feat: Replace Tuple with unary sums (#891)

Closes #864.

Updates the `Display` impl of `Sum` as part of this change, so
```mermaid
graph LR
    subgraph 0 ["(0) CFG"]
        direction LR
        subgraph 2 ["(2) DataflowBlock"]
            direction LR
            3["(3) Input"]
            3--"0:0<br>usize"-->5
            4["(4) Output"]
            5["(5) Tag"]
            5--"0:0<br>Sum(General([TypeRow { types: [Type(Extension(CustomType { extension: IdentList(#quot;prelude#quot;), id: #quot;usize#quot;, args: [], bound: Eq }), Eq)] }, TypeRow { types: [Type(Extension(CustomType { extension: IdentList(#quot;prelude#quot;), id: #quot;usize#quot;, args: [], bound: Eq }), Eq)] }]))"-->4
        end
        2-."0:0".->6
        2-."1:0".->1
        1["(1) ExitBlock"]
        subgraph 6 ["(6) DataflowBlock"]
            direction LR
            7["(7) Input"]
            7--"0:1<br>usize"-->8
            8["(8) Output"]
            9["(9) const:sum:{tag:0, vals:[]}"]
            9--"0:0<br>Sum(UnitSum(1))"-->10
            10["(10) LoadConstant"]
            10--"0:0<br>Sum(UnitSum(1))"-->8
        end
        6-."0:0".->1
    end
```
is now rendered as
```mermaid
graph LR
    subgraph 0 ["(0) CFG"]
        direction LR
        subgraph 2 ["(2) DataflowBlock"]
            direction LR
            3["(3) Input"]
            3--"0:0<br>usize"-->5
            4["(4) Output"]
            5["(5) Tag"]
            5--"0:0<br>[usize]+[usize]"-->4
        end
        2-."0:0".->6
        2-."1:0".->1
        1["(1) ExitBlock"]
        subgraph 6 ["(6) DataflowBlock"]
            direction LR
            7["(7) Input"]
            7--"0:1<br>usize"-->8
            8["(8) Output"]
            9["(9) const:sum:{tag:0, vals:[]}"]
            9--"0:0<br>[]"-->10
            10["(10) LoadConstant"]
            10--"0:0<br>[]"-->8
        end
        6-."0:0".->1
    end
```
And tuples appear directly as `[usize, usize, ...]`.
We were incorrectly using the debug formatter for the internal types.

drive-by: Add rust snapshots to the pre-commit ignores. We don't want it
to modify whitespaces.

.pre-commit-config.yaml

@@ -11,8 +11,19 @@ repos:
       - id: check-yaml
       - id: detect-private-key
       - id: end-of-file-fixer
-        exclude: ^specification/schema/
+        exclude: |
+          (?x)^(
+            specification/schema/.*|
+            .*.snap|
+            .*.snap.new
+          )$
       - id: trailing-whitespace
+        exclude: |
+          (?x)^(
+            specification/schema/.*|
+            .*.snap|
+            .*.snap.new
+          )$
       - id: fix-byte-order-marker
       - id: mixed-line-ending
       # Python-specific

quantinuum-hugr-py/src/quantinuum_hugr/serialization/ops.py

@@ -178,11 +178,9 @@ def insert_child_dfg_signature(self, inputs: TypeRow, outputs: TypeRow) -> None:
         if isinstance(pred, tys.UnitSum):
             self.sum_rows = [[] for _ in range(cast(tys.UnitSum, pred).size)]
         else:
-            assert isinstance(pred, tys.GeneralSum)
             self.sum_rows = []
             for variant in pred.rows:
-                assert isinstance(variant, tys.TupleType)
-                self.sum_rows.append(variant.inner)
+                self.sum_rows.append(variant)
         self.other_outputs = outputs[1:]
 
