tint/intrinsics.def: Add @test_value() annotation

Specifies the value to use for argument values when generating end-to-end tests.

Use this to provide a legal value for atanh().

Change-Id: I008050c856f9d687ab918c68e90678c4e74f3a1d
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/106887
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Dan Sinclair <dsinclair@chromium.org>

tools/src/cmd/gen/main.go

@@ -303,6 +303,7 @@ func (g *generator) bindAndParse(t *template.Template, text string) error {
 		"Title":                 strings.Title,
 		"PascalCase":            pascalCase,
 		"SplitDisplayName":      gen.SplitDisplayName,
+		"Contains":              strings.Contains,
 		"HasPrefix":             strings.HasPrefix,
 		"HasSuffix":             strings.HasSuffix,
 		"TrimPrefix":            strings.TrimPrefix,

tools/src/tint/intrinsic/ast/ast.go

@@ -367,7 +367,7 @@ func (l *Attributes) Take(name string) *Attribute {
 type Attribute struct {
 	Source tok.Source
 	Name   string
-	Values []string
+	Values []any
 }
 
 // Format implements the fmt.Formatter interface

tools/src/tint/intrinsic/gen/permutate.go

@@ -83,9 +83,10 @@ func (p *Permuter) Permute(overload *sem.Overload) ([]Permutation, error) {
 				return nil
 			}
 			o.Parameters = append(o.Parameters, sem.Parameter{
-				Name:    p.Name,
-				Type:    ty,
-				IsConst: p.IsConst,
+				Name:      p.Name,
+				Type:      ty,
+				IsConst:   p.IsConst,
+				TestValue: p.TestValue,
 			})
 		}
 		if overload.ReturnType != nil {

tools/src/tint/intrinsic/lexer/lexer.go

@@ -104,7 +104,23 @@ func (l *lexer) lex() error {
 			case unicode.IsLetter(l.peek(0)) || l.peek(0) == '_':
 				l.tok(l.count(alphaNumericOrUnderscore), tok.Identifier)
 			case unicode.IsNumber(l.peek(0)):
-				l.tok(l.count(unicode.IsNumber), tok.Integer)
+				isFloat := false
+				pred := func(r rune) bool {
+					if unicode.IsNumber(r) {
+						return true
+					}
+					if !isFloat && r == '.' {
+						isFloat = true
+						return true
+					}
+					return false
+				}
+				n := l.count(pred)
+				if isFloat {
+					l.tok(n, tok.Float)
+				} else {
+					l.tok(n, tok.Integer)
+				}
 			case l.match("&&", tok.AndAnd):
 			case l.match("&", tok.And):
 			case l.match("||", tok.OrOr):

tools/src/tint/intrinsic/lexer/lexer_test.go

@@ -20,12 +20,13 @@ import (
 
 	"dawn.googlesource.com/dawn/tools/src/tint/intrinsic/lexer"
 	"dawn.googlesource.com/dawn/tools/src/tint/intrinsic/tok"
+	"github.com/google/go-cmp/cmp"
 )
 
 func TestLexTokens(t *testing.T) {
 	type test struct {
 		src    string
-		expect tok.Token
+		expect []tok.Token
 	}
 
 	filepath := "test.txt"
@@ -34,144 +35,153 @@ func TestLexTokens(t *testing.T) {
 	}
 
