Error if arrays accessed without index

R/parse.R

@@ -184,6 +184,19 @@ parse_check_consistent_dimensions_rhs <- function(eq, dat, call, src = eq$src) {
       "E2019", src, call)
   }
 
+  throw_array_as_scalar <- function(var, rank) {
+    what <- rank_description(rank)
+    if (rank == 1) {
+      dummy_index <- "..."
+    } else {
+      dummy_index <- paste(rep(".", rank), collapse = ", ")
+    }
+    odin_parse_error(
+      c("Trying to use {what} '{var}' without index",
+        i = sprintf("Did you mean '{var}[%s]'", dummy_index)),
+      "E2022", src, call)
+  }
+
   fn_use_whole_array <- c("length", "nrow", "ncol", "OdinReduce",
                           "OdinInterpolate")
 
@@ -233,6 +246,11 @@ parse_check_consistent_dimensions_rhs <- function(eq, dat, call, src = eq$src) {
       } else {
         lapply(expr[-1], check)
       }
+    } else if (is.symbol(expr)) {
+      nm <- as.character(expr)
+      if (nm %in% dat$storage$arrays$name) {
+        throw_array_as_scalar(nm, dim_ranks[[nm]])
+      }
     }
   }
   check(eq$rhs$expr)

tests/testthat/test-parse.R

@@ -1060,3 +1060,30 @@ test_that("don't duplicate offsets when boundary condition used in initial", {
   expect_equal(dat$variables, "x")
   expect_equal(nrow(dat$storage$packing$state), 1)
 })
+
+
+test_that("prevent use of arrays without braces", {
+  err <- expect_error(
+    odin_parse({
+      initial(x[]) <- 0
+      update(x[]) <- b
+      b[] <- x[i]
+      dim(x) <- 5
+      dim(b) <- 5
+    }),
+    "Trying to use vector 'b' without index")
+  expect_match(conditionMessage(err),
+               "Did you mean 'b[...]'", fixed = TRUE)
+
+  err <- expect_error(
+    odin_parse({
+      initial(x[]) <- 0
+      update(x[]) <- b
+      b[, ] <- 1
+      dim(x) <- 5
+      dim(b) <- c(5, 5)
+    }),
+    "Trying to use matrix 'b' without index")
+  expect_match(conditionMessage(err),
+               "Did you mean 'b[., .]'", fixed = TRUE)
+})

vignettes/errors.Rmd

@@ -1097,6 +1097,17 @@ You have tried to set the dimensions of the same variable more than once. For ex
 dim(a, b) <- 2
 dim(b, c) <- 3
 
+# `E2022`
+
+Trying to access an array without using square bracket indexes.  For example if you write:
+
+```r
+dim(b) <- 10
+a[] <- b
+```
+
+you would see this error, as you should have used `b[i]` on the right hand side (*probably!*; you might have meant `a[] <- b[1]`, too).
+
 # `E3001`
 
 An array access would be out of bounds.  This error is thrown where your code would result in you reading or writing out of bounds on an array (or a dimension of an array).  Currently, we throw this error if we are certain that your access is invalid. For example, we would error if your code contains: