transformer: eliminate unreachable branches & redundant branch expressions in MatchExpr (#12174)

vlib/v/ast/ast.v

@@ -866,12 +866,12 @@ pub mut:
 pub struct MatchBranch {
 pub:
 	ecmnts        [][]Comment // inline comments for each left side expr
-	stmts         []Stmt      // right side
 	pos           token.Position
 	is_else       bool
 	post_comments []Comment      // comments below ´... }´
 	branch_pos    token.Position // for checker errors about invalid branches
 pub mut:
+	stmts []Stmt // right side
 	exprs []Expr // left side
 	scope &Scope
 }

vlib/v/transformer/transformer.v

@@ -56,18 +56,19 @@ pub fn (t Transformer) stmt(mut node ast.Stmt) {
 		ast.DeferStmt {}
 		ast.EnumDecl {}
 		ast.ExprStmt {
-			if node.expr is ast.IfExpr {
+			expr := node.expr
-				mut untrans_expr := node.expr as ast.IfExpr
-				expr := t.if_expr(mut untrans_expr)
 			node = &ast.ExprStmt{
 				...node
-					expr: expr
+				expr: match mut expr {
+					ast.IfExpr {
+						t.if_expr(mut expr)
+					}
+					ast.MatchExpr {
+						t.match_expr(mut expr)
+					}
+					else {
+						t.expr(expr)
 					}
-			} else {
-				expr := t.expr(node.expr)
-				node = &ast.ExprStmt{
-					...node
-					expr: expr
 				}
 			}
 		}
@@ -116,10 +117,77 @@ pub fn (t Transformer) expr(node ast.Expr) ast.Expr {
 				index: t.expr(node.index)
 			}
 		}
-		ast.MatchExpr {
+		ast.IfExpr {
 			for mut branch in node.branches {
-				for mut stmt in branch.stmts {
+				branch = ast.IfBranch{
+					...(*branch)
+					cond: t.expr(branch.cond)
+				}
+				for i, mut stmt in branch.stmts {
 					t.stmt(mut stmt)
+
+					if i == branch.stmts.len - 1 {
+						if stmt is ast.ExprStmt {
+							expr := (stmt as ast.ExprStmt).expr
+
+							match expr {
+								ast.IfExpr {
+									if expr.branches.len == 1 {
+										branch.stmts.pop()
+										branch.stmts << expr.branches[0].stmts
+										break
+									}
+								}
+								ast.MatchExpr {
+									if expr.branches.len == 1 {
+										branch.stmts.pop()
+										branch.stmts << expr.branches[0].stmts
+										break
+									}
+								}
+								else {}
+							}
+						}
+					}
+				}
+			}
+			return node
+		}
+		ast.MatchExpr {
+			node = ast.MatchExpr{
+				...node
+				cond: t.expr(node.cond)
+			}
+			for mut branch in node.branches {
+				for mut expr in branch.exprs {
+					expr = t.expr(expr)
+				}
+				for i, mut stmt in branch.stmts {
+					t.stmt(mut stmt)
+
+					if i == branch.stmts.len - 1 {
+						if stmt is ast.ExprStmt {
+							expr := (stmt as ast.ExprStmt).expr
+
+							match expr {
+								ast.IfExpr {
+									if expr.branches.len == 1 {
+										branch.stmts.pop()
+										branch.stmts << expr.branches[0].stmts
+										break
+									}
+								}
+								ast.MatchExpr {
+									if expr.branches.len == 1 {
+										branch.stmts.pop()
+										branch.stmts << expr.branches[0].stmts
+										break
+									}
+								}
+								else {}
+							}
+						}
+					}
 				}
 			}
 			return node
@@ -132,6 +200,9 @@ pub fn (t Transformer) expr(node ast.Expr) ast.Expr {
 
 pub fn (t Transformer) if_expr(mut original ast.IfExpr) ast.Expr {
 	mut stop_index, mut unreachable_branches := -1, []int{cap: original.branches.len}
+	if original.is_comptime {
+		return *original
+	}
 	for i, mut branch in original.branches {
 		for mut stmt in branch.stmts {
 			t.stmt(mut stmt)
@@ -171,6 +242,84 @@ pub fn (t Transformer) if_expr(mut original ast.IfExpr) ast.Expr {
 	return *original
 }
 
