tamer: nir::interp: Do not include original specification in generated desc

This is a really obvious problem in retrospect, which makes me feel rather
silly.

The output was useful, but I don't have time to deal with this any further
right now.  The comments in the commit explain the problem---that the output
ends up being interpolated as part of the fixpoint test, in an incorrect
context, and so the code that we generate is invalid.  Also goes to show why
the fixpoint tests are important.

(Yes, they're still disabled for meta-interp, I'm trying to get them
enabled.)

DEV-13163

tamer/src/nir/interp.rs

@@ -41,7 +41,7 @@
 //!
 //! ```xml
 //!   <param name="@___dsgr_01@"
-//!          desc="Generated from interpolated string `foo{@bar@}baz`">
+//!          desc="Generated from interpolated string">
 //!     <text>foo</text>
 //!     <param-value name="@bar@" />
 //!     <text>baz</text>
@@ -69,6 +69,12 @@
 //!   then it is interpreted as a literal within the context of the template
 //!   system and is echoed back unchanged.
 //!
+//! There is currently no way to escape `{` within a string.
+//! Such a feature will be considered in the future,
+//!   but for the meantime,
+//!   this can be worked around by using metavariables that expand into the
+//!     desired literal.
+//!
 //! Desugared Spans
 //! ---------------
 //! [`Span`]s for the generated tokens are derived from the specification
@@ -107,8 +113,8 @@ use crate::{
     parse::{prelude::*, util::SPair, NoContext},
     span::Span,
     sym::{
-        st::quick_contains_byte, GlobalSymbolIntern, GlobalSymbolResolve,
-        SymbolId,
+        st::{quick_contains_byte, raw::S_GEN_FROM_INTERP},
+        GlobalSymbolIntern, GlobalSymbolResolve, SymbolId,
     },
 };
 use std::{error::Error, fmt::Display};
@@ -286,25 +292,25 @@ impl ParseState for InterpState {
                     .with_lookahead(tok)
             }
 
+            // Note: This historically generated a description containing
+            //     the interpolated string,
+            //       which was useful when looking at generated code.
+            //   But this ends up producing output that is not a fixpoint,
+            //     because if you run it back through the compiler,
+            //     it needs interpolation again,
+            //       but now in an incorrect context.
+            //   We can revisit this
+            //     (see commit introducing this comment)
+            //     when we introduce escaping of some form,
+            //       if it's worth doing.
             GenDesc(sym, gen_ident) => {
                 let s = sym.lookup_str();
 
-                // Description is not interned since there's no use in
-                //   wasting time hashing something that will not be
-                //   referenced
-                //     (it's just informative for a human).
-                // Note that this means that tests cannot compare SymbolId.
-                let gen_desc = format!(
-                    "Generated from interpolated string {}",
-                    TtQuote::wrap(s)
-                )
-                .clone_uninterned();
-
                 // Begin parsing in a _literal_ context,
                 //   since interpolation is most commonly utilized with literal
                 //   prefixes.
                 Transition(ParseLiteralAt(s, gen_ident, 0))
-                    .ok(Nir::Desc(SPair(gen_desc, span)))
+                    .ok(Nir::Desc(SPair(S_GEN_FROM_INTERP, span)))
                     .with_lookahead(tok)
             }
 

tamer/src/nir/interp/test.rs

@@ -22,7 +22,6 @@ use crate::{
     nir::NirEntity,
     parse::{Parsed, ParsedResult, Parser},
     span::dummy::{DUMMY_CONTEXT as DC, *},
-    sym::GlobalSymbolResolve,
 };
 use std::assert_matches::assert_matches;
 use Parsed::*;
@@ -81,7 +80,6 @@ fn does_not_desugar_text() {
 
 fn expect_expanded_header(
     sut: &mut Parser<InterpState, std::vec::IntoIter<Nir>>,
-    given_val: &str,
     span: Span,
 ) -> SymbolId {
     let GenIdentSymbolId(expect_name) = gen_tpl_param_ident_at_offset(span);
@@ -103,9 +101,8 @@ fn expect_expanded_header(
     );
     assert_matches!(
         sut.next(),
-        Some(Ok(Object(Nir::Desc(SPair(desc_str, desc_span)))))
-            if desc_str.lookup_str().contains(given_val)
-                && desc_span == span
+        Some(Ok(Object(Nir::Desc(SPair(S_GEN_FROM_INTERP, desc_span)))))
+            if desc_span == span
     );
 
     expect_name_sym
@@ -133,7 +130,7 @@ fn desugars_spec_with_only_var() {
 
     let mut sut = Sut::parse(toks.into_iter());
 
-    let expect_name = expect_expanded_header(&mut sut, given_val, a);
+    let expect_name = expect_expanded_header(&mut sut, a);
 
     assert_eq!(
         Ok(vec![
@@ -180,7 +177,7 @@ fn concrete_bind_ident_desugars_into_abstract_bind_after_interpolation() {
 
     let mut sut = Sut::parse(toks.into_iter());
 
-    let expect_name = expect_expanded_header(&mut sut, given_val, a);
+    let expect_name = expect_expanded_header(&mut sut, a);
 
     assert_eq!(
         Ok(vec![
@@ -222,7 +219,7 @@ fn desugars_literal_with_ending_var() {
 
     let mut sut = Sut::parse(toks.into_iter());
 
