Add test for -Z unpretty=thir-tree

Author: syvb

src/test/ui/thir-tree.rs

@@ -0,0 +1,4 @@
+// compile-flags: -Z unpretty=thir-tree
+// check-pass
+
+pub fn main() {}

src/test/ui/thir-tree.stdout

@@ -0,0 +1,55 @@
+DefId(0:3 ~ thir_tree[348d]::main):
+Thir {
+    arms: [],
+    exprs: [
+        Expr {
+            ty: (),
+            temp_lifetime: Some(
+                Node(2),
+            ),
+            span: $DIR/thir-tree.rs:4:15: 4:17 (#0),
+            kind: Block {
+                body: Block {
+                    targeted_by_break: false,
+                    region_scope: Node(1),
+                    opt_destruction_scope: None,
+                    span: $DIR/thir-tree.rs:4:15: 4:17 (#0),
+                    stmts: [],
+                    expr: None,
+                    safety_mode: Safe,
+                },
+            },
+        },
+        Expr {
+            ty: (),
+            temp_lifetime: Some(
+                Node(2),
+            ),
+            span: $DIR/thir-tree.rs:4:15: 4:17 (#0),
+            kind: Scope {
+                region_scope: Node(2),
+                lint_level: Explicit(
+                    HirId {
+                        owner: DefId(0:3 ~ thir_tree[348d]::main),
+                        local_id: 2,
+                    },
+                ),
+                value: e0,
+            },
+        },
+        Expr {
+            ty: (),
+            temp_lifetime: Some(
+                Node(2),
+            ),
+            span: $DIR/thir-tree.rs:4:15: 4:17 (#0),
+            kind: Scope {
+                region_scope: Destruction(2),
+                lint_level: Inherited,
+                value: e1,
+            },
+        },
+    ],
+    stmts: [],
+}
+