From 9760a9c6b258017ed728d323cbcd3f7016c40c3b Mon Sep 17 00:00:00 2001
From: kbkpbot <kbkpbot@sina.com>
Date: Mon, 10 Nov 2025 01:21:13 +0800
Subject: [PATCH] checker,transformer: add always true/false branch detection
 for the `if` and `match` constructs (#25674)

---
 cmd/tools/changelog_helper.v                  |   7 -
 vlib/os/filepath.v                            |  14 +-
 vlib/os/os.v                                  |   4 +-
 vlib/v/checker/checker.v                      |  14 +-
 vlib/v/checker/if.v                           |  11 +
 vlib/v/checker/match.v                        |  19 +
 .../tests/always_true_false_branch.out        | 469 ++++++++++++++++++
 .../checker/tests/always_true_false_branch.vv | 204 ++++++++
 .../v/checker/tests/assign_multi_mismatch.out |  39 ++
 .../v/checker/tests/cast_to_interface_err.out |   7 +
 .../tests/function_missing_return_type.out    |   7 +
 .../tests/if_diff_expected_type_err.out       |   7 +
 vlib/v/checker/tests/if_expr_last_stmt.out    |  13 +
 vlib/v/checker/tests/if_expr_mismatch.out     |   6 +
 vlib/v/checker/tests/if_expr_no_else.out      |   6 +
 .../checker/tests/if_expr_with_none_only.out  |   5 +
 vlib/v/checker/tests/if_match_result.out      |  28 ++
 vlib/v/checker/tests/if_mismatch_muls_err.out |   7 +
 .../immutable_array_in_if_expr_index.out      |   7 +
 .../tests/immutable_to_mutable_err.out        |  14 +
 vlib/v/checker/tests/match_else_last_expr.out |  16 +-
 .../checker/tests/match_expr_empty_branch.out |  12 +
 .../tests/match_expr_with_none_only.out       |   7 +
 vlib/v/checker/tests/match_missing.out        |   6 +
 .../tests/match_return_mismatch_type_err.out  |   7 +
 vlib/v/checker/tests/none_match_cond_err.out  |   6 +
 .../tests/option_interface_mismatch.out       |  10 +-
 .../tests/return_missing_comp_if_nested.out   |   6 +-
 .../tests/return_missing_comp_if_nested.vv    |   6 +-
 .../tests/return_missing_if_else_simple.out   |  20 +
 .../checker/tests/return_missing_if_match.out |  25 +-
 .../checker/tests/return_missing_match_if.out |  21 +
 .../v/checker/tests/return_missing_nested.out |  18 +-
 .../v/checker/tests/return_missing_simple.out |  11 +-
 .../tests/return_working_comp_if_nested.vv    |   6 +-
 .../checker/tests/return_working_if_match.out |  21 +
 .../checker/tests/return_working_match_if.out |  21 +
 .../v/checker/tests/return_working_nested.out |  14 +
 .../v/checker/tests/return_working_simple.out |   7 +
 .../v/checker/tests/return_working_two_if.out |  21 +
 .../v/checker/tests/shift_ops_expressions.out |  56 +++
 vlib/v/checker/tests/struct_scope_err.out     |   7 +
 .../checker/tests/unnecessary_parenthesis.out |  20 +
 vlib/v/checker/tests/unreachable_code.out     |   7 +
 vlib/v/gen/js/tests/testdata/compare_ints.v   |  10 +-
 vlib/v/gen/js/tests/testdata/match.v          |   3 +-
 .../repl/conditional_blocks/if.repl           |   4 +-
 .../repl/conditional_blocks/if_else.repl      |   4 +-
 .../skip_unused/generic_call_from_json.vv     |   4 +-
 vlib/v/transformer/transformer.v              | 124 ++++-
 50 files changed, 1340 insertions(+), 48 deletions(-)
 create mode 100644 vlib/v/checker/tests/always_true_false_branch.out
 create mode 100644 vlib/v/checker/tests/always_true_false_branch.vv

diff --git a/cmd/tools/changelog_helper.v b/cmd/tools/changelog_helper.v
index fdb1621a9..d8af93609 100644
--- a/cmd/tools/changelog_helper.v
+++ b/cmd/tools/changelog_helper.v
@@ -111,9 +111,6 @@ fn main() {
 		}
 	}
 	os.write_file(log_txt, lines.join('\n'))!
-	if true {
-		// return
-	}
 	mut app := &App{
 		total_lines: lines.len
 	}
@@ -122,10 +119,6 @@ fn main() {
 		category_titles)
 	os.write_file('CHANGELOG.md', app.result)!
 	changelog_txt := os.read_file('CHANGELOG.md')!.to_lower()
-	if true {
-		// println(changelog_txt)
-		// return
-	}
 	// mut counter := 0 // to display how many commits are left
 	for line in lines {
 		s := line.trim_space()
diff --git a/vlib/os/filepath.v b/vlib/os/filepath.v
index b68ae2b19..6ca73f41b 100644
--- a/vlib/os/filepath.v
+++ b/vlib/os/filepath.v
@@ -218,18 +218,20 @@ fn clean_path(path string) string {
 
 // to_slash returns the result of replacing each separator character in path with a slash (`/`).
 pub fn to_slash(path string) string {
-	if path_separator == '/' {
-		return path
+	return $if windows {
+		path.replace(path_separator, '/')
+	} $else {
+		path
 	}
-	return path.replace(path_separator, '/')
 }
 
 // from_slash returns the result of replacing each slash (`/`) character is path with a separator character.
 pub fn from_slash(path string) string {
-	if path_separator == '/' {
-		return path
+	return $if windows {
+		path.replace('/', path_separator)
+	} $else {
+		path
 	}
-	return path.replace('/', path_separator)
 }
 
 // win_volume_len returns the length of the
diff --git a/vlib/os/os.v b/vlib/os/os.v
index 058e68ea2..948e64c70 100644
--- a/vlib/os/os.v
+++ b/vlib/os/os.v
@@ -44,7 +44,7 @@ fn executable_fallback() string {
 		}
 	}
 	if !is_abs_path(exepath) {
-		other_separator := if path_separator == '/' { '\\' } else { '/' }
+		other_separator := $if windows { '/' } $else { '\\' }
 		rexepath := exepath.replace(other_separator, path_separator)
 		if rexepath.contains(path_separator) {
 			exepath = join_path_single(wd_at_startup, exepath)
@@ -848,7 +848,7 @@ pub fn mkdir_all(opath string, params MkdirParams) ! {
 		}
 		return error('path `${opath}` already exists, and is not a folder')
 	}
-	other_separator := if path_separator == '/' { '\\' } else { '/' }
+	other_separator := $if windows { '/' } $else { '\\' }
 	path := opath.replace(other_separator, path_separator)
 	mut p := if path.starts_with(path_separator) { path_separator } else { '' }
 	path_parts := path.trim_left(path_separator).split(path_separator)
diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index 2ba73ca2f..953c76898 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -152,7 +152,8 @@ mut:
 	v_current_commit_hash string // same as old C.V_CURRENT_COMMIT_HASH
 	assign_stmt_attr      string // for `x := [1,2,3] @[freed]`
 
-	js_string ast.Type = ast.void_type // when `js"string literal"` is used, `js_string` will be equal to `JS.String`
+	js_string           ast.Type                 = ast.void_type // when `js"string literal"` is used, `js_string` will be equal to `JS.String`
+	checker_transformer &transformer.Transformer = unsafe { nil }
 }
 
 pub fn new_checker(table &ast.Table, pref_ &pref.Preferences) &Checker {
@@ -174,6 +175,7 @@ pub fn new_checker(table &ast.Table, pref_ &pref.Preferences) &Checker {
 		)
 		match_exhaustive_cutoff_limit: pref_.checker_match_exhaustive_cutoff_limit
 		v_current_commit_hash:         v_current_commit_hash
+		checker_transformer:           transformer.new_transformer_with_table(table, pref_)
 	}
 	checker.type_resolver = type_resolver.TypeResolver.new(table, checker)
 	checker.comptime = &checker.type_resolver.info
@@ -2109,8 +2111,7 @@ fn (mut c Checker) enum_decl(mut node ast.EnumDecl) {
 				ast.InfixExpr {
 					// Handle `enum Foo { x = 1 + 2 }`
 					c.infix_expr(mut field.expr)
-					mut t := transformer.new_transformer_with_table(c.table, c.pref)
-					folded_expr := t.infix_expr(mut field.expr)
+					folded_expr := c.checker_transformer.infix_expr(mut field.expr)
 
 					if folded_expr is ast.IntegerLiteral {
 						c.check_enum_field_integer_literal(folded_expr, signed, node.is_multi_allowed,
@@ -2120,8 +2121,7 @@ fn (mut c Checker) enum_decl(mut node ast.EnumDecl) {
 				}
 				ast.ParExpr {
 					c.expr(mut field.expr.expr)
-					mut t := transformer.new_transformer_with_table(c.table, c.pref)
-					folded_expr := t.expr(mut field.expr.expr)
+					folded_expr := c.checker_transformer.expr(mut field.expr.expr)
 
 					if folded_expr is ast.IntegerLiteral {
 						c.check_enum_field_integer_literal(folded_expr, signed, node.is_multi_allowed,
@@ -2160,9 +2160,7 @@ fn (mut c Checker) enum_decl(mut node ast.EnumDecl) {
 						if field.expr.kind == .constant && field.expr.obj.typ.is_int() {
 							// accepts int constants as enum value
 							if mut field.expr.obj is ast.ConstField {
-								mut t := transformer.new_transformer_with_table(c.table,
-									c.pref)
-								folded_expr := t.expr(mut field.expr.obj.expr)
+								folded_expr := c.checker_transformer.expr(mut field.expr.obj.expr)
 
 								if folded_expr is ast.IntegerLiteral {
 									c.check_enum_field_integer_literal(folded_expr, signed,
diff --git a/vlib/v/checker/if.v b/vlib/v/checker/if.v
index b81af146a..3986e1859 100644
--- a/vlib/v/checker/if.v
+++ b/vlib/v/checker/if.v
@@ -156,6 +156,17 @@ fn (mut c Checker) if_expr(mut node ast.IfExpr) ast.Type {
 					c.error('non-bool type `${c.table.type_to_str(cond_typ)}` used as if condition',
 						branch.cond.pos())
 				}
+				if !c.pref.translated && !c.file.is_translated {
+					mut check_expr := branch.cond
+					t_expr := c.checker_transformer.expr(mut check_expr)
+					if t_expr is ast.BoolLiteral {
+						if t_expr.val {
+							c.note('condition is always true', branch.cond.pos())
+						} else {
+							c.note('condition is always false', branch.cond.pos())
+						}
+					}
+				}
 			}
 		} else {
 			// else branch
diff --git a/vlib/v/checker/match.v b/vlib/v/checker/match.v
index bdc82ecc3..ced8201e8 100644
--- a/vlib/v/checker/match.v
+++ b/vlib/v/checker/match.v
@@ -235,6 +235,25 @@ fn (mut c Checker) match_expr(mut node ast.MatchExpr) ast.Type {
 			}
 		}
 
