diff --git a/src/check_builtin.cpp b/src/check_builtin.cpp
index 79afef7cd..2770ac430 100644
--- a/src/check_builtin.cpp
+++ b/src/check_builtin.cpp
@@ -3867,10 +3867,6 @@ gb_internal bool check_builtin_procedure(CheckerContext *c, Operand *operand, As
 		default: GB_PANIC("Invalid type"); break;
 		}
 
-		if (type_hint != nullptr && check_is_castable_to(c, operand, type_hint)) {
-			operand->type = type_hint;
-		}
-
 		break;
 	}
 
@@ -3887,7 +3883,7 @@ gb_internal bool check_builtin_procedure(CheckerContext *c, Operand *operand, As
 		if (is_type_untyped(x->type)) {
 			if (x->mode == Addressing_Constant) {
 				if (is_type_numeric(x->type)) {
-					x->type = t_untyped_complex;
+					x->type = t_untyped_quaternion;
 				}
 			} else{
 				convert_to_typed(c, x, t_quaternion256);
@@ -3923,10 +3919,6 @@ gb_internal bool check_builtin_procedure(CheckerContext *c, Operand *operand, As
 		default: GB_PANIC("Invalid type"); break;
 		}
 
-		if (type_hint != nullptr && check_is_castable_to(c, operand, type_hint)) {
-			operand->type = type_hint;
-		}
-
 		break;
 	}
 
diff --git a/src/exact_value.cpp b/src/exact_value.cpp
index 2f82a52cf..5c436fee6 100644
--- a/src/exact_value.cpp
+++ b/src/exact_value.cpp
@@ -1019,6 +1019,10 @@ gb_internal bool compare_exact_values(TokenKind op, ExactValue x, ExactValue y)
 		f64 b = x.value_complex->imag;
 		f64 c = y.value_complex->real;
 		f64 d = y.value_complex->imag;
+		if (isnan(a) || isnan(b) || isnan(c) || isnan(d)) {
+			return op == Token_NotEq;
+		}
+
 		switch (op) {
 		case Token_CmpEq: return cmp_f64(a, c) == 0 && cmp_f64(b, d) == 0;
 		case Token_NotEq: return cmp_f64(a, c) != 0 || cmp_f64(b, d) != 0;
@@ -1026,6 +1030,29 @@ gb_internal bool compare_exact_values(TokenKind op, ExactValue x, ExactValue y)
 		break;
 	}
 
+	case ExactValue_Quaternion: {
+		Quaternion256 a = *x.value_quaternion;
+		Quaternion256 b = *y.value_quaternion;
+		if (isnan(a.real) || isnan(a.imag) || isnan(a.jmag) || isnan(a.kmag) ||
+		    isnan(b.real) || isnan(b.imag) || isnan(b.jmag) || isnan(b.kmag)) {
+			return op == Token_NotEq;
+		}
+
+		switch (op) {
+		case Token_CmpEq:
+			return cmp_f64(a.real, b.real) == 0 &&
+			       cmp_f64(a.imag, b.imag) == 0 &&
+			       cmp_f64(a.jmag, b.jmag) == 0 &&
+			       cmp_f64(a.kmag, b.kmag) == 0;
+		case Token_NotEq:
+			return cmp_f64(a.real, b.real) != 0 ||
+			       cmp_f64(a.imag, b.imag) != 0 ||
+			       cmp_f64(a.jmag, b.jmag) != 0 ||
+			       cmp_f64(a.kmag, b.kmag) != 0;
+		}
+		break;
+	}
+
 	case ExactValue_String: {
 		String a = x.value_string;
 		String b = y.value_string;
diff --git a/tests/internal/test_nan_comparison.odin b/tests/internal/test_nan_comparison.odin
index 5740be477..b47cc9dfc 100644
--- a/tests/internal/test_nan_comparison.odin
+++ b/tests/internal/test_nan_comparison.odin
@@ -89,3 +89,100 @@ compare_variable_nans_f64 :: proc(t: ^testing.T) {
 	testing.expect_value(t, NaN >  NaN,     false)
 	testing.expect_value(t, NaN >= NaN,     false)
 }
+
+// A complex or quaternion compares componentwise, so a NaN in any one lane makes the whole
+// comparison fail. The folded form used to disagree: `cmp_f64` is `(a>b)-(a<b)`, which
+// answers 0 for a NaN -- the same value it uses for "equal".
