forbid bit-selects and part-selects of scalar struct fields

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
 

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

test/error/struct_logic_bit.sv

+// 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

test/error/struct_logic_part_range.sv

+// 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

test/error/struct_logic_part_select.sv

+// 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