+		if !c.pref.translated && !c.file.is_translated {
+			// check for always true/false match branch
+			for mut expr in branch.exprs {
+				mut check_expr := ast.InfixExpr{
+					op:    .eq
+					left:  node.cond
+					right: expr
+				}
+				t_expr := c.checker_transformer.expr(mut check_expr)
+				if t_expr is ast.BoolLiteral {
+					if t_expr.val {
+						c.note('match is always true', expr.pos())
+					} else {
+						c.note('match is always false', expr.pos())
+					}
+				}
+			}
+		}
+
 		if !node.is_comptime || (node.is_comptime && comptime_match_branch_result) {
 			if node.is_expr {
 				c.stmts_ending_with_expression(mut branch.stmts, c.expected_or_type)
diff --git a/vlib/v/checker/tests/always_true_false_branch.out b/vlib/v/checker/tests/always_true_false_branch.out
new file mode 100644
index 000000000..05e0fa7b5
--- /dev/null
+++ b/vlib/v/checker/tests/always_true_false_branch.out
@@ -0,0 +1,469 @@
+vlib/v/checker/tests/always_true_false_branch.vv:5:23: notice: condition is always true
+    3 | fn main() {
+    4 |     x := 1
+    5 |     if_always_true := if x == x {
+      |                          ~~~~~~
+    6 |         1
+    7 |     } else if true {
+vlib/v/checker/tests/always_true_false_branch.vv:7:12: notice: condition is always true
+    5 |     if_always_true := if x == x {
+    6 |         1
+    7 |     } else if true {
+      |               ~~~~
+    8 |         1
+    9 |     } else if !false {
+vlib/v/checker/tests/always_true_false_branch.vv:11:12: notice: condition is always true
+    9 |     } else if !false {
+   10 |         1
+   11 |     } else if true == true {
+      |               ~~~~~~~~~~~~
+   12 |         1
+   13 |     } else if true != false {
+vlib/v/checker/tests/always_true_false_branch.vv:13:12: notice: condition is always true
+   11 |     } else if true == true {
+   12 |         1
+   13 |     } else if true != false {
+      |               ~~~~~~~~~~~~~
+   14 |         1
+   15 |     } else if false == false {
+vlib/v/checker/tests/always_true_false_branch.vv:15:12: notice: condition is always true
+   13 |     } else if true != false {
+   14 |         1
+   15 |     } else if false == false {
+      |               ~~~~~~~~~~~~~~
+   16 |         1
+   17 |     } else if false != true {
+vlib/v/checker/tests/always_true_false_branch.vv:17:12: notice: condition is always true
+   15 |     } else if false == false {
+   16 |         1
+   17 |     } else if false != true {
+      |               ~~~~~~~~~~~~~
+   18 |         1
+   19 |     } else if 'a' == 'a' {
+vlib/v/checker/tests/always_true_false_branch.vv:19:12: notice: condition is always true
+   17 |     } else if false != true {
+   18 |         1
+   19 |     } else if 'a' == 'a' {
+      |               ~~~~~~~~~~
+   20 |         1
+   21 |     } else if 'a' != 'b' {
+vlib/v/checker/tests/always_true_false_branch.vv:21:12: notice: condition is always true
+   19 |     } else if 'a' == 'a' {
+   20 |         1
+   21 |     } else if 'a' != 'b' {
+      |               ~~~~~~~~~~
+   22 |         1
+   23 |     } else if 1 == 1 {
+vlib/v/checker/tests/always_true_false_branch.vv:23:12: notice: condition is always true
+   21 |     } else if 'a' != 'b' {
+   22 |         1
+   23 |     } else if 1 == 1 {
+      |               ~~~~~~
+   24 |         1
+   25 |     } else if 1 != 2 {
+vlib/v/checker/tests/always_true_false_branch.vv:25:12: notice: condition is always true
+   23 |     } else if 1 == 1 {
+   24 |         1
+   25 |     } else if 1 != 2 {
+      |               ~~~~~~
+   26 |         1
+   27 |     } else if 1 >= 1 {
+vlib/v/checker/tests/always_true_false_branch.vv:27:12: notice: condition is always true
+   25 |     } else if 1 != 2 {
+   26 |         1
+   27 |     } else if 1 >= 1 {
+      |               ~~~~~~
+   28 |         1
+   29 |     } else if 1 <= 1 {
+vlib/v/checker/tests/always_true_false_branch.vv:29:12: notice: condition is always true
+   27 |     } else if 1 >= 1 {
+   28 |         1
+   29 |     } else if 1 <= 1 {
+      |               ~~~~~~
+   30 |         1
+   31 |     } else if 1 < 2 {
+vlib/v/checker/tests/always_true_false_branch.vv:31:12: notice: condition is always true
+   29 |     } else if 1 <= 1 {
+   30 |         1
+   31 |     } else if 1 < 2 {
+      |               ~~~~~
+   32 |         1
+   33 |     } else if 2 > 1 {
+vlib/v/checker/tests/always_true_false_branch.vv:33:12: notice: condition is always true
+   31 |     } else if 1 < 2 {
+   32 |         1
+   33 |     } else if 2 > 1 {
+      |               ~~~~~
+   34 |         1
+   35 |     } else if 1.5 == 1.5 {
+vlib/v/checker/tests/always_true_false_branch.vv:35:12: notice: condition is always true
+   33 |     } else if 2 > 1 {
+   34 |         1
+   35 |     } else if 1.5 == 1.5 {
+      |               ~~~~~~~~~~
+   36 |         1
+   37 |     } else if 1.5 != 2.5 {
+vlib/v/checker/tests/always_true_false_branch.vv:37:12: notice: condition is always true
+   35 |     } else if 1.5 == 1.5 {
+   36 |         1
+   37 |     } else if 1.5 != 2.5 {
+      |               ~~~~~~~~~~
+   38 |         1
+   39 |     } else if 1.5 >= 1.5 {
+vlib/v/checker/tests/always_true_false_branch.vv:39:12: notice: condition is always true
+   37 |     } else if 1.5 != 2.5 {
+   38 |         1
+   39 |     } else if 1.5 >= 1.5 {
+      |               ~~~~~~~~~~
+   40 |         1
+   41 |     } else if 1.5 <= 1.5 {
+vlib/v/checker/tests/always_true_false_branch.vv:41:12: notice: condition is always true
+   39 |     } else if 1.5 >= 1.5 {
+   40 |         1
+   41 |     } else if 1.5 <= 1.5 {
+      |               ~~~~~~~~~~
+   42 |         1
+   43 |     } else if 1.5 < 2.5 {
+vlib/v/checker/tests/always_true_false_branch.vv:43:12: notice: condition is always true
+   41 |     } else if 1.5 <= 1.5 {
+   42 |         1
+   43 |     } else if 1.5 < 2.5 {
+      |               ~~~~~~~~~
+   44 |         1
+   45 |     } else if 2.5 > 1.5 {
+vlib/v/checker/tests/always_true_false_branch.vv:45:12: notice: condition is always true
+   43 |     } else if 1.5 < 2.5 {
+   44 |         1
+   45 |     } else if 2.5 > 1.5 {
+      |               ~~~~~~~~~
+   46 |         1
+   47 |     } else if `1` == `1` {
+vlib/v/checker/tests/always_true_false_branch.vv:47:12: notice: condition is always true
+   45 |     } else if 2.5 > 1.5 {
+   46 |         1
+   47 |     } else if `1` == `1` {
+      |               ~~~~~~~~~~
+   48 |         1
+   49 |     } else if `1` != `2` {
+vlib/v/checker/tests/always_true_false_branch.vv:49:12: notice: condition is always true
+   47 |     } else if `1` == `1` {
+   48 |         1
+   49 |     } else if `1` != `2` {
+      |               ~~~~~~~~~~
+   50 |         1
+   51 |     } else if `1` >= `1` {
+vlib/v/checker/tests/always_true_false_branch.vv:51:12: notice: condition is always true
+   49 |     } else if `1` != `2` {
+   50 |         1
+   51 |     } else if `1` >= `1` {
+      |               ~~~~~~~~~~
+   52 |         1
+   53 |     } else if `1` <= `1` {
+vlib/v/checker/tests/always_true_false_branch.vv:53:12: notice: condition is always true
+   51 |     } else if `1` >= `1` {
+   52 |         1
+   53 |     } else if `1` <= `1` {
+      |               ~~~~~~~~~~
+   54 |         1
+   55 |     } else if `1` < `2` {
+vlib/v/checker/tests/always_true_false_branch.vv:55:12: notice: condition is always true
+   53 |     } else if `1` <= `1` {
+   54 |         1
+   55 |     } else if `1` < `2` {
+      |               ~~~~~~~~~
+   56 |         1
+   57 |     } else if `2` > `1` {
+vlib/v/checker/tests/always_true_false_branch.vv:57:12: notice: condition is always true
+   55 |     } else if `1` < `2` {
+   56 |         1
+   57 |     } else if `2` > `1` {
+      |               ~~~~~~~~~
+   58 |         1
+   59 |     } else if 1 == 1 && 2 <= 2 && 3 >= 3 && 4 != 5 {
+vlib/v/checker/tests/always_true_false_branch.vv:59:1: notice: condition is always true
+   57 |     } else if `2` > `1` {
+   58 |         1
+   59 |     } else if 1 == 1 && 2 <= 2 && 3 >= 3 && 4 != 5 {
+      | ^
+   60 |         1
+   61 |     } else if 1 == 1 || 4 > 5 || 6 < 3 || 5 != 5 {
+vlib/v/checker/tests/always_true_false_branch.vv:61:1: notice: condition is always true
+   59 |     } else if 1 == 1 && 2 <= 2 && 3 >= 3 && 4 != 5 {
+   60 |         1
+   61 |     } else if 1 == 1 || 4 > 5 || 6 < 3 || 5 != 5 {
+      | ^
+   62 |         1
+   63 |     } else {
+vlib/v/checker/tests/always_true_false_branch.vv:69:24: notice: condition is always false
+   67 |     dump(if_always_true)
+   68 | 
+   69 |     if_always_false := if x != x {
+      |                           ~~~~~~
+   70 |         1
+   71 |     } else if false {
+vlib/v/checker/tests/always_true_false_branch.vv:71:12: notice: condition is always false
+   69 |     if_always_false := if x != x {
+   70 |         1
+   71 |     } else if false {
+      |               ~~~~~
+   72 |         1
+   73 |     } else if !true {
+vlib/v/checker/tests/always_true_false_branch.vv:75:12: notice: condition is always false
+   73 |     } else if !true {
+   74 |         1
+   75 |     } else if true != true {
+      |               ~~~~~~~~~~~~
+   76 |         1
+   77 |     } else if true == false {
+vlib/v/checker/tests/always_true_false_branch.vv:77:12: notice: condition is always false
+   75 |     } else if true != true {
+   76 |         1
+   77 |     } else if true == false {
+      |               ~~~~~~~~~~~~~
+   78 |         1
+   79 |     } else if false != false {
+vlib/v/checker/tests/always_true_false_branch.vv:79:12: notice: condition is always false
