"unreachable\"; },\lexiting scope_4 stmt if x == 1 { break \'outer ; \"unreachable\"; },\lexiting scope_5 block {\l    if x == 1 { break \'outer ; \"unreachable\"; }\l    if y >= 2 { return; \"unreachable\"; }\l    y -= 3;\l    x -= 5;\l}\l,\lexiting scope_6 expr \'inner:\l    loop  {\l        if x == 1 { break \'outer ; \"unreachable\"; }\l        if y >= 2 { return; \"unreachable\"; }\l        y -= 3;\l        x -= 5;\l    }\l,\lexiting scope_7 stmt \'inner:\l    loop  {\l        if x == 1 { break \'outer ; \"unreachable\"; }\l        if y >= 2 { return; \"unreachable\"; }\l        y -= 3;\l        x -= 5;\l    }\l,\lexiting scope_8 block {\l    \'inner:\l        loop  {\l            if x == 1 { break \'outer ; \"unreachable\"; }\l            if y >= 2 { return; \"unreachable\"; }\l            y -= 3;\l            x -= 5;\l        }\l    \"unreachable\";\l}\l"];
+    N14 -> N15;
+    N15 -> N16;
+    N12 -> N17;
+    N16 -> N17;
+    N17 -> N18;
+    N18 -> N19;
+    N19 -> N20;
+    N20 -> N21;
+    N21 -> N1[label="exiting scope_0 expr \'inner:\l    loop  {\l        if x == 1 { break \'outer ; \"unreachable\"; }\l        if y >= 2 { return; \"unreachable\"; }\l        y -= 3;\l        x -= 5;\l    }\l,\lexiting scope_1 expr \'outer:\l    loop  {\l        \'inner:\l            loop  {\l                if x == 1 { break \'outer ; \"unreachable\"; }\l                if y >= 2 { return; \"unreachable\"; }\l                y -= 3;\l                x -= 5;\l            }\l        \"unreachable\";\l    }\l"];
+    N22 -> N23;
+    N23 -> N24;
+    N20 -> N25;
+    N24 -> N25;
+    N25 -> N26;
+    N26 -> N27;
+    N27 -> N28;
+    N28 -> N29;
+    N29 -> N30;
+    N30 -> N31;
+    N31 -> N32;
+    N32 -> N8;
+    N9 -> N33;
+    N33 -> N34;
+    N34 -> N6;
+    N7 -> N35;
+    N35 -> N1;
+}

src/test/run-make/graphviz-flowgraph/f21.rs

+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#[allow(unreachable_code)]
+pub fn expr_break_label_21() {
+    let mut x = 15;
+    let mut y = 151;
+    'outer: loop {
+        'inner: loop {
+            if x == 1 {
+                break 'outer;
+                "unreachable";
+            }
+            if y >= 2 {
+                return;
+                "unreachable";
+            }
+            y -= 3;
+            x -= 5;
+        }
+        "unreachable";
+    }
+}

