diff --git a/inst/tests/tests.Rraw b/inst/tests/tests.Rraw
index 03fecf3da6..5c1131240c 100644
--- a/inst/tests/tests.Rraw
+++ b/inst/tests/tests.Rraw
@@ -15403,6 +15403,20 @@ DT = data.table(d=sample(seq(as.Date("2015-01-01"), as.Date("2015-01-05"), by="d
 test(2070.01, typeof(DT$d), "double")
 test(2070.02, DT[, .N, keyby=d, verbose=TRUE], output="Column 1.*date.*8 byte double.*no fractions are present.*4 byte integer.*to save space and time")
 
+# coverage along with switch+default pairing
+test(2071.01, dcast(data.table(id=1, grp=1, e=expression(1)), id ~ grp, value.var='e'), error="Unsupported column type in fcast val: 'expression'")
+test(2071.02, is_na(data.table(expression(1))), error="Unsupported column type 'expression'")
+test(2071.03, is_na(data.table(1L), 2L), error="Item 1 of 'cols' is 2 which is outside")
+test(2071.04, is_na(list(1L, 1:2)), error="Column 2 of input list x is length 2, inconsistent")
+test(2071.05, any_na(data.table(1L), 2L), error="Item 1 of 'cols' is 2 which is outside")
+test(2071.06, any_na(list(1L, 1:2)), error="Column 2 of input list x is length 2, inconsistent")
+test(2071.07, any_na(data.table(as.raw(0L))), FALSE)
+test(2071.08, any_na(data.table(c(1+1i, NA))))
+test(2071.09, any_na(data.table(expression(1))), error="Unsupported column type 'expression'")
+test(2071.10, dcast(data.table(a=1, b=1, l=list(list(1))), a ~ b, value.var='l'),
+     data.table(a=1, `1`=list(list(1)), key='a'))
+test(2071.11, dcast(data.table(a = 1, b = 2, c = 3), a ~ b, value.var = 'c', fill = '2'),
+     data.table(a=1, `2`=3, key='a'))
 
 ###################################
 #  Add new tests above this line  #
diff --git a/src/assign.c b/src/assign.c
index d7f5d45785..01a6147ec4 100644
--- a/src/assign.c
+++ b/src/assign.c
@@ -1021,8 +1021,8 @@ void writeNA(SEXP v, const int from, const int n)
     // If there's ever a way added to R API to pass NA_STRING to allocVector() to tell it to initialize with NA not "", would be great
     for (int i=from; i<=to; ++i) SET_STRING_ELT(v, i, NA_STRING);
     break;
-  case VECSXP :
-    // list columns already have each item initialized to NULL
+  case VECSXP : case EXPRSXP :
+    // list & expression columns already have each item initialized to NULL
     break;
   default :
     error("Internal error: writeNA passed a vector of type '%s'", type2char(TYPEOF(v)));  // # nocov
diff --git a/src/bmerge.c b/src/bmerge.c
index ec003ff547..a7246786a8 100644
--- a/src/bmerge.c
+++ b/src/bmerge.c
@@ -265,10 +265,11 @@ void bmerge_r(int xlowIn, int xuppIn, int ilowIn, int iuppIn, int col, int thisg
     }
     if (col>-1 && op[col] != EQ) {
       switch (op[col]) {
-        case LE : xlow = xlowIn; break;
-        case LT : xupp = xlow + 1; xlow = xlowIn; break;
-        case GE : if (ival.i != NA_INTEGER) xupp = xuppIn; break;
-        case GT : xlow = xupp - 1; if (ival.i != NA_INTEGER) xupp = xuppIn; break;
+      case LE : xlow = xlowIn; break;
+      case LT : xupp = xlow + 1; xlow = xlowIn; break;
+      case GE : if (ival.i != NA_INTEGER) xupp = xuppIn; break;
+      case GT : xlow = xupp - 1; if (ival.i != NA_INTEGER) xupp = xuppIn; break;
+      default : error("Internal error in bmerge_r for '%s' column. Unrecognized value op[col]=%d", type2char(TYPEOF(xc)), op[col]); // #nocov
       }
       // for LE/LT cases, we need to ensure xlow excludes NA indices, != EQ is checked above already
       if (op[col] <= 3 && xlow<xupp-1 && ival.i != NA_INTEGER && INTEGER(xc)[XIND(xlow+1)] == NA_INTEGER) {
@@ -376,6 +377,7 @@ void bmerge_r(int xlowIn, int xuppIn, int ilowIn, int iuppIn, int col, int thisg
       case LT : xupp = xlow + 1; if (!isivalNA) xlow = xlowIn; break;
       case GE : if (!isivalNA) xupp = xuppIn; break;
       case GT : xlow = xupp - 1; if (!isivalNA) xupp = xuppIn; break;
+      default : error("Internal error in bmerge_r for '%s' column. Unrecognized value op[col]=%d", type2char(TYPEOF(xc)), op[col]); // #nocov
       }
       // for LE/LT cases, we need to ensure xlow excludes NA indices, != EQ is checked above already
       if (op[col] <= 3 && xlow<xupp-1 && !isivalNA && (!isInt64 ? ISNAN(dxc[XIND(xlow+1)]) : (DtoLL(dxc[XIND(xlow+1)]) == NA_INT64_LL))) {
@@ -546,6 +548,7 @@ void bmerge_r(int xlowIn, int xuppIn, int ilowIn, int iuppIn, int col, int thisg
     if (iupp<iuppIn)
       bmerge_r(xlowIn, xuppIn, iupp-1, iuppIn, col, 1, lowmax && xupp-1==xlowIn, uppmax);
     break;
+  default : break;  // do nothing
   }
 }
 