+   77 |     } else if true == false {
+   78 |         1
+   79 |     } else if false != false {
+      |               ~~~~~~~~~~~~~~
+   80 |         1
+   81 |     } else if false == true {
+vlib/v/checker/tests/always_true_false_branch.vv:81:12: notice: condition is always false
+   79 |     } else if false != false {
+   80 |         1
+   81 |     } else if false == true {
+      |               ~~~~~~~~~~~~~
+   82 |         1
+   83 |     } else if 'a' != 'a' {
+vlib/v/checker/tests/always_true_false_branch.vv:83:12: notice: condition is always false
+   81 |     } else if false == true {
+   82 |         1
+   83 |     } else if 'a' != 'a' {
+      |               ~~~~~~~~~~
+   84 |         1
+   85 |     } else if 'a' == 'b' {
+vlib/v/checker/tests/always_true_false_branch.vv:85:12: notice: condition is always false
+   83 |     } else if 'a' != 'a' {
+   84 |         1
+   85 |     } else if 'a' == 'b' {
+      |               ~~~~~~~~~~
+   86 |         1
+   87 |     } else if 1 != 1 {
+vlib/v/checker/tests/always_true_false_branch.vv:87:12: notice: condition is always false
+   85 |     } else if 'a' == 'b' {
+   86 |         1
+   87 |     } else if 1 != 1 {
+      |               ~~~~~~
+   88 |         1
+   89 |     } else if 1 == 2 {
+vlib/v/checker/tests/always_true_false_branch.vv:89:12: notice: condition is always false
+   87 |     } else if 1 != 1 {
+   88 |         1
+   89 |     } else if 1 == 2 {
+      |               ~~~~~~
+   90 |         1
+   91 |     } else if 1 > 1 {
+vlib/v/checker/tests/always_true_false_branch.vv:91:12: notice: condition is always false
+   89 |     } else if 1 == 2 {
+   90 |         1
+   91 |     } else if 1 > 1 {
+      |               ~~~~~
+   92 |         1
+   93 |     } else if 1 < 1 {
+vlib/v/checker/tests/always_true_false_branch.vv:93:12: notice: condition is always false
+   91 |     } else if 1 > 1 {
+   92 |         1
+   93 |     } else if 1 < 1 {
+      |               ~~~~~
+   94 |         1
+   95 |     } else if 1 >= 2 {
+vlib/v/checker/tests/always_true_false_branch.vv:95:12: notice: condition is always false
+   93 |     } else if 1 < 1 {
+   94 |         1
+   95 |     } else if 1 >= 2 {
+      |               ~~~~~~
+   96 |         1
+   97 |     } else if 2 <= 1 {
+vlib/v/checker/tests/always_true_false_branch.vv:97:12: notice: condition is always false
+   95 |     } else if 1 >= 2 {
+   96 |         1
+   97 |     } else if 2 <= 1 {
+      |               ~~~~~~
+   98 |         1
+   99 |     } else if 1.5 != 1.5 {
+vlib/v/checker/tests/always_true_false_branch.vv:99:12: notice: condition is always false
+   97 |     } else if 2 <= 1 {
+   98 |         1
+   99 |     } else if 1.5 != 1.5 {
+      |               ~~~~~~~~~~
+  100 |         1
+  101 |     } else if 1.5 == 2.5 {
+vlib/v/checker/tests/always_true_false_branch.vv:101:12: notice: condition is always false
+   99 |     } else if 1.5 != 1.5 {
+  100 |         1
+  101 |     } else if 1.5 == 2.5 {
+      |               ~~~~~~~~~~
+  102 |         1
+  103 |     } else if 1.5 > 1.5 {
+vlib/v/checker/tests/always_true_false_branch.vv:103:12: notice: condition is always false
+  101 |     } else if 1.5 == 2.5 {
+  102 |         1
+  103 |     } else if 1.5 > 1.5 {
+      |               ~~~~~~~~~
+  104 |         1
+  105 |     } else if 1.5 < 1.5 {
+vlib/v/checker/tests/always_true_false_branch.vv:105:12: notice: condition is always false
+  103 |     } else if 1.5 > 1.5 {
+  104 |         1
+  105 |     } else if 1.5 < 1.5 {
+      |               ~~~~~~~~~
+  106 |         1
+  107 |     } else if 1.5 >= 2.5 {
+vlib/v/checker/tests/always_true_false_branch.vv:107:12: notice: condition is always false
+  105 |     } else if 1.5 < 1.5 {
+  106 |         1
+  107 |     } else if 1.5 >= 2.5 {
+      |               ~~~~~~~~~~
+  108 |         1
+  109 |     } else if 2.5 <= 1.5 {
+vlib/v/checker/tests/always_true_false_branch.vv:109:12: notice: condition is always false
+  107 |     } else if 1.5 >= 2.5 {
+  108 |         1
+  109 |     } else if 2.5 <= 1.5 {
+      |               ~~~~~~~~~~
+  110 |         1
+  111 |     } else if `1` != `1` {
+vlib/v/checker/tests/always_true_false_branch.vv:111:12: notice: condition is always false
+  109 |     } else if 2.5 <= 1.5 {
+  110 |         1
+  111 |     } else if `1` != `1` {
+      |               ~~~~~~~~~~
+  112 |         1
+  113 |     } else if `1` == `2` {
+vlib/v/checker/tests/always_true_false_branch.vv:113:12: notice: condition is always false
+  111 |     } else if `1` != `1` {
+  112 |         1
+  113 |     } else if `1` == `2` {
+      |               ~~~~~~~~~~
+  114 |         1
+  115 |     } else if `1` < `1` {
+vlib/v/checker/tests/always_true_false_branch.vv:115:12: notice: condition is always false
+  113 |     } else if `1` == `2` {
+  114 |         1
+  115 |     } else if `1` < `1` {
+      |               ~~~~~~~~~
+  116 |         1
+  117 |     } else if `1` > `1` {
+vlib/v/checker/tests/always_true_false_branch.vv:117:12: notice: condition is always false
+  115 |     } else if `1` < `1` {
+  116 |         1
+  117 |     } else if `1` > `1` {
+      |               ~~~~~~~~~
+  118 |         1
+  119 |     } else if `1` >= `2` {
+vlib/v/checker/tests/always_true_false_branch.vv:119:12: notice: condition is always false
+  117 |     } else if `1` > `1` {
+  118 |         1
+  119 |     } else if `1` >= `2` {
+      |               ~~~~~~~~~~
+  120 |         1
+  121 |     } else if `2` <= `1` {
+vlib/v/checker/tests/always_true_false_branch.vv:121:12: notice: condition is always false
+  119 |     } else if `1` >= `2` {
+  120 |         1
+  121 |     } else if `2` <= `1` {
+      |               ~~~~~~~~~~
+  122 |         1
+  123 |     } else if 1 == 2 && 3 >= 3 && 4 <= 5 && 5 != 5 {
+vlib/v/checker/tests/always_true_false_branch.vv:123:1: notice: condition is always false
+  121 |     } else if `2` <= `1` {
+  122 |         1
+  123 |     } else if 1 == 2 && 3 >= 3 && 4 <= 5 && 5 != 5 {
+      | ^
+  124 |         1
+  125 |     } else if 1 == 2 || 2 > 3 || 5 < 4 {
+vlib/v/checker/tests/always_true_false_branch.vv:125:1: notice: condition is always false
+  123 |     } else if 1 == 2 && 3 >= 3 && 4 <= 5 && 5 != 5 {
+  124 |         1
+  125 |     } else if 1 == 2 || 2 > 3 || 5 < 4 {
+      | ^
+  126 |         0
+  127 |     } else {
+vlib/v/checker/tests/always_true_false_branch.vv:134:3: notice: match is always true
+  132 | 
+  133 |     match_always_true_var := match x {
+  134 |         x {
+      |         ^
+  135 |             'haha'
+  136 |         }
+vlib/v/checker/tests/always_true_false_branch.vv:144:3: notice: match is always true
+  142 | 
+  143 |     match_always_true_false_bool := match true {
+  144 |         true {
+      |         ~~~~
+  145 |             'haha'
+  146 |         }
+vlib/v/checker/tests/always_true_false_branch.vv:147:3: notice: match is always false
+  145 |             'haha'
+  146 |         }
+  147 |         false {
+      |         ~~~~~
+  148 |             'cc'
+  149 |         }
+vlib/v/checker/tests/always_true_false_branch.vv:154:3: notice: match is always true
+  152 | 
+  153 |     match_always_true_false_int := match 1 {
+  154 |         1 {
+      |         ^
+  155 |             'haha'
+  156 |         }
+vlib/v/checker/tests/always_true_false_branch.vv:157:3: notice: match is always false
+  155 |             'haha'
+  156 |         }
+  157 |         2 {
+      |         ^
+  158 |             'cc'
+  159 |         }
+vlib/v/checker/tests/always_true_false_branch.vv:167:3: notice: match is always true
+  165 | 
+  166 |     match_always_true_false_f64 := match 1.5 {
+  167 |         1.5 {
+      |         ~~~
+  168 |             'haha'
+  169 |         }
+vlib/v/checker/tests/always_true_false_branch.vv:170:3: notice: match is always false
+  168 |             'haha'
+  169 |         }
+  170 |         2.5 {
+      |         ~~~
+  171 |             'cc'
+  172 |         }
+vlib/v/checker/tests/always_true_false_branch.vv:180:3: notice: match is always true
+  178 | 
+  179 |     match_always_true_false_string := match 'a' {
+  180 |         'a' {
+      |         ~~~
+  181 |             'haha'
+  182 |         }
+vlib/v/checker/tests/always_true_false_branch.vv:183:3: notice: match is always false
+  181 |             'haha'
+  182 |         }
+  183 |         'b' {
+      |         ~~~
+  184 |             'cc'
+  185 |         }
+vlib/v/checker/tests/always_true_false_branch.vv:193:3: notice: match is always true
+  191 | 
+  192 |     match_always_true_false_rune := match `a` {
+  193 |         `a` {
+      |         ~~~
+  194 |             'haha'
+  195 |         }
+vlib/v/checker/tests/always_true_false_branch.vv:196:3: notice: match is always false
+  194 |             'haha'
+  195 |         }
+  196 |         `b` {
+      |         ~~~
+  197 |             'cc'
+  198 |         }
diff --git a/vlib/v/checker/tests/always_true_false_branch.vv b/vlib/v/checker/tests/always_true_false_branch.vv
new file mode 100644
index 000000000..05c4e8477
--- /dev/null
+++ b/vlib/v/checker/tests/always_true_false_branch.vv
@@ -0,0 +1,204 @@
+module main
+
+fn main() {
+	x := 1
+	if_always_true := if x == x {
+		1
+	} else if true {
+		1
+	} else if !false {
+		1
+	} else if true == true {
+		1
+	} else if true != false {
+		1
+	} else if false == false {
+		1
+	} else if false != true {
+		1
+	} else if 'a' == 'a' {
+		1
+	} else if 'a' != 'b' {
+		1
+	} else if 1 == 1 {
+		1
+	} else if 1 != 2 {
+		1
+	} else if 1 >= 1 {
+		1
+	} else if 1 <= 1 {
+		1
+	} else if 1 < 2 {
+		1
+	} else if 2 > 1 {
+		1