-    let expect_name = expect_expanded_header(&mut sut, given_val, a);
+    let expect_name = expect_expanded_header(&mut sut, a);
 
     assert_eq!(
         Ok(vec![
@@ -269,7 +266,7 @@ fn desugars_var_with_ending_literal() {
 
     let mut sut = Sut::parse(toks.into_iter());
 
-    let expect_name = expect_expanded_header(&mut sut, given_val, a);
+    let expect_name = expect_expanded_header(&mut sut, a);
 
     assert_eq!(
         Ok(vec![
@@ -306,7 +303,7 @@ fn desugars_many_vars_and_literals() {
 
     let mut sut = Sut::parse(toks.into_iter());
 
-    let expect_name = expect_expanded_header(&mut sut, given_val, a);
+    let expect_name = expect_expanded_header(&mut sut, a);
 
     assert_eq!(
         Ok(vec![
@@ -356,7 +353,7 @@ fn proper_multibyte_handling() {
 
     let mut sut = Sut::parse(toks.into_iter());
 
-    let expect_name = expect_expanded_header(&mut sut, given_val, a);
+    let expect_name = expect_expanded_header(&mut sut, a);
 
     assert_eq!(
         Ok(vec![
@@ -397,7 +394,7 @@ fn desugars_adjacent_interpolated_vars() {
 
     let mut sut = Sut::parse(toks.into_iter());
 
-    let expect_name = expect_expanded_header(&mut sut, given_val, a);
+    let expect_name = expect_expanded_header(&mut sut, a);
 
     assert_eq!(
         Ok(vec![
@@ -432,7 +429,7 @@ fn error_missing_closing_interp_delim() {
 
     let mut sut = Sut::parse(toks.into_iter());
 
-    let expect_name = expect_expanded_header(&mut sut, given_val, a);
+    let expect_name = expect_expanded_header(&mut sut, a);
 
     assert_eq!(
         vec![
@@ -478,7 +475,7 @@ fn error_nested_delim() {
 
     let mut sut = Sut::parse(toks.into_iter());
 
-    let expect_name = expect_expanded_header(&mut sut, given_val, a);
+    let expect_name = expect_expanded_header(&mut sut, a);
 
     assert_eq!(
         vec![
@@ -527,7 +524,7 @@ fn error_empty_interp() {
 
     let mut sut = Sut::parse(toks.into_iter());
 
-    let expect_name = expect_expanded_header(&mut sut, given_val, a);
+    let expect_name = expect_expanded_header(&mut sut, a);
 
     assert_eq!(
         vec![
@@ -569,7 +566,7 @@ fn error_close_before_open() {
 
     let mut sut = Sut::parse(toks.into_iter());
 
-    let expect_name = expect_expanded_header(&mut sut, given_val, a);
+    let expect_name = expect_expanded_header(&mut sut, a);
 
     assert_eq!(
         vec![

tamer/src/sym/prefill.rs

@@ -733,6 +733,8 @@ pub mod st {
         URI_LV_TPL: uri "http://www.lovullo.com/rater/apply-template",
         URI_LV_WORKSHEET: uri "http://www.lovullo.com/rater/worksheet",
 
+        S_GEN_FROM_INTERP: str "Generated from interpolated string",
+
         // Common whitespace.
         //
         // _This does not represent all forms of whitespace!_

tamer/tests/xmli/meta-interp/expected.xml

@@ -15,21 +15,21 @@
   <template name="_interp-non-bind_"
             desc="Interpolation in non-binding position">
     <param name="@___dsgr_335@"
-           desc="Generated from interpolated string `{@bar@}`">
+           desc="Generated from interpolated string">
       <param-value name="@bar@" />
     </param>
     <param name="@___dsgr_368@"
-           desc="Generated from interpolated string `Prefix {@bar@}`">
+           desc="Generated from interpolated string">
       <text>Prefix </text>
       <param-value name="@bar@" />
     </param>
     <param name="@___dsgr_3a3@"
-           desc="Generated from interpolated string `{@bar@} suffix`">
+           desc="Generated from interpolated string">
       <param-value name="@bar@" />
       <text> suffix</text>
     </param>
     <param name="@___dsgr_3da@"
-           desc="Generated from interpolated string `Prefix {@bar@} suffix`">
+           desc="Generated from interpolated string">
       <text>Prefix </text>
       <param-value name="@bar@" />
       <text> suffix</text>
@@ -45,21 +45,21 @@
   <template name="_with-abstract-ident_"
             desc="Metavariable interpolation in binding position">
     <param name="@___dsgr_4a8@"
-           desc="Generated from interpolated string `{@as@}`">
+           desc="Generated from interpolated string">
       <param-value name="@as@" />
     </param>
     <param name="@___dsgr_4ca@"
-           desc="Generated from interpolated string `prefix-{@as@}`">
+           desc="Generated from interpolated string">
       <text>prefix-</text>
       <param-value name="@as@" />
     </param>
     <param name="@___dsgr_4f4@"
-           desc="Generated from interpolated string `{@as@}-suffix`">
+           desc="Generated from interpolated string">
       <param-value name="@as@" />
       <text>-suffix</text>
     </param>
     <param name="@___dsgr_51e@"
-           desc="Generated from interpolated string `prefix-{@as@}-suffix`">
+           desc="Generated from interpolated string">
       <text>prefix-</text>
       <param-value name="@as@" />
       <text>-suffix</text>