 	for _, test := range []test{
-		{"ident", tok.Token{Kind: tok.Identifier, Runes: []rune("ident"), Source: tok.Source{
+		{"ident", []tok.Token{{Kind: tok.Identifier, Runes: []rune("ident"), Source: tok.Source{
 			S: loc(1, 1, 0), E: loc(1, 6, 5),
-		}}},
-		{"ident_123", tok.Token{Kind: tok.Identifier, Runes: []rune("ident_123"), Source: tok.Source{
+		}}}},
+		{"ident_123", []tok.Token{{Kind: tok.Identifier, Runes: []rune("ident_123"), Source: tok.Source{
 			S: loc(1, 1, 0), E: loc(1, 10, 9),
-		}}},
-		{"_ident_", tok.Token{Kind: tok.Identifier, Runes: []rune("_ident_"), Source: tok.Source{
+		}}}},
+		{"_ident_", []tok.Token{{Kind: tok.Identifier, Runes: []rune("_ident_"), Source: tok.Source{
 			S: loc(1, 1, 0), E: loc(1, 8, 7),
-		}}},
-		{"123456789", tok.Token{Kind: tok.Integer, Runes: []rune("123456789"), Source: tok.Source{
+		}}}},
+		{"123456789", []tok.Token{{Kind: tok.Integer, Runes: []rune("123456789"), Source: tok.Source{
 			S: loc(1, 1, 0), E: loc(1, 10, 9),
-		}}},
-		{"match", tok.Token{Kind: tok.Match, Runes: []rune("match"), Source: tok.Source{
+		}}}},
+		{"1234.56789", []tok.Token{{Kind: tok.Float, Runes: []rune("1234.56789"), Source: tok.Source{
+			S: loc(1, 1, 0), E: loc(1, 11, 10),
+		}}}},
+		{"123.456.789", []tok.Token{
+			{Kind: tok.Float, Runes: []rune("123.456"), Source: tok.Source{
+				S: loc(1, 1, 0), E: loc(1, 8, 7),
+			}},
+			{Kind: tok.Dot, Runes: []rune("."), Source: tok.Source{
+				S: loc(1, 8, 7), E: loc(1, 9, 8),
+			}},
+			{Kind: tok.Integer, Runes: []rune("789"), Source: tok.Source{
+				S: loc(1, 9, 8), E: loc(1, 12, 11),
+			}},
+		}},
+		{"match", []tok.Token{{Kind: tok.Match, Runes: []rune("match"), Source: tok.Source{
 			S: loc(1, 1, 0), E: loc(1, 6, 5),
-		}}},
-		{"fn", tok.Token{Kind: tok.Function, Runes: []rune("fn"), Source: tok.Source{
+		}}}},
+		{"fn", []tok.Token{{Kind: tok.Function, Runes: []rune("fn"), Source: tok.Source{
 			S: loc(1, 1, 0), E: loc(1, 3, 2),
-		}}},
-		{"op", tok.Token{Kind: tok.Operator, Runes: []rune("op"), Source: tok.Source{
+		}}}},
+		{"op", []tok.Token{{Kind: tok.Operator, Runes: []rune("op"), Source: tok.Source{
 			S: loc(1, 1, 0), E: loc(1, 3, 2),
-		}}},
-		{"type", tok.Token{Kind: tok.Type, Runes: []rune("type"), Source: tok.Source{
+		}}}},
+		{"type", []tok.Token{{Kind: tok.Type, Runes: []rune("type"), Source: tok.Source{
 			S: loc(1, 1, 0), E: loc(1, 5, 4),
-		}}},
-		{"init", tok.Token{Kind: tok.Initializer, Runes: []rune("init"), Source: tok.Source{
+		}}}},
+		{"init", []tok.Token{{Kind: tok.Initializer, Runes: []rune("init"), Source: tok.Source{
 			S: loc(1, 1, 0), E: loc(1, 5, 4),
-		}}},
-		{"conv", tok.Token{Kind: tok.Converter, Runes: []rune("conv"), Source: tok.Source{
+		}}}},
+		{"conv", []tok.Token{{Kind: tok.Converter, Runes: []rune("conv"), Source: tok.Source{
 			S: loc(1, 1, 0), E: loc(1, 5, 4),
-		}}},
-		{"enum", tok.Token{Kind: tok.Enum, Runes: []rune("enum"), Source: tok.Source{
+		}}}},
+		{"enum", []tok.Token{{Kind: tok.Enum, Runes: []rune("enum"), Source: tok.Source{
 			S: loc(1, 1, 0), E: loc(1, 5, 4),
-		}}},
-		{":", tok.Token{Kind: tok.Colon, Runes: []rune(":"), Source: tok.Source{
+		}}}},
+		{":", []tok.Token{{Kind: tok.Colon, Runes: []rune(":"), Source: tok.Source{
 			S: loc(1, 1, 0), E: loc(1, 2, 1),
-		}}},
-		{",", tok.Token{Kind: tok.Comma, Runes: []rune(","), Source: tok.Source{
+		}}}},
+		{",", []tok.Token{{Kind: tok.Comma, Runes: []rune(","), Source: tok.Source{
 			S: loc(1, 1, 0), E: loc(1, 2, 1),
-		}}},
-		{"<", tok.Token{Kind: tok.Lt, Runes: []rune("<"), Source: tok.Source{
+		}}}},
+		{"<", []tok.Token{{Kind: tok.Lt, Runes: []rune("<"), Source: tok.Source{
 			S: loc(1, 1, 0), E: loc(1, 2, 1),
-		}}},
-		{">", tok.Token{Kind: tok.Gt, Runes: []rune(">"), Source: tok.Source{
+		}}}},
+		{">", []tok.Token{{Kind: tok.Gt, Runes: []rune(">"), Source: tok.Source{
 			S: loc(1, 1, 0), E: loc(1, 2, 1),
-		}}},
-		{"{", tok.Token{Kind: tok.Lbrace, Runes: []rune("{"), Source: tok.Source{
+		}}}},
+		{"{", []tok.Token{{Kind: tok.Lbrace, Runes: []rune("{"), Source: tok.Source{
 			S: loc(1, 1, 0), E: loc(1, 2, 1),
-		}}},
-		{"}", tok.Token{Kind: tok.Rbrace, Runes: []rune("}"), Source: tok.Source{
+		}}}},
+		{"}", []tok.Token{{Kind: tok.Rbrace, Runes: []rune("}"), Source: tok.Source{
 			S: loc(1, 1, 0), E: loc(1, 2, 1),
-		}}},
-		{"&&", tok.Token{Kind: tok.AndAnd, Runes: []rune("&&"), Source: tok.Source{
+		}}}},
+		{"&&", []tok.Token{{Kind: tok.AndAnd, Runes: []rune("&&"), Source: tok.Source{