+
+@(test)
+compare_constant_nans_complex :: proc(t: ^testing.T) {
+	NaN :: f64(0h7fff_0000_0000_0000)
+	Re  :: complex(NaN, 0)
+	Im  :: complex(0, NaN)
+
+	testing.expect_value(t, Re == Re, false)
+	testing.expect_value(t, Re != Re, true)
+	testing.expect_value(t, Im == Im, false)
+	testing.expect_value(t, Im != Im, true)
+	testing.expect_value(t, Re == Im, false)
+	testing.expect_value(t, Re == 0,  false)
+	testing.expect_value(t, Re != 0,  true)
+	testing.expect_value(t, 0 == Re,  false)
+
+	testing.expect_value(t, complex(f32(0h7fc0_0000), 0) == complex(f32(0h7fc0_0000), 0), false)
+	testing.expect_value(t, complex(f16(0h7e00), 0)      == complex(f16(0h7e00), 0),      false)
+}
+
+@(test)
+compare_variable_nans_complex :: proc(t: ^testing.T) {
+	NaN := f64(0h7fff_0000_0000_0000)
+	Re  := complex(NaN, 0)
+	Im  := complex(0, NaN)
+
+	testing.expect_value(t, Re == Re, false)
+	testing.expect_value(t, Re != Re, true)
+	testing.expect_value(t, Im == Im, false)
+	testing.expect_value(t, Im != Im, true)
+	testing.expect_value(t, Re == Im, false)
+	testing.expect_value(t, Re == 0,  false)
+	testing.expect_value(t, Re != 0,  true)
+	testing.expect_value(t, 0 == Re,  false)
+
+	c64 := complex(f32(0h7fc0_0000), 0)
+	c32 := complex(f16(0h7e00), 0)
+	testing.expect_value(t, c64 == c64, false)
+	testing.expect_value(t, c32 == c32, false)
+}
+
+@(test)
+compare_constant_nans_quaternion :: proc(t: ^testing.T) {
+	NaN :: f64(0h7fff_0000_0000_0000)
+
+	// one per lane: real, imag, jmag, kmag
+	W :: quaternion(w=NaN, x=0, y=0, z=0)
+	X :: quaternion(w=0, x=NaN, y=0, z=0)
+	Y :: quaternion(w=0, x=0, y=NaN, z=0)
+	Z :: quaternion(w=0, x=0, y=0, z=NaN)
+
+	testing.expect_value(t, W == W, false)
+	testing.expect_value(t, X == X, false)
+	testing.expect_value(t, Y == Y, false)
+	testing.expect_value(t, Z == Z, false)
+	testing.expect_value(t, W != W, true)
+	testing.expect_value(t, X != X, true)
+	testing.expect_value(t, Y != Y, true)
+	testing.expect_value(t, Z != Z, true)
+	testing.expect_value(t, W == 0, false)
+	testing.expect_value(t, W != 0, true)
+	testing.expect_value(t, 0 == Z, false)
+
+	testing.expect_value(t, quaternion(w=f32(0h7fc0_0000), x=0, y=0, z=0) == quaternion(w=f32(0h7fc0_0000), x=0, y=0, z=0), false)
+	testing.expect_value(t, quaternion(w=f16(0h7e00), x=0, y=0, z=0)      == quaternion(w=f16(0h7e00), x=0, y=0, z=0),      false)
+}
+
+@(test)
+compare_variable_nans_quaternion :: proc(t: ^testing.T) {
+	NaN := f64(0h7fff_0000_0000_0000)
+
+	W := quaternion(w=NaN, x=0, y=0, z=0)
+	X := quaternion(w=0, x=NaN, y=0, z=0)
+	Y := quaternion(w=0, x=0, y=NaN, z=0)
+	Z := quaternion(w=0, x=0, y=0, z=NaN)
+
+	testing.expect_value(t, W == W, false)
+	testing.expect_value(t, X == X, false)
+	testing.expect_value(t, Y == Y, false)
+	testing.expect_value(t, Z == Z, false)
+	testing.expect_value(t, W != W, true)
+	testing.expect_value(t, X != X, true)
+	testing.expect_value(t, Y != Y, true)
+	testing.expect_value(t, Z != Z, true)
+	testing.expect_value(t, W == 0, false)
+	testing.expect_value(t, W != 0, true)
+	testing.expect_value(t, 0 == Z, false)
+
+	q128 := quaternion(w=f32(0h7fc0_0000), x=0, y=0, z=0)
+	q64  := quaternion(w=f16(0h7e00), x=0, y=0, z=0)
+	testing.expect_value(t, q128 == q128, false)
+	testing.expect_value(t, q64  == q64,  false)
+}
diff --git a/tests/internal/test_quat_cmplx.odin b/tests/internal/test_quat_cmplx.odin
new file mode 100644
index 000000000..bf8df6f0d
--- /dev/null
+++ b/tests/internal/test_quat_cmplx.odin
@@ -0,0 +1,329 @@
+package test_internal
+
+import "core:testing"
+
+// Constant folding of complex and quaternion values, against the answer the backend
+// produces. Every constant case is paired with the same expression on variables: the
+// folded answer and the runtime answer are the same contract, and where they diverged
+// the folded one was always the wrong side.