     class Config:
@@ -346,8 +344,7 @@ def insert_port_types(self, in_types: TypeRow, out_types: TypeRow) -> None:
             assert isinstance(pred, tys.GeneralSum)
             self.sum_rows = []
             for ty in pred.rows:
-                assert isinstance(ty, tys.TupleType)
-                self.sum_rows.append(ty.inner)
+                self.sum_rows.append(ty)
         self.other_inputs = list(in_types[1:])
         self.outputs = list(out_types)
 

quantinuum-hugr-py/src/quantinuum_hugr/serialization/tys.py

@@ -144,13 +144,6 @@ class Array(MultiContainer):
     len: int
 
 
-class TupleType(BaseModel):
-    """Product type, known-size tuple over elements of type row."""
-
-    t: Literal["Tuple"] = "Tuple"
-    inner: "TypeRow"
-
-
 class UnitSum(BaseModel):
     """Simple predicate where all variants are empty tuples."""
 
@@ -286,7 +279,7 @@ class Type(RootModel):
     """A HUGR type."""
 
     root: Annotated[
-        Qubit | Variable | USize | PolyFuncType | Array | TupleType | SumType | Opaque,
+        Qubit | Variable | USize | PolyFuncType | Array | SumType | Opaque,
         WrapValidator(_json_custom_error_validator),
     ] = Field(discriminator="t")
 