+	} else if 1.5 == 1.5 {
+		1
+	} else if 1.5 != 2.5 {
+		1
+	} else if 1.5 >= 1.5 {
+		1
+	} else if 1.5 <= 1.5 {
+		1
+	} else if 1.5 < 2.5 {
+		1
+	} else if 2.5 > 1.5 {
+		1
+	} else if `1` == `1` {
+		1
+	} else if `1` != `2` {
+		1
+	} else if `1` >= `1` {
+		1
+	} else if `1` <= `1` {
+		1
+	} else if `1` < `2` {
+		1
+	} else if `2` > `1` {
+		1
+	} else if 1 == 1 && 2 <= 2 && 3 >= 3 && 4 != 5 {
+		1
+	} else if 1 == 1 || 4 > 5 || 6 < 3 || 5 != 5 {
+		1
+	} else {
+		0
+	}
+
+	dump(if_always_true)
+
+	if_always_false := if x != x {
+		1
+	} else if false {
+		1
+	} else if !true {
+		1
+	} else if true != true {
+		1
+	} else if true == false {
+		1
+	} else if false != false {
+		1
+	} else if false == true {
+		1
+	} else if 'a' != 'a' {
+		1
+	} else if 'a' == 'b' {
+		1
+	} else if 1 != 1 {
+		1
+	} else if 1 == 2 {
+		1
+	} else if 1 > 1 {
+		1
+	} else if 1 < 1 {
+		1
+	} else if 1 >= 2 {
+		1
+	} else if 2 <= 1 {
+		1
+	} else if 1.5 != 1.5 {
+		1
+	} else if 1.5 == 2.5 {
+		1
+	} else if 1.5 > 1.5 {
+		1
+	} else if 1.5 < 1.5 {
+		1
+	} else if 1.5 >= 2.5 {
+		1
+	} else if 2.5 <= 1.5 {
+		1
+	} else if `1` != `1` {
+		1
+	} else if `1` == `2` {
+		1
+	} else if `1` < `1` {
+		1
+	} else if `1` > `1` {
+		1
+	} else if `1` >= `2` {
+		1
+	} else if `2` <= `1` {
+		1
+	} else if 1 == 2 && 3 >= 3 && 4 <= 5 && 5 != 5 {
+		1
+	} else if 1 == 2 || 2 > 3 || 5 < 4 {
+		0
+	} else {
+		0
+	}
+
+	dump(if_always_false)
+
+	match_always_true_var := match x {
+		x {
+			'haha'
+		}
+		else {
+			'cc'
+		}
+	}
+	dump(match_always_true_var)
+
+	match_always_true_false_bool := match true {
+		true {
+			'haha'
+		}
+		false {
+			'cc'
+		}
+	}
+	dump(match_always_true_false_bool)
+
+	match_always_true_false_int := match 1 {
+		1 {
+			'haha'
+		}
+		2 {
+			'cc'
+		}
+		else {
+			'bb'
+		}
+	}
+	dump(match_always_true_false_int)
+
+	match_always_true_false_f64 := match 1.5 {
+		1.5 {
+			'haha'
+		}
+		2.5 {
+			'cc'
+		}
+		else {
+			'bb'
+		}
+	}
+	dump(match_always_true_false_f64)
+
+	match_always_true_false_string := match 'a' {
+		'a' {
+			'haha'
+		}
+		'b' {
+			'cc'
+		}
+		else {
+			'bb'
+		}
+	}
+	dump(match_always_true_false_string)
+
+	match_always_true_false_rune := match `a` {
+		`a` {
+			'haha'
+		}
+		`b` {
+			'cc'
+		}
+		else {
+			'bb'
+		}
+	}
+	dump(match_always_true_false_rune)
+}
diff --git a/vlib/v/checker/tests/assign_multi_mismatch.out b/vlib/v/checker/tests/assign_multi_mismatch.out
index ab078c0d0..16367b912 100644
--- a/vlib/v/checker/tests/assign_multi_mismatch.out
+++ b/vlib/v/checker/tests/assign_multi_mismatch.out
@@ -1,3 +1,42 @@
+vlib/v/checker/tests/assign_multi_mismatch.vv:16:2: notice: match is always false
+   14 | 
+   15 | _, _ := 0, match 4 {
+   16 |     1 { 0 }
+      |     ^
+   17 |     else { 1 }
+   18 | }
+vlib/v/checker/tests/assign_multi_mismatch.vv:20:2: notice: match is always false
+   18 | }
+   19 | _ := match 4 {
+   20 |     1 { f() }
+      |     ^
+   21 |     else { f() }
+   22 | }
+vlib/v/checker/tests/assign_multi_mismatch.vv:24:2: notice: match is always false
+   22 | }
+   23 | _, _ := 0, match 4 {
+   24 |     1 { f() }
+      |     ^
+   25 |     else { f() }
+   26 | }
+vlib/v/checker/tests/assign_multi_mismatch.vv:28:15: notice: condition is always true
+   26 | }
+   27 | 
+   28 | _, _ := 0, if true { 0 } else { 1 }
+      |               ~~~~
+   29 | _ := if true { f() } else { f() }
+   30 | _, _ := 0, if true { f() } else { f() }
+vlib/v/checker/tests/assign_multi_mismatch.vv:29:9: notice: condition is always true
+   27 | 
+   28 | _, _ := 0, if true { 0 } else { 1 }
+   29 | _ := if true { f() } else { f() }
+      |         ~~~~
+   30 | _, _ := 0, if true { f() } else { f() }
+vlib/v/checker/tests/assign_multi_mismatch.vv:30:15: notice: condition is always true
+   28 | _, _ := 0, if true { 0 } else { 1 }
+   29 | _ := if true { f() } else { f() }
+   30 | _, _ := 0, if true { f() } else { f() }
+      |               ~~~~
 vlib/v/checker/tests/assign_multi_mismatch.vv:5:3: error: assignment mismatch: 1 variable 2 values
     3 | }
     4 | 
diff --git a/vlib/v/checker/tests/cast_to_interface_err.out b/vlib/v/checker/tests/cast_to_interface_err.out
index 06cb0184b..9e3525a71 100644
--- a/vlib/v/checker/tests/cast_to_interface_err.out
+++ b/vlib/v/checker/tests/cast_to_interface_err.out
@@ -1,3 +1,10 @@
+vlib/v/checker/tests/cast_to_interface_err.vv:7:5: notice: condition is always true
+    5 | fn foo() !int {
+    6 |     // do something
+    7 |     if true {
+      |        ~~~~
+    8 |         return 1
+    9 |     }
 vlib/v/checker/tests/cast_to_interface_err.vv:20:9: error: `CustomError` doesn't implement method `msg` of interface `IError`
    18 | 
    19 | fn my_error() IError {
diff --git a/vlib/v/checker/tests/function_missing_return_type.out b/vlib/v/checker/tests/function_missing_return_type.out
index 73292af5e..45c8bf59a 100644
--- a/vlib/v/checker/tests/function_missing_return_type.out
+++ b/vlib/v/checker/tests/function_missing_return_type.out
@@ -1,3 +1,10 @@
+vlib/v/checker/tests/function_missing_return_type.vv:13:5: notice: condition is always true
+   11 | 
+   12 | fn (s Abc) abc() &int {
+   13 |     if true {
+      |        ~~~~
+   14 |         return &s.x
+   15 |     }
 vlib/v/checker/tests/function_missing_return_type.vv:1:1: error: missing return at end of function `h`
     1 | fn h() int {
       | ~~~~~~~~~~
diff --git a/vlib/v/checker/tests/if_diff_expected_type_err.out b/vlib/v/checker/tests/if_diff_expected_type_err.out
index db5bc60ca..07f639e64 100644
--- a/vlib/v/checker/tests/if_diff_expected_type_err.out
+++ b/vlib/v/checker/tests/if_diff_expected_type_err.out
@@ -1,3 +1,10 @@
+vlib/v/checker/tests/if_diff_expected_type_err.vv:5:14: notice: condition is always true
+    3 | 
+    4 | fn main() {
+    5 |     runes := if true { &some_runes } else { some_other_runes }
+      |                 ~~~~
+    6 |     println(runes)
+    7 | }
 vlib/v/checker/tests/if_diff_expected_type_err.vv:5:11: error: mismatched types `&[]rune` and `[]rune`
     3 | 
     4 | fn main() {
diff --git a/vlib/v/checker/tests/if_expr_last_stmt.out b/vlib/v/checker/tests/if_expr_last_stmt.out
index 67100d7b9..4afff19cc 100644
--- a/vlib/v/checker/tests/if_expr_last_stmt.out
+++ b/vlib/v/checker/tests/if_expr_last_stmt.out
@@ -1,3 +1,16 @@
+vlib/v/checker/tests/if_expr_last_stmt.vv:2:9: notice: condition is always true
+    1 | fn main() {
+    2 |     _ = if true {
+      |            ~~~~
+    3 |         1
+    4 |     } else if false {
+vlib/v/checker/tests/if_expr_last_stmt.vv:4:12: notice: condition is always false
+    2 |     _ = if true {
+    3 |         1
+    4 |     } else if false {
+      |               ~~~~~
+    5 |     } else {
+    6 |     }
 vlib/v/checker/tests/if_expr_last_stmt.vv:4:4: error: `if` expression requires an expression as the last statement of every branch
     2 |     _ = if true {
     3 |         1
diff --git a/vlib/v/checker/tests/if_expr_mismatch.out b/vlib/v/checker/tests/if_expr_mismatch.out
index 0c45b8883..6b100bd0e 100644
--- a/vlib/v/checker/tests/if_expr_mismatch.out
+++ b/vlib/v/checker/tests/if_expr_mismatch.out
@@ -1,3 +1,9 @@
+vlib/v/checker/tests/if_expr_mismatch.vv:2:10: notice: condition is always true
+    1 | fn main() {
+    2 |     s := if true { '12' } else { 12 }
+      |             ~~~~
+    3 |     println(s)
+    4 | }
 vlib/v/checker/tests/if_expr_mismatch.vv:2:7: error: mismatched types `string` and `int literal`
     1 | fn main() {
     2 |     s := if true { '12' } else { 12 }
diff --git a/vlib/v/checker/tests/if_expr_no_else.out b/vlib/v/checker/tests/if_expr_no_else.out
index 8ccea6c68..02b0460ab 100644
--- a/vlib/v/checker/tests/if_expr_no_else.out
+++ b/vlib/v/checker/tests/if_expr_no_else.out
@@ -1,3 +1,9 @@
+vlib/v/checker/tests/if_expr_no_else.vv:2:9: notice: condition is always true
+    1 | fn main() {
+    2 |     _ = if true {
+      |            ~~~~
+    3 |         1
+    4 |     }
 vlib/v/checker/tests/if_expr_no_else.vv:2:6: error: `if` expression needs `else` clause
     1 | fn main() {
     2 |     _ = if true {
diff --git a/vlib/v/checker/tests/if_expr_with_none_only.out b/vlib/v/checker/tests/if_expr_with_none_only.out
index b0350ccb7..b4a286f79 100644
--- a/vlib/v/checker/tests/if_expr_with_none_only.out
+++ b/vlib/v/checker/tests/if_expr_with_none_only.out
@@ -1,3 +1,8 @@
+vlib/v/checker/tests/if_expr_with_none_only.vv:2:10: notice: condition is always true
+    1 | fn main() {
+    2 |     a := if true { none } else { none }
+      |             ~~~~
+    3 | }
 vlib/v/checker/tests/if_expr_with_none_only.vv:2:2: warning: unused variable: `a`
     1 | fn main() {
     2 |     a := if true { none } else { none }
diff --git a/vlib/v/checker/tests/if_match_result.out b/vlib/v/checker/tests/if_match_result.out
index e0e0f4961..e320d08c1 100644
--- a/vlib/v/checker/tests/if_match_result.out
+++ b/vlib/v/checker/tests/if_match_result.out
@@ -1,3 +1,31 @@
+vlib/v/checker/tests/if_match_result.vv:3:2: notice: match is always false
+    1 | // missing results
+    2 | _ = match 4 {
+    3 |     1 {}
+      |     ^
+    4 |     else {}
+    5 | }
+vlib/v/checker/tests/if_match_result.vv:6:8: notice: condition is always true
+    4 |     else {}
+    5 | }
+    6 | _ = if true {
+      |        ~~~~
+    7 | } else {
+    8 | }
+vlib/v/checker/tests/if_match_result.vv:12:2: notice: match is always false
+   10 | // void results
+   11 | _ = match 4 {
+   12 |     1 { println('') }
+      |     ^
+   13 |     else { exit(0) }
+   14 | }
+vlib/v/checker/tests/if_match_result.vv:15:8: notice: condition is always true