 			S: loc(1, 1, 0), E: loc(1, 3, 2),
-		}}},
-		{"&", tok.Token{Kind: tok.And, Runes: []rune("&"), Source: tok.Source{
+		}}}},
+		{"&", []tok.Token{{Kind: tok.And, Runes: []rune("&"), Source: tok.Source{
 			S: loc(1, 1, 0), E: loc(1, 2, 1),
-		}}},
-		{"||", tok.Token{Kind: tok.OrOr, Runes: []rune("||"), Source: tok.Source{
+		}}}},
+		{"||", []tok.Token{{Kind: tok.OrOr, Runes: []rune("||"), Source: tok.Source{
 			S: loc(1, 1, 0), E: loc(1, 3, 2),
-		}}},
-		{"|", tok.Token{Kind: tok.Or, Runes: []rune("|"), Source: tok.Source{
+		}}}},
+		{"|", []tok.Token{{Kind: tok.Or, Runes: []rune("|"), Source: tok.Source{
 			S: loc(1, 1, 0), E: loc(1, 2, 1),
-		}}},
-		{"!", tok.Token{Kind: tok.Not, Runes: []rune("!"), Source: tok.Source{
+		}}}},
+		{"!", []tok.Token{{Kind: tok.Not, Runes: []rune("!"), Source: tok.Source{
 			S: loc(1, 1, 0), E: loc(1, 2, 1),
-		}}},
-		{"!=", tok.Token{Kind: tok.NotEqual, Runes: []rune("!="), Source: tok.Source{
+		}}}},
+		{"!=", []tok.Token{{Kind: tok.NotEqual, Runes: []rune("!="), Source: tok.Source{
 			S: loc(1, 1, 0), E: loc(1, 3, 2),
-		}}},
-		{"==", tok.Token{Kind: tok.Equal, Runes: []rune("=="), Source: tok.Source{
+		}}}},
+		{"==", []tok.Token{{Kind: tok.Equal, Runes: []rune("=="), Source: tok.Source{
 			S: loc(1, 1, 0), E: loc(1, 3, 2),
-		}}},
-		{"=", tok.Token{Kind: tok.Assign, Runes: []rune("="), Source: tok.Source{
+		}}}},
+		{"=", []tok.Token{{Kind: tok.Assign, Runes: []rune("="), Source: tok.Source{
 			S: loc(1, 1, 0), E: loc(1, 2, 1),
-		}}},
-		{"<<", tok.Token{Kind: tok.Shl, Runes: []rune("<<"), Source: tok.Source{
+		}}}},
+		{"<<", []tok.Token{{Kind: tok.Shl, Runes: []rune("<<"), Source: tok.Source{
 			S: loc(1, 1, 0), E: loc(1, 3, 2),
-		}}},
-		{"<=", tok.Token{Kind: tok.Le, Runes: []rune("<="), Source: tok.Source{
+		}}}},
+		{"<=", []tok.Token{{Kind: tok.Le, Runes: []rune("<="), Source: tok.Source{
 			S: loc(1, 1, 0), E: loc(1, 3, 2),
-		}}},
-		{"<", tok.Token{Kind: tok.Lt, Runes: []rune("<"), Source: tok.Source{
+		}}}},
+		{"<", []tok.Token{{Kind: tok.Lt, Runes: []rune("<"), Source: tok.Source{
 			S: loc(1, 1, 0), E: loc(1, 2, 1),
-		}}},
-		{">=", tok.Token{Kind: tok.Ge, Runes: []rune(">="), Source: tok.Source{
+		}}}},
+		{">=", []tok.Token{{Kind: tok.Ge, Runes: []rune(">="), Source: tok.Source{
 			S: loc(1, 1, 0), E: loc(1, 3, 2),
-		}}},
-		{">>", tok.Token{Kind: tok.Shr, Runes: []rune(">>"), Source: tok.Source{
+		}}}},
+		{">>", []tok.Token{{Kind: tok.Shr, Runes: []rune(">>"), Source: tok.Source{
 			S: loc(1, 1, 0), E: loc(1, 3, 2),
-		}}},
-		{">", tok.Token{Kind: tok.Gt, Runes: []rune(">"), Source: tok.Source{
+		}}}},
+		{">", []tok.Token{{Kind: tok.Gt, Runes: []rune(">"), Source: tok.Source{
 			S: loc(1, 1, 0), E: loc(1, 2, 1),
-		}}},
-		{"@", tok.Token{Kind: tok.Attr, Runes: []rune("@"), Source: tok.Source{
+		}}}},
+		{"@", []tok.Token{{Kind: tok.Attr, Runes: []rune("@"), Source: tok.Source{
 			S: loc(1, 1, 0), E: loc(1, 2, 1),
-		}}},
-		{"(", tok.Token{Kind: tok.Lparen, Runes: []rune("("), Source: tok.Source{
+		}}}},
+		{"(", []tok.Token{{Kind: tok.Lparen, Runes: []rune("("), Source: tok.Source{
 			S: loc(1, 1, 0), E: loc(1, 2, 1),
-		}}},
-		{")", tok.Token{Kind: tok.Rparen, Runes: []rune(")"), Source: tok.Source{
+		}}}},
+		{")", []tok.Token{{Kind: tok.Rparen, Runes: []rune(")"), Source: tok.Source{
 			S: loc(1, 1, 0), E: loc(1, 2, 1),
-		}}},
-		{"|", tok.Token{Kind: tok.Or, Runes: []rune("|"), Source: tok.Source{
+		}}}},
+		{"|", []tok.Token{{Kind: tok.Or, Runes: []rune("|"), Source: tok.Source{
 			S: loc(1, 1, 0), E: loc(1, 2, 1),
-		}}},
-		{"*", tok.Token{Kind: tok.Star, Runes: []rune("*"), Source: tok.Source{
+		}}}},
+		{"*", []tok.Token{{Kind: tok.Star, Runes: []rune("*"), Source: tok.Source{
 			S: loc(1, 1, 0), E: loc(1, 2, 1),
-		}}},
-		{"->", tok.Token{Kind: tok.Arrow, Runes: []rune("->"), Source: tok.Source{
+		}}}},
+		{"->", []tok.Token{{Kind: tok.Arrow, Runes: []rune("->"), Source: tok.Source{
 			S: loc(1, 1, 0), E: loc(1, 3, 2),
-		}}},
-		{"x // y ", tok.Token{Kind: tok.Identifier, Runes: []rune("x"), Source: tok.Source{
+		}}}},
+		{"x // y ", []tok.Token{{Kind: tok.Identifier, Runes: []rune("x"), Source: tok.Source{
 			S: loc(1, 1, 0), E: loc(1, 2, 1),
-		}}},
-		{`"abc"`, tok.Token{Kind: tok.String, Runes: []rune("abc"), Source: tok.Source{
+		}}}},
+		{`"abc"`, []tok.Token{{Kind: tok.String, Runes: []rune("abc"), Source: tok.Source{
 			S: loc(1, 2, 1), E: loc(1, 5, 4),
-		}}},
+		}}}},
 		{`
    //
    ident
 