+
+@(test)
+constant_complex_comparison :: proc(t: ^testing.T) {
+	A :: complex128(2+3i)
+
+	testing.expect_value(t, A == complex128(2+3i), true)
+	testing.expect_value(t, A != complex128(2+3i), false)
+	testing.expect_value(t, A == complex128(9+3i), false)
+	testing.expect_value(t, A == complex128(2+9i), false)
+	testing.expect_value(t, A != complex128(2+9i), true)
+
+	// promotion of an untyped operand, both orders
+	R :: complex128(5+0i)
+	testing.expect_value(t, R == 5,   true)
+	testing.expect_value(t, 5 == R,   true)
+	testing.expect_value(t, R == 5.0, true)
+	testing.expect_value(t, R != 5,   false)
+	testing.expect_value(t, R == 6,   false)
+
+	// every width
+	testing.expect_value(t, complex32(2+3i)  == complex32(2+3i),  true)
+	testing.expect_value(t, complex64(2+3i)  == complex64(2+3i),  true)
+	testing.expect_value(t, complex128(2+3i) == complex128(2+3i), true)
+	testing.expect_value(t, complex32(2+3i)  == complex32(2+4i),  false)
+
+	testing.expect_value(t, complex128(0) == complex128(-0.0), true)
+}
+
+@(test)
+variable_complex_comparison :: proc(t: ^testing.T) {
+	A := complex128(2+3i)
+
+	testing.expect_value(t, A == complex128(2+3i), true)
+	testing.expect_value(t, A != complex128(2+3i), false)
+	testing.expect_value(t, A == complex128(9+3i), false)
+	testing.expect_value(t, A == complex128(2+9i), false)
+	testing.expect_value(t, A != complex128(2+9i), true)
+
+	R := complex128(5+0i)
+	testing.expect_value(t, R == 5,   true)
+	testing.expect_value(t, 5 == R,   true)
+	testing.expect_value(t, R == 5.0, true)
+	testing.expect_value(t, R != 5,   false)
+	testing.expect_value(t, R == 6,   false)
+
+	c32  := complex32(2+3i)
+	c64  := complex64(2+3i)
+	c128 := complex128(2+3i)
+	testing.expect_value(t, c32  == complex32(2+3i),  true)
+	testing.expect_value(t, c64  == complex64(2+3i),  true)
+	testing.expect_value(t, c128 == complex128(2+3i), true)
+	testing.expect_value(t, c32  == complex32(2+4i),  false)
+
+	z := complex128(0)
+	testing.expect_value(t, z == complex128(-0.0), true)
+}
+
+@(test)
+constant_quaternion_comparison :: proc(t: ^testing.T) {
+	A :: quaternion256(1+2i+3j+4k)
+
+	testing.expect_value(t, A == quaternion256(1+2i+3j+4k), true)
+	testing.expect_value(t, A != quaternion256(1+2i+3j+4k), false)
+
+	// each lane on its own, so a compare that ignores one cannot pass
+	testing.expect_value(t, A == quaternion256(9+2i+3j+4k), false)
+	testing.expect_value(t, A == quaternion256(1+9i+3j+4k), false)
+	testing.expect_value(t, A == quaternion256(1+2i+9j+4k), false)
+	testing.expect_value(t, A == quaternion256(1+2i+3j+9k), false)
+	testing.expect_value(t, A != quaternion256(1+2i+3j+9k), true)