diff --git a/src/fcast.c b/src/fcast.c
index 5774e8c5e6..5ef9f70d90 100644
--- a/src/fcast.c
+++ b/src/fcast.c
@@ -5,7 +5,6 @@
 
 // TO DO: margins
 SEXP fcast(SEXP lhs, SEXP val, SEXP nrowArg, SEXP ncolArg, SEXP idxArg, SEXP fill, SEXP fill_d, SEXP is_agg) {
-
   int nrows=INTEGER(nrowArg)[0], ncols=INTEGER(ncolArg)[0];
   int nlhs=length(lhs), nval=length(val), *idx = INTEGER(idxArg);
   SEXP target;
@@ -80,6 +79,7 @@ SEXP fcast(SEXP lhs, SEXP val, SEXP nrowArg, SEXP ncolArg, SEXP idxArg, SEXP fil
         }
       }
       break;
+    default: error("Unsupported column type in fcast val: '%s'", type2char(TYPEOF(thiscol))); // #nocov
     }
     if (count) UNPROTECT(1);
   }
diff --git a/src/frank.c b/src/frank.c
index 00744b35c6..485081865f 100644
--- a/src/frank.c
+++ b/src/frank.c
@@ -62,7 +62,7 @@ SEXP dt_na(SEXP x, SEXP cols) {
     }
       break;
     default:
-      error("Unknown column type '%s'", type2char(TYPEOF(v)));
+      error("Unsupported column type '%s'", type2char(TYPEOF(v)));
     }
   }
   UNPROTECT(1);
@@ -127,6 +127,7 @@ SEXP frank(SEXP xorderArg, SEXP xstartArg, SEXP xlenArg, SEXP ties_method) {
     //       INTEGER(ans)[xorder[j]-1] = k++;
     //   }
     //   break;
+    default: error("Internal error: unknown ties value in frank: %d", ties); // #nocov
     }
   }
   UNPROTECT(1);
@@ -198,7 +199,7 @@ SEXP anyNA(SEXP x, SEXP cols) {
     }
       break;
     default:
-      error("Unknown column type '%s'", type2char(TYPEOF(v)));
+      error("Unsupported column type '%s'", type2char(TYPEOF(v)));
     }
     if (LOGICAL(ans)[0]) break;
   }
diff --git a/src/frollR.c b/src/frollR.c
index e1cf734d89..519c69bf5b 100644
--- a/src/frollR.c
+++ b/src/frollR.c
@@ -188,10 +188,11 @@ SEXP frollfunR(SEXP fun, SEXP obj, SEXP k, SEXP fill, SEXP algo, SEXP align, SEX
         if (!badaptive) frollsum(ialgo, dx[i], inx[i], &dans[i*nk+j], iik[j], ialign, dfill, bnarm, ihasna, bverbose);
         else fadaptiverollsum(ialgo, dx[i], inx[i], &dans[i*nk+j], ikl[j], dfill, bnarm, ihasna, bverbose);
         break;
+      default: error("Internal error: Unknown sfun value in froll: %d", sfun); // #nocov
       }
     }
   }
-  
+
   for (R_len_t i=0; i<nx; i++) {                                // raise errors and warnings, as of now messages are not being produced
     for (R_len_t j=0; j<nk; j++) {
       if (bverbose && (dans[i*nk+j].message[0][0] != '\0')) Rprintf("%s: %d:\n%s", __func__, i*nk+j+1, dans[i*nk+j].message[0]);
@@ -200,7 +201,7 @@ SEXP frollfunR(SEXP fun, SEXP obj, SEXP k, SEXP fill, SEXP algo, SEXP align, SEX
       if (dans[i*nk+j].status == 3) error("%s: %d: %s", __func__, i*nk+j+1, dans[i*nk+j].message[3]); // # nocov because only caused by malloc
     }
   }
-  
+
   if (bverbose) Rprintf("%s: processing of %d column(s) and %d window(s) took %.3fs\n", __func__, nx, nk, omp_get_wtime()-tic);
 
   UNPROTECT(protecti);
diff --git a/src/ijoin.c b/src/ijoin.c
index 97fbd05107..b9302aaf1b 100644
--- a/src/ijoin.c
+++ b/src/ijoin.c
@@ -53,6 +53,7 @@ SEXP lookup(SEXP ux, SEXP xlen, SEXP indices, SEXP gaps, SEXP overlaps, SEXP mul
           if (count[i]) type_count[i] = 1;
       }
       break;
+    default: error("Internal error: unknown type in mult=%d in lookup: %d", mult, type); // #nocov
     }
     break;
 