-   `, tok.Token{Kind: tok.Identifier, Runes: []rune("ident"), Source: tok.Source{
+   `, []tok.Token{{Kind: tok.Identifier, Runes: []rune("ident"), Source: tok.Source{
 			S: loc(3, 4, 10), E: loc(3, 9, 15),
-		}}},
+		}}}},
 	} {
 		got, err := lexer.Lex([]rune(test.src), filepath)
 		name := fmt.Sprintf(`Lex("%v")`, test.src)
-		switch {
-		case err != nil:
+		if err != nil {
 			t.Errorf("%v returned error: %v", name, err)
-		case len(got) != 1:
-			t.Errorf("%v returned %d tokens: %v", name, len(got), got)
-		case got[0].Kind != test.expect.Kind:
-			t.Errorf(`%v returned unexpected token kind: got "%+v", expected "%+v"`, name, got[0], test.expect)
-		case string(got[0].Runes) != string(test.expect.Runes):
-			t.Errorf(`%v returned unexpected token runes: got "%+v", expected "%+v"`, name, string(got[0].Runes), string(test.expect.Runes))
-		case got[0].Source != test.expect.Source:
-			t.Errorf(`%v returned unexpected token source: got %+v, expected %+v`, name, got[0].Source, test.expect.Source)
+			continue
+		}
+		if diff := cmp.Diff(got, test.expect); diff != "" {
+			t.Errorf(`%v: %v`, name, diff)
 		}
 	}
 }

