checker: fix static init var (fix #25203) (#25209)

vlib/v/ast/ast.v

@@ -2306,6 +2306,23 @@ pub fn (expr Expr) pos() token.Pos {
 	}
 }
 
+pub fn (expr Expr) is_constant() bool {
+	return match expr {
+		IntegerLiteral, FloatLiteral, BoolLiteral, StringLiteral {
+			true
+		}
+		InfixExpr, CastExpr, ArrayInit {
+			true
+		}
+		UnsafeExpr {
+			expr.expr.is_constant()
+		}
+		else {
+			return false
+		}
+	}
+}
+
 pub fn (expr Expr) is_lvalue() bool {
 	return match expr {
 		Ident, CTempVar { true }

vlib/v/checker/assign.v

@@ -661,8 +661,13 @@ or use an explicit `unsafe{ a[..] }`, if you do not want a copy of the slice.',
 			}
 		}
 		if mut left is ast.Ident && left.info is ast.IdentVar {
-			if left.info.is_static && right_sym.kind == .map {
+			if left.info.is_static {
-				c.error('maps cannot be static', left.pos)
+				if right_sym.kind == .map {
+					c.error('maps cannot be static', left.pos)
+				} else if !right.is_constant() {
+					c.error('cannot initialized static variable with non-constant value',
+						left.pos)
+				}
 			}
 		}
 		// Single side check

vlib/v/checker/tests/static_init_err.out

@@ -0,0 +1,41 @@
+vlib/v/checker/tests/static_init_err.vv:10:2: warning: function `foo` must be called from an `unsafe` block
+    8 | 
+    9 | fn main() {
+   10 |     foo()
+      |     ~~~~~
+   11 | }
+vlib/v/checker/tests/static_init_err.vv:4:9: warning: unused variable: `aa`
+    2 | fn foo() {
+    3 |     b := 23
+    4 |     static aa := b
+      |            ~~
+    5 |     static bb := 1 + 1
+    6 |     static cc := ''.str()
+vlib/v/checker/tests/static_init_err.vv:5:9: warning: unused variable: `bb`
+    3 |     b := 23
+    4 |     static aa := b
+    5 |     static bb := 1 + 1
+      |            ~~
+    6 |     static cc := ''.str()
+    7 | }
+vlib/v/checker/tests/static_init_err.vv:6:9: warning: unused variable: `cc`
+    4 |     static aa := b
+    5 |     static bb := 1 + 1
+    6 |     static cc := ''.str()
+      |            ~~
+    7 | }
+    8 |
+vlib/v/checker/tests/static_init_err.vv:4:9: error: cannot initialized static variable with non-constant value
+    2 | fn foo() {
+    3 |     b := 23
+    4 |     static aa := b
+      |            ~~
+    5 |     static bb := 1 + 1
+    6 |     static cc := ''.str()
+vlib/v/checker/tests/static_init_err.vv:6:9: error: cannot initialized static variable with non-constant value
+    4 |     static aa := b
+    5 |     static bb := 1 + 1
+    6 |     static cc := ''.str()
+      |            ~~
+    7 | }
+    8 |

vlib/v/checker/tests/static_init_err.vv

@@ -0,0 +1,11 @@
+@[unsafe]
+fn foo() {
+	b := 23
+	static aa := b
+	static bb := 1 + 1
+	static cc := ''.str()
+}
+
+fn main() {
+	foo()
+}