fix(stim-parser)!: follow Stim's tag model

crates/stim-parser/src/ast/extended.rs

@@ -6,7 +6,7 @@
 
 use std::sync::Arc;
 
-use crate::ast::shared::{AnnotationOp, Axis, GateOp, MeasureOp, MppOp, NoiseOp, Tag};
+use crate::ast::shared::{AnnotationOp, Axis, GateOp, MeasureOp, MppOp, NoiseOp};
 use crate::diagnostics::{LineMap, Span};
 
 #[derive(Debug, Clone, PartialEq)]
@@ -51,12 +51,13 @@ pub enum ExtendedInstruction {
         span: Span,
     },
     MPad {
-        tags: Vec<Tag>,
+        tag: String,
         prob: Option<f64>,
         bits: Vec<bool>,
         span: Span,
     },
     Repeat {
+        tag: String,
         count: u64,
         body: Vec<ExtendedInstruction>,
         span: Span,
@@ -167,13 +168,14 @@ mod tests {
     fn measurement_count_scales_with_repeat() {
         let m = ExtendedInstruction::Measure(MeasureOp {
             name: MeasureName::M,
-            tags: vec![],
+            tag: String::new(),
             args: vec![],
             targets: vec![0, 1],
             span: span(),
         });
         let prog = ExtendedProgram {
             instructions: vec![ExtendedInstruction::Repeat {
+                tag: String::new(),
                 count: 3,
                 body: vec![m],
                 span: span(),
@@ -190,14 +192,14 @@ mod tests {
             instructions: vec![
                 ExtendedInstruction::Gate(GateOp {
                     name: GateName::H,
-                    tags: vec![],
+                    tag: String::new(),
                     args: vec![],
                     targets: vec![Target::Qubit(0), Target::Qubit(4)],
                     span: span(),
                 }),
                 ExtendedInstruction::Measure(MeasureOp {
                     name: MeasureName::M,
-                    tags: vec![],
+                    tag: String::new(),
                     args: vec![],
                     targets: vec![2],
                     span: span(),
@@ -212,10 +214,11 @@ mod tests {
     fn num_qubits_recurses_into_repeat() {
         let prog = ExtendedProgram {
             instructions: vec![ExtendedInstruction::Repeat {
+                tag: String::new(),
                 count: 3,
                 body: vec![ExtendedInstruction::Measure(MeasureOp {
                     name: MeasureName::M,
-                    tags: vec![],
+                    tag: String::new(),
                     args: vec![],
                     targets: vec![7],
                     span: span(),
@@ -241,7 +244,7 @@ mod tests {
     fn gate_op_is_shared_with_vanilla() {
         let _ = ExtendedInstruction::Gate(GateOp {
             name: GateName::H,
-            tags: vec![],
+            tag: String::new(),
             args: vec![],
             targets: vec![],
             span: span(),