quantinuum-hugr/src/hugr/views/snapshots/hugr__hugr__views__tests__dot_cfg.snap

@@ -1,5 +1,46 @@
 ---
-source: src/hugr/views/tests.rs
+source: quantinuum-hugr/src/hugr/views/tests.rs
 expression: h.dot_string()
 ---
-"digraph {\n0 [shape=plain label=<<table border=\"1\"><tr><td align=\"text\" border=\"0\" colspan=\"1\">(0) CFG</td></tr></table>>]\n1 [shape=plain label=<<table border=\"1\"><tr><td port=\"in0\" align=\"text\" colspan=\"1\" cellpadding=\"1\" border=\"0\">0</td></tr><tr><td align=\"text\" border=\"0\" colspan=\"1\">(1) ExitBlock</td></tr></table>>]\n2 [shape=plain label=<<table border=\"1\"><tr><td port=\"in0\" align=\"text\" colspan=\"2\" cellpadding=\"1\" border=\"0\">0</td></tr><tr><td align=\"text\" border=\"0\" colspan=\"2\">(2) DataflowBlock</td></tr><tr><td port=\"out0\" align=\"text\" colspan=\"1\" cellpadding=\"1\" border=\"0\">0</td><td port=\"out1\" align=\"text\" colspan=\"1\" cellpadding=\"1\" border=\"0\">1</td></tr></table>>]\n2:out0 -> 6:in0 [style=\"dashed\"]\n2:out1 -> 1:in0 [style=\"dashed\"]\n3 [shape=plain label=<<table border=\"1\"><tr><td align=\"text\" border=\"0\" colspan=\"1\">(3) Input</td></tr><tr><td port=\"out0\" align=\"text\" colspan=\"1\" cellpadding=\"1\" >0: usize</td></tr></table>>]\n3:out0 -> 5:in0 [style=\"\"]\n4 [shape=plain label=<<table border=\"1\"><tr><td port=\"in0\" align=\"text\" colspan=\"1\" cellpadding=\"1\" >0: Sum(General([TypeRow { types: [Type(Extension(CustomType { extension: IdentList(\"prelude\"), id: \"usize\", args: [], bound: Eq }), Eq)] }, TypeRow { types: [Type(Extension(CustomType { extension: IdentList(\"prelude\"), id: \"usize\", args: [], bound: Eq }), Eq)] }]))</td></tr><tr><td align=\"text\" border=\"0\" colspan=\"1\">(4) Output</td></tr></table>>]\n5 [shape=plain label=<<table border=\"1\"><tr><td port=\"in0\" align=\"text\" colspan=\"1\" cellpadding=\"1\" >0: usize</td></tr><tr><td align=\"text\" border=\"0\" colspan=\"1\">(5) Tag</td></tr><tr><td port=\"out0\" align=\"text\" colspan=\"1\" cellpadding=\"1\" >0: Sum(General([TypeRow { types: [Type(Extension(CustomType { extension: IdentList(\"prelude\"), id: \"usize\", args: [], bound: Eq }), Eq)] }, TypeRow { types: [Type(Extension(CustomType { extension: IdentList(\"prelude\"), id: \"usize\", args: [], bound: Eq }), Eq)] }]))</td></tr></table>>]\n5:out0 -> 4:in0 [style=\"\"]\n6 [shape=plain label=<<table border=\"1\"><tr><td port=\"in0\" align=\"text\" colspan=\"1\" cellpadding=\"1\" border=\"0\">0</td></tr><tr><td align=\"text\" border=\"0\" colspan=\"1\">(6) DataflowBlock</td></tr><tr><td port=\"out0\" align=\"text\" colspan=\"1\" cellpadding=\"1\" border=\"0\">0</td></tr></table>>]\n6:out0 -> 1:in0 [style=\"dashed\"]\n7 [shape=plain label=<<table