+   13 |     else { exit(0) }
+   14 | }
+   15 | _ = if true {
+      |        ~~~~
+   16 |     println('')
+   17 | } else {
 vlib/v/checker/tests/if_match_result.vv:2:3: error: assignment mismatch: 1 variable 0 values
     1 | // missing results
     2 | _ = match 4 {
diff --git a/vlib/v/checker/tests/if_mismatch_muls_err.out b/vlib/v/checker/tests/if_mismatch_muls_err.out
index a07132c7a..e2c178061 100644
--- a/vlib/v/checker/tests/if_mismatch_muls_err.out
+++ b/vlib/v/checker/tests/if_mismatch_muls_err.out
@@ -1,3 +1,10 @@
+vlib/v/checker/tests/if_mismatch_muls_err.vv:17:14: notice: condition is always false
+   15 | 
+   16 | fn main() {
+   17 |     dummy := if false {
+      |                 ~~~~~
+   18 |         res := &Dum{
+   19 |             v: 2
 vlib/v/checker/tests/if_mismatch_muls_err.vv:17:11: error: mismatched types `&&Dum` and `&Dum`
    15 | 
    16 | fn main() {
diff --git a/vlib/v/checker/tests/immutable_array_in_if_expr_index.out b/vlib/v/checker/tests/immutable_array_in_if_expr_index.out
index 924921e54..4b2f2c2ea 100644
--- a/vlib/v/checker/tests/immutable_array_in_if_expr_index.out
+++ b/vlib/v/checker/tests/immutable_array_in_if_expr_index.out
@@ -1,3 +1,10 @@
+vlib/v/checker/tests/immutable_array_in_if_expr_index.vv:4:6: notice: condition is always true
+    2 |     array_a := [1, 2, 3]
+    3 |     array_b := [4, 5, 6]
+    4 |     (if true { array_a } else { array_b })[0] = 999
+      |         ~~~~
+    5 |     println(array_a)
+    6 | }
 vlib/v/checker/tests/immutable_array_in_if_expr_index.vv:4:13: error: `array_a` is immutable, declare it with `mut` to make it mutable
     2 |     array_a := [1, 2, 3]
     3 |     array_b := [4, 5, 6]
diff --git a/vlib/v/checker/tests/immutable_to_mutable_err.out b/vlib/v/checker/tests/immutable_to_mutable_err.out
index c8f49dbab..b3d4c1edd 100644
--- a/vlib/v/checker/tests/immutable_to_mutable_err.out
+++ b/vlib/v/checker/tests/immutable_to_mutable_err.out
@@ -1,3 +1,10 @@
+vlib/v/checker/tests/immutable_to_mutable_err.vv:10:20: notice: condition is always true
+    8 | fn main() {
+    9 |     arr := [1, 2, 3] // declared as immutable!
+   10 |     mut arr_mut := if true { arr } else { []int{} }
+      |                       ~~~~
+   11 |     mut arr_mut2 := match true {
+   12 |         true { arr }
 vlib/v/checker/tests/immutable_to_mutable_err.vv:10:27: notice: left-side of assignment expects a mutable reference, but variable `arr` is immutable, declare it with `mut` to make it mutable or clone it
     8 | fn main() {
     9 |     arr := [1, 2, 3] // declared as immutable!
@@ -5,6 +12,13 @@ vlib/v/checker/tests/immutable_to_mutable_err.vv:10:27: notice: left-side of ass
       |                              ~~~
    11 |     mut arr_mut2 := match true {
    12 |         true { arr }
+vlib/v/checker/tests/immutable_to_mutable_err.vv:12:3: notice: match is always true
+   10 |     mut arr_mut := if true { arr } else { []int{} }
+   11 |     mut arr_mut2 := match true {
+   12 |         true { arr }
+      |         ~~~~
+   13 |         else { [0] }
+   14 |     }
 vlib/v/checker/tests/immutable_to_mutable_err.vv:12:10: notice: left-side of assignment expects a mutable reference, but variable `arr` is immutable, declare it with `mut` to make it mutable or clone it
    10 |     mut arr_mut := if true { arr } else { []int{} }
    11 |     mut arr_mut2 := match true {
diff --git a/vlib/v/checker/tests/match_else_last_expr.out b/vlib/v/checker/tests/match_else_last_expr.out
index c3331f18e..135af6aa9 100644
--- a/vlib/v/checker/tests/match_else_last_expr.out
+++ b/vlib/v/checker/tests/match_else_last_expr.out
@@ -1,7 +1,21 @@
+vlib/v/checker/tests/match_else_last_expr.vv:3:3: notice: match is always true
+    1 | fn main() {
+    2 |     match 1 {
+    3 |         1 { println('1') }
+      |         ^
+    4 |         else { println('else') }
+    5 |         4 { println('4') }
+vlib/v/checker/tests/match_else_last_expr.vv:5:3: notice: match is always false
+    3 |         1 { println('1') }
+    4 |         else { println('else') }
+    5 |         4 { println('4') }
+      |         ^
+    6 |     }
+    7 | }
 vlib/v/checker/tests/match_else_last_expr.vv:4:3: error: `else` must be the last branch of `match`
     2 |     match 1 {
     3 |         1 { println('1') }
     4 |         else { println('else') }
       |         ~~~~
     5 |         4 { println('4') }
-    6 |     }
\ No newline at end of file
+    6 |     }
diff --git a/vlib/v/checker/tests/match_expr_empty_branch.out b/vlib/v/checker/tests/match_expr_empty_branch.out
index 927da5aed..290056536 100644
--- a/vlib/v/checker/tests/match_expr_empty_branch.out
+++ b/vlib/v/checker/tests/match_expr_empty_branch.out
@@ -1,3 +1,15 @@
+vlib/v/checker/tests/match_expr_empty_branch.vv:2:2: notice: match is always true
+    1 | _ := match true {
+    2 |     true { 0 }
+      |     ~~~~
+    3 |     false {}
+    4 | }
+vlib/v/checker/tests/match_expr_empty_branch.vv:3:2: notice: match is always false
+    1 | _ := match true {
+    2 |     true { 0 }
+    3 |     false {}
+      |     ~~~~~
+    4 | }
 vlib/v/checker/tests/match_expr_empty_branch.vv:3:2: error: `match` expression requires an expression as the last statement of every branch
     1 | _ := match true {
     2 |     true { 0 }
diff --git a/vlib/v/checker/tests/match_expr_with_none_only.out b/vlib/v/checker/tests/match_expr_with_none_only.out
index c1226c5ff..41fd5f874 100644
--- a/vlib/v/checker/tests/match_expr_with_none_only.out
+++ b/vlib/v/checker/tests/match_expr_with_none_only.out
@@ -1,3 +1,10 @@
+vlib/v/checker/tests/match_expr_with_none_only.vv:3:3: notice: match is always true
+    1 | fn main() {
+    2 |     a := match 1 {
+    3 |         1 { none }
+      |         ^
+    4 |         else { none }
+    5 |     }
 vlib/v/checker/tests/match_expr_with_none_only.vv:2:2: warning: unused variable: `a`
     1 | fn main() {
     2 |     a := match 1 {
diff --git a/vlib/v/checker/tests/match_missing.out b/vlib/v/checker/tests/match_missing.out
index 85f831c7b..7f30b81fc 100644
--- a/vlib/v/checker/tests/match_missing.out
+++ b/vlib/v/checker/tests/match_missing.out
@@ -1,3 +1,9 @@
+vlib/v/checker/tests/match_missing.vv:10:2: notice: match is always false
+    8 | 
+    9 | match true {
+   10 |     'foo' == 'bar' {}
+      |     ~~~~~~~~~~~~~~
+   11 | }
 vlib/v/checker/tests/match_missing.vv:1:1: error: `match` must have at least two branches including `else`, or an exhaustive set of branches
     1 | match true {
       | ~~~~~
diff --git a/vlib/v/checker/tests/match_return_mismatch_type_err.out b/vlib/v/checker/tests/match_return_mismatch_type_err.out
index ca6cf7889..a81d56a23 100644
--- a/vlib/v/checker/tests/match_return_mismatch_type_err.out
+++ b/vlib/v/checker/tests/match_return_mismatch_type_err.out
@@ -1,3 +1,10 @@
+vlib/v/checker/tests/match_return_mismatch_type_err.vv:3:3: notice: match is always true
+    1 | fn main() {
+    2 |     a := match 1 {
+    3 |         1 { 'aa' }
+      |         ^
+    4 |         else { 22 }
+    5 |     }
 vlib/v/checker/tests/match_return_mismatch_type_err.vv:27:6: warning: cannot assign a reference to a value (this will be an error soon) left=string false right=string true ptr=true
    25 | 
    26 |     mut res := ''
diff --git a/vlib/v/checker/tests/none_match_cond_err.out b/vlib/v/checker/tests/none_match_cond_err.out
index 9853c66e4..032f8b9d5 100644
--- a/vlib/v/checker/tests/none_match_cond_err.out
+++ b/vlib/v/checker/tests/none_match_cond_err.out
@@ -1,3 +1,9 @@
+vlib/v/checker/tests/none_match_cond_err.vv:2:2: notice: match is always true
+    1 | match none {
+    2 |     none {}
+      |     ~~~~
+    3 |     else {}
+    4 | }
 vlib/v/checker/tests/none_match_cond_err.vv:1:1: error: `none` cannot be a match condition
     1 | match none {
       | ~~~~~~~~~~~~
diff --git a/vlib/v/checker/tests/option_interface_mismatch.out b/vlib/v/checker/tests/option_interface_mismatch.out
index af522fdb2..c3ed1fb85 100644
--- a/vlib/v/checker/tests/option_interface_mismatch.out
+++ b/vlib/v/checker/tests/option_interface_mismatch.out
@@ -1,6 +1,12 @@
+vlib/v/checker/tests/option_interface_mismatch.vv:11:12: notice: condition is always true
+    9 | 
+   10 | fn give_string(line string) ?MObject {
+   11 |     return if true { 'string' } else { 'string' }
+      |               ~~~~
+   12 | }
 vlib/v/checker/tests/option_interface_mismatch.vv:11:9: error: mismatched types `?MObject` and `string`
-    9 |
+    9 | 
    10 | fn give_string(line string) ?MObject {
    11 |     return if true { 'string' } else { 'string' }
       |            ~~
-   12 | }
\ No newline at end of file
+   12 | }
diff --git a/vlib/v/checker/tests/return_missing_comp_if_nested.out b/vlib/v/checker/tests/return_missing_comp_if_nested.out
index 4c24e859e..97cf99d7d 100644
--- a/vlib/v/checker/tests/return_missing_comp_if_nested.out
+++ b/vlib/v/checker/tests/return_missing_comp_if_nested.out
@@ -1,7 +1,7 @@
 vlib/v/checker/tests/return_missing_comp_if_nested.vv:3:1: error: missing return at end of function `foo`
     1 | fn main() {}
-    2 |
+    2 | 
     3 | fn foo() string {
       | ~~~~~~~~~~~~~~~
-    4 |     $if windows {
-    5 |         if true {
\ No newline at end of file
+    4 |     a := 1
+    5 |     b := 1
diff --git a/vlib/v/checker/tests/return_missing_comp_if_nested.vv b/vlib/v/checker/tests/return_missing_comp_if_nested.vv
index afd02d76b..285034acb 100644
--- a/vlib/v/checker/tests/return_missing_comp_if_nested.vv
+++ b/vlib/v/checker/tests/return_missing_comp_if_nested.vv
@@ -1,13 +1,15 @@
 fn main() {}
 
