wasm: Fix planner to check call expression for false return value

The planner was not checking call expression results for false return
values that ought to cause evaluation to fail. This meant that
evaluation would continue to the next expression.

Signed-off-by: Torin Sandall <torinsandall@gmail.com>

internal/planner/planner.go

@@ -678,7 +678,7 @@ func (p *Planner) planExprCall(e *ast.Expr, iter planiter) error {
 
 		if len(operands) == arity {
 			// rule: f(x) = x { ... }
-			// call: f(x) == 1 or f(x) # result not captured
+			// call: f(x) # result not captured
 			return p.planCallArgs(operands, 0, args, func(args []ir.Local) error {
 				p.ltarget = p.newLocal()
 				p.appendStmt(&ir.CallStmt{
@@ -686,6 +686,19 @@ func (p *Planner) planExprCall(e *ast.Expr, iter planiter) error {
 					Args:   args,
 					Result: p.ltarget,
 				})
+
+				falsy := p.newLocal()
+
+				p.appendStmt(&ir.MakeBooleanStmt{
+					Value:  false,
+					Target: falsy,
+				})
+
+				p.appendStmt(&ir.NotEqualStmt{
+					A: p.ltarget,
+					B: falsy,
+				})
+
 				return iter()
 			})
 		} else if len(operands) == arity+1 {

test/wasm/assets/008_functions.yaml

@@ -103,4 +103,20 @@ cases:
         package x
         f(x) = 1
         f(x) = 2
-    want_error: var assignment conflict
+    want_error: var assignment conflict
+  - note: 'false result'
+    query: data.test.p = x
+    modules:
+      - |
+        package test
+        f(x) = false
+        p = true { f(1) }
+    want_defined: false
+  - note: 'negated false result'
+    query: data.test.p = x
+    modules:
+      - |
+        package test
+        f(x) = false
+        p = true { not f(1) }
+    want_defined: true