Add pretty printing tests for if/else.

The AST pretty printing is a bit wonky. The HIR pretty printing is
extremely wonky.

Author: nnethercote

tests/pretty/hir-if-else.pp

@@ -0,0 +1,48 @@
+#[prelude_import]
+use ::std::prelude::rust_2015::*;
+#[macro_use]
+extern crate std;
+//@ pretty-compare-only
+//@ pretty-mode:hir
+//@ pp-exact:hir-if-else.pp
+
+fn f(x: u32,
+    y:
+        u32) {
+    let mut a = 0;
+    if x > y { a = 1; } else { a = 2; }
+
+            if x < 1
+                    {
+                        a = 1;
+                    } else if x < 2
+                       {
+                           a = 2;
+                       } else if x < 3
+                          {
+                              a = 3;
+                          } else if x < 4 { a = 4; } else { a = 5; }
+
+                             if x < y
+                                     {
+                                         a += 1;
+                                         a += 1;
+                                         a += 1;
+                                         a += 1;
+                                         a += 1;
+                                         a += 1;
+                                     } else { a += 1; a += 1; a += 1; a += 1; a += 1; a += 1; }
+
+                                     if x < 1
+                                             {
+                                                 if x < 2
+                                                         {
+                                                             if x < 3
+                                                                     {
+                                                                         a += 1;
+                                                                     } else if x < 4
+                                                                        { a += 1; if x < 5 { a += 1; } }
+                                                                        } else if x < 6 { a += 1; } }
+                                                                 }
+
+                                                             fn main() { f(3, 4); }

tests/pretty/hir-if-else.rs

@@ -0,0 +1,59 @@
+//@ pretty-compare-only
+//@ pretty-mode:hir
+//@ pp-exact:hir-if-else.pp
+
+fn f(x: u32, y: u32) {
+    let mut a = 0;
+    if x > y {
+        a = 1;
+    } else {
+        a = 2;
+    }
+
+    if x < 1 {
+        a = 1;
+    } else if x < 2 {
+        a = 2;
+    } else if x < 3 {
+        a = 3;
+    } else if x < 4 {
+        a = 4;
+    } else {
+        a = 5;
+    }
+
+    if x < y {
+        a += 1;
+        a += 1;
+        a += 1;
+        a += 1;
+        a += 1;
+        a += 1;
+    } else {
+        a += 1;
+        a += 1;
+        a += 1;
+        a += 1;
+        a += 1;
+        a += 1;
+    }
+
+    if x < 1 {
+        if x < 2 {
+            if x < 3 {
+                a += 1;
+            } else if x < 4 {
+                a += 1;
+                if x < 5 {
+                    a += 1;
+                }
+            }
+        } else if x < 6 {
+            a += 1;
+        }
+    }
+}
+
+fn main() {
+    f(3, 4);
+}

tests/pretty/if-else.pp

@@ -0,0 +1,52 @@
+#![feature(prelude_import)]
+#![no_std]
+#[prelude_import]
+use ::std::prelude::rust_2015::*;
+#[macro_use]
+extern crate std;
+//@ pretty-compare-only
+//@ pretty-mode:expanded
+//@ pp-exact:if-else.pp
+
+fn f(x: u32, y: u32) {
+    let mut a = 0;
+    if x > y { a = 1; } else { a = 2; }
+
+    if x < 1 {
+            a = 1;
+        } else if x < 2 {
+           a = 2;
+       } else if x < 3 { a = 3; } else if x < 4 { a = 4; } else { a = 5; }
+
+    if x < y {
+            a += 1;
+            a += 1;
+            a += 1;
+        } else {
+           a += 1;
+           a += 1;
+           a += 1;
+           a += 1;
+           a += 1;
+           a += 1;
+           a += 1;
+           a += 1;
+           a += 1;
+           a += 1;
+           a += 1;
+           a += 1;
+           a += 1;
+           a += 1;
+           a += 1;
+       }
+
+    if x < 1 {
+            if x < 2 {
+                    if x < 3 {
+                            a += 1;
+                        } else if x < 4 { a += 1; if x < 5 { a += 1; } }
+                } else if x < 6 { a += 1; }
+        }
+}
+
+fn main() { f(3, 4); }

tests/pretty/if-else.rs

@@ -0,0 +1,65 @@
+//@ pretty-compare-only
+//@ pretty-mode:expanded
+//@ pp-exact:if-else.pp
+
+fn f(x: u32, y: u32) {
+    let mut a = 0;
+    if x > y {
+        a = 1;
+    } else {
+        a = 2;
+    }
+
+    if x < 1 {
+        a = 1;
+    } else if x < 2 {
+        a = 2;
+    } else if x < 3 {
+        a = 3;
+    } else if x < 4 {
+        a = 4;
+    } else {
+        a = 5;
+    }
+
+    if x < y {
+        a += 1;
+        a += 1;
+        a += 1;
+    } else {
+        a += 1;
+        a += 1;
+        a += 1;
+        a += 1;
+        a += 1;
+        a += 1;
+        a += 1;
+        a += 1;
+        a += 1;
+        a += 1;
+        a += 1;
+        a += 1;
+        a += 1;
+        a += 1;
+        a += 1;
+    }
+
+    if x < 1 {
+        if x < 2 {
+            if x < 3 {
+                a += 1;
+            } else if x < 4 {
+                a += 1;
+                if x < 5 {
+                    a += 1;
+                }
+            }
+        } else if x < 6 {
+            a += 1;
+        }
+    }
+}
+
+fn main() {
+    f(3, 4);
+}