tools/src/tint/intrinsic/parser/parser.go

@@ -18,6 +18,7 @@ package parser
 
 import (
 	"fmt"
+	"strconv"
 
 	"dawn.googlesource.com/dawn/tools/src/tint/intrinsic/ast"
 	"dawn.googlesource.com/dawn/tools/src/tint/intrinsic/lexer"
@@ -145,10 +146,26 @@ func (p *parser) attributes() ast.Attributes {
 	var out ast.Attributes
 	for p.match(tok.Attr) != nil && p.err == nil {
 		name := p.expect(tok.Identifier, "attribute name")
-		values := []string{}
+		var values []any
 		if p.match(tok.Lparen) != nil {
+		loop:
 			for p.err == nil {
-				values = append(values, string(p.next().Runes))
+				t := p.next()
+				switch t.Kind {
+				case tok.Rparen:
+					break loop
+				case tok.String:
+					values = append(values, string(t.Runes))
+				case tok.Integer:
+					i, _ := strconv.ParseInt(string(t.Runes), 10, 64)
+					values = append(values, int(i))
+				case tok.Float:
+					f, _ := strconv.ParseFloat(string(t.Runes), 64)
+					values = append(values, f)
+				default:
+					p.err = fmt.Errorf("%v invalid attribute value kind: %v", t.Source, t.Kind)
+					return nil
+				}
 				if p.match(tok.Comma) == nil {
 					break
 				}