+
+	I :: quaternion256(0+1i+0j+0k)
+	J :: quaternion256(0+0i+1j+0k)
+	K :: quaternion256(0+0i+0j+1k)
+	testing.expect_value(t, I == J, false)
+	testing.expect_value(t, J == K, false)
+	testing.expect_value(t, I == I, true)
+
+	// promotion from integer, float and complex, both orders
+	R :: quaternion256(5+0i+0j+0k)
+	testing.expect_value(t, R == 5,   true)
+	testing.expect_value(t, 5 == R,   true)
+	testing.expect_value(t, R == 5.0, true)
+	testing.expect_value(t, R != 5,   false)
+	testing.expect_value(t, quaternion256(2+3i+0j+0k) == 2+3i, true)
+	testing.expect_value(t, quaternion256(2+3i+0j+0k) == 2+4i, false)
+
+	// every width
+	testing.expect_value(t, quaternion64(1+2i+3j+4k)  == quaternion64(1+2i+3j+4k),  true)
+	testing.expect_value(t, quaternion128(1+2i+3j+4k) == quaternion128(1+2i+3j+4k), true)
+	testing.expect_value(t, quaternion256(1+2i+3j+4k) == quaternion256(1+2i+3j+4k), true)
+	testing.expect_value(t, quaternion64(1+2i+3j+4k)  == quaternion64(1+2i+3j+9k),  false)
+
+	testing.expect_value(t, quaternion256(0) == quaternion256(-0.0), true)
+}
+
+@(test)
+variable_quaternion_comparison :: proc(t: ^testing.T) {
+	A := quaternion256(1+2i+3j+4k)
+
+	testing.expect_value(t, A == quaternion256(1+2i+3j+4k), true)
+	testing.expect_value(t, A != quaternion256(1+2i+3j+4k), false)
+
+	testing.expect_value(t, A == quaternion256(9+2i+3j+4k), false)
+	testing.expect_value(t, A == quaternion256(1+9i+3j+4k), false)
+	testing.expect_value(t, A == quaternion256(1+2i+9j+4k), false)
+	testing.expect_value(t, A == quaternion256(1+2i+3j+9k), false)
+	testing.expect_value(t, A != quaternion256(1+2i+3j+9k), true)
+
+	I := quaternion256(0+1i+0j+0k)
+	J := quaternion256(0+0i+1j+0k)
+	K := quaternion256(0+0i+0j+1k)
+	testing.expect_value(t, I == J, false)
+	testing.expect_value(t, J == K, false)
+	testing.expect_value(t, I == I, true)
+
+	R := quaternion256(5+0i+0j+0k)
+	testing.expect_value(t, R == 5,   true)
+	testing.expect_value(t, 5 == R,   true)
+	testing.expect_value(t, R == 5.0, true)
+	testing.expect_value(t, R != 5,   false)
+
+	q64  := quaternion64(1+2i+3j+4k)
+	q128 := quaternion128(1+2i+3j+4k)
+	q256 := quaternion256(1+2i+3j+4k)
+	testing.expect_value(t, q64  == quaternion64(1+2i+3j+4k),  true)
+	testing.expect_value(t, q128 == quaternion128(1+2i+3j+4k), true)
+	testing.expect_value(t, q256 == quaternion256(1+2i+3j+4k), true)
+	testing.expect_value(t, q64  == quaternion64(1+2i+3j+9k),  false)
+
+	z := quaternion256(0)
+	testing.expect_value(t, z == quaternion256(-0.0), true)
+}
+
+@(test)
+constant_complex_accessors :: proc(t: ^testing.T) {
+	A :: complex128(2+3i)