+pub fn (t Transformer) match_expr(mut original ast.MatchExpr) ast.Expr {
+	cond, mut terminate := t.expr(original.cond), false
+	original = ast.MatchExpr{
+		...(*original)
+		cond: cond
+	}
+	for mut branch in original.branches {
+		if branch.is_else {
+			continue
+		}
+
+		for mut stmt in branch.stmts {
+			t.stmt(mut stmt)
+		}
+
+		for mut expr in branch.exprs {
+			expr = t.expr(expr)
+
+			match cond {
+				ast.BoolLiteral {
+					if expr is ast.BoolLiteral {
+						if cond.val == (expr as ast.BoolLiteral).val {
+							branch.exprs = [expr]
+							original = ast.MatchExpr{
+								...(*original)
+								branches: [branch]
+							}
+							terminate = true
+						}
+					}
+				}
+				ast.IntegerLiteral {
+					if expr is ast.IntegerLiteral {
+						if cond.val.int() == (expr as ast.IntegerLiteral).val.int() {
+							branch.exprs = [expr]
+							original = ast.MatchExpr{
+								...(*original)
+								branches: [branch]
+							}
+							terminate = true
+						}
+					}
+				}
+				ast.FloatLiteral {
+					if expr is ast.FloatLiteral {
+						if cond.val.f32() == (expr as ast.FloatLiteral).val.f32() {
+							branch.exprs = [expr]
+							original = ast.MatchExpr{
+								...(*original)
+								branches: [branch]
+							}
+							terminate = true
+						}
+					}
+				}
+				ast.StringLiteral {
+					if expr is ast.StringLiteral {
+						if cond.val == (expr as ast.StringLiteral).val {
+							branch.exprs = [expr]
+							original = ast.MatchExpr{
+								...(*original)
+								branches: [branch]
+							}
+							terminate = true
+						}
+					}
+				}
+				else {}
+			}
+		}
+
+		if terminate {
+			break
+		}
+	}
+	return *original
+}
+
 pub fn (t Transformer) infix_expr(original ast.InfixExpr) ast.Expr {
 	mut node := original
 	node.left = t.expr(node.left)
@@ -357,6 +506,76 @@ pub fn (t Transformer) infix_expr(original ast.InfixExpr) ast.Expr {
 				}
 			}
 		}
+		ast.FloatLiteral {
+			match right_node {
+				ast.FloatLiteral {
+					left_val := left_node.val.f32()
+					right_val := right_node.val.f32()
+					match node.op {
+						.eq {
+							return ast.BoolLiteral{
+								val: left_node.val == right_node.val
+							}
+						}
+						.ne {
+							return ast.BoolLiteral{
+								val: left_node.val != right_node.val
+							}
+						}
+						.gt {
+							return ast.BoolLiteral{
+								val: left_node.val > right_node.val
+							}
+						}
+						.ge {
+							return ast.BoolLiteral{
+								val: left_node.val >= right_node.val
+							}
+						}
+						.lt {
+							return ast.BoolLiteral{
+								val: left_node.val < right_node.val
+							}
+						}
+						.le {
+							return ast.BoolLiteral{
+								val: left_node.val <= right_node.val
+							}
+						}
+						.plus {
+							return ast.FloatLiteral{
+								val: (left_val + right_val).str()
+								pos: pos
+							}
+						}
+						.mul {
+							return ast.FloatLiteral{
+								val: (left_val * right_val).str()
+								pos: pos
+							}
+						}
+						.minus {
+							return ast.FloatLiteral{
+								val: (left_val - right_val).str()
+								pos: pos
+							}
+						}
+						.div {
+							return ast.FloatLiteral{
+								val: (left_val / right_val).str()
+								pos: pos
+							}
+						}
+						else {
+							return node
+						}
+					}
+				}
+				else {
+					return node
+				}
+			}
+		}
 		else {
 			return node
 		}