tools/src/tint/intrinsic/parser/parser_test.go

@@ -52,7 +52,7 @@ func TestParser(t *testing.T) {
 						{
 							Attributes: ast.Attributes{{
 								Name:   "attr",
-								Values: []string{},
+								Values: nil,
 							}},
 							Name: "B",
 						},
@@ -85,7 +85,7 @@ func TestParser(t *testing.T) {
 			ast.AST{
 				Types: []ast.TypeDecl{{
 					Attributes: ast.Attributes{
-						{Name: "attr", Values: []string{}},
+						{Name: "attr", Values: nil},
 					},
 					Name: "T",
 				}},
@@ -96,8 +96,8 @@ func TestParser(t *testing.T) {
 			ast.AST{
 				Types: []ast.TypeDecl{{
 					Attributes: ast.Attributes{
-						{Name: "attr_a", Values: []string{}},
-						{Name: "attr_b", Values: []string{}},
+						{Name: "attr_a", Values: nil},
+						{Name: "attr_b", Values: nil},
 					},
 					Name: "T",
 				}},
@@ -107,17 +107,17 @@ func TestParser(t *testing.T) {
 			`@attr("a", "b") type T`, ast.AST{
 				Types: []ast.TypeDecl{{
 					Attributes: ast.Attributes{
-						{Name: "attr", Values: []string{"a", "b"}},
+						{Name: "attr", Values: []any{"a", "b"}},
 					},
 					Name: "T",
 				}},
 			},
 		}, { ///////////////////////////////////////////////////////////////////
 			utils.ThisLine(),
-			`@attr(1, "x") type T`, ast.AST{
+			`@attr(1, "x", 2.0) type T`, ast.AST{
 				Types: []ast.TypeDecl{{
 					Attributes: ast.Attributes{
-						{Name: "attr", Values: []string{"1", "x"}},
+						{Name: "attr", Values: []any{1, "x", 2.0}},
 					},
 					Name: "T",
 				}},
@@ -194,7 +194,7 @@ func TestParser(t *testing.T) {
 					Kind: ast.Builtin,
 					Name: "F",
 					Attributes: ast.Attributes{
-						{Name: "attr", Values: []string{}},
+						{Name: "attr", Values: nil},
 					},
 					Parameters: ast.Parameters{},
 				}},
@@ -318,7 +318,7 @@ func TestParser(t *testing.T) {
 					Kind: ast.Operator,
 					Name: "F",
 					Attributes: ast.Attributes{
-						{Name: "attr", Values: []string{}},
+						{Name: "attr", Values: nil},
 					},
 					Parameters: ast.Parameters{},
 				}},
@@ -344,7 +344,7 @@ func TestParser(t *testing.T) {
 					Name: "F",
 					Parameters: ast.Parameters{
 						{
-							Attributes: ast.Attributes{{Name: "blah", Values: []string{}}},
+							Attributes: ast.Attributes{{Name: "blah", Values: nil}},
 							Type:       ast.TemplatedName{Name: "a"}},
 					},
 				}},
@@ -456,7 +456,7 @@ func TestParser(t *testing.T) {
 					Kind: ast.Initializer,
 					Name: "F",
 					Attributes: ast.Attributes{
-						{Name: "attr", Values: []string{}},
+						{Name: "attr", Values: nil},
 					},
 					Parameters: ast.Parameters{},
 				}},
@@ -580,7 +580,7 @@ func TestParser(t *testing.T) {
 					Kind: ast.Converter,
 					Name: "F",
 					Attributes: ast.Attributes{
-						{Name: "attr", Values: []string{}},
+						{Name: "attr", Values: nil},
 					},
 					Parameters: ast.Parameters{},
 				}},

tools/src/tint/intrinsic/resolver/resolve.go

@@ -17,7 +17,6 @@ package resolver
 import (
 	"fmt"
 	"sort"
-	"strconv"
 
