fix(gnovm): value decl loop (gnolang#2074)

fixes [this](gnolang#1849) by splitting
value declarations with multiple values into single declarations with a
single value.

<details><summary>Contributors' checklist...</summary>

- [x] Added new tests, or not needed, or not feasible
- [x] Provided an example (e.g. screenshot) to aid review or the PR is
self-explanatory
- [x] Updated the official documentation or not needed
- [x] No breaking changes were made, or a `BREAKING CHANGE: xxx` message
was included in the description
- [x] Added references to related issues and PRs

---------

Co-authored-by: Morgan Bazalgette <morgan@morganbaz.com>

gnovm/pkg/gnolang/preprocess.go

@@ -45,11 +45,12 @@ func PredefineFileSet(store Store, pn *PackageNode, fset *FileSet) {
 					// skip declarations already predefined
 					// (e.g. through recursion for a
 					// dependent)
-				} else {
-					// recursively predefine dependencies.
-					d2, _ := predefineNow(store, fn, d)
-					fn.Decls[i] = d2
+					continue
 				}
+
+				// recursively predefine dependencies.
+				d2, _ := predefineNow(store, fn, d)
+				fn.Decls[i] = d2
 			}
 		}
 	}
@@ -63,11 +64,12 @@ func PredefineFileSet(store Store, pn *PackageNode, fset *FileSet) {
 					// skip declarations already predefined
 					// (e.g. through recursion for a
 					// dependent)
-				} else {
-					// recursively predefine dependencies.
-					d2, _ := predefineNow(store, fn, d)
-					fn.Decls[i] = d2
+					continue
 				}
+
+				// recursively predefine dependencies.
+				d2, _ := predefineNow(store, fn, d)
+				fn.Decls[i] = d2
 			}
 		}
 	}
@@ -81,11 +83,12 @@ func PredefineFileSet(store Store, pn *PackageNode, fset *FileSet) {
 					// skip declarations already predefined
 					// (e.g. through recursion for a
 					// dependent)
-				} else {
-					// recursively predefine dependencies.
-					d2, _ := predefineNow(store, fn, d)
-					fn.Decls[i] = d2
+					continue
 				}
+
+				// recursively predefine dependencies.
+				d2, _ := predefineNow(store, fn, d)
+				fn.Decls[i] = d2
 			}
 		}
 	}
@@ -97,11 +100,36 @@ func PredefineFileSet(store Store, pn *PackageNode, fset *FileSet) {
 			if d.GetAttribute(ATTR_PREDEFINED) == true {
 				// skip declarations already predefined (e.g.
 				// through recursion for a dependent)
-			} else {
-				// recursively predefine dependencies.
-				d2, _ := predefineNow(store, fn, d)
-				fn.Decls[i] = d2
+				continue
 			}
+
+			if vd, ok := d.(*ValueDecl); ok && len(vd.NameExprs) > 1 && len(vd.Values) == len(vd.NameExprs) {
+				split := make([]Decl, len(vd.NameExprs))
+
+				for j := 0; j < len(vd.NameExprs); j++ {
+					base := vd.Copy().(*ValueDecl)
+					base.NameExprs = NameExprs{NameExpr{
+						Attributes: base.NameExprs[j].Attributes,
+						Path:       base.NameExprs[j].Path,
+						Name:       base.NameExprs[j].Name,
+					}}
+
+					if j < len(base.Values) {
+						base.Values = Exprs{base.Values[j].Copy().(Expr)}
+					}
+
+					split[j], _ = predefineNow(store, fn, base)
+				}
+
+				fn.Decls = append(fn.Decls[:i], append(split, fn.Decls[i+1:]...)...) //nolint:makezero
+				i += len(vd.NameExprs)
+				continue
+			}
+
+			// recursively predefine dependencies.
+			d2, _ := predefineNow(store, fn, d)
+
+			fn.Decls[i] = d2
 		}
 	}
 }

gnovm/tests/files/var19.gno

@@ -2,6 +2,7 @@ package main
 
 func main() {
 	var a, b, c = 1, a+1
+
 	println(a)
 	println(b)
 	println(c)

gnovm/tests/files/var29.gno

@@ -0,0 +1,14 @@
+package main
+
+func main() {
+	println(a)
+	println(b)
+	println(c)
+}
+
+var a, b, c = 1, a + 1, b + 1
+
+// Output:
+// 1
+// 2
+// 3

gnovm/tests/files/var30.gno

@@ -0,0 +1,17 @@
+package main
+
+func main() {
+	println(a)
+	println(b)
+	println(c)
+	println(d)
+}
+
+var a, b, c = 1, a + d, 3
+var d = a
+
+// Output:
+// 1
+// 2
+// 3
+// 1