[build] Implement registers code generation in the Rust meta crate;

lib/codegen/meta/src/srcgen.rs

@@ -12,24 +12,6 @@ use error;
 
 static SHIFTWIDTH: usize = 4;
 
-struct _IndentedScope {
-    fmt: Formatter,
-    after: Option<String>,
-}
-
-impl _IndentedScope {
-    fn _enter(&mut self) {
-        self.fmt._indent_push();
-    }
-
-    fn _exit(&mut self) {
-        self.fmt._indent_pop();
-        if let Some(ref s) = self.after {
-            self.fmt.line(&s);
-        }
-    }
-}
-
 pub struct Formatter {
     indent: usize,
     lines: Vec<String>,
@@ -46,16 +28,23 @@ impl Formatter {
     }
 
     /// Increase current indentation level by one.
-    pub fn _indent_push(&mut self) {
+    pub fn indent_push(&mut self) {
         self.indent += 1;
     }
 
     /// Decrease indentation by one level.
-    pub fn _indent_pop(&mut self) {
+    pub fn indent_pop(&mut self) {
         assert!(self.indent > 0, "Already at top level indentation");
         self.indent -= 1;
     }
 
+    pub fn indent<T, F: FnOnce(&mut Formatter) -> T>(&mut self, f: F) -> T {
+        self.indent_push();
+        let ret = f(self);
+        self.indent_pop();
+        ret
+    }
+
     /// Get the current whitespace indentation in the form of a String.
     fn get_indent(&self) -> String {
         if self.indent == 0 {
@@ -68,9 +57,9 @@ impl Formatter {
     /// Get a string containing whitespace outdented one level. Used for
     /// lines of code that are inside a single indented block.
     fn _get_outdent(&mut self) -> String {
-        self._indent_push();
+        self.indent_push();
         let s = self.get_indent();
-        self._indent_pop();
+        self.indent_pop();
         s
     }
 
@@ -103,13 +92,6 @@ impl Formatter {
         Ok(())
     }
 
-    /// Return a scope object for use with a `with` statement.
-    /// The optional `before` and `after` parameters are surrounding lines
-    /// which are *not* indented.
-    fn _indented(&self, _before: Option<&str>, _after: Option<&str>) -> _IndentedScope {
-        unimplemented!();
-    }
-
     /// Add one or more lines after stripping common indentation.
     pub fn _multi_line(&mut self, s: &str) {
         parse_multiline(s).into_iter().for_each(|l| self.line(&l));
@@ -158,7 +140,6 @@ fn parse_multiline(s: &str) -> Vec<String> {
         .iter()
         .skip(1)
         .map(|l| l.len() - l.trim_left().len())
-        .filter(|&i| i > 0)
         .min();
 
     // Strip off leading blank lines.
@@ -257,9 +238,9 @@ mod srcgen_tests {
     fn formatter_basic_example_works() {
         let mut fmt = Formatter::new();
         fmt.line("Hello line 1");
-        fmt._indent_push();
+        fmt.indent_push();
         fmt._comment("Nested comment");
-        fmt._indent_pop();
+        fmt.indent_pop();
         fmt.line("Back home again");
         let expected_lines = vec![
             "Hello line 1\n",
@@ -277,9 +258,9 @@ mod srcgen_tests {
         let actual_results = Vec::with_capacity(4);
         (0..3).for_each(|_| {
             fmt.get_indent();
-            fmt._indent_push();
+            fmt.indent_push();
         });
-        (0..3).for_each(|_| fmt._indent_pop());
+        (0..3).for_each(|_| fmt.indent_pop());
         fmt.get_indent();
 
         actual_results
@@ -300,7 +281,7 @@ mod srcgen_tests {
     fn fmt_can_add_indented_line() {
         let mut fmt = Formatter::new();
         fmt.line("hello");
-        fmt._indent_push();
+        fmt.indent_push();
         fmt.line("world");
         let expected_lines = vec!["hello\n", "    world\n"];
         assert_eq!(fmt.lines, expected_lines);