checker: fix match expr with non last if expr (#15500)

vlib/v/ast/ast.v

@@ -1875,26 +1875,6 @@ pub fn (e &Expr) is_lockable() bool {
 	}
 }
 
-// check if stmt can be an expression in C
-pub fn (stmt Stmt) check_c_expr() ? {
-	match stmt {
-		AssignStmt {
-			return
-		}
-		ForCStmt, ForInStmt, ForStmt {
-			return
-		}
-		ExprStmt {
-			if stmt.expr.is_expr() {
-				return
-			}
-			return error('unsupported statement (`$stmt.expr.type_name()`)')
-		}
-		else {}
-	}
-	return error('unsupported statement (`$stmt.type_name()`)')
-}
-
 // CTempVar is used in cgen only, to hold nodes for temporary variables
 pub struct CTempVar {
 pub:

vlib/v/checker/if.v

@@ -238,10 +238,6 @@ pub fn (mut c Checker) if_expr(mut node ast.IfExpr) ast.Type {
 				c.error('`$if_kind` expression requires an expression as the last statement of every branch',
 					branch.pos)
 			}
-			for st in branch.stmts {
-				// must not contain C statements
-				st.check_c_expr() or { c.error('`if` expression branch has $err.msg()', st.pos) }
-			}
 		}
 		if mut branch.cond is ast.IfGuardExpr {
 			sym := c.table.sym(branch.cond.expr_type)

vlib/v/checker/match.v

@@ -46,18 +46,7 @@ pub fn (mut c Checker) match_expr(mut node ast.MatchExpr) ast.Type {
 		c.smartcast_mut_pos = token.Pos{}
 		c.smartcast_cond_pos = token.Pos{}
 		if node.is_expr {
-			if branch.stmts.len > 0 {
+			if branch.stmts.len == 0 && ret_type != ast.void_type {
-				// ignore last statement - workaround
-				// currently the last statement in a match branch does not have an
-				// expected value set, so e.g. IfExpr.is_expr is not set.
-				// probably any mismatch will be caught by not producing a value instead
-				for st in branch.stmts[..branch.stmts.len - 1] {
-					// must not contain C statements
-					st.check_c_expr() or {
-						c.error('`match` expression branch has $err.msg()', st.pos)
-					}
-				}
-			} else if ret_type != ast.void_type {
 				c.error('`match` expression requires an expression as the last statement of every branch',
 					branch.branch_pos)
 			}

vlib/v/checker/tests/if_match_expr.out

@@ -1,35 +0,0 @@
-vlib/v/checker/tests/if_match_expr.vv:9:2: error: `if` expression branch has unsupported statement (`v.ast.Block`)
-    7 | } else {
-    8 |     for {break}
-    9 |     {}
-      |     ^
-   10 |     match true {true {} else {}} // statement not expression
-   11 |     _ = match true {true {1} else {-1}} // OK
-vlib/v/checker/tests/if_match_expr.vv:10:2: error: `if` expression branch has unsupported statement (`v.ast.MatchExpr`)
-    8 |     for {break}
-    9 |     {}
-   10 |     match true {true {} else {}} // statement not expression
-      |     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-   11 |     _ = match true {true {1} else {-1}} // OK
-   12 |     match true {true {1} else {-1}} // result
-vlib/v/checker/tests/if_match_expr.vv:17:3: error: `match` expression branch has unsupported statement (`v.ast.IfExpr`)
-   15 | _ = match true {
-   16 |     true {
-   17 |         if true {} // statement not expression
-      |         ~~
-   18 |         _ = if true {1} else {-1} // OK
-   19 |         if true {1} else {-1} // result
-vlib/v/checker/tests/if_match_expr.vv:22:10: error: `match` expression branch has unsupported statement (`v.ast.AssertStmt`)
-   20 |     }
-   21 |     else {
-   22 |         assert true
-      |                ~~~~
-   23 |         match true {true {} else {}} // statement not expression
-   24 |         _ = match true {true {1} else {-1}} // OK
-vlib/v/checker/tests/if_match_expr.vv:23:3: error: `match` expression branch has unsupported statement (`v.ast.MatchExpr`)
-   21 |     else {
-   22 |         assert true
-   23 |         match true {true {} else {}} // statement not expression
-      |         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-   24 |         _ = match true {true {1} else {-1}} // OK
-   25 |         match true {true {1} else {-1}} // result

vlib/v/checker/tests/if_match_expr.vv

@@ -1,27 +0,0 @@
-// only C expressions are allowed for each statement
-
-_ = if true {
-	if true {} // FIXME should error, if statement
-	_ = if true {1} else {-1} // OK
-	if true {1} else {-1} // result
-} else {
-	for {break}
-	{}
-	match true {true {} else {}} // statement not expression
-	_ = match true {true {1} else {-1}} // OK
-	match true {true {1} else {-1}} // result
-}
-
-_ = match true {
-	true {
-		if true {} // statement not expression
-		_ = if true {1} else {-1} // OK
-		if true {1} else {-1} // result
-	}
-	else {
-		assert true
-		match true {true {} else {}} // statement not expression
-		_ = match true {true {1} else {-1}} // OK
-		match true {true {1} else {-1}} // result
-	}
-}

vlib/v/tests/match_expr_with_non_last_if_expr_test.v

@@ -0,0 +1,20 @@
+fn test_match_expr_with_non_last_if_expr() {
+	out := match true {
+		true {
+			{
+			}
+			if true {
+			} else {
+			}
+			'a'
+		}
+		else {
+			for {
+				break
+			}
+			'b'
+		}
+	}
+	println(out)
+	assert out == 'a'
+}