crates/stim-parser/src/ast/shared.rs

@@ -65,25 +65,6 @@ pub struct PauliFactor {
     pub qubit: usize,
 }
 
-#[derive(Debug, Clone, PartialEq)]
-pub struct Tag {
-    pub name: String,
-    pub params: Vec<TagParam>,
-}
-
-#[derive(Debug, Clone, PartialEq)]
-pub enum TagParam {
-    Positional(f64),
-    /// A `key=value` tag parameter. `had_pi` records whether the value was
-    /// written as a `<n>[*]pi` (or bare `pi`) expression — rotation/U3 tags
-    /// require it (half-turn convention), and the printer re-emits `*pi`.
-    Named {
-        key: String,
-        value: f64,
-        had_pi: bool,
-    },
-}
-
 /// The rotation axis for an extended-dialect `R_X` / `R_Y` / `R_Z` rotation.
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum Axis {
@@ -99,7 +80,7 @@ pub enum Axis {
 #[derive(Debug, Clone, PartialEq)]
 pub struct GateOp {
     pub name: GateName,
-    pub tags: Vec<Tag>,
+    pub tag: String,
     pub args: Vec<f64>,
     pub targets: Vec<Target>,
     pub span: Span,
@@ -108,7 +89,7 @@ pub struct GateOp {
 #[derive(Debug, Clone, PartialEq)]
 pub struct NoiseOp {
     pub name: NoiseName,
-    pub tags: Vec<Tag>,
+    pub tag: String,
     pub args: Vec<f64>,
     pub targets: Vec<usize>,
     pub span: Span,
@@ -117,7 +98,7 @@ pub struct NoiseOp {
 #[derive(Debug, Clone, PartialEq)]
 pub struct MeasureOp {
     pub name: MeasureName,
-    pub tags: Vec<Tag>,
+    pub tag: String,
     pub args: Vec<f64>,
     pub targets: Vec<usize>,
     pub span: Span,
@@ -126,14 +107,15 @@ pub struct MeasureOp {
 #[derive(Debug, Clone, PartialEq)]
 pub struct AnnotationOp {
     pub kind: AnnotationKind,
+    pub tag: String,
     pub args: Vec<f64>,
     pub targets: Vec<usize>,
     pub span: Span,
 }
 
 #[derive(Debug, Clone, PartialEq)]
 pub struct MppOp {
-    pub tags: Vec<Tag>,
+    pub tag: String,
     pub args: Vec<f64>,
     pub products: Vec<Vec<PauliFactor>>,
     pub span: Span,

crates/stim-parser/src/ast/vanilla.rs

@@ -1,12 +1,12 @@
 // SPDX-FileCopyrightText: 2026 The PPVM Authors
 // SPDX-License-Identifier: Apache-2.0
 
-//! Vanilla Stim AST. Tags are preserved verbatim; the parser does not
-//! resolve the Stim dialect — that is the consumer's responsibility.
+//! Vanilla Stim AST. Tags are preserved as decoded opaque strings; the parser
+//! does not resolve the Stim dialect.
 
 use std::sync::Arc;
 
-use crate::ast::shared::{AnnotationOp, GateOp, MeasureOp, MppOp, NoiseOp, Tag};
+use crate::ast::shared::{AnnotationOp, GateOp, MeasureOp, MppOp, NoiseOp};
 use crate::diagnostics::{LineMap, Span};
 
 #[derive(Debug, Clone, PartialEq)]
@@ -17,12 +17,13 @@ pub enum Instruction {
     Annotation(AnnotationOp),
     Mpp(MppOp),
     MPad {
-        tags: Vec<Tag>,
+        tag: String,
         prob: Option<f64>,
         bits: Vec<usize>,
         span: Span,
     },
     Repeat {
+        tag: String,
         count: u64,
         body: Vec<Instruction>,
         span: Span,
@@ -57,7 +58,7 @@ mod tests {
         let p = Program {
             instructions: vec![Instruction::Gate(GateOp {
                 name: GateName::H,
-                tags: vec![],
+                tag: String::new(),
                 args: vec![],
                 targets: vec![],
                 span: Span::new(0, 1),
@@ -72,7 +73,7 @@ mod tests {
         let g = || {
             Instruction::Gate(GateOp {
                 name: GateName::H,
-                tags: vec![],
+                tag: String::new(),
                 args: vec![],
                 targets: vec![],
                 span: Span::new(0, 1),

crates/stim-parser/src/lib.rs

@@ -54,7 +54,7 @@ pub fn parse_extended(src: &str) -> Result<ExtendedProgram, Diagnostics> {
 pub mod prelude {
     pub use crate::ast::{
         AnnotationOp, Axis, ExtendedInstruction, ExtendedProgram, GateOp, Instruction, MeasureOp,
-        MppOp, NoiseOp, PauliAxis, PauliFactor, Program, Tag, TagParam, Target,
+        MppOp, NoiseOp, PauliAxis, PauliFactor, Program, Target,
     };
     pub use crate::diagnostics::{
         Diagnostic, DiagnosticSink, Diagnostics, Flow, LineMap, Severity, Span,