Use view whenever possible (#272)

* use views whenever possible

* formatting

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

* dont view literals

* fixed the failing tests

* added a bunch of get_sections to tests to avoid unnecessary warnings

* formatting

* added comment to describe maybe_unwrap_view

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: Hong Ge <[email protected]>

Author: 3 people

src/compiler.jl

@@ -27,7 +27,7 @@ function isassumption(expr::Union{Symbol,Expr})
                 true
             else
                 # Evaluate the LHS
-                $expr === missing
+                $(maybe_view(expr)) === missing
             end
         end
     end
@@ -36,6 +36,16 @@ end
 # failsafe: a literal is never an assumption
 isassumption(expr) = :(false)
 
+# If we're working with, say, a `Symbol`, then we're not going to `view`.
+maybe_view(x) = x
+maybe_view(x::Expr) = :($(DynamicPPL.maybe_unwrap_view)(@view($x)))
+
+# If the result of a `view` is a zero-dim array then it's just a
+# single element. Likely the rest is expecting type `eltype(x)`, hence
+# we extract the value rather than passing the array.
+maybe_unwrap_view(x) = x
+maybe_unwrap_view(x::SubArray{<:Any,0}) = x[1]
+
 """
     isliteral(expr)
 
@@ -325,7 +335,7 @@ function generate_tilde(left, right)
             $(DynamicPPL.tilde_observe!)(
                 __context__,
                 $(DynamicPPL.check_tilde_rhs)($right),
-                $left,
+                $(maybe_view(left)),
                 $vn,
                 $inds,
                 __varinfo__,
@@ -360,7 +370,7 @@ function generate_dot_tilde(left, right)
             $left .= $(DynamicPPL.dot_tilde_assume!)(
                 __context__,
                 $(DynamicPPL.unwrap_right_left_vns)(
-                    $(DynamicPPL.check_tilde_rhs)($right), $left, $vn
+                    $(DynamicPPL.check_tilde_rhs)($right), $(maybe_view(left)), $vn
                 )...,
                 $inds,
                 __varinfo__,
@@ -369,7 +379,7 @@ function generate_dot_tilde(left, right)
             $(DynamicPPL.dot_tilde_observe!)(
                 __context__,
                 $(DynamicPPL.check_tilde_rhs)($right),
-                $left,
+                $(maybe_view(left)),
                 $vn,
                 $inds,
                 __varinfo__,