cgen: implement fixed array 'for in' for lvalue condition (#6151)

vlib/v/ast/ast.v

@@ -1059,6 +1059,16 @@ pub fn (expr Expr) position() token.Position {
 	}
 }
 
+pub fn (expr Expr) is_lvalue() bool {
+	match expr {
+		Ident {return true}
+		IndexExpr {return expr.left.is_lvalue()}
+		SelectorExpr {return expr.expr.is_lvalue()}
+		else {}
+	}
+	return false
+}
+
 pub fn (stmt Stmt) position() token.Position {
 	match stmt {
 		AssertStmt { return stmt.pos }

vlib/v/gen/cgen.v

@@ -975,6 +975,33 @@ fn (mut g Gen) for_in(it ast.ForInStmt) {
 		}
 		g.stmts(it.stmts)
 		g.writeln('}')
+	} else if it.kind == .array_fixed {
+		atmp := g.new_tmp_var()
+		atmp_type := g.typ(it.cond_type)
+		if !it.cond.is_lvalue() {
+			g.error('for in: unhandled condition `$it.cond`', it.pos)
+		}
+		// TODO rvalue cond
+		g.write('$atmp_type *$atmp = &')
+		g.expr(it.cond)
+		g.writeln(';')
+		i := if it.key_var in ['', '_'] { g.new_tmp_var() } else { it.key_var }
+		cond_sym := g.table.get_type_symbol(it.cond_type)
+		info := cond_sym.info as table.ArrayFixed
+		g.writeln('for (int $i = 0; $i != $info.size; ++$i) {')
+		if it.val_var != '_' {
+			val_sym := g.table.get_type_symbol(it.val_type)
+			if val_sym.kind == .function {
+				g.write('\t')
+				g.write_fn_ptr_decl(val_sym.info as table.FnType, c_name(it.val_var))
+			} else {
+				styp := g.typ(it.val_type)
+				g.write('\t$styp ${c_name(it.val_var)}')
+			}
+			g.writeln(' = (*$atmp)[$i];')
+		}
+		g.stmts(it.stmts)
+		g.writeln('}')
 	} else if it.kind == .map {
 		// `for key, val in map {`
 		g.writeln('// FOR IN map')
@@ -1038,7 +1065,7 @@ fn (mut g Gen) for_in(it ast.ForInStmt) {
 		g.writeln('}')
 	} else {
 		s := g.table.type_to_str(it.cond_type)
-		g.error('`for`: unhandled symbol `$it.cond` of type `$s`', it.pos)
+		g.error('for in: unhandled symbol `$it.cond` of type `$s`', it.pos)
 	}
 }
 

vlib/v/tests/fixed_array_test.v

@@ -4,6 +4,10 @@ fn test_fixed_array_can_be_assigned() {
 	assert v[1] == 0
 	v = [1.0, x, 3.0,4.0,5.0,6.0,7.0,8.0]!!
 	assert v[1] == x
+	v[1] = 2.0
+	for i, e in v {
+		assert e == i + 1
+	}
 	v = [8]f64{}
 	assert v[1] == 0
 	// test slicing
@@ -32,6 +36,9 @@ fn test_fixed_array_can_be_assigned_to_a_struct_field() {
 	ctx.vb = [1.1, x, 3.3, 4.4, 5.0, 6.0, 7.0, 8.9]!!
 	assert ctx.vb[1] == x
 	assert ctx.vb[7] == 8.9
+	for i, e in ctx.vb {
+		assert e == ctx.vb[i]
+	}
 	assert ctx.vb == ctx.vb
 	/*
 	println( ctx.vb[0] )