 fn foo() string {
+	a := 1
+	b := 1
 	$if windows {
-		if true {
+		if a == b {
 		} else {
 			return ''
 		}
 	} $else {
-		if true {
+		if a == b {
 		} else {
 			return ''
 		}
diff --git a/vlib/v/checker/tests/return_missing_if_else_simple.out b/vlib/v/checker/tests/return_missing_if_else_simple.out
index 41eb21bee..c1a6591dc 100644
--- a/vlib/v/checker/tests/return_missing_if_else_simple.out
+++ b/vlib/v/checker/tests/return_missing_if_else_simple.out
@@ -1,3 +1,23 @@
+vlib/v/checker/tests/return_missing_if_else_simple.vv:2:5: notice: condition is always true
+    1 | fn if_no_returns() int {
+    2 |     if true {
+      |        ~~~~
+    3 |         println('no return in then')
+    4 |     } else {
+vlib/v/checker/tests/return_missing_if_else_simple.vv:11:5: notice: condition is always true
+    9 | 
+   10 | fn if_no_return_in_else() int {
+   11 |     if true {
+      |        ~~~~
+   12 |         return 123
+   13 |     } else {
+vlib/v/checker/tests/return_missing_if_else_simple.vv:22:5: notice: condition is always true
+   20 |     // The if here always returns, so the function
+   21 |     // returns too:
+   22 |     if true {
+      |        ~~~~
+   23 |         return 123
+   24 |     } else {
 vlib/v/checker/tests/return_missing_if_else_simple.vv:1:1: error: missing return at end of function `if_no_returns`
     1 | fn if_no_returns() int {
       | ~~~~~~~~~~~~~~~~~~~~~~
diff --git a/vlib/v/checker/tests/return_missing_if_match.out b/vlib/v/checker/tests/return_missing_if_match.out
index d4877d874..179de29f3 100644
--- a/vlib/v/checker/tests/return_missing_if_match.out
+++ b/vlib/v/checker/tests/return_missing_if_match.out
@@ -1,7 +1,28 @@
+vlib/v/checker/tests/return_missing_if_match.vv:4:5: notice: condition is always true
+    2 | 
+    3 | fn foo() string {
+    4 |     if true {
+      |        ~~~~
+    5 |         match 1 {
+    6 |             1 { return '' }
+vlib/v/checker/tests/return_missing_if_match.vv:6:4: notice: match is always true
+    4 |     if true {
+    5 |         match 1 {
+    6 |             1 { return '' }
+      |             ^
+    7 |             2 {}
+    8 |             else { return '' }
+vlib/v/checker/tests/return_missing_if_match.vv:7:4: notice: match is always false
+    5 |         match 1 {
+    6 |             1 { return '' }
+    7 |             2 {}
+      |             ^
+    8 |             else { return '' }
+    9 |         }
 vlib/v/checker/tests/return_missing_if_match.vv:3:1: error: missing return at end of function `foo`
     1 | fn main() {}
-    2 |
+    2 | 
     3 | fn foo() string {
       | ~~~~~~~~~~~~~~~
     4 |     if true {
-    5 |         match 1 {
\ No newline at end of file
+    5 |         match 1 {
diff --git a/vlib/v/checker/tests/return_missing_match_if.out b/vlib/v/checker/tests/return_missing_match_if.out
index 2e7e026f7..f59e9e689 100644
--- a/vlib/v/checker/tests/return_missing_match_if.out
+++ b/vlib/v/checker/tests/return_missing_match_if.out
@@ -1,3 +1,24 @@
+vlib/v/checker/tests/return_missing_match_if.vv:5:3: notice: match is always true
+    3 | fn foo() string {
+    4 |     match 1 {
+    5 |         1 {
+      |         ^
+    6 |             return ''
+    7 |         }
+vlib/v/checker/tests/return_missing_match_if.vv:8:3: notice: match is always false
+    6 |             return ''
+    7 |         }
+    8 |         2 {
+      |         ^
+    9 |             if true {
+   10 |             } else {
+vlib/v/checker/tests/return_missing_match_if.vv:9:7: notice: condition is always true
+    7 |         }
+    8 |         2 {
+    9 |             if true {
+      |                ~~~~
+   10 |             } else {
+   11 |                 return ''
 vlib/v/checker/tests/return_missing_match_if.vv:3:1: error: missing return at end of function `foo`
     1 | fn main() {}
     2 | 
diff --git a/vlib/v/checker/tests/return_missing_nested.out b/vlib/v/checker/tests/return_missing_nested.out
index fce3245d9..be90cc346 100644
--- a/vlib/v/checker/tests/return_missing_nested.out
+++ b/vlib/v/checker/tests/return_missing_nested.out
@@ -1,7 +1,21 @@
+vlib/v/checker/tests/return_missing_nested.vv:4:5: notice: condition is always true
+    2 | 
+    3 | fn foo() string {
+    4 |     if true {
+      |        ~~~~
+    5 |         return ''
+    6 |     } else {
+vlib/v/checker/tests/return_missing_nested.vv:7:6: notice: condition is always true
+    5 |         return ''
+    6 |     } else {
+    7 |         if true {
+      |            ~~~~
+    8 |             return ''
+    9 |         }
 vlib/v/checker/tests/return_missing_nested.vv:3:1: error: missing return at end of function `foo`
     1 | fn main() {}
-    2 |
+    2 | 
     3 | fn foo() string {
       | ~~~~~~~~~~~~~~~
     4 |     if true {
-    5 |         return ''
\ No newline at end of file
+    5 |         return ''
diff --git a/vlib/v/checker/tests/return_missing_simple.out b/vlib/v/checker/tests/return_missing_simple.out
index 80163453c..cd954a258 100644
--- a/vlib/v/checker/tests/return_missing_simple.out
+++ b/vlib/v/checker/tests/return_missing_simple.out
@@ -1,7 +1,14 @@
+vlib/v/checker/tests/return_missing_simple.vv:4:5: notice: condition is always true
+    2 | 
+    3 | fn foo() string {
+    4 |     if true {
+      |        ~~~~
+    5 |         return ''
+    6 |     } else {
 vlib/v/checker/tests/return_missing_simple.vv:3:1: error: missing return at end of function `foo`
     1 | fn main() {}
-    2 |
+    2 | 
     3 | fn foo() string {
       | ~~~~~~~~~~~~~~~
     4 |     if true {
-    5 |         return ''
\ No newline at end of file
+    5 |         return ''
diff --git a/vlib/v/checker/tests/return_working_comp_if_nested.vv b/vlib/v/checker/tests/return_working_comp_if_nested.vv
index fa44a40e1..0c7c61651 100644
--- a/vlib/v/checker/tests/return_working_comp_if_nested.vv
+++ b/vlib/v/checker/tests/return_working_comp_if_nested.vv
@@ -1,14 +1,16 @@
 fn main() {}
 