border=\"1\"><tr><td align=\"text\" border=\"0\" colspan=\"1\">(7) Input</td></tr><tr><td port=\"out0\" align=\"text\" colspan=\"1\" cellpadding=\"1\" >0: usize</td></tr></table>>]\n7:out0 -> 8:in1 [style=\"\"]\n8 [shape=plain label=<<table border=\"1\"><tr><td port=\"in0\" align=\"text\" colspan=\"1\" cellpadding=\"1\" >0: Sum(UnitSum(1))</td><td port=\"in1\" align=\"text\" colspan=\"1\" cellpadding=\"1\" >1: usize</td></tr><tr><td align=\"text\" border=\"0\" colspan=\"2\">(8) Output</td></tr></table>>]\n9 [shape=plain label=<<table border=\"1\"><tr><td align=\"text\" border=\"0\" colspan=\"1\">(9) const:sum:{tag:0, vals:[]}</td></tr><tr><td port=\"out0\" align=\"text\" colspan=\"1\" cellpadding=\"1\" >0: Sum(UnitSum(1))</td></tr></table>>]\n9:out0 -> 10:in0 [style=\"\"]\n10 [shape=plain label=<<table border=\"1\"><tr><td port=\"in0\" align=\"text\" colspan=\"1\" cellpadding=\"1\" >0: Sum(UnitSum(1))</td></tr><tr><td align=\"text\" border=\"0\" colspan=\"1\">(10) LoadConstant</td></tr><tr><td port=\"out0\" align=\"text\" colspan=\"1\" cellpadding=\"1\" >0: Sum(UnitSum(1))</td></tr></table>>]\n10:out0 -> 8:in0 [style=\"\"]\nhier0 [shape=plain label=\"0\"]\nhier0 -> hier2  [style = \"dashed\"] \nhier0 -> hier1  [style = \"dashed\"] \nhier0 -> hier6  [style = \"dashed\"] \nhier1 [shape=plain label=\"1\"]\nhier2 [shape=plain label=\"2\"]\nhier2 -> hier3  [style = \"dashed\"] \nhier2 -> hier4  [style = \"dashed\"] \nhier2 -> hier5  [style = \"dashed\"] \nhier3 [shape=plain label=\"3\"]\nhier4 [shape=plain label=\"4\"]\nhier5 [shape=plain label=\"5\"]\nhier6 [shape=plain label=\"6\"]\nhier6 -> hier7  [style = \"dashed\"] \nhier6 -> hier8  [style = \"dashed\"] \nhier6 -> hier9  [style = \"dashed\"] \nhier6 -> hier10  [style = \"dashed\"] \nhier7 [shape=plain label=\"7\"]\nhier8 [shape=plain label=\"8\"]\nhier9 [shape=plain label=\"9\"]\nhier10 [shape=plain label=\"10\"]\n}\n"
+digraph {
+0 [shape=plain label=<<table border="1"><tr><td align="text" border="0" colspan="1">(0) CFG</td></tr></table>>]
+1 [shape=plain label=<<table border="1"><tr><td port="in0" align="text" colspan="1" cellpadding="1" border="0">0</td></tr><tr><td align="text" border="0" colspan="1">(1) ExitBlock</td></tr></table>>]
+2 [shape=plain label=<<table border="1"><tr><td port="in0" align="text" colspan="2" cellpadding="1" border="0">0</td></tr><tr><td align="text" border="0" colspan="2">(2) DataflowBlock</td></tr><tr><td port="out0" align="text" colspan="1" cellpadding="1" border="0">0</td><td port="out1" align="text" colspan="1" cellpadding="1" border="0">1</td></tr></table>>]
+2:out0 -> 6:in0 [style="dashed"]
+2:out1 -> 1:in0 [style="dashed"]
