cranelift: ISLE printer (#10962)

* skeleton

* setup printer tests

* get one test passing

* tests pass

* support remaining tests

* basic pretty printing

* cleanup

* simplification to fits()

* missing docs

* new_without_pos_tracking constructor

* move printer tests to existing ISLE tests

* destructure self

Author: mmcloughlin

cranelift/isle/isle/build.rs

@@ -15,6 +15,10 @@ fn main() {
     emit_tests(&mut out, "isle_examples/link", "run_link");
     emit_tests(&mut out, "isle_examples/run", "run_run");
 
+    emit_tests(&mut out, "isle_examples/pass", "run_print");
+    emit_tests(&mut out, "isle_examples/link", "run_print");
+    emit_tests(&mut out, "isle_examples/run", "run_print");
+
     let output = out_dir.join("isle_tests.rs");
     std::fs::write(output, out).unwrap();
 }

cranelift/isle/isle/src/lib.rs

@@ -28,6 +28,7 @@ pub mod lexer;
 mod log;
 pub mod overlap;
 pub mod parser;
+pub mod printer;
 pub mod sema;
 pub mod serialize;
 pub mod stablemapset;

cranelift/isle/isle/src/parser.rs

@@ -12,12 +12,20 @@ pub fn parse(lexer: Lexer) -> Result<Vec<Def>> {
     parser.parse_defs()
 }
 
+/// Parse without positional information. Provided mainly to support testing, to
+/// enable equality testing on structure alone.
+pub fn parse_without_pos(lexer: Lexer) -> Result<Vec<Def>> {
+    let parser = Parser::new_without_pos_tracking(lexer);
+    parser.parse_defs()
+}
+
 /// The ISLE parser.
 ///
 /// Takes in a lexer and creates an AST.
 #[derive(Clone, Debug)]
 struct Parser<'a> {
     lexer: Lexer<'a>,
+    disable_pos: bool,
 }
 
 /// Used during parsing a `(rule ...)` to encapsulate some form that
@@ -31,7 +39,17 @@ enum IfLetOrExpr {
 impl<'a> Parser<'a> {
     /// Construct a new parser from the given lexer.
     pub fn new(lexer: Lexer<'a>) -> Parser<'a> {
-        Parser { lexer }
+        Parser {
+            lexer,
+            disable_pos: false,
+        }
+    }
+
+    fn new_without_pos_tracking(lexer: Lexer<'a>) -> Parser<'a> {
+        Parser {
+            lexer,
+            disable_pos: true,
+        }
     }
 
     fn error(&self, pos: Pos, msg: String) -> Error {
@@ -72,9 +90,13 @@ impl<'a> Parser<'a> {
     }
 
     fn pos(&self) -> Pos {
-        self.lexer
-            .peek()
-            .map_or_else(|| self.lexer.pos(), |(pos, _)| *pos)
+        if !self.disable_pos {
+            self.lexer
+                .peek()
+                .map_or_else(|| self.lexer.pos(), |(pos, _)| *pos)
+        } else {
+            Pos::default()
+        }
     }
 
     fn is_lparen(&self) -> bool {