From ff241115c44dcdaeb1e893abae14fc702298f6a7 Mon Sep 17 00:00:00 2001
From: Zachary Snow <zach@zachjs.com>
Date: Mon, 27 Sep 2021 21:51:53 -0600
Subject: [PATCH] forbid bit-selects and part-selects of scalar struct fields

---
 CHANGELOG.md                           | 2 ++
 src/Convert/Struct.hs                  | 9 +++++++++
 test/error/struct_logic_bit.sv         | 7 +++++++
 test/error/struct_logic_part_range.sv  | 7 +++++++
 test/error/struct_logic_part_select.sv | 7 +++++++
 5 files changed, 32 insertions(+)
 create mode 100644 test/error/struct_logic_bit.sv
 create mode 100644 test/error/struct_logic_part_range.sv
 create mode 100644 test/error/struct_logic_part_select.sv

diff --git a/CHANGELOG.md b/CHANGELOG.md
index a63d9d5a..b0f8268a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -32,6 +32,8 @@
 * Non-positive integer size casts are now detected and forbidden
 * Negative indices in struct pattern literals are now detected and forbidden
 * Escaped vendor block comments in macro bodies are now tolerated
+* Illegal bit-selects and part-selects of scalar struct fields are now detected
+  and forbidden, rather than yielding an internal assertion failure
 
 ### Bug Fixes
 
diff --git a/src/Convert/Struct.hs b/src/Convert/Struct.hs
index d680f8b7..560be7ba 100644
--- a/src/Convert/Struct.hs
+++ b/src/Convert/Struct.hs
@@ -386,6 +386,9 @@ convertSubExpr scopes (Range (Dot e x) NonIndexed rOuter) =
         (UnknownType, orig')
     else if structIsntReady subExprType then
         (replaceInnerTypeRange NonIndexed rOuter' fieldType, orig')
+    else if null dims then
+        error $ "illegal access to range " ++ show (Range Nil NonIndexed rOuter)
+            ++ " of " ++ show (Dot e x) ++ ", which has type " ++ show fieldType
     else
         (replaceInnerTypeRange NonIndexed rOuter' fieldType, undotted)
     where
@@ -408,6 +411,9 @@ convertSubExpr scopes (Range (Dot e x) mode (baseO, lenO)) =
         (UnknownType, orig')
     else if structIsntReady subExprType then
         (replaceInnerTypeRange mode (baseO', lenO') fieldType, orig')
+    else if null dims then
+        error $ "illegal access to range " ++ show (Range Nil mode (baseO, lenO))
+            ++ " of " ++ show (Dot e x) ++ ", which has type " ++ show fieldType
     else
         (replaceInnerTypeRange mode (baseO', lenO') fieldType, undotted)
     where
@@ -438,6 +444,9 @@ convertSubExpr scopes (Bit (Dot e x) i) =
         (dropInnerTypeRange backupType, orig')
     else if structIsntReady subExprType then
         (dropInnerTypeRange fieldType, orig')
+    else if null dims then
+        error $ "illegal access to bit " ++ show i ++ " of " ++ show (Dot e x)
+            ++ ", which has type " ++ show fieldType
     else
         (dropInnerTypeRange fieldType, Bit e' iFlat)
     where
diff --git a/test/error/struct_logic_bit.sv b/test/error/struct_logic_bit.sv
new file mode 100644
index 00000000..4400fd16
--- /dev/null
+++ b/test/error/struct_logic_bit.sv
@@ -0,0 +1,7 @@
+// pattern: illegal access to bit 0 of s\.x, which has type logic
+module top;
+    struct packed {
+        logic x;
+    } s;
+    initial s.x[0] = 1;
+endmodule
diff --git a/test/error/struct_logic_part_range.sv b/test/error/struct_logic_part_range.sv
new file mode 100644
index 00000000..1a6d2b36
--- /dev/null
+++ b/test/error/struct_logic_part_range.sv
@@ -0,0 +1,7 @@
+// pattern: illegal access to range \[0:0\] of s\.x, which has type logic
+module top;
+    struct packed {
+        logic x;
+    } s;
+    initial s.x[0:0] = 1;
+endmodule
diff --git a/test/error/struct_logic_part_select.sv b/test/error/struct_logic_part_select.sv
new file mode 100644
index 00000000..cd5a9853
--- /dev/null
+++ b/test/error/struct_logic_part_select.sv
@@ -0,0 +1,7 @@
+// pattern: illegal access to range \[0\+:1\] of s\.x, which has type logic
+module top;
+    struct packed {
+        logic x;
+    } s;
+    initial s.x[0+:1] = 1;
+endmodule