+3 [shape=plain label=<<table border="1"><tr><td align="text" border="0" colspan="1">(3) Input</td></tr><tr><td port="out0" align="text" colspan="1" cellpadding="1" >0: usize</td></tr></table>>]
+3:out0 -> 5:in0 [style=""]
+4 [shape=plain label=<<table border="1"><tr><td port="in0" align="text" colspan="1" cellpadding="1" >0: [usize]+[usize]</td></tr><tr><td align="text" border="0" colspan="1">(4) Output</td></tr></table>>]
+5 [shape=plain label=<<table border="1"><tr><td port="in0" align="text" colspan="1" cellpadding="1" >0: usize</td></tr><tr><td align="text" border="0" colspan="1">(5) Tag</td></tr><tr><td port="out0" align="text" colspan="1" cellpadding="1" >0: [usize]+[usize]</td></tr></table>>]
+5:out0 -> 4:in0 [style=""]
+6 [shape=plain label=<<table border="1"><tr><td port="in0" align="text" colspan="1" cellpadding="1" border="0">0</td></tr><tr><td align="text" border="0" colspan="1">(6) DataflowBlock</td></tr><tr><td port="out0" align="text" colspan="1" cellpadding="1" border="0">0</td></tr></table>>]
+6:out0 -> 1:in0 [style="dashed"]
+7 [shape=plain label=<<table border="1"><tr><td align="text" border="0" colspan="1">(7) Input</td></tr><tr><td port="out0" align="text" colspan="1" cellpadding="1" >0: usize</td></tr></table>>]
+7:out0 -> 8:in1 [style=""]
+8 [shape=plain label=<<table border="1"><tr><td port="in0" align="text" colspan="1" cellpadding="1" >0: []</td><td port="in1" align="text" colspan="1" cellpadding="1" >1: usize</td></tr><tr><td align="text" border="0" colspan="2">(8) Output</td></tr></table>>]
+9 [shape=plain label=<<table border="1"><tr><td align="text" border="0" colspan="1">(9) const:sum:{tag:0, vals:[]}</td></tr><tr><td port="out0" align="text" colspan="1" cellpadding="1" >0: []</td></tr></table>>]
+9:out0 -> 10:in0 [style=""]
+10 [shape=plain label=<<table border="1"><tr><td port="in0" align="text" colspan="1" cellpadding="1" >0: []</td></tr><tr><td align="text" border="0" colspan="1">(10) LoadConstant</td></tr><tr><td port="out0" align="text" colspan="1" cellpadding="1" >0: []</td></tr></table>>]
+10:out0 -> 8:in0 [style=""]
+hier0 [shape=plain label="0"]
+hier0 -> hier2  [style = "dashed"] 
+hier0 -> hier1  [style = "dashed"] 
+hier0 -> hier6  [style = "dashed"] 
+hier1 [shape=plain label="1"]
+hier2 [shape=plain label="2"]
+hier2 -> hier3  [style = "dashed"] 
+hier2 -> hier4  [style = "dashed"] 
+hier2 -> hier5  [style = "dashed"] 
+hier3 [shape=plain label="3"]
+hier4 [shape=plain label="4"]
+hier5 [shape=plain label="5"]
+hier6 [shape=plain label="6"]
+hier6 -> hier7  [style = "dashed"] 
+hier6 -> hier8  [style = "dashed"] 
+hier6 -> hier9  [style = "dashed"] 
+hier6 -> hier10  [style = "dashed"] 
+hier7 [shape=plain label="7"]
+hier8 [shape=plain label="8"]
+hier9 [shape=plain label="9"]
+hier10 [shape=plain label="10"]
+}