+	testing.expect_value(t, real(A), 2)
+	testing.expect_value(t, imag(A), 3)
+
+	testing.expect_value(t, real(complex32(2+3i)),  2)
+	testing.expect_value(t, imag(complex32(2+3i)),  3)
+	testing.expect_value(t, real(complex64(2+3i)),  2)
+	testing.expect_value(t, imag(complex64(2+3i)),  3)
+
+	// untyped constants
+	testing.expect_value(t, real(3i), 0)
+	testing.expect_value(t, imag(3i), 3)
+	testing.expect_value(t, real(3),  3)
+	testing.expect_value(t, imag(3),  0)
+}
+
+@(test)
+variable_complex_accessors :: proc(t: ^testing.T) {
+	A := complex128(2+3i)
+	testing.expect_value(t, real(A), 2)
+	testing.expect_value(t, imag(A), 3)
+
+	c32 := complex32(2+3i)
+	c64 := complex64(2+3i)
+	testing.expect_value(t, real(c32), 2)
+	testing.expect_value(t, imag(c32), 3)
+	testing.expect_value(t, real(c64), 2)
+	testing.expect_value(t, imag(c64), 3)
+}
+
+@(test)
+constant_quaternion_accessors :: proc(t: ^testing.T) {
+	// w/x/y/z map onto real/imag/jmag/kmag, and every lane is distinct here so a
+	// swapped accessor cannot pass by accident
+	A :: quaternion(w=1, x=2, y=3, z=4)
+	testing.expect_value(t, real(A), 1)
+	testing.expect_value(t, imag(A), 2)
+	testing.expect_value(t, jmag(A), 3)
+	testing.expect_value(t, kmag(A), 4)
+
+	B :: quaternion256(1+2i+3j+4k)
+	testing.expect_value(t, real(B), 1)
+	testing.expect_value(t, imag(B), 2)
+	testing.expect_value(t, jmag(B), 3)
+	testing.expect_value(t, kmag(B), 4)
+
+	testing.expect_value(t, jmag(quaternion64(1+2i+3j+4k)),  3)
+	testing.expect_value(t, kmag(quaternion64(1+2i+3j+4k)),  4)
+	testing.expect_value(t, jmag(quaternion128(1+2i+3j+4k)), 3)
+	testing.expect_value(t, kmag(quaternion128(1+2i+3j+4k)), 4)
+
+	// a typed constant with empty j/k lanes
+	Q :: quaternion256(3)
+	testing.expect_value(t, real(Q), 3)
+	testing.expect_value(t, jmag(Q), 0)
+	testing.expect_value(t, kmag(Q), 0)
+}
+
+@(test)
+variable_quaternion_accessors :: proc(t: ^testing.T) {
+	A := quaternion(w=1, x=2, y=3, z=4)
+	testing.expect_value(t, real(A), 1)
+	testing.expect_value(t, imag(A), 2)
+	testing.expect_value(t, jmag(A), 3)
+	testing.expect_value(t, kmag(A), 4)
+
+	q64  := quaternion64(1+2i+3j+4k)
+	q128 := quaternion128(1+2i+3j+4k)
+	testing.expect_value(t, jmag(q64),  3)
+	testing.expect_value(t, kmag(q64),  4)
+	testing.expect_value(t, jmag(q128), 3)
+	testing.expect_value(t, kmag(q128), 4)
+
+	q: quaternion256
+	testing.expect_value(t, real(q), 0)
+	testing.expect_value(t, jmag(q), 0)
+	testing.expect_value(t, kmag(q), 0)
+}
+
+// The `j` and `k` suffixes are the only way to write an untyped quaternion constant, and
+// these are the shapes `jmag`/`kmag` used to reject outright.