 fn foo() string {
+	a := 1
+	b := 1
 	$if windows {
-		if true {
+		if a == b {
 			return ''
 		} else {
 			return ''
 		}
 	} $else {
-		if true {
+		if a == b {
 			return ''
 		} else {
 			return ''
diff --git a/vlib/v/checker/tests/return_working_if_match.out b/vlib/v/checker/tests/return_working_if_match.out
index e69de29bb..f7e84c03a 100644
--- a/vlib/v/checker/tests/return_working_if_match.out
+++ b/vlib/v/checker/tests/return_working_if_match.out
@@ -0,0 +1,21 @@
+vlib/v/checker/tests/return_working_if_match.vv:4:5: notice: condition is always true
+    2 | 
+    3 | fn foo() string {
+    4 |     if true {
+      |        ~~~~
+    5 |         match 1 {
+    6 |             1 { return '' }
+vlib/v/checker/tests/return_working_if_match.vv:6:4: notice: match is always true
+    4 |     if true {
+    5 |         match 1 {
+    6 |             1 { return '' }
+      |             ^
+    7 |             2 { return '' }
+    8 |             else { return '' }
+vlib/v/checker/tests/return_working_if_match.vv:7:4: notice: match is always false
+    5 |         match 1 {
+    6 |             1 { return '' }
+    7 |             2 { return '' }
+      |             ^
+    8 |             else { return '' }
+    9 |         }
diff --git a/vlib/v/checker/tests/return_working_match_if.out b/vlib/v/checker/tests/return_working_match_if.out
index e69de29bb..0c157486c 100644
--- a/vlib/v/checker/tests/return_working_match_if.out
+++ b/vlib/v/checker/tests/return_working_match_if.out
@@ -0,0 +1,21 @@
+vlib/v/checker/tests/return_working_match_if.vv:5:3: notice: match is always true
+    3 | fn foo() string {
+    4 |     match 1 {
+    5 |         1 {
+      |         ^
+    6 |             return ''
+    7 |         }
+vlib/v/checker/tests/return_working_match_if.vv:8:3: notice: match is always false
+    6 |             return ''
+    7 |         }
+    8 |         2 {
+      |         ^
+    9 |             if true {
+   10 |                 return ''
+vlib/v/checker/tests/return_working_match_if.vv:9:7: notice: condition is always true
+    7 |         }
+    8 |         2 {
+    9 |             if true {
+      |                ~~~~
+   10 |                 return ''
+   11 |             } else {
diff --git a/vlib/v/checker/tests/return_working_nested.out b/vlib/v/checker/tests/return_working_nested.out
index e69de29bb..667144227 100644
--- a/vlib/v/checker/tests/return_working_nested.out
+++ b/vlib/v/checker/tests/return_working_nested.out
@@ -0,0 +1,14 @@
+vlib/v/checker/tests/return_working_nested.vv:4:5: notice: condition is always true
+    2 | 
+    3 | fn foo() string {
+    4 |     if true {
+      |        ~~~~
+    5 |         return ''
+    6 |     } else {
+vlib/v/checker/tests/return_working_nested.vv:7:6: notice: condition is always true
+    5 |         return ''
+    6 |     } else {
+    7 |         if true {
+      |            ~~~~
+    8 |             return ''
+    9 |         }
diff --git a/vlib/v/checker/tests/return_working_simple.out b/vlib/v/checker/tests/return_working_simple.out
index e69de29bb..6000815f2 100644
--- a/vlib/v/checker/tests/return_working_simple.out
+++ b/vlib/v/checker/tests/return_working_simple.out
@@ -0,0 +1,7 @@
+vlib/v/checker/tests/return_working_simple.vv:4:5: notice: condition is always true
+    2 | 
+    3 | fn foo() string {
+    4 |     if true {
+      |        ~~~~
+    5 |         return ''
+    6 |     } else {
diff --git a/vlib/v/checker/tests/return_working_two_if.out b/vlib/v/checker/tests/return_working_two_if.out
index e69de29bb..49ca3dd4d 100644
--- a/vlib/v/checker/tests/return_working_two_if.out
+++ b/vlib/v/checker/tests/return_working_two_if.out
@@ -0,0 +1,21 @@
+vlib/v/checker/tests/return_working_two_if.vv:4:5: notice: condition is always true
+    2 | 
+    3 | fn foo() string {
+    4 |     if true {
+      |        ~~~~
+    5 |         if true {
+    6 |             return ''
+vlib/v/checker/tests/return_working_two_if.vv:5:6: notice: condition is always true
+    3 | fn foo() string {
+    4 |     if true {
+    5 |         if true {
+      |            ~~~~
+    6 |             return ''
+    7 |         }
+vlib/v/checker/tests/return_working_two_if.vv:9:6: notice: condition is always true
+    7 |         }
+    8 | 
+    9 |         if true {
+      |            ~~~~
+   10 |             return ''
+   11 |         } else {
diff --git a/vlib/v/checker/tests/shift_ops_expressions.out b/vlib/v/checker/tests/shift_ops_expressions.out
index cad80513e..447106cc2 100644
--- a/vlib/v/checker/tests/shift_ops_expressions.out
+++ b/vlib/v/checker/tests/shift_ops_expressions.out
@@ -5,6 +5,13 @@ vlib/v/checker/tests/shift_ops_expressions.vv:4:2: notice: shifting a value from
       |     ^
     5 |     if true {
     6 |         a << 2
+vlib/v/checker/tests/shift_ops_expressions.vv:5:5: notice: condition is always true
+    3 |     mut arr := []int{}
+    4 |     a << 1
+    5 |     if true {
+      |        ~~~~
+    6 |         a << 2
+    7 |     }
 vlib/v/checker/tests/shift_ops_expressions.vv:6:3: notice: shifting a value from a signed type `int` can change the sign
     4 |     a << 1
     5 |     if true {
@@ -12,6 +19,13 @@ vlib/v/checker/tests/shift_ops_expressions.vv:6:3: notice: shifting a value from
       |         ^
     7 |     }
     8 |     c := if true { a << 111 } else { a << 333 }
+vlib/v/checker/tests/shift_ops_expressions.vv:8:10: notice: condition is always true
+    6 |         a << 2
+    7 |     }
+    8 |     c := if true { a << 111 } else { a << 333 }
+      |             ~~~~
+    9 |     println(c)
+   10 |     a << 1
 vlib/v/checker/tests/shift_ops_expressions.vv:8:17: notice: shifting a value from a signed type `int` can change the sign
     6 |         a << 2
     7 |     }
@@ -26,6 +40,27 @@ vlib/v/checker/tests/shift_ops_expressions.vv:10:2: notice: shifting a value fro
       |     ^
    11 |     println(a)
    12 |     5 << 9
+vlib/v/checker/tests/shift_ops_expressions.vv:20:5: notice: condition is always true
+   18 |     //
+   19 |     arr << 1
+   20 |     if true {
+      |        ~~~~
+   21 |         arr << 2
+   22 |     }
+vlib/v/checker/tests/shift_ops_expressions.vv:23:10: notice: condition is always true
+   21 |         arr << 2
+   22 |     }
+   23 |     d := if true {
+      |             ~~~~
+   24 |         arr << 111
+   25 |         777
+vlib/v/checker/tests/shift_ops_expressions.vv:32:10: notice: condition is always true
+   30 |     println(d)
+   31 |     //
+   32 |     x := if true {
+      |             ~~~~
+   33 |         a << 1
+   34 |         999
 vlib/v/checker/tests/shift_ops_expressions.vv:33:3: notice: shifting a value from a signed type `int` can change the sign
    31 |     //
    32 |     x := if true {
@@ -40,6 +75,27 @@ vlib/v/checker/tests/shift_ops_expressions.vv:37:3: notice: shifting a value fro
       |         ^
    38 |         println('---')
    39 |         555
+vlib/v/checker/tests/shift_ops_expressions.vv:47:5: notice: condition is always true
+   45 |     mut rr := 12
+   46 |     rr >> 1
+   47 |     if true {
+      |        ~~~~
+   48 |         rr >> 2
+   49 |     }
+vlib/v/checker/tests/shift_ops_expressions.vv:50:10: notice: condition is always true
+   48 |         rr >> 2
+   49 |     }
+   50 |     c := if true { rr >> 111 } else { rr >> 333 }
+      |             ~~~~
+   51 |     println(c)
+   52 |     rr >> 1
+vlib/v/checker/tests/shift_ops_expressions.vv:61:10: notice: condition is always true
+   59 |     }
+   60 |     //
+   61 |     x := if true {
+      |             ~~~~
+   62 |         rr >> 1
+   63 |         999
 vlib/v/checker/tests/shift_ops_expressions.vv:4:2: error: unused expression
     2 |     mut a := 12
     3 |     mut arr := []int{}
diff --git a/vlib/v/checker/tests/struct_scope_err.out b/vlib/v/checker/tests/struct_scope_err.out
index c1f20f41d..5aa90af53 100644
--- a/vlib/v/checker/tests/struct_scope_err.out
+++ b/vlib/v/checker/tests/struct_scope_err.out
@@ -1,3 +1,10 @@
+vlib/v/checker/tests/struct_scope_err.vv:8:5: notice: condition is always true
+    6 |     }
+    7 | 
+    8 |     if true {
+      |        ~~~~
+    9 |         fb := Foobar{5, 6}
+   10 |         println(fb.foo)
 vlib/v/checker/tests/struct_scope_err.vv:16:8: error: unknown type `Foobar`
    14 | 
    15 | fn x() {
diff --git a/vlib/v/checker/tests/unnecessary_parenthesis.out b/vlib/v/checker/tests/unnecessary_parenthesis.out
index 3f1a34036..3fb5171d8 100644
--- a/vlib/v/checker/tests/unnecessary_parenthesis.out
+++ b/vlib/v/checker/tests/unnecessary_parenthesis.out
@@ -1,3 +1,23 @@
+vlib/v/checker/tests/unnecessary_parenthesis.vv:2:5: notice: condition is always true
+    1 | fn main() {
+    2 |     if (1 == 1) {
+      |        ~~~~~~~~
+    3 |         println('yeay')
+    4 |     } else if (1 == 2) {
+vlib/v/checker/tests/unnecessary_parenthesis.vv:4:12: notice: condition is always false
+    2 |     if (1 == 1) {
+    3 |         println('yeay')
+    4 |     } else if (1 == 2) {
+      |               ~~~~~~~~
+    5 |         println("oh no :'(")
+    6 |     } else if (1 == 3) {
+vlib/v/checker/tests/unnecessary_parenthesis.vv:6:12: notice: condition is always false
+    4 |     } else if (1 == 2) {
+    5 |         println("oh no :'(")
+    6 |     } else if (1 == 3) {
+      |               ~~~~~~~~
+    7 |         println("what's wrong with physics ????")
+    8 |     }
 vlib/v/checker/tests/unnecessary_parenthesis.vv:2:2: warning: unnecessary `()` in `if` condition, use `if expr {` instead of `if (expr) {`.
     1 | fn main() {
     2 |     if (1 == 1) {
diff --git a/vlib/v/checker/tests/unreachable_code.out b/vlib/v/checker/tests/unreachable_code.out
index 3c00f08cc..627a65ded 100644
--- a/vlib/v/checker/tests/unreachable_code.out
+++ b/vlib/v/checker/tests/unreachable_code.out
@@ -1,3 +1,10 @@
+vlib/v/checker/tests/unreachable_code.vv:27:12: notice: condition is always true
+   25 |         return 3
+   26 |     }
+   27 |     return if 1 == 1 { 1 } else { 2 }
+      |               ~~~~~~
+   28 |     a := 1
+   29 |     println(a)
 vlib/v/checker/tests/unreachable_code.vv:15:3: error: unreachable code
    13 |         continue
    14 |         // ...
diff --git a/vlib/v/gen/js/tests/testdata/compare_ints.v b/vlib/v/gen/js/tests/testdata/compare_ints.v
index f2144661b..e32416a70 100644
--- a/vlib/v/gen/js/tests/testdata/compare_ints.v
+++ b/vlib/v/gen/js/tests/testdata/compare_ints.v
@@ -1,15 +1,17 @@
-if 2 > 1 {
+a := 2
+b := 1
+if a > b {
 	println('2 > 1')
 }
 