 	"dawn.googlesource.com/dawn/tools/src/container"
 	"dawn.googlesource.com/dawn/tools/src/tint/intrinsic/ast"
@@ -184,15 +183,15 @@ func (r *resolver) ty(a ast.TypeDecl) error {
 		if len(d.Values) != 1 {
 			return fmt.Errorf("%v expected a single value for 'display' attribute", d.Source)
 		}
-		t.DisplayName = d.Values[0]
+		t.DisplayName = fmt.Sprint(d.Values[0])
 	}
 	if d := a.Attributes.Take("precedence"); d != nil {
 		if len(d.Values) != 1 {
 			return fmt.Errorf("%v expected a single integer value for 'precedence' attribute", d.Source)
 		}
-		n, err := strconv.Atoi(d.Values[0])
-		if err != nil {
-			return fmt.Errorf("%v %v", d.Source, err)
+		n, ok := d.Values[0].(int)
+		if !ok {
+			return fmt.Errorf("%v @precedence value must be an integer", d.Source)
 		}
 		t.Precedence = n
 	}
@@ -358,7 +357,11 @@ func (r *resolver) intrinsic(
 				overload.ConstEvalFunction = "Conv"
 			}
 		case 1:
-			overload.ConstEvalFunction = constEvalFn.Values[0]
+			fn, ok := constEvalFn.Values[0].(string)
+			if !ok {
+				return fmt.Errorf("%v optional @const value must be a string", constEvalFn.Source)
+			}
+			overload.ConstEvalFunction = fn
 		default:
 			return fmt.Errorf("%v too many values for @const attribute", constEvalFn.Source)
 		}
@@ -405,13 +408,25 @@ func (r *resolver) intrinsic(
 		if attribute := p.Attributes.Take("const"); attribute != nil {
 			isConst = true
 		}
+		testValue := 1.0
+		if attribute := p.Attributes.Take("test_value"); attribute != nil {
+			switch v := attribute.Values[0].(type) {
+			case int:
+				testValue = float64(v)
+			case float64:
+				testValue = v
+			default:
+				return fmt.Errorf("%v @test_value must be an integer or float", p.Attributes[0].Source)
+			}
+		}
 		if len(p.Attributes) != 0 {
 			return fmt.Errorf("%v unknown attribute", p.Attributes[0].Source)
 		}
 		overload.Parameters[i] = sem.Parameter{
-			Name:    p.Name,
-			Type:    usage,
-			IsConst: isConst,
+			Name:      p.Name,
+			Type:      usage,
+			IsConst:   isConst,
+			TestValue: testValue,
 		}
 	}
 

tools/src/tint/intrinsic/sem/sem.go

@@ -242,9 +242,10 @@ func (o Overload) Format(w fmt.State, verb rune) {
 
 // Parameter describes a single parameter of a function overload
 type Parameter struct {
-	Name    string
-	Type    FullyQualifiedName
-	IsConst bool // Did this parameter have a @const attribute?
+	Name      string
+	Type      FullyQualifiedName
+	IsConst   bool    // Did this parameter have a @const attribute?
+	TestValue float64 // Value to use for end-to-end tests
 }
 
 // Format implements the fmt.Formatter interface

tools/src/tint/intrinsic/tok/tok.go

@@ -26,6 +26,7 @@ const (
 	InvalidToken Kind = "<invalid>"
 	Identifier   Kind = "ident"
 	Integer      Kind = "integer"
+	Float        Kind = "float"
 	String       Kind = "string"
 	Match        Kind = "match"
 	Function     Kind = "fn"