src/test/run-make/graphviz-flowgraph/f22.dot-expected.dot

+digraph block {
+    N0[label="entry"];
+    N1[label="exit"];
+    N2[label="expr 15"];
+    N3[label="local mut x"];
+    N4[label="expr 151"];
+    N5[label="local mut y"];
+    N6[label="(dummy_node)"];
+    N7[label="expr \'outer:\l    loop  {\l        \'inner:\l            loop  {\l                if x == 1 { continue \'outer ; \"unreachable\"; }\l                if y >= 2 { return; \"unreachable\"; }\l                x -= 1;\l                y -= 3;\l            }\l        \"unreachable\";\l    }\l"];
+    N8[label="(dummy_node)"];
+    N9[label="expr \'inner:\l    loop  {\l        if x == 1 { continue \'outer ; \"unreachable\"; }\l        if y >= 2 { return; \"unreachable\"; }\l        x -= 1;\l        y -= 3;\l    }\l"];
+    N10[label="expr x"];
+    N11[label="expr 1"];
+    N12[label="expr x == 1"];
+    N13[label="expr continue \'outer"];
+    N14[label="(dummy_node)"];
+    N15[label="expr \"unreachable\""];
+    N16[label="block { continue \'outer ; \"unreachable\"; }"];
+    N17[label="expr if x == 1 { continue \'outer ; \"unreachable\"; }"];
+    N18[label="expr y"];
+    N19[label="expr 2"];
+    N20[label="expr y >= 2"];
+    N21[label="expr return"];
+    N22[label="(dummy_node)"];
+    N23[label="expr \"unreachable\""];
+    N24[label="block { return; \"unreachable\"; }"];
+    N25[label="expr if y >= 2 { return; \"unreachable\"; }"];
+    N26[label="expr 1"];
+    N27[label="expr x"];
+    N28[label="expr x -= 1"];
+    N29[label="expr 3"];
+    N30[label="expr y"];
+    N31[label="expr y -= 3"];
+    N32[label="block {\l    if x == 1 { continue \'outer ; \"unreachable\"; }\l    if y >= 2 { return; \"unreachable\"; }\l    x -= 1;\l    y -= 3;\l}\l"];
+    N33[label="expr \"unreachable\""];
+    N34[label="block {\l    \'inner:\l        loop  {\l            if x == 1 { continue \'outer ; \"unreachable\"; }\l            if y >= 2 { return; \"unreachable\"; }\l            x -= 1;\l            y -= 3;\l        }\l    \"unreachable\";\l}\l"];
+    N35[label="expr \"unreachable\""];
+    N36[label="block {\l    let mut x = 15;\l    let mut y = 151;\l    \'outer:\l        loop  {\l            \'inner:\l                loop  {\l                    if x == 1 { continue \'outer ; \"unreachable\"; }\l                    if y >= 2 { return; \"unreachable\"; }\l                    x -= 1;\l                    y -= 3;\l                }\l            \"unreachable\";\l        }\l    \"unreachable\";\l}\l"];
+    N0 -> N2;
+    N2 -> N3;
+    N3 -> N4;
+    N4 -> N5;
+    N5 -> N6;
+    N6 -> N8;
+    N8 -> N10;
+    N10 -> N11;
+    N11 -> N12;
+    N12 -> N13;
+    N13 -> N6[label="exiting scope_0 expr continue \'outer,\lexiting scope_1 stmt continue \'outer ;,\lexiting scope_2 block { continue \'outer ; \"unreachable\"; },\lexiting scope_3 expr if x == 1 { continue \'outer ; \"unreachable\"; },\lexiting scope_4 stmt if x == 1 { continue \'outer ; \"unreachable\"; },\lexiting scope_5 block {\l    if x == 1 { continue \'outer ; \"unreachable\"; }\l    if y >= 2 { return; \"unreachable\"; }\l    x -= 1;\l    y -= 3;\l}\l,\lexiting scope_6 expr \'inner:\l    loop  {\l        if x == 1 { continue \'outer ; \"unreachable\"; }\l        if y >= 2 { return; \"unreachable\"; }\l        x -= 1;\l        y -= 3;\l    }\l,\lexiting scope_7 stmt \'inner:\l    loop  {\l        if x == 1 { continue \'outer ; \"unreachable\"; }\l        if y >= 2 { return; \"unreachable\"; }\l        x -= 1;\l        y -= 3;\l    }\l,\lexiting scope_8 block {\l    \'inner:\l        loop  {\l            if x == 1 { continue \'outer ; \"unreachable\"; }\l            if y >= 2 { return; \"unreachable\"; }\l            x -= 1;\l            y -= 3;\l        }\l    \"unreachable\";\l}\l"];
+    N14 -> N15;
+    N15 -> N16;
+    N12 -> N17;
+    N16 -> N17;
+    N17 -> N18;
+    N18 -> N19;
+    N19 -> N20;
+    N20 -> N21;
+    N21 -> N1[label="exiting scope_0 expr \'inner:\l    loop  {\l        if x == 1 { continue \'outer ; \"unreachable\"; }\l        if y >= 2 { return; \"unreachable\"; }\l        x -= 1;\l        y -= 3;\l    }\l,\lexiting scope_1 expr \'outer:\l    loop  {\l        \'inner:\l            loop  {\l                if x == 1 { continue \'outer ; \"unreachable\"; }\l                if y >= 2 { return; \"unreachable\"; }\l                x -= 1;\l                y -= 3;\l            }\l        \"unreachable\";\l    }\l"];
+    N22 -> N23;
+    N23 -> N24;
+    N20 -> N25;
+    N24 -> N25;
+    N25 -> N26;
+    N26 -> N27;
+    N27 -> N28;
+    N28 -> N29;
+    N29 -> N30;
+    N30 -> N31;
+    N31 -> N32;
+    N32 -> N8;
+    N9 -> N33;
+    N33 -> N34;
+    N34 -> N6;
+    N7 -> N35;
+    N35 -> N36;
+    N36 -> N1;
+}

src/test/run-make/graphviz-flowgraph/f22.rs

+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#[allow(unreachable_code)]
+pub fn expr_break_label_21() {
+    let mut x = 15;
+    let mut y = 151;
+    'outer: loop {
+        'inner: loop {
+            if x == 1 {
+                continue 'outer;
+                "unreachable";
+            }
+            if y >= 2 {
+                return;
+                "unreachable";
+            }
+            x -= 1;
+            y -= 3;
+        }
+        "unreachable";
+    }
+    "unreachable";
+}