-if 2 < 1 {
+if a < b {
 	println('2 < 1')
 }
 
-if 2 == 1 {
+if a == b {
 	println('2 == 1')
 }
 
-if 2 == 0 {
+if a == 0 {
 	println('2 == 0')
 }
diff --git a/vlib/v/gen/js/tests/testdata/match.v b/vlib/v/gen/js/tests/testdata/match.v
index 61796f1b1..e197b2d4f 100644
--- a/vlib/v/gen/js/tests/testdata/match.v
+++ b/vlib/v/gen/js/tests/testdata/match.v
@@ -24,7 +24,8 @@ fn match_vec(v Vec) {
 }
 
 fn match_classic_num() {
-	match 42 {
+	a := 42
+	match a {
 		0 {
 			assert false
 			(false)
diff --git a/vlib/v/slow_tests/repl/conditional_blocks/if.repl b/vlib/v/slow_tests/repl/conditional_blocks/if.repl
index 9b3b2d6c5..2b17e8974 100644
--- a/vlib/v/slow_tests/repl/conditional_blocks/if.repl
+++ b/vlib/v/slow_tests/repl/conditional_blocks/if.repl
@@ -1,4 +1,6 @@
-if true {
+a := 5
+b := 5
+if a == b {
   println('foo')
 }
 ===output===
diff --git a/vlib/v/slow_tests/repl/conditional_blocks/if_else.repl b/vlib/v/slow_tests/repl/conditional_blocks/if_else.repl
index b44b66eed..a51c5b9e5 100644
--- a/vlib/v/slow_tests/repl/conditional_blocks/if_else.repl
+++ b/vlib/v/slow_tests/repl/conditional_blocks/if_else.repl
@@ -1,4 +1,6 @@
-if false {
+a := 6
+b := 5
+if a == b {
   println('foo')
 } else {
   println('bar')
diff --git a/vlib/v/tests/skip_unused/generic_call_from_json.vv b/vlib/v/tests/skip_unused/generic_call_from_json.vv
index e29d27112..de9a739ff 100644
--- a/vlib/v/tests/skip_unused/generic_call_from_json.vv
+++ b/vlib/v/tests/skip_unused/generic_call_from_json.vv
@@ -16,7 +16,9 @@ fn f() ! {
 }
 
 fn main() {
-	if false {
+	a := 5
+	b := 6
+	if a == b {
 		f()!
 	}
 	println('ok')
diff --git a/vlib/v/transformer/transformer.v b/vlib/v/transformer/transformer.v
index b0d187304..c2c0a32fd 100644
--- a/vlib/v/transformer/transformer.v
+++ b/vlib/v/transformer/transformer.v
@@ -1024,7 +1024,129 @@ pub fn (mut t Transformer) infix_expr(mut node ast.InfixExpr) ast.Expr {
 					else {}
 				}
 			}
-			else {}
+			ast.CharLiteral {
+				match mut node.right {
+					ast.CharLiteral {
+						left_val := node.left.val.runes()[0]
+						right_val := node.right.val.runes()[0]
+
+						match node.op {
+							.eq {
+								return ast.BoolLiteral{
+									val: left_val == right_val
+								}
+							}
+							.ne {
+								return ast.BoolLiteral{
+									val: left_val != right_val
+								}
+							}
+							.gt {
+								return ast.BoolLiteral{
+									val: left_val > right_val
+								}
+							}
+							.ge {
+								return ast.BoolLiteral{
+									val: left_val >= right_val
+								}
+							}
+							.lt {
+								return ast.BoolLiteral{
+									val: left_val < right_val
+								}
+							}
+							.le {
+								return ast.BoolLiteral{
+									val: left_val <= right_val
+								}
+							}
+							.plus {
+								return ast.CharLiteral{
+									val: (left_val + right_val).str()
+									pos: pos
+								}
+							}
+							.mul {
+								return ast.CharLiteral{
+									val: (left_val * right_val).str()
+									pos: pos
+								}
+							}
+							.minus {
+								return ast.CharLiteral{
+									val: (left_val - right_val).str()
+									pos: pos
+								}
+							}
+							.div {
+								return ast.CharLiteral{
+									val: (left_val / right_val).str()
+									pos: pos
+								}
+							}
+							.mod {
+								return ast.CharLiteral{
+									val: (left_val % right_val).str()
+									pos: pos
+								}
+							}
+							.xor {
+								return ast.CharLiteral{
+									val: (left_val ^ right_val).str()
+									pos: pos
+								}
+							}
+							.pipe {
+								return ast.CharLiteral{
+									val: (left_val | right_val).str()
+									pos: pos
+								}
+							}
+							.amp {
+								return ast.CharLiteral{
+									val: (left_val & right_val).str()
+									pos: pos
+								}
+							}
+							.left_shift {
+								return ast.CharLiteral{
+									val: (unsafe { left_val << right_val }).str()
+									pos: pos
+								}
+							}
+							.right_shift {
+								return ast.CharLiteral{
+									val: (left_val >> right_val).str()
+									pos: pos
+								}
+							}
+							.unsigned_right_shift {
+								return ast.CharLiteral{
+									val: (u64(left_val) >>> right_val).str()
+									pos: pos
+								}
+							}
+							else {}
+						}
+					}
+					else {}
+				}
+			}
+			else {
+				// for `a == a`, `a != a`, `struct.f != struct.f`
+				// Note: can't compare `f32` or `f64` here, as `NaN != NaN` will return true in IEEE 754
+				if node.left.type_name() == node.right.type_name()
+					&& node.left_type !in [ast.f32_type, ast.f64_type] && node.op in [.eq, .ne] {
+					left_name := '${node.left}'
+					right_name := '${node.right}'
+					if left_name == right_name {
+						return ast.BoolLiteral{
+							val: if node.op == .eq { true } else { false }
+						}
+					}
+				}
+			}
 		}
 		return node
 	}
-- 
2.39.5