+
+@(test)
+untyped_constant_quaternion_accessors :: proc(t: ^testing.T) {
+	testing.expect_value(t, jmag(3j), 3)
+	testing.expect_value(t, kmag(3k), 3)
+	testing.expect_value(t, jmag(3k), 0)
+	testing.expect_value(t, kmag(3j), 0)
+	testing.expect_value(t, real(3j), 0)
+	testing.expect_value(t, imag(3j), 0)
+
+	testing.expect_value(t, real(1+2i+3j+4k), 1)
+	testing.expect_value(t, imag(1+2i+3j+4k), 2)
+	testing.expect_value(t, jmag(1+2i+3j+4k), 3)
+	testing.expect_value(t, kmag(1+2i+3j+4k), 4)
+
+	// an untyped constant that is not a quaternion answers zero, as `imag` does
+	testing.expect_value(t, jmag(3),   0)
+	testing.expect_value(t, kmag(3),   0)
+	testing.expect_value(t, jmag(3.5), 0)
+	testing.expect_value(t, kmag(3.5), 0)
+	testing.expect_value(t, jmag(3i),  0)
+	testing.expect_value(t, kmag(3i),  0)
+}
+
+// the accessors answer an untyped float, so the result takes its type from the context
+// rather than being pinned to f64
+
+@(test)
+accessor_results_are_untyped :: proc(t: ^testing.T) {
+	J16 : f16 : jmag(3j)
+	J32 : f32 : jmag(3j)
+	J64 : f64 : jmag(3j)
+	K16 : f16 : kmag(3k)
+	K32 : f32 : kmag(3k)
+	K64 : f64 : kmag(3k)
+	R32 : f32 : real(2+3i)
+	I32 : f32 : imag(2+3i)
+
+	testing.expect_value(t, J16, 3)
+	testing.expect_value(t, J32, 3)
+	testing.expect_value(t, J64, 3)
+	testing.expect_value(t, K16, 3)
+	testing.expect_value(t, K32, 3)
+	testing.expect_value(t, K64, 3)
+	testing.expect_value(t, R32, 2)
+	testing.expect_value(t, I32, 3)
+}
+
+// An enclosing conversion passes its destination down as a type hint, and the accessors
+// used to adopt it as their own result type. That decides which type the arithmetic
+// inside the conversion happens in, so the wrong answer is observable: the division
+// below was checked in i8, where `3.2` does not exist.
+
+@(test)
+accessors_ignore_the_enclosing_conversions_type :: proc(t: ^testing.T) {
+	c: complex128 = 10
+	testing.expect_value(t, i8(real(c) / 3.2), 3)
+	testing.expect_value(t, i8(imag(c) / 3.2), 0)
+
+	d: complex128 = 0 + 10i
+	testing.expect_value(t, i8(imag(d) / 3.2), 3)
+
+	q: quaternion256 = quaternion(w=10, x=10, y=10, z=10)
+	testing.expect_value(t, i8(real(q) / 3.2), 3)
+	testing.expect_value(t, i8(imag(q) / 3.2), 3)
+	testing.expect_value(t, i8(jmag(q) / 3.2), 3)
+	testing.expect_value(t, i8(kmag(q) / 3.2), 3)
+
+	// the same on constants
+	C :: complex128(10)
+	Q :: quaternion256(1+2i+3j+4k)
+	testing.expect_value(t, int(real(C) / 2.5), 4)
+	testing.expect_value(t, int(kmag(Q) / 0.5), 8)
+}
+
+// `transmute` supplies a hint too, and it is the spelling that failed silently: the
+// accessor was retyped to the destination, so what got reinterpreted was already an
+// integer and the float's bits were gone. Naming the intermediate was the workaround,
+// so a named one is the control here.
+
+@(test)
+accessors_keep_their_bits_through_transmute :: proc(t: ^testing.T) {
+	c32  : complex32  = complex(f16(1.5), f16(2.5))
+	c64  : complex64  = complex(f32(1), f32(2))
+	c128 : complex128 = complex(f64(1), f64(2))
+
+	n := real(c32)
+	r := real(c64)
+	i := imag(c128)
+
+	testing.expect_value(t, transmute(u16)real(c32),  transmute(u16)n)
+	testing.expect_value(t, transmute(u32)real(c64),  transmute(u32)r)
+	testing.expect_value(t, transmute(u64)imag(c128), transmute(u64)i)
+
+	testing.expect_value(t, transmute(u16)real(c32),  15872)
+	testing.expect_value(t, transmute(u32)real(c64),  1065353216)
+	testing.expect_value(t, transmute(u64)imag(c128), 4611686018427387904)
+
+	q : quaternion256 = quaternion(w=1, x=2, y=3, z=4)
+	j := jmag(q)
+	k := kmag(q)
+	testing.expect_value(t, transmute(u64)jmag(q), transmute(u64)j)
+	testing.expect_value(t, transmute(u64)kmag(q), transmute(u64)k)
+}