Allow usage of array literals on LHS of ~ (#261)

* treat vectors on LHS as literals

* version bump

* added test for array literals

* simplified the isliteral check

* formatting

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

* dont allow empty literals

* added some tests for isliteral

* formatting

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

* fixed typo in tests

* bump Bijectors for tests

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

Author: 3 people

Project.toml

@@ -1,6 +1,6 @@
 name = "DynamicPPL"
 uuid = "366bfd00-2699-11ea-058f-f148b4cae6d8"
-version = "0.11.2"
+version = "0.11.3"
 
 [deps]
 AbstractMCMC = "80f14c24-f653-4e6a-9b94-39d6b0f70001"

src/compiler.jl

@@ -36,6 +36,15 @@ end
 # failsafe: a literal is never an assumption
 isassumption(expr) = :(false)
 
+"""
+    isliteral(expr)
+
+Return `true` if `expr` is a literal, e.g. `1.0` or `[1.0, ]`, and `false` otherwise.
+"""
+isliteral(e) = false
+isliteral(::Number) = true
+isliteral(e::Expr) = !isempty(e.args) && all(isliteral, e.args)
+
 """
     check_tilde_rhs(x)
 
@@ -240,7 +249,7 @@ variables.
 """
 function generate_tilde(left, right)
     # If the LHS is a literal, it is always an observation
-    if !(left isa Symbol || left isa Expr)
+    if isliteral(left)
         return quote
             $(DynamicPPL.tilde_observe)(
                 __context__,
@@ -290,7 +299,7 @@ Generate the expression that replaces `left .~ right` in the model body.
 """
 function generate_dot_tilde(left, right)
     # If the LHS is a literal, it is always an observation
-    if !(left isa Symbol || left isa Expr)
+    if isliteral(left)
         return quote
             $(DynamicPPL.dot_tilde_observe)(
                 __context__,

test/Project.toml

@@ -21,7 +21,7 @@ Zygote = "e88e6eb3-aa80-5325-afca-941959d7151f"
 [compat]
 AbstractMCMC = "2.1, 3.0"
 AbstractPPL = "0.1.3"
-Bijectors = "0.8.2, 0.9"
+Bijectors = "0.9.5"
 Distributions = "0.24, 0.25"
 DistributionsAD = "0.6.3"
 Documenter = "0.26.1"

test/compiler.jl

@@ -423,4 +423,30 @@ end
         x = [Laplace(), Normal(), MvNormal(3, 1.0)]
         @test DynamicPPL.check_tilde_rhs(x) === x
     end
+    @testset "isliteral" begin
+        @test DynamicPPL.isliteral(:([1.0]))
+        @test DynamicPPL.isliteral(:([[1.0], 1.0]))
+        @test DynamicPPL.isliteral(:((1.0, 1.0)))
+
+        @test !(DynamicPPL.isliteral(:([x])))
+        @test !(DynamicPPL.isliteral(:([[x], 1.0])))
+        @test !(DynamicPPL.isliteral(:((x, 1.0))))
+    end
+
+    @testset "array literals" begin
+        # Verify that we indeed can parse this.
+        @test @model(function array_literal_model()
+            # `assume` and literal `observe`
+            m ~ MvNormal(2, 1.0)
+            return [10.0, 10.0] ~ MvNormal(m, 0.5 * ones(2))
+        end) isa Function
+
+        @model function array_literal_model()
+            # `assume` and literal `observe`
+            m ~ MvNormal(2, 1.0)
+            return [10.0, 10.0] ~ MvNormal(m, 0.5 * ones(2))
+        end
+
+        @test array_literal_model()() == [10.0, 10.0]
+    end
 end