quantinuum-hugr/src/hugr/views/snapshots/hugr__hugr__views__tests__dot_dfg.snap

@@ -1,5 +1,27 @@
 ---
-source: src/hugr/views/tests.rs
+source: quantinuum-hugr/src/hugr/views/tests.rs
 expression: h.dot_string()
 ---
-"digraph {\n0 [shape=plain label=<<table border=\"1\"><tr><td align=\"text\" border=\"0\" colspan=\"1\">(0) DFG</td></tr></table>>]\n1 [shape=plain label=<<table border=\"1\"><tr><td align=\"text\" border=\"0\" colspan=\"2\">(1) Input</td></tr><tr><td port=\"out0\" align=\"text\" colspan=\"1\" cellpadding=\"1\" >0: qubit</td><td port=\"out1\" align=\"text\" colspan=\"1\" cellpadding=\"1\" >1: qubit</td></tr></table>>]\n1:out0 -> 3:in0 [style=\"\"]\n1:out1 -> 3:in1 [style=\"\"]\n2 [shape=plain label=<<table border=\"1\"><tr><td port=\"in0\" align=\"text\" colspan=\"1\" cellpadding=\"1\" >0: qubit</td><td port=\"in1\" align=\"text\" colspan=\"1\" cellpadding=\"1\" >1: qubit</td></tr><tr><td align=\"text\" border=\"0\" colspan=\"2\">(2) Output</td></tr></table>>]\n3 [shape=plain label=<<table border=\"1\"><tr><td port=\"in0\" align=\"text\" colspan=\"3\" cellpadding=\"1\" >0: qubit</td><td port=\"in1\" align=\"text\" colspan=\"3\" cellpadding=\"1\" >1: qubit</td></tr><tr><td align=\"text\" border=\"0\" colspan=\"6\">(3) test.quantum.CX</td></tr><tr><td port=\"out0\" align=\"text\" colspan=\"2\" cellpadding=\"1\" >0: qubit</td><td port=\"out1\" align=\"text\" colspan=\"2\" cellpadding=\"1\" >1: qubit</td><td port=\"out2\" align=\"text\" colspan=\"2\" cellpadding=\"1\" border=\"0\"></td></tr></table>>]\n3:out0 -> 4:in1 [style=\"\"]\n3:out1 -> 4:in0 [style=\"\"]\n3:out2 -> 4:in2 [style=\"dotted\"]\n4 [shape=plain label=<<table border=\"1\"><tr><td port=\"in0\" align=\"text\" colspan=\"2\" cellpadding=\"1\" >0: qubit</td><td port=\"in1\" align=\"text\" colspan=\"2\" cellpadding=\"1\" >1: qubit</td><td port=\"in2\" align=\"text\" colspan=\"2\" cellpadding=\"1\" border=\"0\"></td></tr><tr><td align=\"text\" border=\"0\" colspan=\"6\">(4) test.quantum.CX</td></tr><tr><td port=\"out0\" align=\"text\" colspan=\"3\" cellpadding=\"1\" >0: qubit</td><td port=\"out1\" align=\"text\" colspan=\"3\" cellpadding=\"1\" >1: qubit</td></tr></table>>]\n4:out0 -> 2:in0 [style=\"\"]\n4:out1 -> 2:in1 [style=\"\"]\nhier0 [shape=plain label=\"0\"]\nhier0 -> hier1  [style = \"dashed\"] \nhier0 -> hier2  [style = \"dashed\"] \nhier0 -> hier3  [style = \"dashed\"] \nhier0 -> hier4  [style = \"dashed\"] \nhier1 [shape=plain label=\"1\"]\nhier2 [shape=plain label=\"2\"]\nhier3 [shape=plain label=\"3\"]\nhier4 [shape=plain label=\"4\"]\n}\n"
+digraph {
+0 [shape=plain label=<<table border="1"><tr><td align="text" border="0" colspan="1">(0) DFG</td></tr></table>>]
+1 [shape=plain label=<<table border="1"><tr><td align="text" border="0" colspan="2">(1) Input</td></tr><tr><td port="out0" align="text" colspan="1" cellpadding="1" >0: qubit</td><td port="out1" align="text" colspan="1" cellpadding="1" >1: qubit</td></tr></table>>]
+1:out0 -> 3:in0 [style=""]
+1:out1 -> 3:in1 [style=""]
+2 [shape=plain label=<<table border="1"><tr><td port="in0" align="text" colspan="1" cellpadding="1" >0: qubit</td><td port="in1" align="text" colspan="1" cellpadding="1" >1: qubit</td></tr><tr><td align="text" border="0" colspan="2">(2) Output</td></tr></table>>]
+3 [shape=plain label=<<table border="1"><tr><td port="in0" align="text" colspan="3" cellpadding="1" >0: qubit</td><td port="in1" align="text" colspan="3" cellpadding="1" >1: qubit</td></tr><tr><td align="text" border="0" colspan="6">(3) test.quantum.CX</td></tr><tr><td port="out0" align="text" colspan="2" cellpadding="1" >0: qubit</td><td port="out1" align="text" colspan="2" cellpadding="1" >1: qubit</td><td port="out2" align="text" colspan="2" cellpadding="1" border="0"></td></tr></table>>]
+3:out0 -> 4:in1 [style=""]
+3:out1 -> 4:in0 [style=""]
+3:out2 -> 4:in2 [style="dotted"]
+4 [shape=plain label=<<table border="1"><tr><td port="in0" align="text" colspan="2" cellpadding="1" >0: qubit</td><td port="in1" align="text" colspan="2" cellpadding="1" >1: qubit</td><td port="in2" align="text" colspan="2" cellpadding="1" border="0"></td></tr><tr><td align="text" border="0" colspan="6">(4) test.quantum.CX</td></tr><tr><td port="out0" align="text" colspan="3" cellpadding="1" >0: qubit</td><td port="out1" align="text" colspan="3" cellpadding="1" >1: qubit</td></tr></table>>]
+4:out0 -> 2:in0 [style=""]
+4:out1 -> 2:in1 [style=""]
+hier0 [shape=plain label="0"]
+hier0 -> hier1  [style = "dashed"] 
+hier0 -> hier2  [style = "dashed"] 
+hier0 -> hier3  [style = "dashed"] 
+hier0 -> hier4  [style = "dashed"] 
+hier1 [shape=plain label="1"]
+hier2 [shape=plain label="2"]
+hier3 [shape=plain label="3"]
+hier4 [shape=plain label="4"]
+}