@@ -117,8 +118,10 @@ SEXP lookup(SEXP ux, SEXP xlen, SEXP indices, SEXP gaps, SEXP overlaps, SEXP mul
         }
       }
       break;
+    default: error("Internal error: unknown type in mult=%d in lookup: %d", mult, type); // #nocov
     }
     break;
+  default: error("Internal error: unknown mult in lookup: %d", mult); // #nocov
   }
   pass1 = clock() - start;
   if (LOGICAL(verbose)[0])
@@ -154,6 +157,7 @@ SEXP lookup(SEXP ux, SEXP xlen, SEXP indices, SEXP gaps, SEXP overlaps, SEXP mul
       INTEGER(VECTOR_ELT(lookup, to[i]-1))[idx[to[i]-1]++] = i+1;
     }
     break;
+  default: error("Internal error: unknown type lookup should have been caught earlier: %d", type); // #nocov
   }
   Free(idx);
   // generate type_lookup
@@ -204,9 +208,11 @@ SEXP lookup(SEXP ux, SEXP xlen, SEXP indices, SEXP gaps, SEXP overlaps, SEXP mul
         //     for (j=0; j<type_count[i]; j++)
         //         INTEGER(tt)[j] = INTEGER(vv)[j];
         // }
-        break;
+        break; // #nocov
+      default: error("Internal error: unknown type in mult=%d in lookup should have been caught earlier: %d", mult, type); // #nocov
       }
-      break;
+     break;
+    default: error("Internal error: unknown mult in lookup: %d", mult); // #nocov
     }
   }
   pass3 = clock() - start;
@@ -314,6 +320,7 @@ SEXP overlaps(SEXP ux, SEXP imatches, SEXP multArg, SEXP typeArg, SEXP nomatchAr
           ++totlen;
       }
       break;
+    default: error("Internal error: unknown type in mult=ALL in overlaps: %d", mult, type); // #nocov
     }
   } else totlen = rows;
   end1 = clock() - start;
@@ -454,12 +461,13 @@ SEXP overlaps(SEXP ux, SEXP imatches, SEXP multArg, SEXP typeArg, SEXP nomatchAr
          }
       }
       break;
+    default: error("Internal error: unknown type in mult=%d in overlaps: %d", mult, type); // #nocov
     }
     break;
 
   case FIRST:
     switch (type) {
-      case START: case END:
+    case START: case END:
       for (i=0; i<rows; i++) {
         len = thislen;
         INTEGER(f1__)[thislen] = i+1;
@@ -560,6 +568,7 @@ SEXP overlaps(SEXP ux, SEXP imatches, SEXP multArg, SEXP typeArg, SEXP nomatchAr
         }
       }
       break;
+    default: error("Internal error: unknown type in mult=%d in overlaps: %d", mult, type); // #nocov
     }
     break;
 
@@ -708,8 +717,10 @@ SEXP overlaps(SEXP ux, SEXP imatches, SEXP multArg, SEXP typeArg, SEXP nomatchAr
          }
       }
       break;
+    default: error("Internal error: unknown type in mult=%d in overlaps: %d", mult, type); // #nocov
     }
     break;
+  default: error("Internal error: unknown mult in overlaps: %d", mult); // #nocov
   }
   end2 = clock() - start;
   if (LOGICAL(verbose)[0])
diff --git a/src/nafill.c b/src/nafill.c
index 1f1a1344bf..916a1e3052 100644
--- a/src/nafill.c
+++ b/src/nafill.c
@@ -209,7 +209,7 @@ SEXP nafillR(SEXP obj, SEXP type, SEXP fill, SEXP inplace, SEXP cols, SEXP verbo
   if (!strcmp(CHAR(STRING_ELT(type, 0)), "const")) itype = 0;
   else if (!strcmp(CHAR(STRING_ELT(type, 0)), "locf")) itype = 1;
   else if (!strcmp(CHAR(STRING_ELT(type, 0)), "nocb")) itype = 2;
-  else error("Internal error: invalid type argument in nafillR function, should have been caught before. please report to data.table issue tracker."); // # nocov
+  else error("Internal error: invalid type argument in nafillR function, should have been caught before. Please report to data.table issue tracker."); // # nocov
 
   if (itype==0 && length(fill)!=1)
     error("fill must be a vector of length 1");
@@ -235,6 +235,7 @@ SEXP nafillR(SEXP obj, SEXP type, SEXP fill, SEXP inplace, SEXP cols, SEXP verbo
     case INTSXP : {
       nafillInteger(ix[i], inx[i], itype, ifill, &vans[i], bverbose);
     } break;
+    default: error("Internal error: invalid type argument in nafillR function, should have been caught before. Please report to data.table issue tracker."); // # nocov
     }
   }
   if (bverbose) toc = omp_get_wtime();