quantinuum-hugr/src/hugr/views/snapshots/hugr__hugr__views__tests__dot_empty_dfg.snap

@@ -1,5 +1,15 @@
 ---
-source: src/hugr/views/tests.rs
+source: quantinuum-hugr/src/hugr/views/tests.rs
 expression: h.dot_string()
 ---
-"digraph {\n0 [shape=plain label=<<table border=\"1\"><tr><td align=\"text\" border=\"0\" colspan=\"1\">(0) DFG</td></tr></table>>]\n1 [shape=plain label=<<table border=\"1\"><tr><td align=\"text\" border=\"0\" colspan=\"1\">(1) Input</td></tr><tr><td port=\"out0\" align=\"text\" colspan=\"1\" cellpadding=\"1\" >0: Sum(UnitSum(2))</td></tr></table>>]\n1:out0 -> 2:in0 [style=\"\"]\n2 [shape=plain label=<<table border=\"1\"><tr><td port=\"in0\" align=\"text\" colspan=\"1\" cellpadding=\"1\" >0: Sum(UnitSum(2))</td></tr><tr><td align=\"text\" border=\"0\" colspan=\"1\">(2) Output</td></tr></table>>]\nhier0 [shape=plain label=\"0\"]\nhier0 -> hier1  [style = \"dashed\"] \nhier0 -> hier2  [style = \"dashed\"] \nhier1 [shape=plain label=\"1\"]\nhier2 [shape=plain label=\"2\"]\n}\n"
+digraph {
+0 [shape=plain label=<<table border="1"><tr><td align="text" border="0" colspan="1">(0) DFG</td></tr></table>>]
+1 [shape=plain label=<<table border="1"><tr><td align="text" border="0" colspan="1">(1) Input</td></tr><tr><td port="out0" align="text" colspan="1" cellpadding="1" >0: []+[]</td></tr></table>>]
+1:out0 -> 2:in0 [style=""]
+2 [shape=plain label=<<table border="1"><tr><td port="in0" align="text" colspan="1" cellpadding="1" >0: []+[]</td></tr><tr><td align="text" border="0" colspan="1">(2) Output</td></tr></table>>]
+hier0 [shape=plain label="0"]
+hier0 -> hier1  [style = "dashed"] 
+hier0 -> hier2  [style = "dashed"] 
+hier1 [shape=plain label="1"]
+hier2 [shape=plain label="2"]
+}

quantinuum-hugr/src/hugr/views/snapshots/hugr__hugr__views__tests__mmd_cfg.snap

@@ -1,5 +1,5 @@
 ---
-source: src/hugr/views/tests.rs
+source: quantinuum-hugr/src/hugr/views/tests.rs
 expression: h.mermaid_string()
 ---
 graph LR
@@ -11,7 +11,7 @@ graph LR
             3--"0:0<br>usize"-->5
             4["(4) Output"]
             5["(5) Tag"]
-            5--"0:0<br>Sum(General([TypeRow { types: [Type(Extension(CustomType { extension: IdentList(#quot;prelude#quot;), id: #quot;usize#quot;, args: [], bound: Eq }), Eq)] }, TypeRow { types: [Type(Extension(CustomType { extension: IdentList(#quot;prelude#quot;), id: #quot;usize#quot;, args: [], bound: Eq }), Eq)] }]))"-->4
+            5--"0:0<br>[usize]+[usize]"-->4
         end
         2-."0:0".->6
         2-."1:0".->1
@@ -22,9 +22,9 @@ graph LR
             7--"0:1<br>usize"-->8
             8["(8) Output"]
             9["(9) const:sum:{tag:0, vals:[]}"]
-            9--"0:0<br>Sum(UnitSum(1))"-->10
+            9--"0:0<br>[]"-->10
             10["(10) LoadConstant"]
-            10--"0:0<br>Sum(UnitSum(1))"-->8
+            10--"0:0<br>[]"-->8
         end
         6-."0:0".->1
     end

quantinuum-hugr/src/hugr/views/snapshots/hugr__hugr__views__tests__mmd_empty_dfg.snap

@@ -1,11 +1,11 @@
 ---
-source: src/hugr/views/tests.rs
+source: quantinuum-hugr/src/hugr/views/tests.rs
 expression: h.mermaid_string()
 ---
 graph LR
     subgraph 0 ["(0) DFG"]
         direction LR
         1["(1) Input"]
-        1--"0:0<br>Sum(UnitSum(2))"-->2
+        1--"0:0<br>[]+[]"-->2
         2["(2) Output"]
     end

quantinuum-hugr/src/hugr/views/tests.rs

@@ -71,7 +71,7 @@ fn node_connections(
 #[case::empty_dfg("dot_empty_dfg", crate::builder::test::simple_dfg_hugr())]
 #[cfg_attr(miri, ignore)] // Opening files is not supported in (isolated) miri
 fn dot_string(#[case] test_name: &str, #[case] h: Hugr) {
-    insta::assert_yaml_snapshot!(test_name, h.dot_string());
+    insta::assert_snapshot!(test_name, h.dot_string());
 }
 
 /// Render some hugrs into mermaid format.